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1992 Part 2     Front Cover (1992 - Part 2)    No author information available Summary: Not available         Table of Contents (1992 - Part 2)    No author information available Summary: Not available         Multifilamentary Bi-2223 composite tapes made by a metallic precursor route    A. Otto, L.J. Masur, J. Gannon, E. Podtburg, D. Daly, G.J. Yurek and A.P. Malozemoff Summary: A process based on metallic precursors has been developed for manufacturing high filament count oxide superconductor-silver composite tapes with critical current densities of up to 7.5 kA/cm/sup 2/ at 77 K in zero field. A 30-cm prototype multistrand conductor made of these tapes has a critical current of 240 A at 77 K over a 9 cm gauge length, with an average critical current density of 6 kA/cm/sup 2/. The mechanical properties of tapes made from metallic precursors containing up to 10000 Bi-2223 superconducting oxide filaments were investigated. Critical tensile strains average 0.6%, and bend tests show negligible dropoff in current density up to a 0.70% surface strain. The critical current decrease beyond the 0.70% surface bend strain follows a simple model based on extensive filament damage beyond the critical tensile strain. Increased flow stresses of the composite tapes, compared to similarly processed silver, indicate considerable strengthening of the composite by the oxide filaments.         Superconducting current leads of Bi-based oxide    Y. Yamada, T. Yanagiya, T. Hasebe, K. Jikihara, M. Ishizuka, S. Yasuhara and M. Ishihara Summary: The application of Bi-based oxide bulk superconductors to current leads for various types of superconducting devices was investigated. The bulk was manufactured in the form of a cylindrical tube (inner diameter: 10 to 30 mm; wall thickness: 1.2 to 1.4 mm; length: 200 mm) and had the composition (Bi+Pb):Sr:Ca:Cu=2:2:2:3. Values greater than 1000 A/cm/sup 2/ were obtained for critical current density at 77 K under self-magnetic field. The maximum critical current was 1600 A. Heat leakage was measured between 77 K and 4.2 K while a DC current was passed through the conductor. The heat leakage of a bulk lead pair was 0.16 W, less than one-tenth of that of conventional gas-cooled Cu leads.         Development and performance characteristics of Bi-2212/Ag superconducting wires    R. Wesche, B. Jakob and G. Pasztor Summary: A series of Bi-2212/Ag composite wires have been fabricated by the 'powder in tube' method. Heat treatment studies have been performed to investigate their effect on superconducting properties. The critical current density was found to be strongly influenced by the phase composition of the calcined powder. The wires with T/sub c/ of 85 K reached at 4.2 K j/sub c/ values up to 66500 A/cm/sup 2/ (0 T). The index of resistive transition n was found to correlate with the critical current density, suggesting that n could be useful as an indicator of microstructural inhomogeneities. Since practical applications require stability of the superconducting phase, measurements of the effect of aging and thermal shocks on j/sub c/ were made and are discussed.         Effects of heating temperature and atmosphere on critical current density of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/Ag/sub 0.8/O/sub y/ Ag-sheathed tapes    A. Endo and S. Nishikida Summary: In partial melt processing of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/Ag/sub 0.8/O/sub y/ silver sheathed tapes, the effects of heating temperature and atmosphere on the critical current density, J/sub c/, were studied. It was found that J/sub c/ is higher for the samples treated in pure oxygen than those in air and has the maximum value at a heating temperature of 885 degrees C. During partial melting, nonsuperconducting Sr-Ca-Cu-O precipitates grew in size with increasing temperature and caused a decrease of J/sub c/. The composition of the Sr-Ca-Cu-O phases in the tapes treated at 885 degrees C was (Sr,Ca)/sub 1/Cu/sub 1/O/sub y/ in air and (Sr,Ca)/sub 3/Cu/sub 5/O/sub y/ in oxygen. The size of precipitates in oxygen was smaller than in air. The highest J/sub c/ value, 1.2*10/sup 5/ A/cm/sup 2/ at 8 T and 4.2 K, was achieved in oxygen.         Fabrication of superconducting joints for Bi-2212 pancake coils    K. Shibutani, T. Egi, S. Hayashi, Y. Fukumoto, I. Shigaki, Y. Masuda, R. Ogawa and Y. Kawate Summary: To evaluate the possibility of persistent current operation for NMR/MRI using a Bi/sub 2/Sr/sub 2/CaCuO/sub 8/ (Bi-2212) superconductor at 4.2 K, the temperature dependence of magnetic relaxation of the single crystal has been measured. It was found that the operating current must be one-fourth of J/sub c/ at 4.2 K to satisfy the stability condition for NMR/MRI operation ( Delta J/J less than 0.005 ppm/h). A superconducting coil made of Bi-2212 silver-sheathed wire was fabricated by the partial melt growth process. The authors were successful in generating 1.60 T in a zero external magnetic field at 4.2 K with a coil made of silver-sheathed Bi-2212 tape which was 100- mu m thick, 10-mm wide and 150-m long. Superconducting jointed pancake coils with critical current reaching 80 A in an external magnetic field of 1.0 T at 4.2 K were also fabricated.         Design and fabrication of Bi-based superconducting coil    T. Kitamura, T. Hasegawa and H. Ogiwara Summary: Two prototype coils were constructed using silver-sheathed (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ superconducting wires fabricated by the powder-in-tube technique. One was designed as a coil for an iron core magnet which generated a magnetic field of 0.2 T at 77.3 K. The other was an insert coil for a hybrid magnet which generated 0.8 T in a background field of 7 T at 4.2 K. These results suggest that Bi-based superconducting coils can be used in magnet applications.         Multifilament BPSCCO superconductor: fabrication and heat treatment study    L.R. Motowidlo, P. Haldar, S. Jin and N.D. Spencer Summary: The fabrication of long lengths of multifilament antimony-doped BPSCCO (Bi/sub 1.6/Pb/sub 0.3/Sb/sub 0.1/Sr/sub 2/ Ca/sub 2/Cu/sub 3/O/sub x/) wire or tape by conventional processing methods is reported. A combination of intermediate heat treatment followed by rolling and final anneals is utilized to obtain textured filaments in a silver matrix. The addition of antimony has been found to improve the irreversibility line as compared to the undoped samples, which may be useful for obtaining improved performance in BPSCCO wires.         Superconducting joints formed between powder-in-tube Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub z//Ag tapes    J.E. Tkaczyk, R.H. Arendt, P.J. Bednarczyk, M.F. Garbauskas, B.A. Jones, R.J. Kilmer and K.W. Lay Summary: Superconducting joints between Ag-clad, Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub z/ tapes have been obtained with approximately 1/2 the current capacity of the tapes themselves. The Ag sheath is removed from one side of each tape without significantly disturbing the superconducting core. The exposed superconducting core of the two tapes is brought into contact and pressed so as to again seal the superconductor in a Ag sheath. A reaction anneal is performed to join the two cores together and repair damage associated with the removal of Ag and the pressing. Transport measurements using multiple voltage taps have been found useful in characterizing the critical current variation across the joint.         Critical current measurements on Ag/Bi-Pb-Sr-Ca-Cu-O composite coils as a function of temperature and external magnetic field    S.W. Schwenterly, J.W. Lue, M.S. Lubell, J.N. Luton and C.H. Joshi Summary: Transport critical currents have been measured on two coils of high-temperature superconducting (HTSC) tape as a function of temperature and external magnetic field. The sample coil windings have inside and outside diameters of roughly 25 mm and 40 mm, respectively, and a length of 50 mm. They contain about 300 turns of filamentary Bi-Pb-Sr-Ca-Cu-O 2223 HTSC material sheathed in Ag to form a 0.18-mm by 2.54-mm tape, with a total length of about 30 m. Critical current results are reported for temperatures between 4.2 K and 90 K, in magnetic fields ranging up to 5.5 T.         Distribution of the transport critical current in Ag-(Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ reinforced tape-form conductors    B.A. Glowacki, W. Lo, J. Yuan, J. Jackiewicz and W.Y. Liang Summary: The spatial distribution of the transport critical current, I/sub c/, in the reinforced-tape-form, silver-clad (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ conductor manufactured by cold multistep rolling has been established by the in-situ measurements as a function of the thickness of the ceramic core. The measurements show that current is almost uniformly distributed through the whole cross-section of the core in the wire, almost independently of the initial I/sub c/ value of the tape. The effect of densification, texturing, and surface diffusion on the formation of the intergrain connectivity along the a-b plane of the core, at the silver-ceramic interface, and in the core has been investigated and is discussed in detail. The I/sub c/ anisotropy measurements and a study of magnetically aligned and randomly oriented samples lead to a functional relationship between the crystallographic orientation, morphology and connectivity of the grains in the tape. The variation of the hole concentration near the grain boundary region of the 2223 phase has been investigated by transmission electron energy loss spectroscopy.         Transport critical current in silver sheathed BiPbSrCaCuO tapes    C. Takahashi, M. Komatsu, Y. Yaegashi, M. Nagano, H. Takahashi, K. Hamada and A. Nagata Summary: The temperature and magnetic field dependences of transport critical current density, J/sub c/, in silver-sheathed Bi/sub 2.1/Pb/sub 0.4/Sr/sub 2.2/Ca/sub 3.4/0/sub 4.2/ tapes have been studied. J/sub c/ was weakly dependent on magnetic fields at temperatures below 30 K. The effect of field-variation history on J/sub c/ was observed in the same temperature region. The magnetic field dependence of J/sub c/ and its anisotropy with respect to the field direction increased rapidly with increasing temperature. The irreversibility field and its anisotropy were also studied. Flux pinning and weak coupling properties are discussed.         Electrical properties of multifilamentary Bi(Pb)-2223/Ag tapes    L. Martini, S. Bonazzi, M. Majoros, V. Ottoboni and S. Zannella Summary: The electric and magnetic characterization of superconducting tapes of the 110 K phase Bi(Pb)-2223 (Bi/sub 1.7/Pb/sub 0.3/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/) fabricated by the powder-in-tube method and an intermediate rolling and sintering process are reported. Besides multifilamentary tapes, specimens with a new geometrical arrangement of the superconducting areas inside the silver matrix, showing large current capabilities, were fabricated. Wires and tapes with up to four concentric superconducting rings with transport critical current, I/sub c/, at 77.3 K and zero magnetic field higher than 85 A (corresponding to J/sub c/>9000 A/cm/sup 2/) and at 4.2 K and zero field higher than 400 A (corresponding to J/sub c/>40000 A/cm/sup 2/) were reproducibly obtained. Magnetic measurements were also compared with the above transport results.         The current-carrying characteristics in the Bi-Pb-Sr-Ca-Cu-O/Ag textured tape by powder in tube process    H. Zhang, E.Y. Zhou, H.G. Yu and H. Wu Summary: Current-carrying characteristics have been investigated for Bi/sub 1.8/Pb/sub 0.4/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x//Ag textured composite tapes fabricated by the powder-in-tube process. It is found that: intermediate uniaxially pressing can effectively raise J/sub c/; the strain-tolerance of J/sub c/ can be much improved in multicore composites; the composite tapes have strong J/sub c/ anisotropy with the angle between the magnetic field and the normal of tape surface, and the anisotropy increases with an increase in magnetic field; the V-I curve at low voltage can be fitted by power law V=AI/sup n/, where n varies with J/sub c/; and the averaged potential for flux motion is estimated from the magnetic relaxation measurement to be 130 MeV.         Effects of initial, intermediate and final sinterings in preparation of Ag-sheathed Bi-2223 tapes    D.Y. Jeong, I.Y. Han, M.H. Sohn, S.K. Han and Y.C. Kim Summary: Effects of initial, intermediate and final sintering on superconducting properties, morphology, and critical current density, J/sub c/, were studied in Ag-sheathed Bi(Pb)-Sr-Ca-Cu-O tapes prepared using the powder-in-tube method and repetitions of a combined process of pressing and sintering. The variables in the repetitive process were a history by which the calcined constituent powders were heat treated before filled into Ag-tubes, and duration periods of the intermediate and final sinterings. The effects are discussed in terms of conversion of 2212 phase to 2223 and vice versa, the formation mechanism of 2223 phase, and alignment and connection of the 2223 grains. In the present study, a J/sub c/ on the order to 10/sup 4/ A/cm/sup 2/ at 77 K and 0 T was obtained.         Phase chemistry and microstructure evolution in silver-clad (Bi/sub 2-x/Pb/sub x/)Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ wires    J.S. Luo, N. Merchant, E. Escorcia-Aparicio, V.A. Maroni, D.M. Gruen, B.S. Tani, G.N. Riley Jr. and W.L. Carter Summary: The reaction kinetics and mechanism that control the conversion of (Bi,Pb)/sub 2/Sr/sub 2/CaCu/sub 2/O/sub z/ (Bi-2212)+alkaline earth cuprates to (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ (Bi-2223) in silver-clad wires were investigated as a function of equilibration temperature and time at a fixed oxygen partial pressure (7.5% O/sub 2/). Measured values for the fractional conversion of Bi-2223 versus time were evaluated based on the Avrami equation. SEM studies of partially and fully converted wires suggest: (1) the transformation to Bi-2223 is two-dimensional and controlled by a diffusion process; (2) liquid phases are present during part of the Bi-2212 to Bi-2223 conversion; and (3) growth of the (Sr,Ca)/sub 14/Cu/sub 24/O/sub 41/ phase accompanies Bi-2223 formation.         Controlled superconducting transition of YBaCuO thin films prepared by plasma-enhanced MOCVD    K. Ebihara, T. Fujishima, T. Ikegami, M. Shiga and K. Harada Summary: Several types of plasma-enhanced metalorganic chemical vapor deposition (MOCVD) systems are developed to prepare YBaCuO superconducting thin films. RF and microwave plasmas are used to enhance the decomposition of the source materials under moderated process conditions. Uniform YBaCuO films of large size were prepared with good reproducibility using a controlled material feeder.         Some aspects of fabrication of YBCO thin films by inverted cylindrical magnetron sputtering in large area    L. Yuan, H.S. Huang, Z.Y. Wu, M.L. Liu, Q.M. Jie, Z.B. Zhou, Y.C. Yang, S.Z. Cai and J.G. Fang Summary: The use of inverted cylindrical magnetron sputtering to produce high-quality superconducting thin films is investigated. The critical parameters in the sputtering process have been identified, and 10-mm*10-mm YBCO thin films with critical temperatures (T/sub c/'s) of 85-90 K and critical current densities (J/sub c/'s) of 1*10/sup 6/ A/cm/sup 2/ (77 K, 0 T) have been deposited reproducibly in optimal conditions. In order to extend the work to a large area, the sputtering gun and the heater have been redesigned. The film's thickness and stoichiometric variation are less than +or-5% over a 50-mm*50-mm area. The uniformity of substrate temperature plays an important role in large-area in situ deposition of YBCO films. At optimum conditions, the variation of T/sub c/ is found to be less than +or-1 K.         Development of a niobium-tin multifilamentary wire with artificial tantalum inclusions    K. De Moranville, D. Yu and J. Wong Summary: A multifilament Nb/sub 3/Sn conductor containing Nb/Ta composite filaments was manufactured using bronze route processing. The Ta inclusions deformed uniformly during the fabrication process with little ductility problems. Ta to Ta spacings of less than 60 nm were obtained at final wire sizes. Samples were reacted using various heat treatment conditions and compared to a multifilament Nb(Ti)/sub 3/Sn conductor processed from a Nb 1.5 Ti alloy. The Ta inclusions reduce the grain growth of the A15 phase during the final reaction heat treatment and were responsible for a 15-20% increase in J/sub c/ (9 T, 4.2 K) as compared to the Nb(Ti)/sub 3/Sn wire. In addition, Ta dissolved in the A15 phase resulted in an enhanced upper critical field. Improvement of the filament uniformity through the use of fine-grained sheets was confirmed by magnetization and image analysis.         Artificial flux pinning in Nb and Nb/sub 3/Sn superconductors    R. Zhou, S. Hong, W. Marancik and B. Kear Summary: Some results on artificial flux pinning centers (APCs) introduced into Nb filaments are reported. The APCs are copper in a nanometer scale which is comparable to the fluxon diameter. The preliminary results show a significant current density increase in APC samples compared with the cold worked Nb samples. The effect of APC on the upper critical field and superconducting transition temperature is also investigated. The effect of APC on the superconducting properties of Nb/sub 3/Sn which is formed by solid state diffusion process is also studied.         Critical current densities and magnetic hysteresis losses in submicron filament bronze-processed Nb/sub 3/Sn wires (1992)    S. Sakai, K. Miyashita, K. Kamata, K. Endoh, K. Tachikawa and H. Tanaka Summary: Submicron-filament bronze-processed multifilamentary Nb/sub 3/Sn wires with Cu-5at%Sn-X (X: Mn, Ni, Si, Ge, B, P, Zn, Al) ternary alloy matrix and Nb-1at.%Ta alloy cores were fabricated. The cross-sectional structure of wires was the central-Cu-stabilizer type to facilitate, by external Sn diffusion, improvements in critical current density and hysteresis losses. The Nb-1Ta core decreased the hysteresis loss in spite of the increase of the critical current densities. By the addition of Zn, Al, the critical current densities and the hysteresis losses were improved. Although hysteresis losses were not decreased by Sn plating, the critical current densities were apparently improved at relatively low temperature heat treatment.         Properties of bronze-processed multifilamentary Nb/sub 3/Sn wires for fusion experimental reactor    H. Sakamoto, K. Yamada, N. Yamada, Y. Tanaka and T. Ando Summary: The fabrication of bronze-processed multifilamentary Nb/sub 3/Sn wires having a critical current density of 840 A/mm/sup 2/ (4.2 K, 12 T) and an effective filament diameter of 6 mu m is reported. These values satisfy the specification required for the ITER Central Solenoid Scalable Model Coil. The measured time constant of the coupling loss in the wire is 4 ms at 12 T, in good agreement with the calculated result using B. Turck's formula (1979).         Development of bronze-processed (NbTi)/sub 3/Sn superconducting wires for central solenoid model coil of ITER    G. Iwaki, S. Sakai, K. Kamata, K. Sasaki, S. Inaba, H. Moriai and K. Yoshida Summary: Investigations to improve the critical current density of bronze-processed (NbTi)/sub 3/Sn superconducting wires for the central solenoid model coils in ITER were carried out. The effects of concurrent additions of Ti to the bronze matrix and of Ta to the filaments on the critical current density of the bronze-processed (NbTi)/sub 3/Sn wires were examined. By applying a high Sn concentration bronze matrix, a wire with a non-Cu J/sub c/ of 772 A/mm/sup 2/ at 12 T was developed.         Nb/sub 3/Sn superconductor for fusion application: facing NET-ITER specifications, evaluation of industrial capability    J.L. Duchateau, D. Ciazynski and J.C. Vallier Summary: The industrial capability for producing significant amounts of Nb/sub 3/Sn superconductor that meet the NET-ITER specifications has been evaluated by extensive tests on thousands meters of multifilamentary composites ordered from two different companies. In particular, the following points have been investigated: weight and length of the delivered units, heat treatment and critical current, chrome plating, residual resistivity ratio (RRR), and AC losses measurements. With regard to RRR and losses some difficulties have been encountered. The consequences for the different coils of the NET-ITER project are discussed.         Nb/sub 3/Sn multifilamentary wires with CuNb reinforcing stabilizer    K. Watanabe, A. Hoshi, S. Awaji, K. Katagiri, K. Noto, K. Goto, M. Sugimoto, T. Saito and O. Kohno Summary: A bronze processed multifilamentary Nb/sub 3/Sn superconducting wire with CuNb reinforcing stabilizer (CuNb/Nb/sub 3/Sn), which exhibits a residual resistance ratio of 20 and a magnetoresistance of 0.2 mu Omega -cm at 23 T and 4.2 K, has been developed. The yield stress at 4.2 K, was noticeably improved; a value of 22 kg/mm/sup 2/ was obtained even after heat treatment of Nb/sub 3/Sn formation at 700 degrees C for 200 h. The effect of strain on critical current density, J/sub c/, was described well by using the upper critical field in the prestrain state. It was verified that the CuNb/Nb/sub 3/Sn wire mechanical and superconducting properties need to perform under an enormous electromagnetic force in high magnetic fields.         Multifilamentary Nb/sub 3/Al wires reacted at high temperature for short time    M. Kosuge, Y. Iijima, T. Takeuchi, K. Inoue, T. Kiyoshi, H. Irie and K. Watanabe Summary: An attempt was made to carry out a high-temperature/short-time heat treatment of Nb tube-processed multifilamentary wires. The wires were heated passing a large alternative current for 0.1 s through the 0.74-mm-diameter Nb/Al composite wires or by irradiating the composite wires with a 50-kV, 22-34-mA electron beam at a scanning rate of 83 mm/s. Superconducting properties and microstructural aspects did not show significant differences for the two techniques. With increasing heat treatment temperatures, critical temperature, T/sub c/, and critical current density, J/sub c/, increased at first, reached a maximum, and then decreased. They were optimized when the single-core Nb/Al filaments in the first stack had completely reacted and become indistinguishable from each other. The highest T/sub c/, obtained just after the high-temperature heat treatment, was 17 K, and the peak height was further increased by 1 K after a subsequent heat treatment at 700 degrees C for 48 h. The peak effect appeared in the J/sub c/-B characteristics, and the peak J/sub c/ of 2*10/sup 8/ A/m/sup 2/ at 17 T at 4.2 K was shifted toward higher magnetic field with the subsequent heat treatment.         Superconductivity of Nb/sub 3/Al formed by solid state reaction of Nb with Ag-based alloy    T. Takeuchi, M. Kosuge, Y. Iijima and K. Inoue Summary: It is shown that replacement of bronze with Ag-based solid solution prevents the formation of the ternary compound which corresponds to the mu phase and/or C14 Laves phase in the Cu-Nb-Al system, and thus Nb/sub 3/Al, together with Nb/sub 2/Al, is formed by a solid-state diffusion reaction between Nb filaments and Ag-(2 approximately 15)at.%Al solid solution matrix in the temperature range of 750 approximately 900 degrees C. Metastable Nb/sub 3/Al with high T/sub c/ forms at the early stage of the reaction and decomposes after long heat treatment. The highest T/sub c/ and H/sub c/ (4.2 K) are 13.9 K and 14 T, respectively, for the single-core composite. Since the layer thickness of Nb/sub 3/Al is much less than 1 mu m, a multifilamentary structure that introduces a large number of matrix/core interfaces greatly improves the overall J/sub c/.         Evaluation of Cu:SC ratio measurements by chemical etching, electrical resistivity, and image analysis    T. Pyon, W.H. Warnes and M. Siddall Summary: A comparison is made of the techniques for measuring the copper to superconductor ratio (Cu:SC) in a set of commercial laboratory composite superconducting wires produced for the Superconducting Super Collider (SSC). The simplest and most straightforward technique, chemical etching, was found to display the best reproducibility. The electrical resistivity technique shows the most variation and sensitivity to measurement errors, as well as being the most difficult to perform. The image analysis technique is fast and fairly reproducible.         Mechanical behavior of fine filament Nb-Ti as a function of processing (composite superconductors)    Z. Guo and W.H. Warnes Summary: Experimental data on the mechanical properties of Nb-Ti filaments during standard wire processing from first heat treatment size to final wire size are presented. The fiber characteristics examined include fiber geometry, hardness, Young's modulus and ultimate strength. The mechanical behavior of fine filament Nb-Ti was studied under two different processing treatments. This research is relevant to the mechanical modeling of the Cu/Nb-Ti composite system.         History effect of critical current density in superconducting multifilamentary Nb-Ti wire    E.S. Otabe, T. Matsushita, K. Yamafuji, K. Matsumoto and Y. Tanaka Summary: DC magnetization and four-probe resistive measurements were carried out for Nb-Ti multifilamentary wires, and critical current densities in the filament and matrix were separated. The Campbell method was also used for measuring the effect of magnetic field history on critical current density in the matrix. The history dependence was found only for the current density induced in the matrix due to the proximity effect. This close correlation between the proximity effect and history effect shows a similarity to the phenomenon in high-T/sub c/ superconductors. The possible reason for the history effect in critical current density is discussed.         New analytical results for the electromagnetic response of a composite superconducting wire in parallel fields    E.M.J. Niessen and P.J. Zandbergen Summary: Analytical results are presented concerning the electromagnetic response of a composite superconducting wire in fields parallel to the wire axis, using the Maxwell equations supplemented with constitutive equations. The problem is nonlinear due to the nonlinearity in the constitutive equation describing the superconducting filaments. It is shown that the nonlinear behavior of the wire can be studied by analytical means. The method used gives an exact description of the response of a wire with nonconducting matrix material surrounding filaments with zero filament radius. For a composite wire it provides a very good approximation.         Flux pinning by 211 precipitates in melt-processed YBa/sub 2/Cu/sub 3/O/sub x/    D. Shi, S. Sengupta, M. Smith, Z. Wang, A.C. Biondo, U. Balachandran and K.C. Goretta Summary: Magnetic hysteresis data have been taken at 4.2 and 50 K over a wide range of magnetic fields on melt-textured (MT) and quench-melt-growth-processed (QMGP) YBa/sub 2/Cu/sub 3/O/sub x/ samples with 6 vol.% of Y/sub 2/BaCuO/sub x/ (211). In order to obtain accurate comparisons of the intragranular critical current densities, the magnetization measurements were performed on finely powdered samples, the average particle size of which was less than the grain size of the original sample. The QMGP samples exhibited substantially larger hysteresis, indicating significantly enhanced flux pinning at these temperatures. At 4.2 K and 5 T, J/sub c/, critical current density, increased from 4*10/sup 4/ A/cm/sup 2/ in the MT sample to 5.5*10/sup 5/ A/cm/sup 2/ in the QMGP sample. A possible pinning mechanism related to the observed hysteretic behavior is discussed.         Isothermal melting and continuous isothermal melt texturing of YBaCuO    M. Arnott, B.A. Glowacki, B. Soylu and J.E. Evetts Summary: A study of isothermal melt texturing, whereby the O/sub 2/ partial pressure dependence of the melting point of YBCO is exploited to substitute for the slow cooling and temperature gradient of the melt textured growth method, is presented. A melt pool is produced by lowering the O/sub 2/ partial pressure locally with a jet of Ar directed onto the center of a YBCO slab within an O/sub 2/-filled furnace, and its development is investigated as a function of temperature, Ar/O/sub 2/ ratio, and time. If the pool is allowed to cool slowly, a large grained microstructure is formed, with 123 crystals of around 1-mm average cross section. The critical current density is around 2000 A/cm/sup 2/ at 77 K (B=0 T). In a further set of experiments the jet is driven slowly across the surface, melting a track. When the jet moves sufficiently slowly, a large grained microstructure is formed by continuous, isothermal processing.         Improvement of persistent magnetic field trapping in bulk Y-Ba-Cu-O superconductors    I.-G. Chen and R. Weinstein Summary: For type-II superconductors, magnetic field can be trapped due to persistent internal supercurrent. Quasi-persistent magnetic fields near 2 T at 60 K (and 1.4 T at 77 K) have been measured in minimagnets made of proton-irradiated melt-textured Y-Ba-Cu-O (MT-Y123) samples. Using the trapping effect, high-field permanent magnets with dipole, quadrupole, or more complicated configurations can be made of existing MT-Y123 material, thus bypassing the need for high-temperature superconductor (HTS) wires. A phenomenological current model has been developed to account for the trapped field intensity and profile in HTS samples. This model is also a guide to select directions of materials development to further improve field trapping properties. General properties such as magnetic field intensities, spatial distributions, stabilities, and temperature dependence of trapped field are discussed.         Weak link property in superconducting Y-Ba-Cu-O prepared by QMG process    T. Matsushita, E.S. Otabe, T. Fukunaga, K. Kuga, K. Yamafuji, K. Kimura and M. Hashimoto Summary: The weak link property in a QMG (quench and melt growth)-processed single-grain Y-Ba-Cu-O specimen was investigated by measuring the dependence of the critical current density on temperature, history of magnetic field application, and its enhancement under a longitudinal field geometry. The results show that weak-link regions still remain in the specimen. It is speculated that these link regions, which can transport superconducting currents at low temperatures, are degraded with increasing temperature and lose superconductivity around 20 K.         Evaluation of YBa/sub 2/Cu/sub 3/O/sub 7-x/ bulk superconductors for high field magnet applications    K.Y. Blohowiak, D.F. Garrigus, T.S. Luhman, K.E. McCrary, M. Strasik, I.A. Aksay, F. Dogan, W.B. Hicks, J. Liu and M. Sarikaya Summary: Processing of YBCO single crystals was carried out by solidification of semi-liquid YBCO composition using a seeding technique. Microstructural characterization of the pinning centers was investigated by transmission electron microscopy. Characterization of single crystals was carried out, relating grain size and shape to the corresponding flux profiles. Current densities were calculated based on measured trapped fields. Once circulating currents were established, flux pumping and quenching experiments were conducted. These large single crystals will be incorporated into electromagnetic forming devices for use in the military and commercial aircraft manufacturing and service industries.         Comparison between two kinds of Y-Ba-Cu-O films deposited from single sintered targets with Ba-poor 1:2:3 (=Y:Ba:Cu) compositions    M. Suzuki, K. Ohtsuka and H. Morita Summary: Films of Y-Ba-Cu-O (YBCO) with zero resistance transition temperature exceeding 85 K were reproducibly prepared by DC magnetron sputtering using single sintered targets with nonstoichiometric (Ba-poor) compositions under the conditions of low oxygen partial pressure (0.6 Pa) and high argon-oxygen pressure (40 Pa). Their critical temperature, T/sub c/, correlates well with the Cu/Ba ratio in the films. The relation of T/sub c/ to the c-axis lattice parameter is very different from that for bulk ceramics and films deposited from a stoichiometric target at high oxygen partial pressure (4 Pa).         Dynamics during pulsed laser ablation of high T/sub c/ superconductor    T. Nakamiya, T. Ikegami and K. Ebihara Summary: The ablation of high critical temperature (T/sub c/) YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting bulk (1-mm thickness) by a nanosecond-pulse KrF excimer laser ( lambda =248 nm) is studied numerically. The dynamics of ablation is simulated by solution of the one-dimensional heat flow equation. The finite-element method is applied to solve the equation, including the temperature dependence of the thermal conductivity of the bulk, the movement of a vapor-liquid interface, the latent heat of melting and ablation, and the energy of the laser-generated plume. The melting threshold energy density is found to be 0.08 J/cm/sup 2/, and the ablation threshold energy density is estimated to be 0.22 J/cm/sup 2/. The mean velocity of the laser-generated plume increases with the increase of laser energy density from 0.93*10/sup 4/ m/s (2 J/cm/sup 2/) to 1.95*10/sup 4/ m/s (10 J/cm/sup 2/).         Growth and surface morphology of laser ablated YBaCuO films analysed by SEM    G. Adrian, W. Wilkens, C. Stolzel, G. Grabe and V. Windte Summary: The dependence of the surface morphology, particularly the general surface roughness, the existence of outgrowths, and the density of droplets, on preparation conditions under the requirement of retaining good superconducting properties has been investigated. The variation of the oxygen partial pressure, the substrate temperature, or the deposition rate while keeping all other parameters constant strongly influences the roughness and outgrowing of particles. The density and size of the droplets depend sensitively on the laser-target-substrate geometry, the deposition rate per pulse, the target density, and the film thickness. The study reveals that deposition parameters exist that enable good superconducting films with smooth surfaces and a droplet density below 1/(100 mu m)/sup 2/ to be obtained.         Growth properties of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7- delta / thin film on CeO/sub 2/(/MgO) buffer layer for the biepitaxial boundary function    D. Youm and S. Lee Summary: In the fabrication of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO)/CeO/sub 2//MgO/SrTiO/sub 3//SrTiO/sub 3/ biepitaxial grain boundary junctions, the substrate temperature window for the growth of good quality superconducting YBCO overlayers on CeO/sub 2//MgO/SrTiO/sub 3/ is lower and narrower than for growth of YBCO on CeO/sub 2//SrTiO/sub 3/. Results of X-ray diffraction 2 theta and phi scan measurements reveal that the lattice structure of the CeO/sub 2/ layer on the MgO seed layer is 2 approximately 3 times more distorted than for CeO/sub 2/ on a bare SrTiO/sub 3/ substrate. It is found that the instability of the crystal formation of the YBCO layer on the CeO/sub 2//MgO/SrTiO/sub 3/ is accompanied by the loss of stoichiometry at slightly higher substrate temperature.         Properties of epitaxial YBa/sub 2/Cu/sub 3/O/sub y/ thin films on sapphire with PrBa/sub 2/Cu/sub 3/O/sub y/ buffer layers    V. Boffa, G. Paterno, C. Romeo, V. Rossi, M. Penna, D. Di Gioacchino, U. Gambardella, S. Barbanera and F. Murtas Summary: YBa/sub 2/Cu/sub 3/O/sub y/ epitaxial thin films have been grown on a PrBa/sub 2/Cu/sub 3/O/sub y/ layer deposited on a sapphire substrate, using XeCl excimer laser ablation for both depositions. The films were deposited in situ by means of a rotating multitarget system carrying the two targets. The substrate holder was heated by a CO/sub 2/ laser beam. The as-deposited films show a zero resistance critical temperature of 87 K and a high degree of epitaxiality with c-axis orientation. The samples have been patterned in the shape of strips of variable width between 10 mu m and 30 mu m. DC transport critical current densities for YBa/sub 2/Cu/sub 3/O/sub y/ grown on PrBa/sub 2/Cu/sub 3/O/sub y//Al/sub 2/O/sub 3/ have been measured as a function of the temperature and an applied magnetic field.         Combination of YBa/sub 2/Cu/sub 3/O/sub 7- delta / with semiconducting substrates    W. Prusseit, S. Corsepius, B. Utz, F. Baudenbacher, K. Hirata, P. Berberich, H. Kinder and O. Eibl Summary: Epitaxial YBa/sub 2/Cu/sub 3/O/sub 7- delta / films were grown on silicon and gallium arsenide substrates. The common problem of strong interdiffusion at the elevated deposition temperatures was solved by employing appropriate buffer layers. The large differential thermal expansion between silicon and YBa/sub 2/Cu/sub 3/O/sub 7- delta /, which can lead to a fracture of thicker films, was addressed by improving the fracture toughness of the films. Arsenic contamination of films on GaAs, originating from the sides and the back of the wafer, was completely solved by a proper encapsulation, yielding YBa/sub 2/Cu/sub 3/O/sub 7- delta / films comparable to those on standard substrates.         Fabrication by LPE and characterization of YBa/sub 2/Cu/sub 3/O/sub 7- delta / thin films on NdGaO/sub 3/ substrates    S.N. Barilo, G.I. Bychkov, A.V. Zubets, N.S. Orlova, V.I. Gatalskaya, D.I. Zhigunov, L.A. Kurnevich, N.M. Olekhnovich and A.V. Pushkarev Summary: The superconducting c-axis oriented YBa/sub 2/Cu/sub 3/O/sub 7- delta / as well as bilayer films of PrBa/sub 2/Cu/sub 3/O/sub 7- delta //YBa/sub 2/Cu/sub 3/O/sub 7- delta / have been prepared by the liquid phase epitaxy (LPE) technique on (001) NdGaO/sub 3/ substrates. The film thickness varied from 1 to 100 mu m, depending on the growth time. A high quality of epitaxy has been confirmed by X-ray diffraction analyses. The as-grown films, after annealing in an oxygen plasma for a few hours, have a critical temperature, T/sub c/, of 93 K and a Delta T/sub c/ about 0.4 K. The magnetic measurements show high critical current density for the prepared films.         Laser ablation of YBCO: utilizing /sup 18/O to investigate the incorporation of oxygen into the laser plume    S.C. Tidrow, W.D. Wilber and M.Z. Tidrow Summary: /sup 18/O has been used as a tracer to measure the transfer of oxygen from the chamber atmosphere into the laser induced plume. The amount of oxygen incorporated into the plume was found by laser ablating from a polycrystalline YBCO target onto a room temperature carbon substrate in an atmosphere of 50% /sup 16/O and 50% /sup 18/O. A series of such samples was prepared using deposition pressures ranging from 0.5 to 260 mTorr. The film stoichiometry, including, most importantly, the atomic fraction of /sup 18/O, for each sample was determined using Rutherford backscattering. The results show that the incorporation of /sup 18/O from the deposition atmosphere increases with increasing deposition pressure (50% /sup 16/O and 50% /sup 18/O) up to approximately 25 mTorr and then, unexpectedly, decreases for higher pressures.         Variation of the oxygen content in YBa/sub 2/Cu/sub 3/O/sub 7-x/ films deposited by high oxygen pressure DC-sputtering    M.I. Faley, U. Poppe, H. Soltner, U. Dahne, N. Klein, H. Schulz, W. Evers and K. Urban Summary: The authors have investigated the effect of the variation of the oxygen deficiency on critical temperature, T/sub c/, and the normal-state resistivity rho (T) of high-quality [001]- and [110]- or [103]-oriented epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-x/ films deposited by high-oxygen-pressure DC-sputtering. Oxygenation in a microwave oxygen plasma can increase T/sub c/ to up to 95 K and completely restores the film properties suppressed by deoxygenation in molecular oxygen at the same pressure and temperature conditions. The second derivative of the normal-state resistivity has a higher value for the nearly fully oxygenated films and better microstructure. A linear dependence rho (T>150 K) was received for an oxygen deficiency of about 0.1 or for nearly fully oxygenated films with a less perfect microstructure.         Low-pressure oxidation of YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films in purified ozone    A. Sawa, S. Kosaka, H. Obara and K. Aoki Summary: The oxidation of YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films with purified ozone has been studied by in-situ resistivity measurements during annealing, and the oxidizing activity of ozone was compared with that of molecular oxygen. The experimental results suggest that ozone partial pressure, which yields the YBa/sub 2/Cu/sub 3/O/sub 7-x/ phase with a certain oxygen content, is about 5 orders of magnitude smaller than the pressure of molecular oxygen which yields the same oxygen content of YBa/sub 2/Cu/sub 3/O/sub 7-x/. The pressure-temperature phase diagram in ozone was also generated from these results. The YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin film with a superconducting transition temperature of 86 K was deposited at an ozone pressure of 9*10/sup -5/ Torr.         Microwave processing of high T/sub c/ oxide superconductors at oxygen atmosphere    G.W. Qiao, J.S. Zhang, J.G. Huang, Y.J. Yang, L.H. Cao, Y.Z. Wang and M. Jiang Summary: A YBCO specimen with texture was manufactured by melt texture growth (MTG) processing. The bulk specimens of YBa/sub 2/Cu/sub 3/O/sub 6.4/ absorbed oxygen in a flowing oxygen atmosphere in a single-mode microwave furnace (TE10M) and during conventional postheat-treatment process. Their oxygen content was determined by weighing and by X-ray diffraction (XRD), and the superconductivity was also measured. The results indicated that the microwave process greatly enhanced oxygen diffusion and significantly increased the post-heat treatment-period compared with conventional processing.         Non-silver paste method for making thermal contact to substrates for high T/sub c/ film growth    R.P. Robertazzi and B.D. Oh Summary: The authors describe a procedure for using thin layers of gold foil to make thermal contact between insulating substrates and Haynes alloy heater blocks. This method has several advantages over using silver paste compounds to improve the thermal contact. Samples are easily removed from the metal blocks after heating up to 850 degrees C, and no prebake process is required prior to sample loading into the deposition chamber since no organic binder is used. Because only a thin layer (1- mu m thick) of gold foil is required, the method is extremely economical. Thermal contact resistance measurements performed using MgO substrates demonstrate that this technique promotes thermal contact between the substrate and heater block comparable to silver paste. These measurements are presented along with a design for a fixture capable of holding wafers up to 0.75 in diameter.         The role of vacuum isothermal annealing in synthesis of YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films    S. Chromik, M. Jergel, S. Benacka, F. Hanic and J. Liday Summary: A low-oxygen-pressure annealing process which enables fluorine to be removed from YBa/sub 2/Cu/sub 3/O/sub x/ thin films prepared by sequential deposition of BaF/sub 2/, Cu, and Y constituents onto MgO single-crystal substrates has been examined. The annealing process is performed in the absence of water vapor. X-ray diffraction and Auger electron spectroscopy analyses of films obtained at various steps during the annealing have shown that the reduction of fluorine starts during the first stages of annealing. Possible chemical reactions characterizing this process are discussed.         Microwave surface resistance of epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-x/ films: studies on oxygen deficiency and disordering    N. Klein, U. Poppe, N. Tellmann, H. Schulz, W. Evers, U. Dahne and K. Urban Summary: The authors have studied the microwave surface resistance R/sub S/ at 19 GHz of epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-x/ films prepared by high oxygen pressure DC-sputtering on NdGaO/sub 3/ and LaAlO/sub 3/ substrates. Oxygen deficiency x, O         Planar transmission line resonators from YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films and epitaxial SIS multilayers    W. Rauch, E. Gornik, A.A. Valenzuela, G. Solkner, F. Fox, H. Behner, G. Gieres and P. Russer Summary: The authors have grown c-axis-oriented YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin films and epitaxial YBCO/NdAlO/sub 3//YBCO trilayers by sputtering. From the YBCO films, coplanar half-wavelength transmission line resonators were patterned. At 77 K the unloaded quality factors of coplanar stripline resonators were up to 2570 at 5.6 GHz. The attenuation constant of such a line was evaluated to be 0.6 dB/m at 77 K and at 5.6 GHz. Coplanar waveguide resonators yielded quality factors up to 1200 at 77 K and at 6.2 GHz resulting in an attenuation constant of 1.8 dB/m. From these measurements the surface resistance values R/sub S/ of the films were determined. The lowest R/sub S/ was 105 mu Omega at 77 K and at 6.2 GHz. Trilayer structures with a dielectric as thick as 800 nm were patterned into microstrip resonators. At 50 K the authors measured a quality factor of 85 at 4.7 GHz, resulting in an attenuation of 26 dB/m and a surface resistance of 340 mu Omega . For thick dielectrics the upper YBCO film already contains significant portions of polycrystalline material.         Nonlinear surface resistance in YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films    D.E. Oates, P.P. Nguyen, G. Dresselhaus, M.S. Dresselhaus and C.C. Chin Summary: A complete characterization of the nonlinearity of the surface impedance Z/sub s/ of YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films is presented. Z/sub s/(H/sub rf/, the RF magnetic field), has been measured for H/sub rf/ from 0 to approximately 1 kOe vs. temperature from 4.2 K to critical temperature T/sub c/ and vs. frequency from 1.5 to 10 GHz, using a stripline resonator. The results are compared to a coupled-grain model. Good agreement is found for R/sub s/(H/sub rf/). The imaginary part of Z/sub s/(H/sub rf/), i.e. X/sub s/(H/sub rf/), however, does not fit the model.         Transmission and reflection of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ films at 35 GHz    E.K. Moser, W.J. Tomasch, J.K. Furdyna, M.W. Coffey and J.R. Clem Summary: Microwave transmission and reflection measurements were carried out simultaneously on thin films ( approximately 2000 AA) of YBa/sub 2/Cu/sub 3/O/sub 7-x/ with their c axes perpendicular to the LaAlO/sub 3/ substrate. Power transmission and reflection fractions (T,R) were determined as functions of temperature and magnetic field (0         Development of technical high-T/sub c/ superconductor wires and tapes    J. Tenbrink, M. Wilhelm, K. Heine and H. Krauth Summary: High-temperature superconductor (HTSC) BiSrCaCuO-based wires and tapes have been produced using oxide dispersion hardened Ag alloys as sheath material. The use of such sheath material results in superior mechanical properties. The 0.1% yield strength R/sub p0.1/ of wires with 50% HTSC volume fraction exceeds 100 MPa and may reach values up to 150 MPa depending on the respective alloy. The thermal shock resistance also is improved very much. This progress in mechanical properties removes a major obstacle towards application of HTSC in magnet technology. Work concentrating on upscaling of wire production and especially on improving homogeneity is presented. It is shown that filamentization of Bi-2212 wires may lead to improved critical current densities compared to monofilamentary wires.         Fabrication and properties of high-T/sub c/ tapes and coils made from silver-clad Bi-2223 superconductors    P. Haldar, J.G. Hoehn Jr., J.A. Rice, L.R. Motowidlo, U. Balachandran, C.A. Youngdahl, J.E. Tkaczyk and P.J. Bednarczyk Summary: Long lengths of flexible silver-cell Bi-2223 high-T/sub c/ (critical temperature) superconductors have been fabricated by the powder-in-tube technique. By improving process conditions DC transport measurement at liquid helium (4.2 K) and hydrogen (20 K) temperatures yield J/sub c/'s (critical current densities) greater than 10/sup 5/ A/cm/sup 2/ at zero field and exceed 3*10/sup 4/ A/cm/sup 2/ at liquid nitrogen (77 K) temperature in short tape samples. Detailed microstructural analysis and J/sub c/ measurements with applied fields up to 20 T are reported. Coils have been fabricated from 1-m lengths of conductor with J/sub c/'s at 77 K approaching 10/sup 4/ A/cm/sup 2/. Measurements on small pancake coils made from 10-m tapes are also reported.         Composite reaction texturing of Bi-based 2212 compound    B. Soylu, N. Adamopoulos, W.J. Clegg, D.M. Glowacka and J.E. Evetts Summary: Textured Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8+x/ (2212) conductors have been fabricated by a method termed composite reaction texturing (CRT), which makes use of inert whiskers or fibers to align superconducting grains and control their morphology. The process has two stages: the initial alignment of fiber material in a precursor, followed by a composite reaction stage to develop a textured ceramic microstructure. Two different methods of achieving this fiber alignment are compared. Disc-shaped pellets of 2212 with random MgO whisker alignment in the pellet plane are compared with polymer processed material with unidirectional whisker alignment. Although the resulting textures are strikingly different, the transport current densities are high for both materials. Samples with dimensions up to 200 mm*100 mm*2 mm have been fabricated, and the method clearly has promise for the production by wind-and-react or form-and-react techniques of high critical current conductors with large cross-sections as well as complex shapes.         Enhanced flux pinning through a phase formation-decomposition-recovery process in Ag-sheathed Bi(Pb)SrCaCuO wires    S.X. Dou, H.K. Liu, Y.C. Guo and D.L. Shi Summary: A high-critical temperature, T/sub c/, phase formation-decomposition-recovery (PFDR) process has been developed for fabrication of Ag-sheathed (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10+y/ (2223) wires with a short period of melt during the heat treatment. A critical current density, J/sub c/, of 40000 A/cm/sup 2/ at 77 K and 0 T and of 9000 A/cm/sup 2/ at 77 K and 1 T has been achieved. The irreversibility line for the PFDR tape is shifted to much higher temperature than those for normal tape and powder sample for fields up to 6 T. The PFDR processed samples contain a large amount of small spheres of Sr- and Ca-rich phase with a diameter of 1 mu m to 3 mu m, well aligned 2223 grains, highly dispersed, textured 2212 and high concentrations of dislocations (10/sup 10//cm/sup 2/) and stacking faults. The strong coupling between grains is attributed to the interfacial pinning.         Microstructure, resistivity and critical currents of Ag-Bi/Pb(2223) tapes    B. Hensel, J.-C. Grivel, A. Jeremie, A. Perin, A. Pollini, F. Liniger and R. Flukiger Summary: The temperature and field dependences of critical current density, j/sub c/, in Ag-Bi/Pb(2223) tapes, prepared by the standard powder-in-tube method, have been measured between 4.2 K and 110 K in magnetic fields up to 15 T. The j/sub c/'s reproducibly reached values up to 20000 A/cm/sup 2/ at 77.35 K in zero magnetic field. After stripping or etching away the Ag-sheath, the microstructure of the superconductor core has been investigated by SEM, EDX and X-ray diffraction. On etched samples the resistance of the Bi(2223) filament has been measured. A value below 500 mu Omega -cm has been found for the resistivity at 130 K.         Transport and magnetization currents in BSCCO/Ag tapes    M.E. McHenry, P.J. Kung, M.P. Maley, J.O. Willis and J.Y. Coulter Summary: A (Bi,Pb)SrCaCuO-2223/Ag tape has been produced by thermomechanical processing. Transport critical current densities, J/sub c/'s, have been measured between H=0 and 7 T and T=7 to 75 K. Magnetization currents have been determined for similar temperatures and fields (0 to 5 T) oriented parallel and orthogonal to the thickness of the tape. Dimensional scaling arguments show that flux penetrates most quickly along the tape thickness direction (for fields parallel to the tape plane and therefore the ab planes of the textured BSCCO grains). This implies that the anisotropy ratio of J/sub c/ and J/sub ab/ is reduced in tapes as compared with single crystals, which is consistent with predictions of the brick wall model. The H dependence of the magnetization currents and effective pinning potentials were also measured for similar field orientations. Fast magnetic relaxation causes an exponential field dependence of transport and magnetization currents. Temperature dependences for H/sub 0/ for transport and magnetization measurements are interpreted in terms of different time scales (or voltage criteria).         Phase diagram effects in rapid thermal processing of REBa/sub 2/Cu/sub 3/O/sub 7- delta /    R.W. McCallum, M.J. Kramer and S.T. Weir Summary: Recent investigations of rapid thermal processing of REBa/sub 2/Cu/sub 3/O/sub 7- delta / by drop tube melting, laser surface treatment, and shock compaction have shown that the microstructure resulting from these processes is a complex mixture of nonequilibrium phases. It is demonstrated that with the exception of extremely rapid solidification from above the liquidus, the microstructure and phase distribution results from the heating rather than the cooling part of the curve. Since all of the above processes induce nonuniform heating, different parts of the sample reach different maximum temperatures. The maximum temperature reached and the time spent near that maximum uniquely determine the starting state of the quench. If the entire sample is not above the liquidus, the sluggishness of the peritectic reactions results in similar microstructure regardless of the quench rate. Upon annealing the final microstructure is much more dependent on the number of nucleation sites than on the type of site, resulting in a uniform REBa/sub 2/Cu/sub 3/O/sub 7- delta / microstructure over a broad range of processing parameters.         Recrystallization of amorphous and nanocrystalline NdBa/sub 2/Cu/sub 3/O/sub 7-x/ and GdBa/sub 2/Cu/sub 3/O/sub 7-x/    T.J. Folkerts, K.W. Dennis, S.I. Yoo, Y. Xu, M.J. Kramer and R.W. McCallum Summary: Using a novel melt-spinning technique, the authors have produced both amorphous and nanocrystalline NdBa/sub 2/Cu/sub 3/O/sub 7-x/ and GdBa/sub 2/Cu/sub 3/O/sub 7-x/ materials. Samples melt-spun in O/sub 2/ consist of nanocrystals with the tetragonal 123 structure while those processed in N/sub 2/ show an amorphous matrix with small amounts of crystalline BaCu/sub 2/O/sub 2/, as shown by X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. The difference is due to the strong dependence of the phase relations on the O/sub 2/ partial pressure. Superconductivity can be fully restored by heating above 1000 degrees C followed by a 450 degrees C anneal in O/sub 2/. High-temperature XRD studies show that the 123 phase crystallizes directly from the amorphous matrix below 800 degrees C. Restoration of the orthorhombic 123 phase does not necessarily ensure good superconducting properties, a result attributed to disorder on the heavy metal sites.         Effects of process variables on the properties of YBa/sub 2/Cu/sub 3/O/sub 7-x/ ceramics formed by investment casting    M.W. Hooker, T.D. Taylor, H.D. Leigh, S.A. Wise, J.D. Buckley, P. Vasquez, G.M. Buck and L.P. Hicks Summary: An investment casting process has been developed to produce net-shape, superconducting ceramics. In this work, a factorial experiment was performed to determine the critical process parameters for producing cast YBa/sub 2/Cu/sub 3/O/sub 7/ ceramics with optimum properties. An analysis of variance procedure indicated that the key variables in casting superconductive ceramics are the particle size distribution and sintering temperature. Additionally, the interactions between the sintering temperature and the other process parameters (e.g. particle size distribution and the use of silver dopants) were also found to influence the density, porosity, and critical current density of the fired ceramics.         The magnetic hysteresis of polycrystalline YBa/sub 2/Cu/sub 3/O/sub x/    S.J. Penn, N.M. Alford, T.W. Button and G.R. Court Summary: The use of polycrystalline YBCO is generally limited by the granularity of the material. To study the magnetic hysteresis due to the granularity of the material, the magnetization curves of polycrystalline YBCO have been measured in fields up to 25 mT and over a range of temperatures, from 4.2 K to just below critical temperature, T/sub c/. In the region where the hysteresis is dominated by flux trapped between grains, the curves have been modeled using a critical state model with a variety of critical state relations J/sub c/(B). Although the model fits individual curves surprisingly well, there are significant discrepancies in the model parameters for curves measured at the same temperature but different fields.         Bulk YBa/sub 2/Cu/sub 3/O/sub 7-x/-Ag superconductor via synthesized precursor containing BaCuO/sub 2.5/    S.N. Sinha and H.G. Lee Summary: An intermediate precursor containing 0.5Y/sub 2/O/sub 3/+2BaCuO/sub 2.5/+CuO+0.325 Ag is synthesized. By attrition milling of metals and barium nitrate and subsequent controlled heat treatment the precursor was obtained. To prepare orthorhombic YBa/sub 2/Cu/sub 3/O/sub 7-x/-0.325 Ag superconductor, the silver tubes packed with the precursor was heat treated for 40 min at 950 degrees C in air and subsequently either quenched or cooled slowly in air at 100 degrees C/h. If the sample was heat treated for 30 min or less at 950 degrees C in air and quenched, tetragonal YBa/sub 2/Cu/sub 3/O/sub z/ formed.         The possibility of critical current enhancement at far-infrared-irradiated high-T/sub c/ superconducting weak links    J. Takeya, S. Akita, R. Ishikawa and K. Uyeda Summary: The possibility of enhancing critical current in a grain boundary superconducting weak link by irradiating with far-infrared light is investigated theoretically. This method is based on the effect that the critical current in a Josephson junction can be enlarged when irradiated by electromagnetic waves having frequency corresponding to the energy gap of electrode superconductors and power in a certain range. In a high critical temperature, T/sub c/, case, critical current is enhanced severalfold. A high-T/sub c/ superconducting switching device whose ON and OFF states are switched by the electromagnetic wave irradiation is proposed.         On the optimum silver content in silver-doped high temperature granular superconductors    S.A. Sergeenkov Summary: A processing-dependent criterion for the optimum silver content in Ag/HTS (high-temperature superconductor) composites is proposed. It is based on competition between tunneling and proximity characteristics of the initial (undoped) ceramics. Silver-induced stabilization of the critical current density in an external magnetic field is briefly discussed as well.         Superconducting properties and structures of high-T/sub c/ oxides prepared by a citric acid salt process    Y. Shiomi, T. Asaka and K. Tachikawa Summary: YBa/sub 2/Cu/sub 3/O/sub 7-x/ (123) high critical temperature, T/sub c/, oxide superconductor was successfully prepared through a citric acid salt process. The effects of Ag addition as well as Zr substitution for Y on the structures and the superconducting properties of the specimens were studied. The addition of 10-30 wt.% Ag decreases the optimum sintering temperature to achieve highest T/sub c/ by 50 degrees C. Furthermore, the effect of fine Ag precipitates on critical current density, J/sub c/, was studied. The 5 at.% Zr substitution for Y produces much smaller 123 grains with uniform grain size. Both the Ag addition and the Zr substitution enhance the J/sub c/ (77 K, 0 T) of 123 specimen by a factor of several. The simultaneous addition of Ag and Zr suppresses the decreasing of J/sub c/ by the prolonged sintering.         Effects of Ag addition on the diffusion reaction in high-T/sub c/ oxides    K. Tachikawa, Y. Hikichi, K. Zama, T. Moriyasu and T. Suzuki Summary: The effects of Ag addition on the diffusion reaction for synthesizing high critical temperature, T/sub c/, oxides are described. The Ag addition to the diffusion component enhances the diffusion, and decreases the optimum reaction temperature. In the Y-123 and Bi-2212 diffusion specimens, the Ag goes up to the surface of the specimen, improving the grain alignment of the diffusion layer. In the Tl-2223 diffusion specimen, an offset T/sub c/ of 116 K and a large critical current (77 K, 0 T) are obtained. The diffusion layer composed of Sr-Ca-Cu oxides formed in the (Bi/sub 0.8/Pb/sub 0.2/)/sub 2/CuO/sub y/+Ag/SrCaCuO/sub 3/ diffusion composite shows a sharp resistance drop around 150 K and an offset of T/sub c/ of 120 K.         Melt processing of the Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ superconductor in oxygen and argon atmospheres    T.G. Holesinger, D.J. Miller and L.S. Chumbley Summary: Solidification and subsequent annealing of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ (2212) in oxygen and argon atmospheres were investigated in order to identify alternative processing routes for controlling microstructures and superconducting properties. In addition to 2212, several other phases formed on cooling in O/sub 2/ and did not disappear upon subsequent annealing. Crystallization in Ar resulted in a divorced eutectic structure of Bi/sub 2/Sr/sub 3-x/Ca/sub x/O/sub y/ and Cu/sub 2/O/CuO. The superconductor was formed on subsequent anneals. Samples melted in Ar and then annealed generally possessed a more uniform microstructure compared with samples that were melted in oxygen and annealed. Compositional measurements of the 2212 phase suggest that CaO segregation in the melt may be minimized with an overall composition such as Bi/sub 2.15/Sr/sub 2/Ca/sub 0.85/Cu/sub 2/O/sub y/.         Enhanced superconducting properties in Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub y/ by thermal and mechanical processing    D.J. Miller, T.G. Holesinger, J.D. Hettinger, K.C. Goretta and K.E. Gray Summary: The effect of processing on transition temperature, grain boundary coupling, and flux pinning has been examined for Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub y/. Enhancement of critical temperature based on composition can be achieved by control of crystallization and subsequent annealing processes while thermomechanical processing may be used to modify weak link and flux pinning behavior. The microstructural basis for these changes is related to the composition of the superconducting phase and the presence of defects associated with deformation processing. The implications of these results for conductor development are related to the selection of alloy composition for optimum transition temperature and controlled thermomechanical processing which yields a uniform defect structure.         Critical current enhancement by neutron irradiation of rapidly textured Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/    M.J. Kramer, J.W. Farmer, S.R. Arrasmith and R.W. McCallum Summary: The authors have investigated the effect of fast neutron irradiation on c-axis-aligned Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/ (Bi2212) produced using a new technique. Amorphous Bi2212 was crystallized under 20 MPa uniaxial stress at 870 degrees C for 6 h. DC superconducting quantum interference device (SQUID) shows a transition onset of 90 K. Material was cut into 2*2*0.150 mm slabs, sealed in quartz ampules, and irradiated at fluences of 10/sup 16/, 5*10/sup 16/, 2.5*10/sup 17/, and 7*10/sup 17/ n/cm/sup 2/. DC SQUID results show that critical current density, J/sub c/, is increased by a factor of 2.5 at 10 K for fluences of 7.2*10/sup 17/ for H parallel to c-axis for fields less than 3 T. The higher the fluence, the lower the dependency of J/sub c/ on applied field and temperature. Critical temperature, T/sub c/, decreased by 1 K for a fluence of 2.5*10/sup 17/ n/cm/sup 2/ with an additional 2 K drop for 7.2*10/sup 17/ n/cm/sup 2/. The increase in the width of the high field hysteresis loops for increasing fluence is more pronounced for samples measured normal to the c-axis.         Strong decrease of anisotropy by lead-substitution in Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+y/    F.X. Regi, J. Schneck, H. Savary, C. Daguet and F. Huet Summary: The in-plane ( rho /sub ab/) and out-of-plane ( rho /sub c/)/sub c/ resistivities were measured above the critical temperature, T/sub c/, in several lead-substituted single crystals of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+y/ and compared to the results obtained for lead-free samples. It was found that the lead substitution induces an important decrease of rho /sub c/, resulting in a lowering of the anisotropy rho /sub c// rho /sub ab/ by two orders of magnitude near T/sub c/. Moreover, rho /sub c/ changes its behavior from a semiconducting type of behavior to a metallic one. These results are related to the role of lead, which was recently inferred from structural considerations. The possibility of improving the out-of-plane critical current by lead substitution is discussed.         Critical current density, irreversibility line, and flux creep activation energy in silver-sheathed Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ superconducting tapes    D. Shi, Z. Wang, S. Sengupta, M. Smith, L.F. Goodrich, S.X. Dou, H.K. Liu and Y.C. Guo Summary: Experimental transport data, magnetic hysteresis, and flux creep activation energy results are presented for silver-sheathed high-T/sub c/ Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ superconducting tapes. The 110 K superconducting phase was formed by lead doping in a Bi-Sr-Ca-Cu-O system. The transport critical current density was measured at 4.0 K to be 0.7*10/sup 5/ A/cm/sup 2/ (the corresponding critical current is 74 A) at zero field and 1.6*10/sup 4/ A/cm/sup 2/ at 12 T for H// ab. Excellent grain alignment in the a-b plane was achieved by a short-melting method, which considerably improved the critical current density and irreversibility line. Flux creep activation energy as a function of current is obtained based on the magnetic relaxation measurements.         Epitaxial Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ films with very low microwave surface resistance up to 110 K    W.L. Holstein, L.A. Parisi, C. Wilker and R.B. Flippen Summary: Very-low-surface-resistance epitaxial Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ films have been prepared on one or both sides of (100) LaAlO/sub 3/ substrates up to 5 cm (2 in) in diameter. The critical temperature, T/sub c/, of the films was 120.5+or-0.5 K, as measured by AC magnetic susceptibility. Surface resistance at 10 GHz measured with a high-temperature-superconductor-sapphire resonator was 24+or-10 mu Omega at 4.2 K, 181+or-10 mu Omega at 77 K, and 359+or-20 mu Omega at 100 K. Identical T/sub c/ and surface resistance were observed for films prepared on both sides of substrates. A microstrip resonator prepared from a double side-coated film on a LaAlO/sub 3/ substrate exhibited an unloaded Q-value of 7200 at 100 K and 8.7 GHz and continued to demonstrate performance superior to similar copper resonators even at 115 K. This is the highest temperature reported to date for operation of a superconducting device.         Synthesis and processing of thin films in the Tl-Ca-Ba-Cu-O system    D.S. Ginley, J.S. Martens, E.L. Venturini, C.P. Tigges, C. Ashby and S. Volk Summary: A number of key processing issues have been identified for the film growth and the subsequent processing of thin films in the Tl-Ca-Ba-Cu-O system. The interrelationship between the precursor and the typical ex-situ process schemes is examined. An aqueous photolithographic process technology for submicron device fabrication without significant degradation of the surface resistance and the use of rapid thermal processing for contact anneals are discussed.         Low temperature phase formation of Tl-based superconducting thin films in reduced oxygen atmosphere    C.Y. Wu, F. Foong, S.H. Liou and J.C. Ho Summary: Tl-Ba-Cu-Cu-O superconducting thin films were prepared by magnetron sputtering with postannealing in a reduced oxygen atmosphere. Single-phase Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ can form on the MgO substrate at 800 degrees C under P(O/sub 2/) approximately=0.1 atm. However, the phase formation temperature can be affected by the starting composition of the film. Tl/sub 1/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ phase can be formed by simply lowering the Tl/sub 2/O pressure. The thermal stability of Tl/sub 1/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ phase was studied by resistivity measurements at high temperatures.         Effect of substrate-twin-induced microstructure on transport properties of epitaxial Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub x/ films in a magnetic field    D.H. Kim, D.J. Miller, J.D. Hettinger, K.E. Gray, P.G. Landis, J.E. Sharping and M. Eddy Summary: The role of substrate-induced microstructure on transport properties in c-axis-oriented epitaxial Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub x/ films grown on LaAlO/sub 3/ and SrTiO/sub 3/ has been studied. For a magnetic field parallel to the Cu-O planes, resistivity and the critical current density, J/sub c/, have been measured as a function of angle theta between the applied field and the direction of transport current. Resistivity dips and enhancement of J/sub c/ were observed for magnetic fields applied parallel to the substrate twins in LaAlO/sub 3/ in high fields (>or=2 T). For films on SrTiO/sub 3/, resistivity and J/sub c/ were Lorentz-force independent.         Current transport across grain boundaries in TlBa/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ thick polycrystalline films and YBa/sub 2/Cu/sub 3/O/sub 7/ step edges    J.D. Hettinger, D.H. Kim, D.J. Miller, J.G. Hu, K.E. Gray, J.E. Sharping, K. Daly, C. Pettiette-Hall, J.E. Tkaczyk and J. Deluca Summary: The authors have performed transport measurements in magnetic fields (H//c) up to 10 T on a series of YBa/sub 2/Cu/sub 3/O/sub 7/ grain boundaries induced by epitaxial growth on a substrate containing a series of step edges. An activation energy which goes as U(T) approximately (1-t) is found. Electric field versus current density curves taken at a constant temperature while varying the magnetic field allows a determination of the magnetic field dependence of the activation energy using the Ambagaokar-Halperin model. These values agree with results extracted from the resistive transitions. Similar characterizations of a sample of TlBa/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ are also presented. The temperature dependence of the activation energy for this system may be represented as U(T) approximately (1-t)/sup 2/, suggesting that the grain boundaries behave as SNS (superconducting-normal-superconducting) junctions.         Microstructural characterization of Ag-sheathed Tl-Ba-Ca-Cu-O and Bi-Sr-Ca-Cu-O superconducting tapes by analytical electron microscopy    J.G. Hu, D.J. Miller, K.C. Goretta and R.B. Poeppel Summary: The microstructures of Tl(1223) and Pb-doped Bi(2223) silver tapes produced by the powder-in-tube (PIT) method have been examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS). The Tl tapes annealed below the melting point exhibited fine grains and a high density of pores while tapes subjected to partial melting prior to solid state annealing were fully dense with large grains. However, these tapes also showed an increase in the size and density of impurity particles, particularly CaO and a Ba-Cu rich phase. Silver powders added to the precursors tended to promote the growth of Tl(1223) at lower temperatures but also interfered with the development of texture by providing nucleation sites of random orientations. In contrast, the Bi(2223) tape exhibited a high degree of texture and alignment. The incorporation of silver within the superconducting phase was found to be negligible for both the Tl(1223) and Bi(2223) tapes.         Transport and magnetization critical densities in TlBa/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ tapes    J.O. Willis, M.P. Maley, P.J. Kung, J.Y. Coulter, D.E. Peterson, P.G. Wahlbeck, J.F. Bingert and D.S. Phillips Summary: The powder-in-tube process was used to produce silver-sheathed tapes of TlBa/sub 2/Ca/sub 2/Cu/sub 3/O/sub 8+x/ (Tl-1223). The powder was produced by thalliating a precursor powder mixture to produce the Tl-1223 phase and then heating to drive off excess Tl and reach the Tl-2223 stoichiometry. The tapes were rolled and pressed, each step followed by a 3-h sintering. The 200- mu m-thick tapes show little sign of texturing; however, the critical current shows a small ( approximately 50%) dependence on the direction of the applied magnetic field. Both transport and magnetization measurements indicate relatively strong pinning at high temperatures. The 75 K self-field critical current density is 62 MA/m/sup 2/. Transport measurements reveal the presence of weak links at all temperatures, but with a relatively weak field dependence above approximately=0.1 T.         Microstructural and electronic properties of highly oriented Tl/sub 0.5/Pb/sub 0.5/Sr/sub 2/Cu/sub 2/O/sub 7/ films on LaAlO/sub 3/    D.J. Kountz, P.L. Gai, C. Wilker, W.L. Holstein, F.M. Pellicone and R.J. Brainard Summary: Epitaxial Tl/sub 0.5/Pb/sub 0.5/Sr/sub 2/CaCu/sub 2/O/sub 7/ films produced by RF magnetron sputtering followed by annealing in the presence of thallium oxide vapor have been produced on (100) LaAlO/sub 3/ substrates. These films are highly c-axis-oriented with rocking curve full width at half maximum less than 0.4 degrees . The resulting two copper oxide layer films exhibit microwave surface resistance at 10 GHz of 60+or-3 mu Omega at 4.2 K and 498+or-10 mu Omega at 70 K (T/sub c/=88+or-2 K). The degree of lattice mismatch between this phase and the LaAlO/sub 3/ substrate is very small, resulting in epitaxial thin films. This material exhibits very little intrinsic defect structure.         Effective activation energy in the Bi-Sr-Ca-Cu-O systems    S. Sengupta, D. Shi, Z. Wang, M. Smith and P.J. McGinn Summary: Magnetic relaxation in the Bi-Sr-Ca-Cu-O systems was investigated over a wide temperature regime. Previously reported studies of the effective activation energy, U, have been controversial in terms of temperature and field dependence of the critical current density, j/sub c/. The authors considered the temperature dependence of j/sub c/ and constructed the U-j (or M) curves for the Bi-Sr-Ca-Cu-O system. They found that at a constant driving force and temperature, U is considerably higher for 2245 samples than for 2223 samples. This enhancement can be attributed to the flux pinning from finely dispersed calcium- and copper-rich precipitates.         Sample size dependence and irreversibility of the critical current density of ceramic high-temperature superconductors    K.-H. Muller and D.N. Matthews Summary: The intergranular critical state model is employed to calculate the sample-size dependence of the transport critical current density of polycrystalline high-temperature superconductors. Good agreement with experimental data has been found. The generalized London equation is used to determine the Josephson current across grain boundaries when magnetic flux is trapped inside grains. The field at which the critical current density peaks when the applied field is decreased under zero field cooled (ZFC) conditions is predicted and agrees well with experimental observations.         Superconductivity and flux pinning in Nd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 7+ delta /    S.I. Yoo, M.J. Kramer and R.W. McCallum Summary: The substitution of Nd/sup +3/ for Ba/sup +2/ in Nd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 7/ (Nd123ss) increases the occupation of O(5) sites. For x>0.1 there is a significant depression of T/sub c/, and for x<0.1 there is no substantial decrease in T/sub c/ within experimental error. T/sub c/ vs. x is characterized by two plateaus, analogously to T/sub c/ vs. delta in YBa/sub 2/Cu/sub 3/O/sub 7- delta / (Y123). Analysis of oxygen contents of Nd123ss suggests the analogy with Y123 is valid. The transition width and Meissner fraction for all Nd123ss samples are strongly dependent on the sintering temperatures. While T/sub c/ is not affected over the range 0         Effect of intensive flux creep on voltage-current curves and thermal stability of high T/sub c/ composite conductors    Y.M. Lvovsky Summary: Basic dissipative and voltage-current curves of high-T/sub c/ conductors with normal metal matrix are obtained directly from the description of thermally activated flux creep. The effect of different criteria for j/sub c/ is discussed, and current sharing between superconducting and normal layers is analyzed. A comparison with the critical-state model is given. Intensive creep is shown to change considerably the real characteristics of high-T/sub c/ composites, increasing their thermal stability.         Large magnetic field induced fluctuation effect in superconducting Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ tape    Q. Li, M. Suenaga, T. Hikata and K. Sato Summary: The magnetic-field-induced fluctuation effect in a highly textured Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ tape is studied, based on magnetization measurements. Extremely large induced excess diamagnetism in high fields was observed at temperatures down to 75 K. In weak fields, fluctuation significantly reduced the diamagnetism of this system just below T/sub c/. The role this large extended fluctuation effect plays in the application of the Bi-based superconductor family is discussed.         Similarities in the superconducting magnetic transitions of Nb powders and YBa/sub 2/Cu/sub 3/O/sub 7-y/    R. Andrade Jr., M.A. Avila, S.P. de Campos and O.F. de Lima Summary: Similarities in the AC susceptibility curves and critical fields in the region near the transition onset are examined for Nb powder and YBa/sub 2/Cu/sub 3/O/sub 7-y/ in the low-field region. The results are interpreted as a general behavior of any granular sample, possibly linked with the surface sheath superconductivity.         Scaling laws for the critical current density of NbN films in high magnetic fields    D.P. Hampshire, K.E. Gray and R.T. Kampwirth Summary: The authors have measured the critical current density (J/sub c/) of two NbN films (500-AA and 1550-AA thick) as a function of temperature in magnetic fields up to 25 T using transport measurements. In both films, the functional form of the volume pinning force F/sub p/ obeys the Fietz-Webb scaling law throughout the entire magnetic field and temperature range. Values of J/sub c/ derived from DC magnetization data using Bean's model show qualitative agreement with the transport measurements throughout the superconducting phase. Despite the marked granularity in the microstructure of these films, the results are interpreted as evidence that a flux pinning mechanism determines the transport current density in NbN films in high magnetic fields.         Critical currents in NbZr superconducting thin films    U. Gambardella, D. Di Gioacchino, V. Boffa, G. Paterno, S. Barbanera and F. Murtas Summary: The fabrication by sputtering of Nb/sub 0.75/Zr/sub 0.25/ thin films that showed critical temperature as high as 10.5 K is described. Transport critical current measurements on Nb/sub 0.75/Zr/sub 0.25/ films whose geometries were photolithographically defined in the micrometer range are reported. The measurements were performed as a function both of the temperature and of the magnetic field up to 6 T. The temperature behavior is compared with the Kim-Anderson model, and the magnetic field behavior of the resulting pinning force is compared with existing models.         A model for the V-I characteristics in brick-wall-like structures    N. Adamopoulos and J.E. Evetts Summary: An analysis of brick-wall-like structures in high T/sub c/ polycrystalline ceramics with elongated grains is presented in order to predict and explain the voltage-current characteristics in these materials. The current path is determined by two different critical current densities in the direction of the long and short dimensions of the grains. The resistive transition and the n-values are studied in the limit of no longitudinal current transfer by using a statistical analysis of the distribution of the critical currents. This simple case illustrates the different aspects of the problem of modeling the general and more complicated structure.         Possible explanation for the shape of I-V curves of superconductors and a more meaningful definition of I/sub c/    R.J. Soulen Jr. Summary: A flux creep model is used to calculate the shape of the I-V characteristic of a superconductor. The functional form mimics an empirical equation, V approximately I/sup n/, frequently used to fit data, and thus offers a physical justification for its application. The magnetic field dependence of the exponent n is also predicted and compared with experiments. The fits so obtained are encouraging, but call for some experiments specifically designed to test all of the ramifications of the proposed model.         n-value and second derivative of the superconductor voltage-current characteristic    L.F. Goodrich, A.N. Srivastava, M. Yuyama and H. Wada Summary: The authors studied the n-value (V varies as I/sup n/) and second derivative (d/sup 2/V/dI/sup 2/) of the voltage-current curve of high- and low-temperature superconductors and superconductor simulators. They used these parameters for diagnosing problems with sample heating and data acquisition, and as indicators of the superconducting-to-normal state transition. The superconductor simulator may be useful in testing the measurement system integrity and reducing measurement variability since its characteristics are highly repeatable.         Extended measurements of the resistive critical current transition    G. Narang and W.H. Warnes Summary: The resistive critical current transition has been measured in a variety of Nb-Ti wires over several decades in voltage. The measurements were made as a function of magnetic field for wires with a variety of processing conditions, leading to both intrinsic and extrinsic limitations to the critical current (I/sub c/). Measurements of the wire geometry by image analysis have been used to assess the extent of extrinsic limitation of I/sub c/ and to see if any correlation exists between the V(I) transition and the filament geometry. A weak correlation between the linear variation in the cross-sectional area of the filaments and the I/sub c/ distribution of the samples was observed.         New devices for measuring the critical current in a tape as a function of the axial and transverse strain, the magnetic field and temperature    B. ten Haken, A. Godeke and H.H.J. ten Kate Summary: A set of instruments is developed to induce strain in various directions inside a superconductor. The common goal of these tools is to investigate the influence of the different components in the strain tensor on the current carrying capacity of a Nb/sub 3/Sn tape. This two-dimensional structure is selected as a simple mechanical model system. The first experimental results on the critical current and the critical temperature as a function of the strain in several directions are presented.         A study of the proximity effect at oxide superconductor-normal metal interfaces    J.H. Claassen, P.R. Broussard, V.C. Cestone and R. Hu Summary: A novel kinetic inductance technique has been used to screen several samples of oxide-superconductor/noble-metal thin film bilayers for a signature of the proximity effect in the noble metal. To date no evidence of significant induction of a superconducting pair potential in the normal metal has been observed.         Pauli-limited critical field of Ba/sub 1-x/K/sub x/BiO/sub 3/ determined from quasiparticle tunneling    G. Roesler, P.M. Tedrow, E.S. Hellman and E.H. Hartford Summary: A planar tunnel diode with Ba/sub 1-x/K/sub x/BiO/sub 3/ (BKBO) and Ag electrodes were fabricated. The dynamic conductance of the junction was similar to that found with conventional BCS superconductors. Using weak coupling theory, the undepaired transition temperature, spin-orbit scattering rate, and diffusion constant of BKBO were determined. The Pauli-limited critical field was calculated and compared to the measured resistive transitions of the BKBO film in magnetic fields. The Pauli-limited field is observed to occur generally at the field where the normal-state resistance is restored.         Preparation and characterization of c-axis in-plane YBa/sub 2/Cu/sub 3/O/sub 7/ thin films and YBCO/PrBCO superlattices by high pressure sputtering    P. Przyslupski, R. Herzog, A.J. Pauza, R.E. Somekh and J.E. Evetts Summary: Epitaxial YBa/sub 2/Cu/sub 3/O/sub 7/ c-axis in-plane thin films and YBCO/PrBCO superlattices have been grown on single-crystal [100] and [110] SrTiO/sub 3/ substrates by high-pressure DC sputtering. The orientation of the deposited films is a function of the deposition temperature, T/sub s/. Preliminary studies of the dissipative behavior of the flux line system in the mixed state of YBCO thin films on [110] SrTiO/sub 3/ substrates were performed. Dissipation processes in both Lorentz force free and Lorentz force configurations are discussed in terms of flux dynamics under the influence of the strong pinning potential intrinsic to the layered structure. Preliminary results for a modulated structure composed of layers of YBCO and insulating PrBCO in a-axis orientation and for the first time [110]-oriented YBCO/PrBCO superlattices are presented.         ab-orientation YBa/sub 2/Cu/sub 3/O/sub 7/ films grown on MgO substrates with a c-axis layer buffer by RF-sputtering method    S. Wu and K.-W. Ng Summary: An ab-plane-oriented YBa/sub 2/Cu/sub 3/O/sub 7/ thin film has been deposited on a thin c-axis layer with MgO as substrate by RF sputtering. Superconducting transition is much better than that deposited directly on the MgO substrate. The differences have been investigated by X-ray diffraction, reflection high energy electron diffraction, and scanning electron microscopy. The same technique has been applied to yttrium stabilized zirconia and yielded similar results.         Surface characterization of a-axis EuBa/sub 2/Cu/sub 3/O/sub 7-y/ thin films    H. Asano, M. Asahi, M. Suzuki and Y. Kimachi Summary: The surface characterization of a-axis EuBa/sub 2/Cu/sub 3/O/sub 7-y/ (EBCO) films sputtered onto SrTiO/sub 3/ (001) has been performed with a view to developing fabrication techniques for multilayer devices. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies indicate that a-axis EBCO films have fairly smooth surfaces. In addition, an electron cyclotron resonance (ECR) ion beam is used for surface cleaning of a-axis EBCO films. Surface analysis using X-ray photoelectron spectroscopy (XPS), and reflection high-energy electron diffraction (RHEED) show that the ECR oxygen ion beam treatment reduces the contaminated layer on a film surface and leaves a crystalline surface with an improved surface chemistry. ECR treatment at room temperature can result in reduced silver-contact resistivities in the 10/sup -8/-10/sup -7/ Omega -cm/sup 2/ range. The surface processing using an ECR source would be useful in the fabrication of high-T/sub c/ multilayer devices.         Morphology of barrier layer formed on YBCO    T. Matsui, T. Suzuki, T. Ishii, K. Tsuda, M. Nagano and K. Mukae Summary: The morphology of barrier layers, such as LaSrGaO/sub 4/ (LSGO) and SrTiO/sub 3/ (STO), was investigated using an atomic force microscope (AFM) and tunnel junctions with an Au/barrier/YBCO layered structure. The barrier morphology depended strongly on both the surface roughness of YBCO films and the deposition temperature of the barrier materials. It was improved by reducing the surface roughness of the YBCO films and keeping the deposition temperature lower than 400 degrees C during the barrier formation. The experiments performed are described, and the results are presented and discussed.         Study of proximity effect in superconductor/Au using scanning tunneling spectroscopy    M. Koyanagi, S. Kashiwaya, A. Shoji, H. Akoh, S. Kohjiro, M. Matsuda, F. Hirayama and K. Kajimura Summary: A search for a proximity effect between a-, c- and (103)-oriented YBCO and Au was carried out using low-temperature scanning tunneling microscopy at 4.2 K. BCS-like conductance spectra were observed only at the small part of the surface of Au thin film deposited in situ on the (103)-oriented YBCO thin film made by the coevaporation method.         Electrical properties of YBa/sub 2/Cu/sub 3/O/sub 7-x//PrBa/sub 2/Cu/sub 3/O/sub 7-x/ bi-layers    H. Terai, S. Sanada, A. Fujimaki, Y. Takai and H. Hayakawa Summary: The authors, investigated the electrical properties of YBa/sub 2/Cu/sub 3/O/sub 7-x/(YBCO)/PrBa/sub 2/Cu/sub 3/O/sub 7-x/(PBCO) bi-layers by fabricating YBCO/PBCO/Au/Nb junctions. For 5-nm-, 10-nm- and 20-nm-thick PBCO, supercurrents could be observed and uniformly distributed in the junction. The normal coherence length xi /sub n/ of PBCO was estimated to be 4 nm at 4.2 K from the relationship between I/sub c/R product and PBCO thickness. However, the junction resistance R was extremely small, compared with that of bulk PBCO for thicker PBCO. The temperature dependence of R posed the problem that a long-range interaction at least up to 300 nm existed between YBCO and PBCO below the critical temperature of YBCO in spite of the short coherence length xi /sub n/ of PBCO.         Fabrication of YBa/sub 2/Cu/sub 3/O/sub 7//AlO/sub x//Nb quasiparticle tunnel junctions    S.G. Lee, Y.H. Lee, H.C. Kwon, K. Park, Y.K. Park and J.C. Park Summary: The authors have fabricated superconductor-insulator-normal metal (SIN) tunnel junctions with c-axis-oriented YBCO thin films as the superconducting electrodes and studied the tunneling characteristics of the junctions by measuring the zero-bias junction resistance as a function of temperature and dI/dV as a function of the bias voltage. Measured junction resistance showed characteristic tunneling properties with a strong semiconducting background, which is ascribed to the imperfect tunnel barrier. dI/dV curves indicated gap structures at 27 mV and 4.5 mV, respectively, with a parabolic background.         Investigation of in-situ Ag/YBCO contacts for SNS devices    R.P. Robertazzi, A.W. Kleinsasser, R.B. Laibowitz, R.H. Koch and K.G. Stawiasz Summary: Using a completely in-situ process, the authors have investigated Ag metal contacts to thin films of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/, in order to study the properties of the Ag/YBCO interface as well as the Josephson effect in SNS (superconductor-normal-superconductor) bridges made with this technique. Measurements of the temperature dependence of the Josephson current in these devices have been made and are compared to recent theoretical predictions. SNS devices which exhibited Josephson effects had the critical-current-resistance products of the junctions limited by the high specific contact resistance of the SN interfaces. The lowest values of the specific contact resistance obtained were on the order of 10/sup -8/ Omega -cm/sup 2/ for contacts in the c-axis direction. The influence of the specific contact resistance on the magnitude of the Josephson current in SNS bridges is discussed.         Tunneling characteristics of YBa/sub 2/(Cu/sub 1-x/Fe/sub x/)/sub 3/O/sub y/ junctions    A.M. Cucolo, R. Di Leo, A. Nigro, F. Licci and J. Colino Summary: The authors have measured the tunneling characteristics of planar junctions realized on YBa/sub 2/(Cu/sub 1-x/Fe/sub x/)/sub 3/O/sub y/ single crystals with x=0.04. In comparison with the undoped 90 K phase of this material, the conductance curves of the doped junctions show gap-like structures broadened and reduced in amplitude. This behavior is similar to what has been observed in junctions fabricated on YBa/sub 2/Cu/sub 3/O/sub 7- delta / single crystals with T/sub c/=60 K. At low temperatures the background conductance is linear up to about 100 mV and shows a parabolic behavior for higher voltages, as found in the undoped 90 K system. From the analysis of the parabola, the barrier height and thickness are deduced. In the doped junctions anomalies are frequently observed as a conductance peak centered at zero-bias. They appear to result from scattering that involves spin exchange between tunneling electrons and Fe ions localized at the metal-oxide interface.         Low energy gap-like structure in YBa/sub 2/Cu/sub 3/O/sub 7-x//metal junctions    S. Benacka, A. Plecenik and S. Chromik Summary: Low-energy gap-like structures were experimentally observed in different types of tunnel junctions with base electrodes of high-temperature superconductor (HTS) and upper electrodes of low-temperature superconductor (LTS) or normal metal. The resulting structures are interpreted as arising from a sum of LTS and HTS gaps resulting from the strong depression of superconductivity in HTS near the tunneling barrier due to the outdiffusion of oxygen. This conclusion is confirmed by the temperature and magnetic field dependence of the structures. The energy gap of a degraded HTS layer was found to be about 1.6 meV, with ratio 2 Delta /sub L//k/sub B/T/sub c/=4.1 and critical temperature T/sub c/ equivalent to 9 K.         Specific boundary resistance in Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x//Au thin-film bilayer    D.R. Smirnov, O.V. Snigirev and V.G. Yakunin Summary: The specific boundary resistance R/sub b/ of the Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x//Au thin-film bilayer has been studied. Reduction of R/sub b/ from an initial value close to 10/sup -5/ Omega -cm/sup 2/ to approximately 10/sup -10/ Omega -cm/sup 2/ was observed after annealing in oxygen at 500 degrees C. The magnitude of the parameter upsilon /sub b/ varies as R/sub b/, which characterizes the value of the order parameter discontinuity across the S-N interface, was less than 100. After oxygen annealing a high level of diffusion of Ba and Cu atoms in the Au film was found by Auger spectroscopy.         HIP synthesized Nb/sub 3/Sn bulk materials with extraordinary homogeneity    W. Goldacker, R. Ahrens, M. Nindel, B. Obst and C. Meingast Summary: The authors present a simple powder metallurgical approach to synthesizing Nb/sub 3/Sn bulk materials by heat treatment under hot isostatic pressure (HIP) conditions that yields very homogeneous and fully densified large Nb/sub 3/Sn samples. The total width of the superconducting transition obtained from a specific heat measurement was only 0.4 K, corresponding to a variation of the Sn content of less than +or-0.1 at.% over the macroscopic sample size. The physical and superconducting properties of such samples are characterized, and possible application of the resulting materials are given.         Improved superconducting Nb/sub 3/Sn wire using Nb(Ti), Sn(Ga), Cu, and Ag powders    C.L.H. Thieme and S. Foner Summary: Superconducting Nb/sub 3/Sn wire was produced by means of the powder metallurgy process using Nb-2.9 at.% Ti and Sn-6.2 at.% Ga powders to which small quantities of Cu, Ag or Cu+Ag powders were added. Using heat treatments at 950 degrees C and 750 degrees C, these additions increased the overall critical current density to 10/sup 8/ A/cm/sup 2/ at 22.8 T and 4.2 K. B/sub c2/ versus T measurements showed an increase in B/sub c2/ at temperatures of 6-18 K, of about 1 T, and T/sub c/ was increased by about 0.4 K. In a different wire annealed in a U-shape, the overall J/sub c/ at 23.5 T was 0.5*10/sup 8/ A/m/sup 2/ at 4.2 K, 1.4*10/sup 8/ A/cm/sup 2/ at 2.5 K, and 1.9*10/sup 8/ A/m/sup 2/ at 1.6 K. n-values were measured at fields up to 23 T. The different chemical activities of Ga and Sn when dissolved in Cu are discussed.         An improved method of introducing additional alloying elements in Nb/sub 3/Sn    G.M. Ozeryansky, E. Gregory and B.A. Zeitlin Summary: It is shown that in the internal-tin process for producing multifilamentary Nb/sub 3/Sn, the introduction of Ti into the filaments from the matrix produces properties equivalent to those obtained when the filaments are prealloyed. A fabrication process is based on the tubular tin source approach. Test results are given.         Critical current degradation in Nb/sub 3/Sn cables under transverse pressure    H.H.J. ten Kate, H.W. Weijers and J.M. van Oort Summary: The critical current degradation of a few sample Rutherford-type Nb/sub 3/Sn cables is investigated as a function of transverse pressure. A comparison is made between Nb/sub 3/Sn strands produced by the powder-in-tube, bronze, and modified jelly roll processes. The (keystoned) Rutherford cables are charged at 11 T under transverse pressures up to 250 MPa. Large differences in critical current reduction are observed, ranging from 6 to about 60% at 200 MPa, depending on the type of Nb/sub 3/Sn. It appears that about 40% of the total reduction is irreversible. Moreover, the irreversible part shows relaxation, and a partial recovery is possible by thermal cycling.         Critical-current degradation in multifilamentary Nb/sub 3/Al wires from transverse compressive and axial tensile stress    S.L. Bray, J.W. Ekin and T. Kuroda Summary: The effect of transverse compressive stress and axial tensile stress on the critical current of multifilamentary Nb/sub 3/Al superconducting wires has been measured. Compared with commercial Nb/sub 3/Sn, Nb/sub 3/Al exhibits a relatively small sensitivity to both axial and transverse stress. For a given degradation of critical current at 9 T, Nb/sub 3/Al will tolerate about twice as much axial stress as Nb/sub 3/Sn and about five times the transverse stress. The elastic modulus of Nb/sub 3/Al, 169+or-20 GPa, was measured for the first time at cryogenic temperatures and found comparable to that of Nb/sub 3/Sn. A comparison between the effect of axial and transverse stress showed that Nb/sub 3/Al, like Nb/sub 3/Sn, is more sensitive to transverse stress than axial stress. For a given level of critical-current degradation, the transverse stress tolerance of Nb/sub 3/Al is about half the axial stress tolerance. The favorable electromechanical characteristics of Nb/sub 3/Al, compared with Nb/sub 3/Sn, may allow increased operating limits for the next generation of large high-field superconducting magnets.         First results of stress effects on I/sub c/ of Nb/sub 3/Al cable in conduit fusion superconductors    W. Specking, H. Kiesel, H. Nakajima, T. Ando, H. Tsuji, Y. Yamada and M. Nagata Summary: The effect of axial strain, epsilon /sub a/, on the critical current, I/sub c/, of Nb/sub 3/Al cable-in-conduit subconductors has been measured for I/sub c/         Mechanisms of formation of intermetallic compounds at the interfaces of niobium-shielded filaments    R. Taillard, J. Foct, C.E. Bruzek and H.-G. Ky Summary: The problem of determining a minimum thickness for niobium coatings that hinder the formation of deleterious intermetallic compounds is addressed. The location at the primary compounds form as well as the mechanisms of permeation of the barrier are investigated, and the relative importance of mechanical alloying and of thermal diffusion is determined. The result is an estimate of the minimum of thickness of the Nb layer at the beginning of the last heat treatment. It is found that the estimate is, however, likely to be insufficient because of mechanical damage to the barrier.         Experimental results on Nb 25 wt.% Ta 45 wt.% Ti superconducting wire    H. Liu, E. Gregory, N.D. Rizzo, J.D. McCambridge, X.S. Ling and D.E. Prober Summary: Several small billets with NbTi binary and Nb 25 wt.% Ta 45 wt.% Ti ternary alloy filaments were made and fabricated into fine wire after subjecting the alloys to different treatment conditions. J/sub c/ results at 4.2 K and 1.8 K from binary and ternary materials, which were prepared under the identical conditions, are compared. The results of an alpha -Ti precipitation study on the two alloys are also presented. The J/sub c/ results are compared with those from some earlier work on a Nb 15 wt.% Ta 44 wt.% Ti material.         Microstructure property relationships in Nb-Ti-Ta    P.J. Lee, D.C. Larbalestier, J.C. McKinnell and A.D. McInturff Summary: The microstructures produced by conventional precipitation heat treatment of Nb-44.4 wt.%Ti-15.4 wt.%Ta have been observed and quantified. The precipitate morphology was found to be qualitatively the same as for similarly processed Nb-47 wt.%Ti providing that a prestrain in excess of 6.5-7 was applied prior to heat treatment. Heat treatments at 420 degrees C for 80 h produced approximately=10% more alpha -Ti than in the binary alloy but the J/sub c/ at 4.2 K was lower in the ternary.         Characterization and coil test results for a multifilamentary NbTi conductor utilizing artificial pinning center technology    R.M. Scanlan, D.R. Dietderich, P. McManaman and W. Ghiorso Summary: The introduction of pinning centers via the controlled addition of a second phase, with the correct size and spacing, has been proposed as a method for producing a material with optimum flux pinning and hence a higher critical current density in practical superconductors. The demonstration of such artificial pinning center (APC) materials has been the aim of recent collaborative efforts with several US manufacturers. This paper reports the coil test results for a multifilamentary NbTi conductor fabricated using an APC technique. The conductor showed improved performance compared to earlier APC conductors, and its performance is comparable to that found in conventional multifilamentary NbTi conductors. In addition to coil test results. results of low-field magnetization, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are reported and compared with similar results on conventional NbTi.         Effects of artificial pins on the flux pinning force and other superconducting properties in NbTi superconductors    K. Matsumoto, Y. Tanaka, K. Yamafuji, K. Funaki, M. Iwakuma and T. Matsushita Summary: A marked enhancement of global pinning strength in Nb-50 wt.%Ti alloy was obtained by introducing ribbon-shaped artificial pins. Simultaneously, however, depression of B/sub c2/ was observed. This behavior is analyzed theoretically, and a satisfactory explanation of the experimental results is obtained.         Multifilamentary NbTi with artificial pinning centers: the effect of alloy, pin material, and geometry on the superconducting properties    L.R. Motowidlo, B.A. Zeitlin, M.S. Walker, P. Haldar, J.D. McCambridge, N.D. Rizzo, X.S. Ling and D.E. Prober Summary: Low temperature superconductors containing artificial pinning centers (APC) in NbTi have shown critical current densities (below 4 T) substantially higher than metallurgically fabricated and optimized NbTi superconductors. Peak current densities are achieved when the pinning center spacing is matched to the spacing of the flux line lattice (FLL) at field of operation. It is shown that the choice of the superconducting alloy as well as the pin material has a marked effect on both the characteristic pinning force, F/sub p/, and the critical magnetic field, H/sub c2/. In addition, the design approach or geometry, such as the size of the artificial superconducting filament, the area of the pinning material, and the position of the pins, can be important factors in determining the strength of the pinning force on the FLL.         Influence of structure of fine filament NbTi composite on its electromagnetic characteristics    I. Hlasnik, O. Tsukamoto, S. Fukui, T. Kumano, M. Polak, J. Kokavec, M. Majoros, L. Krempasky and E. Suzuki Summary: The study of the influence of filament diameter d/sub f/, filament spacing b/sub n/, and B on critical current density J/sub c/ and AC losses p/sub s/ in one type of fine filament composite (FFC) has revealed two components of J/sub c/, the bulk and surface critical current densities J/sub cb/ and J/sub cs/, respectively. A simple relationship between them, J/sub c/, and geometrical parameters of FFC including those with different types of artificial pinning centers (APCs) is formulated. It is used to explain measured J/sub c/(B,d/sub f/) dependence in FFC with island-type APC as well as to discuss the prospects of both types of APC in FFC for AC use. To verify the theoretical results, a series of FFC samples with sheet-type APC has been prepared and measured. Experimental values of J/sub c/(B,d/sub f/) obtained in this series of samples are smaller than expected. One possible reason for this difference is suggested.         Material and electro-magnetic aspects of newly developed Nb-Ti wires for AC use with Cu-Si alloy matrix    K. Tachikawa, S. Koyama, S. Akita, S. Torii, H. Kasahara, Y. Tanaka and K. Matsumoto Summary: The material characteristics of Cu-Si alloy as a new matrix material for AC superconducting wires are presented. The successful trial fabrication of submicron-diameter Nb-Ti multifilamentary wires with Cu-2.5 wt.% Si alloy matrix is described. The wires, which had filament diameters down to 0.1 mu m, showed high enough critical current density and low AC loss compared to Nb-Ti AC superconductors with a Cu-Ni alloy matrix.         Magnetic flux distribution in polycrystalline Bi,Pb-Sr-Ca-Cu-O superconductors in a cyclic state    J. Paasi, M. Polak, M. Lahtinen, J.-T. Eriksson and V. Plechacek Summary: The authors have studied magnetic flux distribution in polycrystalline (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10+x/ superconductors at 77 K at different stages of an external magnetic field cycle using a movable miniature Hall sensor. The measured magnetic field profiles are compared to profiles achieved by numerical field calculations. The existence of both inter- and intragranular currents causes deviations to the field profiles predicted by classical critical state models, leading to incorrect critical current density estimations, when using standard magnetization measurements.         Magnetic hysteresis and flux creep of YBa/sub 2/Cu/sub 3/O/sub x/ grown by the melt-powder-melt-growth (MPMG) process    P.J. Kung, M.P. Maley, J.O. Willis, M.E. McHenry, M. Murakami and S. Tanaka Summary: Magnetic hysteresis and flux creep of melt-powder-melt-growth (MPMG) YBa/sub 2/Cu/sub 3/O/sub x/ containing nominal 0, 25, and 40 mole% Y/sub 2/BaCuO/sub 5/ (211) were measured in the temperature range from 5 to 80 K and in magnetic fields up to 5 T. With the introduction of finely dispersed second-phase 211 particles, the critical magnetization current density J/sub c/ shows a weak field dependence over a wide range of temperature, and the effective pinning energy U/sub eff/ is greatly enhanced. From these results, a functional expression for U/sub eff/(J, T) is obtained. The observed power-law relationship for U/sub eff/(J, T) clearly demonstrates two of the three regimes predicted by the theory of collective flux creep, J         High activation energy for TAFF and pinning by fine inclusions in melt textured Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7- delta /    M. Ullrich, D. Muller, K. Heinemann, L. Niel and H.C. Freyhardt Summary: In Bridgman melt-textured Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO) the activation energy, U/sub 0/, for thermally activated flux flow (TAFF) has been found to be almost four times higher than in conventional sintered bulk material by measuring rho (T, B) curves. One reason could be very fine inclusions with an average diameter of 35 nm and associated dislocations. An estimation of core pinning by these fine particles yields critical current densities, j/sub c/, at 1 T of 4.8*10/sup 4/ A/cm/sup 2/ and 2*10/sup 5/ A/cm/sup 2/ for 77.3 K and 4.2 K, respectively. This calculated current density is on the same order of magnitude as the j/sub c/,/sub Delta M/ value estimated from M(B) measurements at 4.2 K and 1 T, but at 77.3 K and 1 T the calculated current density is about one order of magnitude higher than the j/sub c/,/sub Delta M/ value. The lower critical current density at 77.3 K could be caused by TAFF or oxygen deficient regions near the small angle grain boundaries, which become normally conducting at high fields and temperatures.         Critical current densities and activation energy of BiPbSrCaCuO tapes    A. Gladun, G. Fuchs, K. Fischer, D. Busch, R. Eujen and J. Huedepohl Summary: The critical current density and the resistive transition curves of Ag-sheathed, textured (Bi/sub 1-x/Pb/sub x/)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ tapes have been studied in magnetic fields up to 12 T. The results can be described by the modified flux creep model proposed by E. Zeldov et al. (1990). It is shown that this model yields a simple explanation for the exponential field dependence of the critical current density in high-temperature superconductors.         Angular dependence of the zero resistance superconducting glass state in YBCO thin films    R.M. Silver, A.L. de Lozanne and M. Thompson Summary: The authors present current versus voltage and resistivity data as a function of angle, magnetic field, and temperature. The critical scaling exponents extracted from the data are consistent with the new theories of the vortex and Bose glass. However, the angle dependence of the glass transition temperature is inconsistent with the vortex glass model and is explainable in a model utilizing both the vortex and Bose glass theories. The samples, high quality epitaxial thin films of YBCO, were also studied using the atomic force microscope and X-ray diffraction techniques. The effects of the microstructure on angle-dependent current versus voltage measurements within the vortex glass framework are discussed.         Dynamic measurement of flux flow resistivity in YBa/sub 2/Cu/sub 3/O/sub 7/ wires    T.R. Askew, J.G. Nestell, R.B. Flippen, D.M. Groski and N.McN. Alford Summary: Polycrystalline samples of YBa/sub 2/Cu/sub 3/O/sub 7/ have been pushed deep into the flux flow regime using submillisecond feedback-controlled current ramps. Thermal stability has been maintained in the 65-93 K range in spite of current densities that exceed J/sub c/ by a factor of four or more. Linear I-V relations are observed, and the measured flux flow resistivity shows a simple dependence on the microstructure of the samples. The resistivity of unoriented ceramic samples shows essentially no dependence on magnetic field between 0.05 T and 0.5 T, and shows a slight dependence on temperature that mirrors the linear behavior of the normal state resistivity down to about 72 K. Below 72 K the flux flow resistivity begins to rise with dropping temperature. In contrast, directionally solidified samples show a much lower flux flow resistivity with almost no temperature dependence. A strong field dependence appears in this latter case, one that is reminiscent of the Bardeen-Stephen flux flow resistivity of low T/sub c/ materials.         Critical current in Josephson junction arrays    R. De Luca, S. Pace and A. Saggese Summary: A numerical analysis of the stationary magnetic states realized in a planar system of Josephson junctions (JJs) coupled through identical inductances is presented. The flux and current distribution in the system is found in the presence of an external magnetic field applied in the direction orthogonal to the plane of the network after zero field cooling (ZFC). By this analysis a clear definition of the critical current in these types of arrays is given. In the irreversible magnetic regime stationary states quite similar to the approximate states of a critical state model are realized.         Penetration field studies on melt-textured YBa/sub 2/Cu/sub 3/O/sub 7- delta/ from low field ultrasonic measurements    Z.-X. Li, M. Levy, B.K. Sarma, S. Salem-Sugui Jr., D. Shi and G.W. Crabtree Summary: Both attenuation and velocity measurements have been performed in low magnetic fields on a melt-textured sample of YBa/sub 2/Cu/sub 3/O/sub 7- delta /. Transverse waves propagated along the c-axis at 76 MHz while the temperature was kept constant. Four orientations of the magnetic field H were used. In the a-b plane the field was perpendicular, at 45 degrees , or parallel to the polarization direction. The fourth orientation was parallel to the c-axis. The results suggest that the penetration field observed by the ultrasonic measurements is associated with flux line penetration into the matrix surrounding the oriented crystallites. The velocity jump changes as the inverse of the separation between the vortex lines, and the maximum in the attenuation jump appears to be the result of the fact that the attenuation is proportional to the density of the flux lines but the interaction is described by a thermally activated process.         Numerical solutions to the mass tensor form of the Ginzburg-Landau equations    K.G. Herd Summary: The finite-element method (FEM) has been used to solve the mass-tensor form of the Ginzburg-Landau equations. The spatial variation of the local magnetic flux density, the supercurrent density, and the superelectron pair density has been computed for the anisotropic vortex lattice structure. The Gibbs free energy of the triangular vortex lattice was found to be less than that of the rectangular vortex lattice for all applied fields between the lower critical field and the upper critical field.         Flux-motion related AC losses in high T/sub c/ superconductors    Q.Y. Chen Summary: The AC losses of high-temperature superconductors in the flux-depinned mixed-state have been treated using the classical magnetic diffusion equation in conjunction with various models of flux-motion. With the imaginary part representing the AC losses, the field- and frequency-dependent AC susceptibilities were investigated. The imaginary component was found to obey a scaling rule with a characteristic frequency, estimated to be approximately 10/sup 5/-10/sup 9/ Hz, that depended on the sample size and normal state resistivity. This frequency range agrees with earlier experimental results, which could not be accounted for previously based upon the notion of thermally activated hopping of vortices. The frequency scaling behaviors using flux-creep and flux-flow models are presented.         Estimation of AC losses of polycrystalline YBCO by two different methods    H. Ishii, S. Hirano, T. Hara and T. Yamamoto Summary: AC losses of polycrystalline YBa/sub 2/Cu/sub 3/O/sub y/ were evaluated using AC transport and magnetization techniques. As alternating currents were passed through a cylindrically sintered specimen, effectively resistive voltages were detected by means of a lock-in amplifier and were shown to be linked with AC losses of the specimen. The field dependence of magnetically estimated AC losses for a small chip, synthesized in the same manner, exhibited a plateau region beginning at several tens of oersteds. This field was found to be equal to the self-induced magnetic field created by the DC critical current of the cylindrical specimen and could be attributed to the grain decoupling field. Below this field, the two methods provided almost equivalent AC losses, which also semiquantitatively agreed with theoretical estimation using C.P. Bean's (1962) critical state model.         Dielectric properties of SrTiO/sub 3/ thin films at low temperature    A.Z. Kain, C.L. Pettiette-Hall, K.P. Daly, A.E. Lee, R. Hu and J.F. Burch Summary: The authors have fabricated YBCO (or Ag)/SrTiO/sub 3//YBCO capacitors for low-frequency measurements and SrTiO/sub 3//YBCO/LaAlO/sub 3/ coplanar-waveguide end-coupled resonators for high-frequency measurements of the SrTiO/sub 3/ dielectric constant at low temperatures. From the capacitor measurements, values for the dielectric constant ranging from approximately 200 to 800 were obtained for films of various thicknesses. This behavior of the thin-film dielectric constant was found to differ from that of the bulk crystal.         Sr/sub 2/AlTaO/sub 6//YBa/sub 2/Cu/sub 3/O/sub 7/ heterostructures for superconducting device applications    A.T. Findikoglu, S. Bhattacharya, C. Doughty, M.S. Pambianchi, Q. Li, X.X. Xi, S.M. Anlage, R.E. Fahey, A.J. Strauss, J.M. Phillips and T. Venkatesan Summary: Using pulsed laser deposition, the authors have prepared epitaxial heterostructures of a new insulating perovskite Sr/sub 2/AlTaO/sub 6/ (SAT) and the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) on LaAlO/sub 3/ substrates. X-ray rocking curve and Rutherford backscattering channeling measurements on (001) SAT films on (001) LaAlO/sub 3/ substrates yield full width at half-maximum of <0.3 degrees and minimum backscattering yield /sub chi min/ of 5%, indicating good crystallinity. From capacitance measurements on SAT films, the real part of the relative dielectric constant epsilon /sub r/ is found to be approximately 23-30, with approximately 6*10/sup 7/ V/m static breakdown electric field. A 100-nm*10- mu m*50- mu m YBCO film on SAT shows zero-field critical current density of approximately 1.3*10/sup 6/ A/cm/sup 2/ at 77 K. A dielectric resonator at 24.5 GHz was used to measure the resistive energy dissipation at the surface of a YBCO/SAT/YBCO trilayer. An effective surface resistance value of approximately 12 m Omega at 77 K, which is within a factor of four of the value obtained for a single-layer YBCO film, was found.         Epitaxial YBa/sub 2/Cu/sub 3/O/sub 7- delta / thin films on LaMgAl/sub 11/O/sub 19/: new substrates with low dielectric losses    G.C. Xiong, G.J. Lian, X. Zhu, J. Li, Y.J. Li, Z.Z. Gan, D. Jing, K. Shao and H.Z. Guo Summary: Pulsed laser ablation was used to deposit superconducting YBa/sub 2/Cu/sub 3/O/sub 7- delta / thin films with T/sub c/=89.5 K on an LaMgAl/sub 11/O/sub 19/ substrate. X-ray diffraction patterns show that the YBa/sub 2/Cu/sub 3/O/sub 7- delta / films were epitaxially grown with their c-axis perpendicular to the substrate surface. LaMgAl/sub 11/O/sub 19/ has low dielectric constant and small loss tangent. Using the LaMgAl/sub 11/O/sub 19/ substrates, YBa/sub 2/Cu/sub 3/O/sub 7- delta / microstrip resonators were fabricated.         Measurements of surface resistance of grain-aligned bulk material as a function of DC magnetic field; weak link study    J. Wosik, L.M. Xie, J. Halbritter, R. Chau, A. Samaan, J.C. Wolfe, V. Selvamanickam and K. Salama Summary: The temperature and DC magnetic field dependences of the surface resistance of grain-aligned YBa/sub 2/Cu/sub 3/O/sub x/ bulk material were measured at 9.5 and 75 GHz. Experiments were conducted on a-b-plane- and a-c-plane-oriented sample surfaces. A nonlinear increase of R/sub s/(H/sub dc/) at low fields, which turns into a linear dependence on H at fields larger than H/sub c1/, was observed and explained. A model that allows a quantitative fit using as parameters the lower critical field of the weak links or the grain, the decoupling parameter, and the slope alpha was employed. Two different sets of these parameters must be used to fit all of the data, indicating the existence of two kinds of weak links. The parameter values indicate that there exist inter- and intragrain weak links that contain Josephson fluxons, and a bulk crystal region that contains Abrikosov fluxons. The field-modulated microwave absorption method was used to identify intergrain weak links with lower critical fields <10/sup -4/ T. The correlation between microstructure of the samples and the angular dependence of the field modulated microwave absorption lines is discussed.         Transport and microwave properties of YBa/sub 2/Cu/sub 3/O/sub x/ thin films in low magnetic fields    M. Mahel, S. Benacka, R. Adam, M. Darula and S. Chromik Summary: Measurements of the transport critical current and the modulated microwave absorption in low magnetic fields up to 15 mT are presented for c-axis-oriented YBa/sub 2/Cu/sub 3/O/sub x/ thin films at 4.2 K and 77 K. Both the transport critical current and the microwave losses are believed to be determined by the weak links. The intergranular critical state and the influence of the intragranular magnetization are introduced in order to account for the magnetic hysteresis effects. The experimental results agree with those obtained are fitted by a theoretical model.         YBa/sub 2/Cu/sub 3/O/sub 7- delta //LaAlO/sub 3//YBa/sub 2/Cu/sub 3/O/sub 7- delta / trilayer transmission lines for measuring the superconducting penetration depth    J.M. Pond, K.R. Carroll, J.S. Horwitz and D.B. Chrisey Summary: Microstrip transmission lines fabricated from two YBa/sub 2/Cu/sub 3/O/sub 7- delta / films separated by a deposited LaAlO/sub 3/ dielectric film provide a technique for measuring the penetration depth. When weakly coupled to a microwave signal, this structure permits precise measurements of the resonant frequencies. The absolute value of the penetration depth as a function of temperature can be calculated from the phase velocity. With this method, there is no need to assume a particular functional form for the temperature dependence. The sensitivities of this method to possible asymmetries in the superconducting film properties and uncertainties in the dielectric constant have also been analyzed. Recently reported microwave measurements are analyzed.         Microwave surface impedance of a Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/ single crystal and derivation of rho /sub c/(T,B)    N. Exon, M. Lancaster, A. Porch, G. Yang and C.E. Gough Summary: Microwave surface impedance measurements are reported for a high-quality Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/ single crystals platelet over a wide range of temperatures in DC fields parallel and perpendicular to the ab-planes. A large field and frequency dependent peak is observed in the loss component below T/sub c/. Because of the giant anisotropy of resistivities parallel and perpendicular to the ab-planes, microwave penetration from the thin edges of the platelet is as important as that across the major faces in the normal state and becomes the dominant source of microwave loss in the superconducting state. To analyze the measurements, a theoretical expression has been derived for microwave absorption in an anisotropic long rectangular slab. The observed temperature and field dependences of microwave losses for the superconducting and normal states are simulated using model temperature and field-dependent conductivities. Microwave losses are used to derive the linear, thermally activated resistivity in the c-direction.         Measurements of low magnetic field microwave absorption in 110-K superconducting Bi-Sr-Ca-Cu-O thin films    W. Kula and R. Sobolewski Summary: Studies on magnetic-field dependent microwave absorption in Bi(Pb)-Sr-Ca-Cu-O thin films superconducting above 100 K are reported. The films were DC magnetron sputtered on MgO and CaNdAlO/sub 4/ single crystals from Pb-rich targets and post-annealed at high temperatures in air for less than 1 h. The measurements were performed as a function of temperature, DC magnetic field, and the film magnetic history. The results show that the microwave absorption measurements are a very sensitive tool for high-T/sub c/ thin-film characterization, since even small variations in the film phase homogeneity, granularity, or crystalline orientation are clearly visible on the modulated absorption curves. It was found that the films characterized by the lowest absorption exhibited the highest critical current densities.         RF power dependence of YBCO thick films    T.W. Button, P.A. Smith, Z. Wu, N.McN. Alford, L.E. Davis and S.J. Penn Summary: The dependence of Q on incident power has been measured for an all-thick-film YBa/sub 2/Cu/sub 3/O/sub x/ cavity resonating in the TE/sub 011/ mode at 5.66 GHz and 77 K. The high unloaded Q of 715000 measured at low incident power levels decreases as the power level is increased, but remains over 200000 with 1.4 W incident on the cavity, which corresponds to 0.7 W dissipated in the cavity. The data have been used to calculate the RF power dependence of the R/sub s/ of thick-film YBa/sub 2/Cu/sub 3/O/sub x/, which is shown to be approximately linear for RF fields between 0 and 0.5 mT.         Surface resistance of superconducting films by a microstrip ring resonator technique    A. Andreone, A. DiChiara, G. Peluso, U.S. di Uccio, C. Attanasio, L. Maritato, S. Marra, R. Vaglio, E. Milani and M. Montuori Summary: A ring microstrip resonator technique has been set up to measure the surface impedance of superconducting films in the range 1-20 GHz as a function of temperature and both DC and RF field amplitude. The method has been tested on Nb films and extended to both metallic compounds of interest for thin-film-coated accelerating cavity applications (NbTiN) and high T/sub c/ oxide superconducting films of potential interest for microwave circuit applications such as high-quality YBCO and BSCCO compounds, including, in the latter compound, samples obtained by liquid phase epitaxy. The results confirm that losses at the grain boundaries or twinning planes play an important role in determining the residual term and the high magnetic field degradation of the surface resistance in both metallic and high-T/sub c/ superconducting films.         A sapphire resonator for microwave characterization of superconducting thin films    C. Wilker, Z.-Y. Shen, V.X. Nguyen and M.S. Brenner Summary: A simple technique has been developed for the high-frequency characterization of superconducting thin films. A microwave resonator is formed by sandwiching a high-purity c-axis-oriented sapphire rod between a pair of superconducting thin films. For the TE/sub 011/ resonant mode, the theoretical treatment allows for the surface resistance and the RF current density to be calculated from the unloaded Q-value and the dissipated power. This technique is especially useful since it has: no sample preparation; no calibration; great sensitivity; great accuracy; great repeatability; great dynamic range; high internal power levels with only moderate input power levels; and broad temperature coverage (4.2 to over 120 K). A round robin experiment using HTS thin films was performed to deconvolute the films' surface resistance and also to provide a statistical analysis of the method's reproducibility. The standard error for a single measurement is better than 2%. A Nb thin film was measured to verify the technique.         Cooper pair breaking in lead measured by pulsed terahertz spectroscopy    J.F. Federici, B.I. Greene, P.N. Saeta, D.R. Dykaar, F. Sharifi and R.C. Dynes Summary: A technique for characterizing pulsed far-infrared radiation with a demonstrated resolution of approximately 100 fs is used to measure directly Cooper pair breaking in superconducting lead. A 100-fs pulse of visible light is used to excite a thin-film lead sample while the Cooper pair density is optically probed using a pulse of broadband far-infrared radiation. Subsequent to the absorption of the visible pulse, a rapid (<1 ps) change in the far-infrared optical transmission is observed, corresponding to the breaking of Cooper pairs. These results have implications for thin-film superconducting transmission lines carrying short electrical pulses.         New two-fluid superconduction model applied to penetration depth and microwave surface resistance    G.F. Dionne Summary: A two-fluid theory of superconductivity derived from an analysis of covalent interactions in the polaronic high-T/sub c/ cuprates is used to predict the penetration depth of YBa/sub 2/Cu/sub 3/O/sub 7/ as a function of temperature. In a related study, the model is applied to the temperature dependence of microwave surface resistance measurements on both YBa/sub 2/Cu/sub 3/O/sub 7/ and Nb films. The results suggest that polaronic cuprates can be superconducting with a much smaller fraction of available carriers than metals. It therefore follows that superconduction would survive to higher temperatures than in metals. If supercarrier populations are governed by Boltzmann tails as proposed in this model, however, the lower carrier densities in high-T/sub c/ materials would become even smaller as temperatures approach the critical limit.         Impurity pinning in epitaxial YBa/sub 2/(Cu/sub 1-x/TM/sub x/)/sub 3/O/sub 7- delta / (TM=Zn, Ni)-thin films    C. Tome-Rosa, M. Schmitt, A. Walkenhorst, T. Kluge, M. Speckmann, P. Wagner and H. Adrian Summary: The dependence of resistive transitions, thermal activation energies, and critical current densities of YBa/sub 2/(Cu/sub 1-x/Zn/sub x/)/sub x/O/sub 7- delta / and YBa/sub 2/(Cu/sub 1-x/Ni/sub x/)/sub 3/O/sub 7-x/- thin films on B, T, and the angle Theta between the magnetic field and the c-axis is studied. A decrease of the critical temperature T/sub c/ with increasing doping concentration x is observed. For small x an increase of the activation energy is found, with a maximum around 0.2%. This can be explained by a model assuming local pinning potentials due to the impurity atoms, which begin to overlap for higher concentrations. The films exhibit higher j/sub c/ values for small dopant concentrations than without doping. If the angle Theta is changed, a different j/sub c/(B, T, Theta ) behavior is found than in high-quality undoped films, with additional structures in the curves.         Characterization of thin film composite mixtures of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-y/ and Y/sub 2/Ba/sub 1/Cu/sub 1/O/sub 5/    P.R. Broussard, V.C. Cestone, L.H. Allen and S.A. Wolf Summary: Thin-film samples composed of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-y/ (123) and Y/sub 2/Ba/sub 1/Cu/sub 1/O/sub 5/ (211) have been prepared by off-axis sputtering from separate targets of 123 and 211 material. X-ray diffraction studies of the films show the presence of c-axis-oriented 123, but no indication of ordered 211 lines. The c-axis lattice constant does not show any change compared to the pure 123 films. As the volume percentage of 211 material increases, a reduction in T/sub c/ and J/sub c/ and an increase in the resistivity are seen. The temperature and field dependence of the critical current are different for the composites than for the pure 123 films.         Concerning factors which determine whether flux-lattice shear or pin breaking limits the critical current density of superconductors    D.O. Welch Summary: An elementary model that illustrates the conditions under which flux-lattice shear, rather than pin breaking, limits the critical current density is presented. An expression for the shear strength of the flux-lattice, based on the plasticity of metals and alloys, is used to derive the critical current density, including the effect of thermal activation in the flux creep regime. Expressions are also derived for the flow stress and dislocation density of the flux-line lattice (FLL) and are combined to yield the magnetic-field- and temperature-dependent critical current density in the absence of thermal activated flux creep. The rate theory of plastic deformation is used to derive the electric-field vs. current-density relation and J/sub c/ to be expected when thermally activated processes make the dominant contribution to FLL shear.         Transport properties across high-angle bicrystals of melt-textured YBa/sub 2/Cu/sub 3/O/sub 6+x/    M.B. Field, X.Y. Cai, S.E. Babcock and D.C. Larbalestier Summary: The transport properties of eight individual bicrystals in melt-textured YBa/sub 2/Cu/sub 3/O/sub 6+x/ were investigated in low and high fields at 4 K and 77 K. Bicrystals were cut from samples produced by the melt texture process with 10% and 20% added Y/sub 2/BaCuO/sub 5/. Misorientations between the crystals were determined by pole figure analysis, backscatter channeling patterns and light microscopy. The bicrystals exhibited a wide range of misorientations in both the ab planes and c-axis direction and all boundaries were high angle. Contrary to many reported expectations for melt-textured materials, all of the grain boundaries were weakly coupled. However, the strength of the coupling varied with misorientation angle and a weaker field dependence of J/sub c/ was observed in the samples with lower misorientation angle and lower grain boundary resistivity.         A comparison of twin boundary pinning in nearly fully stoichiometric and oxygen deficient YBa/sub 2/Cu/sub 3/O/sub 7- delta/    S. Fleshler, W.K. Kwok, U. Welp, J. Downey and G.W. Crabtree Summary: The angular dependence of the magnetoresistance was measured on the same single crystal of YBa/sub 2/Cu/sub 3/O/sub 7- delta / prepared initially with a superconducting transition temperature of 93 K and then annealed to obtain a transition temperature of 56.9 K. A second oxygen deficient sample was produced with a transition temperature of 57.0 K and nearly identical transport characteristics. Twin boundary pinning superimposed on flux flow behavior was observed in both the 56.9 K and 93.0 K states for magnetic field rotation in the ab plane. For magnetic field rotations off the c-axis, twin boundary pinning is observed only for the nearly stoichiometric state. The broadening of the resistive transition in magnetic field (H//c) is observed to occur over a much larger interval of reduced temperature in the deoxygenated state. The enhanced broadening of the resistive transition in magnetic field and absence of twin boundary pinning may indicate that the vortex system is two-dimensional, and, in general, defects are rendered ineffective in pinning due to the absence of three-dimensional collective elastic effects.         The angular dependence of the critical current density of textured YBaCuO    T.L. Francavilla, M.M. Miller, R.J. Soulen Jr., V. Selvamanickam and K. Salama Summary: Highly textured bulk YBaCuO samples consisting of dense highly oriented platelets were prepared by a liquid phase process. Critical current density measurements at 77 K and at 6 T were made as the angle between the transport current and the externally applied magnetic field was varied in the ab-plane. At all times, the c-axis was perpendicular to both the DC transport current and the external magnetic field. The critical current density values were found to achieve a maximum of 7000 A/cm/sup 2/ when the magnetic field was parallel to the transport current and a minimum of 2000 A/cm/sup 2/ when the magnetic field was close to an orientation perpendicular to the transport current, with one notable exception: a small increase to approximately 3000 A/cm/sup 2/ from the minimum value of 2000 A/cm/sup 2/ was observed when the magnetic field was perpendicular to the transport current. Ignoring this exception, the angular variation of critical current density is qualitatively consistent with the variation expected from the Lorentz force acting upon the vortices.         Enhancements of the critical currents of YBaCuO single crystals by neutron (n) and proton (p) irradiation    B.M. Vlcek, M.C. Frischherz, H.K. Vishwanathan, U. Welp, G.W. Crabtree and M.A. Kirk Summary: The results of magnetization hysteresis and T/sub c/ measurements on neutron- and proton-irradiated YBaCuO single crystals are presented. The crystals used for comparison were irradiated to a fluence of 2*10/sup 17/ n/cm/sup 2/ (E>0.1 MeV) and 1*10/sup 16/ p/cm/sup 2/ (E=3.5 MeV). The critical currents at 1 T and 10 K are enhanced by a factor of five for the neutron-irradiated and a factor of nine for the proton-irradiated samples. After irradiation the crystals were annealed at 100, 200 and 300 degrees C for 8 h each in air. Following each annealing step the critical temperature and the magnetization hysteresis at 10 and 70 K were measured. Upon annealing, a decrease of the critical currents, which is more pronounced for the proton irradiated sample, is observed. This decrease is related to the removal of point defects or their small clusters. Thus, their contribution to pinning can be studied. The critical temperature decreases after both types of irradiation by about 0.5 K and is fully recovered after annealing.         Critical current enhancement in YBa/sub 2/Cu/sub 3/O/sub 7- delta / single crystal by 200 MeV proton irradiation    Q. Qiang, M.J. Kramer, D.K. Finnemore and C.L. Snead Jr. Summary: Radiation damage studies have been carried out using a beam of 200-MeV protons directed along the two major symmetry directions of YBa/sub 2/Cu/sub 3/O/sub 7- delta /. These beams create rather light damage tracks along their path, usually of single ion displacements. Strong pinning then depends on a line of pinning sites parallel to the vortex core. For radiation parallel to the ab-plane, relatively small doses greatly enhance the critical currents parallel to the c-axis and a strong anisotropy is observed depending on the direction of the vortices relative to the damage tracks. In the limit of high dose, 10/sup 16/ protons/cm/sup 2/, the damage is so uniform that the anisotropy effects are less pronounced.         Effect of ion-vacancies and partial element substitutions on flux pinning in YBa/sub 2/Cu/sub 3/O/sub 7- delta /    Zhengkuan Jiao, Minghu Fang, Jonghen Li, Gangjin Hu and Qirui Zhang Summary: It is found that at 77 K the existence of Y, Ba, Cu and O vacancies enhances the flux pinning in varying degrees, and among them the vacancies have the highest enhancement of flux pinning. The Ba existence of Cu vacancies only improves the flux pinning under lower field. The pinning effect resulting from partial substitutions of rare earth elements with various atomic radii and magnetic moments for Y in Y/sub 1-x/M/sub x/Ba/sub 2/Cu/sub 3/O/sub 7- delta / (M=Gd, Eu, Sm) is also studied. The results show that the pinning strength increases with increasing the atomic radius of M, and the magnetic moment seems absent. These defects sometimes have different behaviors in higher fields than in lower fields. Possible pinning mechanisms are discussed.         Overview on the recent progress on Chevrel phases and the impact on the development of PbMo/sub 6/S/sub 8/ wires    M. Decroux, P. Selvam, J. Cors, B. Seeber, O. Fischer, R. Chevrel, P. Rabiller and M. Sergent Summary: The critical current density J/sub c/ of PbMo/sub 6/S/sub 8/ (PMS) wires has not reached a value required for industrial applications. However, large intragrain J/sub c/ has been observed, indicating that the grain connections play a dominant role in the J/sub c/ limitation. This behavior is similar to that of high-T/sub c/ oxides, where this limitation is thought to have an intrinsic origin related to their extremely short coherence lengths. But the coherence length of PMS lies between those of conventional superconductors and high-T/sub c/ materials. Therefore, it has been argued that an intrinsic granularity behavior is not expected for PMS and that the observed tendency towards granularity has another origin. Recent results on the phase stability, a possible structural transition, and the degradation of the grain boundaries of PMS point to different possible origins for the J/sub c/ limitation. A critical analysis of these investigations is presented, and their impact on the performance of wires is discussed.         In-plane texturing control of Y-Ba-Cu-O thin films on polycrystalline substrates by ion-beam-modified intermediate buffer layers    Y. Iijima, K. Onabe, N. Futaki, N. Tanabe, N. Sadakata, O. Kohno and Y. Ikeno Summary: Biaxially aligned YBCO thin films were successfully formed on polycrystalline Ni-based alloy by using ion-beam-modified yttria-stabilized-zirconia (YSZ) intermediate layers. YSZ layers were deposited by ion-beam-assisted deposition (IBAD) with concurrent off-axis ion beam bombardment. The YSZ (100) axis was oriented normal to the substrate, and a YSZ (111) axis was aligned to the bombarding ion beam axis. Explicit in-plane ordering was achieved on polycrystalline metallic substrates without epitaxial relationships. C-axis-oriented YBCO thin films were grown on those buffer layers, with controlled in-plane a- and b-axes, by pulsed laser deposition. At 77 K 0 T and at 77 K, 0.6 T, 4.3*10/sup 5/ A/cm/sup 2/ and 1.1*10/sup 5/ A/cm/sup 2/ were achieved, respectively.         In situ growth and properties of epitaxial TlBa/sub 2/CaCu/sub 2/O/sub 7/ and TlBa/sub 2/(Ca/sub 1-x/Y/sub x/)Cu/sub 2/O/sub 7/ thin films    D.W. Face and J.P. Nestlerode Summary: Epitaxial TlBa/sub 2/CaCu/sub 2/O/sub 7/ thin films have been grown on single-crystal LaAlO/sub 3/, NdGaO/sub 3/, and CeO/sub 2/ buffered sapphire substrates by in situ off-axis magnetron sputtering in the presence of Tl/sub 2/O vapor. Phase formation in this system has been investigated for substrate temperatures from 490 degrees C to 600 degrees C and deposition pressures from 50 mTorr to 300 mTorr. The effect of Tl/sub 2/O evaporation rate has also been studied. X-ray diffraction shows that films deposited under optimum conditions are highly epitaxial with the c-axis perpendicular to the substrate surface and (100) TlBa/sub 2/CaCu/sub 2/O/sub 7/ aligned with pseudo-cubic (100) NdGaO/sub 3/ and LaAlO/sub 3/. Film surfaces are also smooth to within several unit cells ( approximately 40 AA). The effect of 20% and 40% Y substitution for Ca has also been explored. TlBa/sub 2/(Ca/sub 0.6/Y/sub 0.4/)Cu/sub 2/O/sub 7/ films have T/sub c/'s up to 71 K, whereas TlBa/sub 2/(Ca/sub 0.8/Y/sub 0.2/)Cu/sub 2/O/sub 7/ films have T/sub c/'s up to 91 K. In situ TlBa/sub 2/(Ca/sub 0.6/Y/sub 0.4/)Cu/sub 2/O/sub 7/ films grown on CeO/sub 2/ buffered sapphire are comparable to those on LaAlO/sub 3/ and NdGaO/sub 3/.         The effects of added gases in the sputter deposition of YBa/sub 2/Cu/sub 3/O/sub 7/ thin films    E.J. Cukauskas, G.K. Sherrill, L.H. Allen and R.T. Holm Summary: YBa/sub 2/Cu/sub 3/O/sub 7/ thin films have been deposited on MgO substrates by off-axis magnetron sputtering in argon, oxygen, and an additional gas. Additions of nitrogen, hydrogen, methane, air, and water vapor in amounts of up to 25% were used in this investigation. Each gas stabilized the target voltage and growth rate for the duration of the deposition. Growth rates improved by over 50% with as little as 3% hydrogen. When used with a target which had degraded after more than 150 h of use, the added gas improved T/sub c/ and J/sub c/ beyond levels attained from the new target. T/sub c/ increased from 82 K without hydrogen to 89 K with hydrogen and J/sub c/ (12 K) from 3*10/sup 4/ to >7*10/sup 6/ A/cm/sup 2/. Nitrogen yielded less dramatic effects. These improvements are attributed to the catalytic effect of these gases in maintaining elevated levels of atomic oxygen during film growth.         MBE synthesis of YBa/sub 2/Cu/sub 3/O/sub y/ superconducting thin films    V.C. Matijasevic, H.M. Appelboom, F. Mathu, P. Hadley, D. van der Marel and J.E. Mooij Summary: Issues concerning molecular beam epitaxy (MBE) of the superconductor YBa/sub 2/Cu/sub 3/O/sub y/ are discussed. Films have been prepared by MBE at low pressures using molecular oxygen and ozone. A minimum incidence rate of each of these species for synthesis of YBa/sub 2/Cu/sub 3/O/sub y/ is established and compared with the thermodynamic stability data and lower kinetic limits. For ozone, the lower limit appears to be determined by the growth rate. The best films that are made at low pressures (less than 10/sup -2/ mbar of oxygen or with ozone) have, in general, slightly lower transition temperatures and expanded c-axes, but still sharp transitions and high critical currents. Cation disorder is suggested as a likely explanation for these properties. The model for solubility of Ba on the Y sites is discussed and found to be consistent with experimental results.         Pulsed laser deposition of novel HTS multilayers for passive and active device applications    D.B. Chrisey, J.S. Horwitz, J.M. Pond, K.R. Carrol, P. Lubitz, K.S. Grabowski, R.E. Leuchtner, C.A. Carosella and C.V. Vittoria Summary: Multilayered structures have been fabricated from binary combinations of the high-T/sub c/ superconductor YBa/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO) and the ferrite BaFe/sub 12/O/sub 19/ (BFO) or the ferroelectric Sr/sub 0.5/Ba/sub 0.5/TiO/sub 3/ (SBT). The combination of YBCO and BFO was found to destroy the superconductivity of the YBCO layer. Vibrating sample magnetometer measurements of the BFO layer still indicated a large uniaxial anisotropy. The underlying YBCO layer of an SBT/YBCO bilayer still had high quality transport properties unaffected by the SBT layer (T/sub c/ approximately 91 K. J/sub c/(77 K) approximately 2*10/sup 6/ A/cm/sup 2/). A thin-film, normal metal/SBT transmission line, patterned in microstrip, demonstrated a wealth of temperature and electric field dependent dielectric information for the frequency range tested (f         Critical current anisotropy and flux pinning in YBCO [001] and YBCO [110] superconducting thin films prepared by KrF pulsed laser ablation    J.Y. Juang, K.H. Wu, S.J. Wang, T.C. Lai, R.T. Kao, C.L. Wu, T.M. Uen and Y.S. Gou Summary: Direct transport critical current density (J/sub c/) measurements were performed on laser-ablated high-quality Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/ superconducting thin films with T/sub co/>or=90 K, J/sub c/ approximately=5*10/sup 6/ A/cm/sup 2/ at 77 K, and intentionally controlled film orientations to investigate the J/sub c/ anisotropy and predominant pinning mechanisms in these films. It was found that, for films with [001] oriented normal to the substrate, the field dependencies of the critical current densities J/sub c/(H) showed very different behavior for different field orientations, indicating that the active pinning mechanisms may be different in two field directions. For [110]-oriented films with field applied normal to the film surface, the pinning mechanism was found to follow the manifestation of surface-core pinning. At zero field, however, the temperature dependence of J/sub c/ revealed that, in all cases, the critical current was limited by flux creep with essentially the same creep kinetic factor expected for high-T/sub c/ cuprates. Detailed results on the scaling behaviors of the pinning force density as functions of both field and temperatures for fields up to 7 T are presented and compared for different films and field orientations.         Magnetic-field angle dependence of the critical current density in high-quality Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ thin films    H. Yamasaki, K. Endo, S. Kosaka, M. Umeda, S. Misawa, S. Yoshida and K. Kajimura Summary: Critical current densities, J/sub c/, have been investigated in as-deposited Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ thin films with c-axis orientation, which were prepared by metalorganic chemical vapor deposition (MOCVD). One of these films showed record high J/sub c/ values for Bi-oxide thin films: 1.3*10/sup 10/ A/m/sup 2/ at 70 K; 10/sup 11/ A/m/sup 2/ at 30 K. Almost-field-independent J/sub c/ was observed in the magnetic fields applied parallel to the film surface (a-b plane) in a wide temperature range (         Tunneling studies in Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+x/    A.M. Cucolo, R. Di Leo, A. Nigro and F.S. Razavi Summary: Planar tunnel junctions have been realized on liquid-etched Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+x/ (BSCCO) single crystals with natural barriers and Pb, Pb-Bi, Au counterelectrodes. At T=4.2 K and I-V characteristics of these junctions often show multiple switches that disappear at the T/sub c/ of the BSCCO compound. The dV/dI vs. V curves show gaplike structures at about +or-22 mV and second features at about +or-40 mV. These are very similar to the double structure observed in YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) junctions. The background resistance above the gaplike features is flat in the majority of the junctions, while about 20% of the junctions show decreasing resistance with bias. For Pb and PbBi counterelectrodes, negligible leakage currents at low temperatures indicate good quality tunnel barriers, continuous and pin-hole free. The phonon structures of these materials indicate a single-step tunneling process. The behavior of the zero-bias resistance dip observed in some junctions is discussed.         Effects of deposition conditions on stoichiometry of off-axis RF sputtered BiSrCaCuO thin films    Y.F. Yang, J.E. Nordman and J.U. Lee Summary: The composition of as-grown BiSrCaCuO superconducting thin films has been investigated as a function of the RF magnetron sputtering variables, i.e. total sputtering pressure, substrate temperature, and oxygen partial pressure in an off-axis configuration. This study shows that use of off-axis geometry alone is insufficient to completely overcome the resputtering problem due to energetic particle bombardment on the substrate. The bismuth loss in the sputtered films at low sputtering pressure and copper loss at high pressure, both of which were aggravated at increasing temperatures, were observed. The mechanisms of thermally enhanced resputtering and gas scattering effects at high pressure are proposed to interpret the discrepancy between target and film composition.         An XPS study of as-grown superconducting Bi-Sr-Ca-Cu-O thin film with Tc/sub 0/ of 98 K    K. Ohbayashi, H. Matsushita, K. Yoshida, M. Anma, Y. Takai and H. Hayakawa Summary: As-grown highly oriented BiSrCaCuO 2223 single-phase films were prepared by three-target RF magnetron sputtering with a regulated shuttering technique. Using this technique, 2223 films (700 AA) were deposited on the 2201 buffer layer (70 AA) prepared on an MgO (100) substrate at 765 degrees C. The highest critical temperature of the as-grown films was 98 K (zero-resistivity). The value of the critical temperature strictly depended on the Bi content of the film. Films with various critical temperatures from 98 K to 66 K were prepared by changing the Bi content. The Bi 4f core level electron spectra are decomposed into two components. These components are assigned to BiO and to Bi/sub 2/O/sub 3/, which is located at an energy higher than the peak of BiO by about 1 eV. The critical temperature of the film increased with a decrease in the Bi mean valence. It was empirically determined that the critical temperature can be controlled by the Bi mean valence, and changes irrespective of the number of Cu-O planes.         Potential of NdCeCuO thin films for electronic applications    A. Kussmaul, P.M. Tedrow and A. Gupta Summary: Films of NdCeCuO with high crystalline quality (channeling yield of 6%) were deposited on the low-loss material LaAlO/sub 3/, making it possible to measure the microwave surface losses at 18.29 GHz. An encouraging value of 1 m Omega was found at 4.2 K. The T/sub c/ is still lower than on SrTiO/sub 3/, but this is attributed to the fact that the deposition parameters have not yet been explored as systematically as for SrTiO/sub 3/. The deposition on artificial SrTiO/sub 3/ bicrystals yields grain boundaries with nonlinear I-V characteristics. The dynamic conductance looks similar to that observed on tunnel junctions of other high-T/sub c/ compounds, suggesting that quasiparticle tunneling is taking place for high-angle grain boundaries.         Oxidation and reduction during fabrication of high quality Nd/sub 1.85/Ce/sub 0.15/CuO/sub 4-y/ superconducting thin films    S.N. Mao, X.X. Xi, S. Bhattacharya, Q. Li, J.L. Peng, J. Mao, D.H. Wu, S.M. Anlage, R.L. Greene and T. Venkatesan Summary: Using pulsed-laser deposition and N/sub 2/O reactive gas, the authors have fabricated very high quality c-axis n-type Nd/sub 1.85/Ce/sub 0.15/CuO/sub 4-y/ (NCCO) oxide epitaxial superconducting thin films on different substrates. The film shows a superconducting transition temperature T/sub c/ (R=0 Omega ) of 22.4 K and a transition width of 0.2 K from AC susceptibility measurements. The critical current density J/sub c/ is 8*10/sup 5/ A/cm/sup 2/ at 4.2 K in zero magnetic field. The microwave surface resistance measured at 9.6 GHz shows a value of 3 m Omega at 4.2 K in 500-nm-thick NCCO film, the best result reported so far for NCCO thin films. The oxygen deficiency is necessary to achieve the superconductivity in NCCO, and the oxygen reduction during and after film deposition is critical. The oxidation and reduction processes are studied systematically for various substrate temperatures, atmospheres, and annealing durations.         Superconducting Ba/sub 1-x/K/sub x/BiO/sub 3/ thin film by in-situ sputtering    R. Hu, A.E. Lee, H.W. Chan and C.L. Pettiette-Hall Summary: Superconducting Ba/sub 1-x/K/sub x/BiO/sub 3/ thin films with T/sub c/ (R=0) as high as 29.2 K have been grown using off-axis RF magnetron sputtering. Films are routinely deposited with zero resistance between 25 K and 29 K. High pressure during deposition is considered to be responsible for higher-T/sub c/ films. The films grow epitaxially with (100) orientation on (100) SrTiO/sub 3/ substrates. Superconducting Ba/sub 1-x/K/sub x/BiO/sub 3/ films have also been deposited on YBa/sub 2/Cu/sub 3/O/sub 7-x/ films.         Thin film Ba/sub 0.6/K/sub 0.4/BiO/sub 3/ microwave devices    R.A. Schweinfurth, D.J. Van Harlingen, J. Kruse, J. Laskar, M. Feng, C.E. Platt and M.R. Teepe Summary: Microwave structures utilizing superconducting thin films of Ba/sub 0.6/K/sub 0.4/BiO/sub 3/ (BKBO) have been fabricated and tested. A high-quality BKBO thin film (T/sub c/>28 K, J/sub c/>1 MA/cm/sup 2/) grown by pulsed laser deposition on a (100) MgO substrate was patterned into a resonator and coplanar transmission line. The 2.5-mm coplanar transmission line had an insertion loss of -2.1 dB at 20 GHz and 21 K. The resonator showed an unloaded Q (quality factor) of 230 at 15 K and 15.8 GHz. It was only possible to infer that the surface impedance (R/sub s/)         Deposition of barium potassium bismuth oxide (BKBO) thin films by laser ablation    R.C. Lacoe, J.P. Wendt and P.M. Adams Summary: High-transition-temperature barium potassium bismuth oxide (BKBO) thin films have been deposited by pulsed-laser ablation. The best results were obtained by ablating from a potassium-rich single target in a pure argon background onto [100] SrTiO/sub 3/ substrates. Films with superconducting onset and zero-resistance temperatures of 28.5 and 27.5 K, respectively, were routinely obtained, with room-temperature resistivity as low as 250 mu Omega -cm. X-ray diffraction analysis showed the films were single crystal and epitaxially oriented in the [100] direction. X-ray rocking curves of the BKBO [200] reflection revealed a full width at half maximum of approximately 0.7 degrees Delta theta and indicated that the BKBO [100] lattice direction was misoriented with respect to that of the SrTiO/sub 3/ substrate by 0.13 degrees .         Artificial barriers for Ba-K-Bi-O tunnel junctions    B.A. Baumert and J. Talvacchio Summary: The authors have grown epitaxial bilayers and trilayers which utilize Ba/sub 1-x/K/sub x/BiO/sub 3/ (BKBO) base electrodes, native or artificial (MgO or SrTiO/sub 3/) insulating barriers, and Ag or BKBO counterelectrodes, respectively. The layers were deposited in situ by RF magnetron sputtering and characterized in situ. Electron diffraction showed the layers to be epitaxial with the symmetry of the desired structure maintained even in the first monolayer at the surface. X-ray photoelectron spectroscopy (XPS) showed no evidence of a chemical reaction at the BKBO/barrier interfaces. Tunneling measurements through a native insulating layer grown by exposing BKBO surfaces to air showed a gap of approximately 25 mV to be present. In the range of thicknesses used for artificial barriers, 3-6 nm, the barriers apparently contained pin holes which caused the junctions to short. The BKBO films were K-rich with x approximately=0.5. Critical temperatures and lattice constants were consistent with reports for bulk superconductors with this composition. Normal-state resistivities of 70-100 mu Omega -cm at 30 K were the lowest ever reported in this system.         Preparation of infinite-layer structural (Sr, Nd)CuO/sub y/ thin films    M. Ichikawa, N. Sugii, K. Kubo, K. Yamamoto and H. Yamauchi Summary: Sr/sub 1-x/Nd/sub x/CuO/sub y/ thin films were grown by both RF magnetron sputtering and laser ablation on SrTiO/sub 3/ (100) substrates. The crystallographic properties of films were investigated by X-ray diffraction (XRD) and transmission electron spectroscopy (TEM). The sputter-deposited films formed an infinite-layer structure whose lattice parameters were a=0.392 nm and c=0.347 nm. The films with x<0.05 were nearly single phase. However, the films with x>or=0.05 were multiphase, containing an infinite-layer structure and another complex structure. All the films were semiconductive and did not exhibit superconductivity. The laser-ablated films with x         The role of Sn addition on the improvement of J/sub c/ in PbMo/sub 6/S/sub 8/    P. Selvam, D. Cattani, J. Cors, M. Decroux, P. Niedermann, O. Fischer, R. Chevrel and T. Pech Summary: The influence of Sn on the enhancement of critical current densities, J/sub c/, in bulk samples of PbMo/sub 6/S/sub 8/ has been systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Auger electron spectroscopy (AES), AC susceptibility, and specific heat experiments. The results indicate that the addition of Sn, as an adjunction (dopant) or as a substitution, has a considerable effect on the structural, superconducting, microstructural and grain boundary properties. The observed increase in J/sub c/ is discussed in terms of improved interconnectivity between the grains, better homogeneity of the samples, and, more importantly, lower grain boundary contamination.         Interpretation of magnetization measurement data obtained on hot pressed Pb/sub 1-x/Sn/sub x/Mo/sub 6/S/sub 8/ samples    T. Pech, J. Cors, M. Decroux, P. Selvam and R. Chevrel Summary: Magnetization measurements have been carried out on samples prepared with varied Sn contents, using constant parallel applied field sweep rates in the range of 30 to 190 mT/s. The hysteresis loops observed up to about 6 T at 4.2 K are earmarked by characteristic flux jump phenomena. J/sub c/ critical current densities deduced from the loop widths can be interpreted, in agreement with the fine analyses of the loops, in terms of global critical screening currents, related to very good connectivity between the grains.         Grain size dependence of critical current densities in hot isostatically pressed SnMo/sub 6/S/sub 8/    L.A. Bonney, T.C. Willis and D.C. Larbalestier Summary: The dependence of critical current density on the heat treatment and microstructure of SnMo/sub 6/S/sub 8/ was systematically studied. Powders with minimal initial oxygen contamination were processed by hot isostatic pressing at 800 degrees C to produce a sample having a mid-point inductive critical temperature of 14.2 K, a magnetization critical current density of 820 A/mm/sup 2/ (9 T, 4.2 K) and electromagnetically nongranular behavior. The microstructure was controlled by varying subsequent heat-treatment temperature and time and was examined by scanning and transmission electron microscopies. In each sample grains appeared well connected and ranged over two orders of magnitude in size, with average grain sizes being between 0.2 and 0.5 mu m. Critical current density decreased with increasing annealing temperature and time and at fields <8 T was inversely proportional to the grain size. These results show that Chevrel phase materials are not intrinsically weakly coupled and that grain boundaries are sites of Abrikosov vortex pinning.         Scanned probe microscopy of YBa/sub 2/Cu/sub 3/O/sub x/ thin-film device structures on Si substrates    J. Moreland, T.E. Harvey, R.H. Ono and A. Roshko Summary: Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) have been used to image YBa/sub 2/Cu/sub 3/O/sub x/ (YBCO) films grown on yttria stabilized zirconia (YSZ) buffer layers on Si substrates. The effects of deposition and patterning conditions on device topography and performance are being investigated. Evidence is found for pinhole formation in YSZ buffer layers and microcracking in the YBCO films. AFM images of 0.25- mu m-wide YBCO lines on Si made using electron-beam lithography and ion milling are presented.         Influence of deposition parameters on properties of laser ablated YBa/sub 2/Cu/sub 3/O/sub 7- delta / films    A. Roshko, D.A. Rudman, L.R. Vale, L.F. Goodrich, J. Moreland and H.L. Beck Summary: YBa/sub 2/Cu/sub 3/O/sub 7- delta / films have been laser ablated, under a variety of conditions, onto four different substrate materials. Using scanning tunneling microscopy it was observed that the films grow by an island nucleation and growth mechanism. The properties of the films were studied as functions of the deposition conditions. Films on LaAlO/sub 3/ had the best and most reproducible properties. The superconducting transition temperatures of films deposited on LaAlO/sub 3/ proved to be fairly insensitive to the substrate temperature during deposition; T/sub c/'s>90 K were obtained for films deposited over a temperature range from 760 degrees C to 850 degrees C. The oxygen partial pressure during the deposition had a large effect on the transition temperature; the highest T/sub c/'s were obtained for films deposited in 26.7-Pa (200-mTorr) oxygen. Measurements of transport critical current indicate that films deposited at lower temperatures are less sensitive to magnetic fields, suggesting that they may contain more defects which act as flux pinning sites.         In-situ RHEED studies of YBCO-film growth during pulsed laser deposition    H. Karl and B. Stritzker Summary: In-situ reflection high-energy electron diffraction (RHEED) measurements during laser ablation of YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) on SrTiO/sub 3/[100], [305] and on SrTiO/sub 3/[100] misoriented 2 degrees and 3 degrees towards [110] were performed. The specularly reflected electron intensity oscillation is modulated by the laser pulse deposition frequency. The crystallization of the deposited material is directly monitored by an exponential intensity rise of the specular intensity. From the time constant the critical laser repetition frequency can be estimated. Oscillations were not observed during the growth on 3 degrees vicinal SrTiO/sub 3/[100] and on SrTiO/sub 3/[305] substrates. For these substrates well-aligned steps parallel to the [100] direction exist due to growth by step movement. From this a mean diffusion length between 7.5 nm and 11 nm at 720 degrees C was determined.         In-situ RHEED-TRAXS analysis during the preparation of YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films    Y. Aoki, M. Kamei, S. Ogota, T. Usui and T. Morishita Summary: Reflection high-energy electron diffraction (RHEED) with total-reflection-angle X-ray spectroscopy (TRAXS) has been applied to the chemical and structure analysis during preparation of YB/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) films. The characteristic X-rays of YL alpha , BaL alpha , and CuK alpha emitted even from 0.8-AA-thick YBCO were clearly observed by TRAXS. In addition, the surface sensitivity of this method was found to be comparable to or higher than that of Auger electron spectroscopy. From the RHEED observation, it was revealed that the lattice spacing drastically changes from 4.09 AA to 3.8 AA at a mean thickness of less than one unit cell of YBCO at the early growth stage.         A method to determine the crystallographic perfection of superconducting epitaxial films    A.S. Kovalev and A.N. Obraztsov Summary: The anisotropy of polarized light reflection in the spectral range 1-3 eV, as well as Raman scattering spectra, have been investigated for YBa/sub 2/Cu/sub 3/O/sub 7-x/ films deposited by laser ablation. Large areas (up to 1 mm) with reflectance anisotropy equal to that of untwinned single crystal were revealed. The existence of large untwinned areas on high-temperature epitaxial films was shown by this method.         Predicted absorptance of YBa/sub 2/Cu/sub 3/O/sub 7//YSZ/Si multilayer structures for infrared detectors    Z.M. Zhang and M.I. Flik Summary: High-T/sub c/ superconducting YBa/sub 2/Cu/sub 3/O/sub 7/ films deposited on silicon substrates with yttria-stabilized-zirconia (YSZ) buffer layers have significant potential for radiation detectors. The infrared absorptance of a YBa/sub 2/Cu/sub 3/O/sub 7//YSZ/Si multilayer structure, which strongly influences the detector performance and depends on the layer thicknesses, is analyzed here. The electromagnetic field inside the layers is determined based on the Maxwell equations and the optical constants of these materials. The film thicknesses yielding maximum absorptance are obtained for different wavelengths. The spatial distribution of power flux is determined by integrating the Poynting vector over a finite spectral region. The analytical method presented in this study is recommended for the radiative design of high-T/sub c/ superconducting detectors based on absorbing multilayer structures.         The resistive hotspot and voltage-current characteristics in thin Y-Ba-Cu-O films    A.S. Fix, I.L. Maksimov, K.V. Morozov and V.V. Osipov Summary: Current-voltage characteristics of thin Y-Ba-Cu-O films have been investigated. The power-law dependence in the lower voltage region observed from 77 K to 92 K and for H         Electron transport and magnetic penetration depth in niobium-silicon multilayers    G.K. Sherrill, E.J. Cukauskas and L.H. Allen Summary: Thin niobium-silicon multilayers have been sputtered with niobium thicknesses less than the coherence length and silicon thicknesses that allow tunneling between layers. The multilayer structure has been confirmed by X-ray diffraction, and the films have been electrically characterized with respect to T/sub c/ and J/sub c/. For constant Nb thickness, both T/sub c/ and J/sub c/ increase with decreasing Si thickness, indicating increased coupling between the Nb layers. When a multilayer forms the barrier in a tunnel structure, the resulting I(V) characteristic resembles that for a series of single-barrier junctions, and further evidence of Nb interlayer coupling is observed. These multilayers have also been incorporated as the base in several tunnel structures in order to measure the multilayer penetration depth via the magnetic field dependence of I/sub c/. Preliminary results indicate that the theoretically predicted enhancement of penetration depth in a multilayer does occur.         Properties of multilayer films of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ and composites of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x//LaAlO/sub 3/    L.H. Allen, G.K. Sherrill, R.T. Holm and E.J. Cukauskas Summary: Multilayer films of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ with composites of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ and LaAlO/sub 3/ have been grown on (100) LaAlO/sub 3/ substrates by co-sputtering. Inductive and resistive T/sub c/'s have been measured for multilayers with various amounts of LaAlO/sub 3/ in the composite layers and for multilayers with different composite layer thicknesses. T/sub c/'s generally drop as the amount of LaAlO/sub 3/ in the composite layer increases or the thickness of the composite layer increases. J/sub c/'s of these films have values below those for single-layer composite films grown on MgO substrates, but this can be accounted for by the introduction of grain boundaries into the films from substrate twinning. Initial photoresponse measurements were also made and have magnitudes comparable to the single-layer YBCO/LAO composite films.         Very high critical current densities in YBa/sub 2/Cu/sub 3/O/sub 7- delta //Nd/sub 1.83/Ce/sub 0.17/CuO/sub x/ superlattices    A. Beck, D. Koelle, L. Alff, K.-D. Husemann and R. Gross Summary: The critical current density of YBa/sub 2/Cu/sub 3/O/sub 7- delta //Nd/sub 1.83/Ce/sub 0.17/CuO/sub x/ (Y/Nd) superlattices grown heteroepitaxially by hollow cathode magnetron sputtering was measured in magnetic fields perpendicular and parallel to the c-axis. The thickness d/sub Y/ and d/sub Nd/ of the individual Y and Nd layers ranged between 50 and 400 AA. In superlattices with modulation periods below a critical wavelength Lambda /sub c/=450 AA the Y layers are coherently strained, whereas in those with modulation periods above Lambda /sub c/ the coherency strain starts to relax, resulting in the formation of a high density of misfit dislocations. Very high zero field critical current densities up to 1.1*10/sup 7/ A/cm/sup 2/ were observed for multilayers with a modulation period just above Lambda /sub c/. For B perpendicular to the c-axis, the critical current density J/sub c perpendicular to / is almost independent at B up to a certain field ( approximately=2 T for d/sub y/=100 AA) that corresponds to the lower critical field of the Y layers. J/sub c perpendicular to / values as high as 2*10/sup 6/ A/cm/sup 2/ were obtained for B=1 T and T=77 K. The angular dependence J/sub c/( phi ) is determined solely by the magnetic field component parallel to the c-axis demonstrating the two-dimensional nature of the superlattices.         Superconductivity of YBa/sub 2/Cu/sub 3/O/sub 7//PrBa/sub 2/Cu/sub 3/O/sub 7/-superlattices    G. Jakob, M. Schmitt, T. Hahn, C. Stolzel, T. Kluge and H. Adrian Summary: The preparation of heterostructures is a precondition for a large variety of high-T/sub c/ thin film devices. As a simple model system for high-T/sub c/ thin-film devices, the authors studied YBa/sub 2/Cu/sub 3/O/sub 7//PrBa/sub 2/Cu/sub 3/O/sub 7/-superlattices. High-quality superlattices show satellite peaks up to the 9/sup th/ order in X-ray diffraction diagrams. From comparison of the X-ray data with theoretical simulations the maximum amount of disorder and interdiffusion are deduced. Transmission electron microscopy (TEM) investigations of the films confirm the high degree of structural order. From resistive transition curves the authors determined thermal activation energies. The Arrhenius-plots are linear down to T/T/sub c/<0.5. From the dependence of the measured resistive and critical current on the angle between the magnetic field and the c-axis of the film, a two-dimensional behavior of the system is deduced. Even superlattices with a modulation Y:Pr=10:1 behave in this manner up to temperatures of 0.9 T/sub c/.         Field-cooled magnetization of YBa/sub 2/Cu/sub 3/O/sub y//PrBa/sub 2/Cu/sub 3/O/sub y/ layered structures    H. Obara, S. Kosaka, A. Eguchi, A. Sawa and Y. Kimura Summary: Using molecular beam epitaxy (MBE) with pure ozone, YBa/sub 2/Cu/sub 3/O/sub y//PrBa/sub 2/Cu/sub 3/O/sub y/ (YBCO/PBCO) layered structures (multilayers) have been fabricated successfully. Differential pumping was used, making a stable rate of evaporation and the effective oxidation of films possible. The films were characterized using X-ray diffraction (XRD) spectra, in situ X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Magnetization measurements were used to observe the dynamics of flux in superconductors. The magnetization properties of the layered structure depended on the thickness of YBCO and PBCO layers. The intrinsic properties of the multilayers, such as the coupling effect of YBCO layers, were observed using field-cooled magnetization measurements. The correlation between the two dimensionality and the flux dynamics of these multilayers is discussed.         Persistent magnetic flux and mapping of intergranular junctions in melt textured YBa/sub 2/Cu/sub 3/O/sub 7/    V. Gomis, D. Castello, I. Catalan, B. Martinez, J. Fontcuberta, A. Fuertes and X. Obradors Summary: Melt-textured superconductors have been prepared with a microstructure characterized by large domains having misaligned growth fronts. An RF mutual inductance microprobe has been developed to identify and characterize the weak-link behavior of the high-angle grain boundaries separating the domains. The mechanisms of flux penetration and trapping in a single-domain sample have been analyzed in a H/sub //c/ configuration at low temperature, 25 K, where J/sub c/ is essentially field independent. A consistent description of flux penetration, isothermal remanence and magnetic hysteresis is reached in the framework of the Bean model. The small value of the lower critical field deduced from this analysis suggests that the Bean-Livingston surface barriers are strongly reduced in melt-textured ceramics as compared to single crystals.         Substrate temperature measurement for growth of large-area high-T/sub c/ superconducting films    B.I. Choi, M.I. Flik and A.C. Anderson Summary: The substrate temperature has been measured and controlled by an adaptively calibrated pyrometer during the YBa/sub 2/Cu/sub 3/O/sub 7/ film deposition process. The experimental results show that a feedback control system based on this pyrometer can maintain the substrate temperature accurately at a set value. Thermal problems associated with the fabrication of multilayer structures are discussed. The study demonstrates accurate substrate temperature measurement and control for large-area film growth, facilitating the fabrication of high-quality superconducting electronic devices.         AC impedance measurements of two-dimensional superconductors    Y. Jaccard, R. Theron, B. Jeanneret, R. Meyer, C. Leemann and P. Martinoli Summary: The superconducting transition of two-dimensional systems is accurately characterized with a two-coil mutual inductance technique. A knowledge of the normal state sheet resistance R/sub N/ is necessary to incorporate the effect of eddy currents above the transition temperature. It is shown that, when carefully done, these measurements allow a determination of the real part of the impedance from R/sub N/ down to 10/sup -5/ R/sub N/, provided R/sub N/ is not exceedingly large.         Local critical current measurements on (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ tape with an electromagnetic probe    K.L. Telschow, T.K. O'Brien, M.T. Lanagan and D.Y. Kaufman Summary: The use of induced currents from a small noncontacting electromagnetic probe to determine the critical current density in a (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x//Ag tape on a local scale is described. The technique forces full field penetration into the tape locally and infers the critical current density from the Bean critical state model, accounting for the Ag overlayers. Critical current images of the tape can be obtained by scanning the probe over the tape surface with spatial resolution on the order of 1.0 mm. Results for tapes with different microstructures are discussed.         Growth of CaO precipitates in superconducting Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8+ delta /    M. Xu, J. Polonka, A.I. Goldman, D.K. Finnemore and S. McKernan Summary: Crystallization studies of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8+ delta / have been undertaken in order to explore the possibility of growing large oriented grains of this superconductor so that they contain a fine dispersion of tiny CaO precipitates. At low oxygen partial pressure, CaO forms preferentially over the alkaline earth cuprates and it is found to be the dominant precipitate when there is excess Ca. Hot stage environmental electron microscopy and in-situ high temperature X-ray studies have been used as the primary diagnostic tools to determine the best conditions for the growth of this fine dispersion. Because CaO is cubic, it forms equiaxed precipitates with diameters in the range of 1 to 3 mu m.         On the evolution of phases in polycrystalline Li-doped 2212 BSCCO and enhanced superconducting behaviour via n(Li, alpha )T reactions    J. Schwartz, S. Wu, G.W. Raban Jr. and J.C. Rynes Summary: The authors report on the evolution of phases upon cooling of partially melted Bi-Sr-Ca-Cu-Li-O powders and tapes and on enhanced magnetic flux-pinning through irradiation. Enhanced resistive transitions have been obtained despite significant amounts of (Sr/sub 1- delta /, Ca/sub delta /)/sub n/CuO/sub x/ phases (n=1 or 2). The evolution of phases is investigated in Li-doped and undoped 2212 via extensive microstructural characterizations. To enhance the flux-pinning, Li-doped and undoped 2212 have been neutron irradiated. In addition to the neutron-collision-induced damage, fission reactions produce a homogeneous distribution of high- and low-energy charged particles. Effects of irradiation on the magnetically measured T/sub c/ and J/sub c.m/(H) are reported. Differences between the effects upon doped and undoped superconducting powders are discussed, highlighting the effects of the charged particle damage.         Large shaped parts of melt cast BSCCO for applications in electrical engineering    J. Bock, H. Bestgen, S. Elschner and E. Preisler Summary: A melt casting process (MCP) that is tailor made for BSCCO, especially for the 2212 phase, is described. It is reported that melt casting offers an easy access to a variety of different shapes and sizes. The properties of the material obtained by MCP have been significantly improved by admixing strontium sulphate. J/sub c/ values superior to those of sintered ceramics of YBCO or BSCCO have been obtained: J/sub c/ values at 55000 A/cm/sup 2/ (4 K) and 2200 A/cm/sup 2/ (77 K) were achieved without external fields; large bulk parts exhibited more than 2000 A (77 K) in their self-field. The peculiarities of MCP allow the integration of noble metal current contacts which exhibit total resistances         Growth of BSCCO and YBCO single crystals using large temperature gradients    G. Yang, S. Sutton, P. Shang, C.E. Gough and J.S. Abell Summary: A large temperature-gradient technique for growing BSCCO single crystals is reported. For comparison, the growth of YBCO single crystals using the same technique is also reported. BSCCO crystals grown using different cooling rates have been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical microscopy. It is found that the cooling-rate must be related to the crystal growth-rate to obtain good quality crystals. The growth mechanism and resulting growth steps, dislocation networks, transition temperature and anomalous magnetization are discussed.         Grain-aligned YBCO superconducting current leads for conduction-cooled applications    K.G. Herd, B. Dorri, E.T. Laskaris, J.E. Tkaczyk and K.W. Lay Summary: Grain-aligned YBCO superconductors have been developed for use in a conduction-cooled, cryogen-free superconducting magnet application. A magnetic alignment technique has been used to orient the c-axis of the YBCO grains. Current leads 0.3*1.4*6.4 cm were fabricated and thermally connected between the first and second stage of a Gifford-McMahon cryocooler. The heat conduction down the leads was determined from a load map of the cryocooler. With operating temperatures of 40 K on the first stage and 10 K on the second stage, the measured heat leak was 0.15 W/lead. The YBCO current leads were used to power a conduction-cooled Nb/sub 3/Sn magnet at 10 K to 250 A. Test results for the YBCO leads are reported.         Anomalous magnetisation of YBCO and BSCCO single crystals    G. Yang, J.S. Abell and C.E. Gough Summary: Anomalous magnetization characteristics of YBa/sub 2/Cu/sub 3/O/sub y/ and Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ single crystals and their oxygen vacancy dependences are reported. In these crystals the magnetization exhibits a maximum as a function of the applied field. Significant differences in the anomalous magnetization of the YBCO and BSCCO crystals indicate different origins. Several possible explanations are compared with experimental results. Two kinds of pinning centers with different T/sub c/'s could explain the anomalous magnetization of YBCO, while 2-D pancake vortices matching a 2-D defect structure may account for the BSCCO results.         The effects of heavy-ion irradiation on superconductivity in YBa/sub 2/Cu/sub 3/O/sub 7/ epitaxial films    R.C. Budhani, Y. Zhu and M. Suenaga Summary: The authors report a comparative study of superconducting behavior of YBa/sub 2/Cu/sub 3/O/sub 7/ epitaxial films irradiated with Ag and Au ions of several hundred megaelectronvolt energy. The irradiation results in columnar defects of average diameter approximately 55 AA and approximately 110 AA for Ag/sup +21/ and Au/sup +24/ ions, respectively. A universal linear scaling is observed between the fractional areal damage vs. the superconducting transition temperature and normal state resistivity. The results also show that in these films, which have intrinsically strong pinning, a marginal enhancement in the critical current density (J/sub c/) occurs when the defect density is         Continued improvement of large area, in situ sputter deposition of superconducting YBCO thin films    J.K. Truman, W.R. White, P.H. Ballentine, D.S. Mallory and A.M. Kadin Summary: The deposition of thin films of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ onto substrates of up to 3-in diameter by an integrated off-axis sputtering is reported. The substrate is located above the center of an 8-in-diameter YBCO planar target, and, in conjunction with a negative ion shield, negative ion effects are avoided. A large radiant heater provides backside, noncontact heating of the bare substrates. YBCO films have been grown on polished 1-cm/sup 2/ MgO and LaAlO/sub 3/ substrates with T/sub c/>or=90 K, J/sub c/>or=2.5*10/sup 6/ A/cm/sup 2/ at 77 K, and microwave surface resistance R/sub S/<0.4 m Omega at 77 K and 10 GHz. The films have a very smooth surface morphology. Uniformity data for LaAlO/sub 3/ substrates are less than +or-5% in R/sub s/. Thickness uniformity results for 3-in substrates indicate less than 10% variation. The growth of epitaxial insulating films for use with YBCO films and application of the YBCO films in microwave devices are briefly discussed.         High performance superconducting thin films on large area substrates    A. Lauder, C. Wilker, D.J. Kountz, W.L. Holstein and D.W. Face Summary: The first fabrication of 3-in-diameter, thin films of thallium-based superconductors is reported. (Tl/sub 0.5/Pb/sub 0.5/)Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 9/ thin films on LaAlO/sub 3/ are found to display the best surface resistance (R/sub s/) properties of any superconductor at higher temperatures and show approximately 50* better performance than copper at 100 K and 10 GHz. A Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ thin film, processed as a 1.8-m-long, 10- mu m-wide meander line carries about 1*10/sup 7/ A/cm/sup 2/ at 4.2 K and 2*10/sup 6/ A/cm/sup 2/ at 80 K. The thallium-based superconductors are compared to YBa/sub 2/Cu/sub 3/O/sub 7/ with respect to T/sub c/, R/sub s/, and Q.         Improved on-axis DC magnetron sputtering for large-area deposition of YBa/sub 2/Cu/sub 3/O/sub 7/-films    U. Kruger, R. Kutzner and R. Wordenweber Summary: A method of stabilizing the plasma during high-pressure DC sputter-deposition of YBa/sub 2/Cu/sub 3/O/sub 7/ is introduced. The plasma is monitored by optical emission spectroscopy and Langmuir probes. Strong changes of the plasma intensity and intensity profile above the target, which lead to unstable and inhomogeneous deposition of high-T/sub c/ material, can be observed. These changes are counteracted by an adequate variation of the process gas composition (Ar-O/sub 2/ mixture) at the target. The intensity of the plasma flicker is thus reduced by a factor of 4-5, and long-term drifts in the plasma intensity are eliminated. By this method a stable, reproducible and uniform deposition of epitaxial, c-axis-oriented YBa/sub 2/Cu/sub 3/O/sub 7/-films with extremely smooth surfaces over a 2-in wafer area was achieved.         Characteristics of high J/sub c/ Y-Ba-Cu-O tape on metal substrate prepared by chemical vapor deposition    S. Aoki, T. Yamaguchi, Y. Iijima, O. Kohno, S. Nagaya and T. Inoue Summary: With the goal of utilizing oxide superconductors as long wires in electric power applications, high-critical current density (J/sub c/) YBaCuO (YBCO) thin film was prepared on metal substrate with a good buffer at 700 degrees C by chemical vapor deposition (CVD). The best YBCO film on in-plane-aligned yttria-stabilized zirconia (YSZ(100)) buffer had a critical temperature (T/sub c/) above 90 K and J/sub c/ of 7.1*10/sup 4/ A/cm/sup 2/ (77.3 K, 0 T) and 3.0*10/sup 3/ A/cm/sup 2/ (77.3 K, 7 T). A new CVD system has been developed for rapid formation of the long YBCO tapes. It has a continuous powder vaporizer and a long substrate conveyer. One-meter-long homogeneous YBCO tapes have been obtained on Hastelloy C-276 with a YSZ buffer. The tapes had T/sub c/ of 84 K and J/sub c/ of 330 A/cm/sup 2/ (77.3 K, 0 T).         Assessment of thick film YBCO for flux transformer and magnetic screening applications    C.M. Muirhead, F. Wellhofer, T.W. Button and N.McN. Alford Summary: Measurements on the flux creep properties of a series of thick-film YBCO tubes and rings that have been processed at a range of different temperatures are reported, and their potential for use in large-area flux transformers and shields for superconducting quantum interference device (SQUID) magnetometers is considered. It is found that films showing flux creep rates adequate for flux transformer or low-field ( approximately 100- mu T) magnetic shielding applications can be made without recourse to special doping or heat treatment techniques. Application of flux creep theory to the data and observations of the microstructure in similar films implies that the scale over which the supercurrents are flowing is on the order of tens of mm and that this would place a lower limit on fabrication accuracy. For screening the earth's magnetic field, the films reported here would be adequate; for higher fields, thicker or multiple shields may by required.         Continuous melt processing of YBCO thick films on zirconia rods    T.B. Holt, C.R.M. Grovenor, T.W. Button, N.M. Alford and D. Dew-Hughes Summary: Studies of 50- mu m-thick films of YBa/sub 2/Cu/sup 3/O/sub 7- delta / on yttria-stabilized zirconia rods, which have been melt-processed using an infrared furnace, are reported. The results indicate that J/sub c/'s higher than the 3000 A/cm/sup 2/ achieved so far are not impossible. Transport and magnetization results suggest that the increase in J/sub c/ is due to alignment of the grains along the axis of the rod. This is confirmed by the scanning electron microscopy photographs, which show an increase in grain size and alignment.         Partial melt processing of magnetically-aligned YBa/sub 2/Cu/sub 3/O/sub 7- delta / thick films    J.A. Lewis, T. Suratwala and K.C. Arndt Summary: Textured YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thick films were fabricated in the green state by casting particulate-based suspensions in an applied magnetic field (7 T) at ambient temperature. These films, along with nonaligned films, were fired to various temperatures above the peritectic temperature ( approximately= 1020 degrees C) to evaluate the effects of partial melt processing on their microstructural development and performance properties. The degree of domain alignment in the fired films was measured by X-ray diffraction (XRD) analysis. This showed that the aligned films had a high degree of c-axis texture. Examination by scanning electron microscopy (SEM) revealed distinct differences in both the film density and texture development between aligned and nonaligned films. The magnetic properties of each film were measured at 5 K using a superconducting quantum interference device (SQUID) magnetometer (5.5 T maximum field). These measurements indicated that a high degree of anisotropy was present only in the partial melt processed aligned YBCO films.         Alignment of high-T/sub c/ superconductor Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub z/ thick film in magnetic field    Young Cheol Kim, Seok Kil Han, Hyung Kook Kim and Min Su Jang Summary: High-T/sub c/ superconducting thick films were prepared using a method combining grain shape alignment and low magnetic field alignment. The superconducting films with a thickness of about 100 mu m exhibiting T/sub c/(zero) higher than 90 K were successfully obtained. X-ray diffraction data showed the thick Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub z/ film having grain alignment. The orientation along the c-axis is pronounced with an increase in the heat-treatment temperature and time in magnetic field.         Microwave properties of double-sided YBa/sub 2/Cu/sub 3/O/sub 7- delta/ thin films deposited by metalorganic chemical vapor deposition    H.S. Newman and W.J. DeSisto Summary: High-quality thin films of YBa/sub 2/Cu/sub 3/O/sub 7- delta / have been deposited by metalorganic chemical vapor deposition on both sides of 15-mm*15-mm <100> LaAlO/sub 3/ substrates without requiring the use of heat-sinking compounds. Typical transport data exhibited T/sub c/'s >87 K, transition widths <1 K, and J/sub c/'s >10/sup 6/ A/cm/sup 2/ (measured inductively at 77 K, 0 T). Microwave surface resistance measurements (36.4 GHz) at temperatures between 20 K and 100 K, made using a copper-cavity end-wall-replacement technique, showed a sharp drop through the transition temperature and yielded values at 77 K that were better than a 20* improvement over copper metal when scaled to 10 GHz. Double-sided coatings have been obtained by sequentially depositing each side of the substrate. Contamination of the backside during growth of the first-side film and of the first-side film during growth of the second-side film has been avoided by coating the susceptor with gold.         A novel microstrip-compatible technique for depositing YBa/sub 2/Cu/sub 3/O/sub 7- delta / on both surfaces of a substrate    J.M. Pond, K.R. Carroll, D.B. Chrisey, J.S. Horwitz and V.C. Cestone Summary: A technique for the deposition of YBa/sub 2/Cu/sub 3/O/sub 7- delta / on both the top and bottom surfaces of a substrate by pulsed laser deposition is reported. This approach employs a metallic buffer layer to protect the first YBa/sub 2/Cu/sub 3/O/sub 7- delta / film while the second film is deposited. It is particularly applicable to microstrip-based circuit topologies where the ground plane conductor requires minimal patterning. The performance of microstrip ring resonators, fabricated by this technique, is substantially better than can be achieved with microstrip ring resonators which consist of a superconducting ring and a normal-conductor ground plane. This approach allows the deposition of YBa/sub 2/Cu/sub 3/O/sub 7- delta / on both sides of the substrate without the need for radiative heating schemes and can accommodate any size and shape of substrate.         Microwave resonances with partially untwinned YBCO films near 10 GHz    A. Vogt, R. Herwig, P. Marienhoff, M. Neuhaus, T. Scherer and W. Jutzi Summary: Partially untwinned YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) films on twin-free NdGaO/sub 3/-substrates have been fabricated by off-axis sputtering. The ratio of the a- and b-axis DC resistances is on the same order as untwinned crystals. The film DC resistances values differ by less than a factor of two from those of untwinned crystals. The surface resistance in the a- and b-direction near 10 GHz has been measured with only one parallel plate resonator of rectangular area. The anisotropy ratio of the surface resistance at 4.2 K is on the order of 1.9. The b-axis surface resistance at 10 GHz and 4.2 K is about 25 mu Omega .         Surface impedance measurements of YBa/sub 2/Cu/sub 3/O/sub 7/ thin films using coplanar resonators    A. Porch, M.J. Lancaster, R.G. Humphreys and N.G. Chew Summary: The microwave response of linear and meander coplanar resonators fabricated from patterned thin films of YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) on MgO substrates was studied. Unloaded quality factors in excess of 45000 at 2.36 GHz and 12 K were measured. From the calculated microwave current distribution in the resonator, upper limits of the intrinsic surface resistance of the best film at 15.9 GHz of 150 mu Omega and 690 mu Omega at 12 K and 77 K, respectively, were obtained. Values of the magnetic penetration depth lambda (0) in the films were estimated to be in the range 165-220 nm. It is possible to accurately fit 1/ lambda (T)/sup 2/ to the function 1-(T/T/sub c/)/sup 2/ over the whole of the available temperature range. This behavior is unlike that predicted by BCS theory, but it is probably extrinsic and can be explained by the enhanced field penetration at the film edges due to superconducting weak links.         Microwave properties of bulk and thick film YBCO    B.A. Tonkin and Y.G. Proykova Summary: The surface impedance of bulk polycrystalline and melt-processed thick film YBCO specimens has been measured using a TE/sub 0mn/ resonant cavity endwall-replacement technique over the frequency range 9-18 GHz and the temperature range 10-200 K. A comparison between the two forms of the material confirms the superiority of the thick film at 77 K, but, because of large residual losses associated with the thick film, the bulk polycrystalline material is better below 50 K. Intrinsic behavior has been observed within a limited temperature range and comparison made with the Pippard and BCS expressions.         YBCO thin films for microwave applications by post-annealing at low oxygen partial pressure with F monitoring    A. Mogro-Campero, L.G. Turner, A.M. Kadin and D.S. Mallory Summary: YBa/sub 2/Cu/sub 3/O/sub 7/ thin films postannealed at low oxygen partial pressure are shown to exhibit improved properties compared to equivalent samples postannealed in 1 atm of oxygen. The magnetic penetration depth of these films has been measured and is shown to be a factor of 2 lower at low temperatures for the samples postannealed at low oxygen partial pressure, consistent with the lower value of surface resistance found for these samples. It is also shown that the eddy-current response at megahertz frequencies can be used as a rapid qualitative test to select samples with good microwave properties.         On microwave properties of high-T/sub c/ oxides    A. Andreone and V.S. Kresin Summary: The surface resistance of the high-T/sub c/ oxides in the low temperature region is studied. The dependence of the losses on the mean free path is evaluated. The peculiar microwave properties of YBa/sub 2/Cu/sub 3/O/sub 7-x/ are explained in the framework of the two-gap model.         GdBa/sub 2/Cu/sub 3/O/sub x/ for microwave applications: preparation, properties and devices    D. Jedamzik, T.P. Trowles, S.J. Zammattio, R.E. Stephan, K. Lamacraft, W.A. Phillips, S.J. Hedges, M. Adams and B.F. Nicholson Summary: GdBa/sub 2/Cu/sub 3/O/sub 7/, which has very similar properties to YBa/sub 2/Cu/sub 3/O/sub 7/ but appears to be more tolerant of processing conditions, is studied. Thin films have been prepared by inverted cylindrical magnetron sputtering on MgO single crystals and routinely give transition temperatures above 92 K and critical currents above 10/sup 6/ A/cm/sup -2/ at 77 K. Films with areas exceeding 12 cm/sup 2/ have been fabricated on 0.5-mm-thick substrates. Structural and compositional studies show a high degree of film perfection. Measurements of surface resistance, using a cavity endwall replacement technique at 60 GHz, give values <20 m Omega at 77 K (uncorrected for film thickness. typically 0.4-0.5 mu m) and suspended substrate stripline resonators give Q values over an order of magnitude larger than the corresponding gold resonator. A 2% 4-GHz filter has been realized in microstrip with a minimum insertion loss below 0.6 dB.         Transmittance of YBa/sub 2/Cu/sub 3/O/sub 7/ thin films in the millimeter wave region    M. Hangyo, T. Nagashima, N. Nagasaki, S. Nakashima, H. Enami and Y. Murakami Summary: Temperature dependence of the transmittance of YBa/sub 2/Cu/sub 3/O/sub 7/ films on MgO substrates has been measured in the frequency range of 75-110 GHz. The transmittance was analyzed by taking account of the multiple reflection in the YBa/sub 2/Cu/sub 3/O/sub 7/ and MgO layers. Linear increase of the transmittance with temperature in the normal phase was explained by the Drude model, in which parameters (plasma frequency, relaxation time) obtained from the far-infrared measurements were used. The transmittance below T/sub c/ was analyzed by using the two-fluid model. Less steep increase of the transmittance above 50 K in the superconducting phase indicates that considerable amount of normal carriers exist even at temperatures sufficiently below T/sub c/.         Growth and characterization of YBCO/insulator/YBCO trilayers    N. Missert, C.D. Reintsema, J.A. Beall, T.E. Harvey, R.H. Ono, D.A. Rudman, D. Galt and J.C. Price Summary: Multilevel circuits for high-frequency applications of high-T/sub c/ superconductors require low-dielectric-constant insulators between superconducting layers. Initial studies of CeO/sub 2/ thin films as the insulating layer in YBCO/insulator/YBCO structures revealed insufficient isolation between YBCO layers. Trilayer structures employing thin-film composite dielectrics of CeO/sub 2/ and SrTiO/sub 3/ were therefore investigated. Each layer grows epitaxially with a morphology comparable to that of a single YBCO film. Transport critical current density measurements of the top YBCO layer resulted in J/sub c/=2*10/sup 5/ A/cm/sup 2/ at 77 K, a factor of 10 lower than for single films. Trilayer structures had a microwave surface resistance at 10 GHz and 4 K of 50 mu Omega , comparable to that of single films. Preliminary low-temperature measurements of the dielectric constant of composite insulator structures gave values an order of magnitude lower than for pure SrTiO/sub 3/.         Potential of polycrystalline YBCO layers for applications    M. Hein, F. Hill, G. Muller, H. Piel, H.P. Schneider and M. Strupp Summary: The granular properties of polycrystalline YBCO layers are characterized by their surface impedance, Z/sub s/, measured as a function of temperature, frequency and magnetic field. A model for Z/sub s/, based on grain-boundaries acting as resistively and inductively shunted Josephson junctions, is used for a conclusive analysis of the field sensitivity of Z/sub s/ and of the frequency dependence of the surface resistance. It is shown that reducing the granular character of polycrystalline samples leads to a lower absolute level and to a stronger frequency dependence of R/sub s/. As a result, the frequency-dependent improvement r=R/sub s/(Cu)/R/sub s/(YBCO), as well as the frequency at which r=1, can be increased.         Processing, electrical and microwave properties of sputtered Tl-Ca-Ba-Cu-O superconducting thin films    G. Subramanyam, V.J. Kapoor, C.M. Chorey and K.B. Bhasin Summary: A reproducible fabrication process has been established for TlCaBaCuO thin films on LaAlO/sub 3/ substrates by RF magnetron sputtering and post-deposition processing methods. Electrical transport properties of the thin films were measured on patterned four-probe test devices. Microwave properties of the films were obtained from unloaded Q measurements of all-superconducting ring resonators. This paper describes the processing, electrical and microwave properties of Tl/sub 2/Ca/sub 1/Ba/sub 2/Cu/sub 2/O/sub x/ (2122) phase thin films.         Synthesis and microwave characterisation of DC sputtered Tl-Ba-Ca-Cu-O thin films    S.M. Morley, A.P. Jenkins, L.Y. Su, M.J. Adams, D. Dew-Hughes and C.R.M. Grovenor Summary: Single- and double-sided superconducting Tl-Ba-Ca-Cu-O thin films (2- mu m thick) have been prepared on MgO (100) and LaAlO/sub 3/ (100) substrates by DC sputtering followed by a two-step anneal process. Films produced have T/sub c/ between 90 and 110 K with transport critical current densities typically 10/sup 3/ to 10/sup 5/ A/cm/sup -2/. Surface resistance (R/sub s/) measurements at 50 GHz and 60 GHz over the temperature range 18-200 K have been made using a TE/sub 01/ mode cavity end wall replacement technique giving R/sub s/ of 380 m Omega at 50 GHz and 77 K. Preliminary results for patterned resonator structures show an improvement in Q over silver at 3.2 GHz and 77 K.         Microwave response of Bi- and Tl-oxide superconductors    J.D. Chern, A. Guldeste, H.C. Lai, S. Aslam, D.H.T. Wu, D. Dew-Hughes, M.J. Goringe, C.R.M. Grovenor and B. Minokovic Summary: The measurement of the nonbolometric microwave response of a superconducting film may provide a method of detecting the coexistence of different phases of the film. Experimental results suggest that increased granularity of a film leads to a larger nonbolometric effect. The main mechanism of the nonbolometric microwave response is thought to be due to the interaction between microwave radiation and the intergranular weak links in the film.         Niobium and niobium-titanium nitrides for RF applications    P. Fabbricatore, G. Gemme, R. Musenich, R. Parodi, M. Viviani, B. Zhang and V. Buscaglia Summary: The application of niobium and niobium-titanium nitrides in RF devices is studied. Nitride samples, prepared by diffusion of nitrogen in bulk niobium and alloy, have been characterized by X-ray diffraction, SEM and AC magnetic measurements. Several phases of niobium nitride have been observed: the phase with higher nitrogen content, at the sample surface, has critical temperature about 15 K but inclusions of both lower T/sub c/ and nonsuperconducting phases enhance the RF surface resistance. The niobium-titanium nitride surface is composed by a phase having critical temperature up to 17 K and unwanted phases were not observed.         Surface resistance of epitaxial and polycrystalline NbCN films in submillimeter wave region    S. Kohjiro, S. Kiryu and A. Shoji Summary: Surface resistances, R/sub s/'s, of epitaxial and polycrystalline NbCN films in submillimeter-wave region were evaluated from measurements of Fiske-resonant modes in Josephson tunnel junctions. It is found that epitaxial NbCN films have about one order of magnitude smaller R/sub s/ values than those for polycrystalline NbCN films. It is also found that the frequency dependence of R/sub s/ of epitaxial and polycrystalline NbCN films can be explained by the two-fluid model.         Author Index (1992 - Part 2)    No author information available Summary: Not available

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