Sponsored by: Jt. EMPMD/SMD Superconducting Materials Committee, MSD Electronic, Magnetic and Optical Phenomena Committee, and FEMS (Federation of European Materials Societies)
Program Organizers: U. Balachandran, Energy Technology Division, Argonne National Laboratory, Argonne, IL 60439; Paul J. McGinn, University of Notre Dame, Notre Dame, IN 46556; and Stuart Abell, University of Birmingham, Edgbaston, Birmingham B152TT, UK
Tuesday, AM Room: B7
February 6, 1996 Location: Anaheim Convention Center
Session Chairpersons: D. J. Miller, Argonne National Laboratory, Argonne, IL 60439; V. Selvamanickam, Intermagnetics General Corporation, Latham, NY 12110
8:30 am
PROCESSING OF Tl-1223 TAPES BY PARTIAL MELTING: J. C. Moore, S. Fox, D. Hyland, D. Dew-Hughes, C. R. M. Grovenor, Dept. of Materials, Oxford Univ., Parks Road, Oxford, OX1 3PH, United Kingdom; Oxford Univ., Oxford, OX1 3PJ, UK
In common with several other groups, we have shown that it is quite simple to prepare Tl-1223 tapes carrying critical current densities of 1-2.104 A/cm2, but that in only very modest magnetic fields (0.1 T) at 77 K the Jc drops by a factor of about 20-50. We have also shown that by using a carefully controlled partial melting process it is possible to increase the grain size in the 1223 core by a factor of 100, and to achieve much improved field tolerance. This paper will describe the chemical reactions that occur inside the core during the melting and re-annealing processes in Bi- and Pb- substituted 1223, and report on the best current carrying properties.
8:50 am
PREPARATION AND PROPERTIES OF Ag(Au)-SHEATHED Tl(1223) TAPES: R. E. Gladyshevskii, A. Perin, B. Hensel, and R. Flükiger, Departement de Physique de la Matiere Condensee, 24, quai Ernest-Ansermet, 1211 Genève 4, Switzerland
Superconducting (Tl,Pb,Bi)(Sr,Ba)2Ca2Cu3O9- tapes were produced by the powder-in-tube technique from either a pre-reacted Tl(1223) powder or a mixture of precursors in Ag-based tubes. High-purity powders (>95 wt% Tl(1223), Tc ~120 K) were prepared by reaction under high pressure (He) which avoids Tl losses, allowing a better control of the composition. A critical current density of 14 kA/cm2 (77 K, deg.2 T) was reached for Ag-sheathed tapes with pre-reacted powder. Values of 9 kA/cm2 were obtained for Ag(Au)-sheathed tapes with in-tape-reacted powder ic at 0.5 T being decreased by a factor of 16 with respect to the value at 0 T (23 for Ag-sheathed tapes). A small anisotropy of ic was introduced during the tape preparation, the ratio of the critical current densities parallel and perpendicular to the tape surface exceeding 1.7. Increasing the reaction time had a positive effect on the grain growth, but a progressive decomposition of the Tl(1223) phase was observed. Locally textured samples with up to 50 m-large plate-like grains were obtained by in-tape-reaction involving partial melting.
9:10 am Invited
OPTIMIZATION OF SUPERCONDUCTING TRANSITION TEMPERATURE IN THE Tl-2223 AND Tl-1223 PHASES VIA ADJUSTING CHEMICAL COMPOSITION AND PROCESSING: R. S. Liu, Department of Chemistry, National Taiwan University, Taipei, Taiwan, China
An efficient and highly reproducible method for the preparation of monophasic Tl-2223 and Tl-1223 materials by fine tuning the chemical compositions Tl2-xBa2Ca2+xCu3O9-, and (Tl0.5Pb0.5.)sr2-xCa2+xCu3O9- respectively, has been developed. The as-synthesized samples of x = 0.4 in both Tl2-xBa2Ca2+xCU3)O10- and (Tl0.5Pb0.5)Sr2-xCa2+xCu3O9- compositions have Tc's around 120 K and 115 K, respectively. The Tc's can be further increased up to 128 K and 124 K in both Tl2-xBa2Ca2+xCu3O10- and (Tl0.5Pb0.5)Sr2-xCa2+xCu3O9- samples, respectively, after the appropriate post-annealing process. The corresponding phase transformation and microstructure studies will be reported.
9:30 am Invited
DEVELOPMENT OF LONG LENGTH Tl-1223 CONDUCTORS: V. Selvamanickam, P. Haldar, Intermagnetics General Corp., Latham, NY 12110; E. J. Peterson, K. V. Salazaar, Los Alamos National Laboratory, Los Alamos, NM 87545
Tl-1223 superconductor is an attractive candidate for conductor applications at liquid nitrogen temperatures because of its strong flux pinning properties. Tl-1223 conductors by powder-in-tube (PIT) and thick film approaches. Thermomechanical treatments have been developed in both approaches to achieve current densities in the order of 104 A/cm2 at 77 K in short tapes (4 cm long). While densification of the core is the key factor in the achievement of high current densities in PIT tapes, development of a high friction of c-axis textured regions is one of the main factors in attaining high current densities in thick film deposits. We are investigating the scale-up of Tl-1223 conductors to long lengths (10+ m) with current densities in the range of those of short tapes. Uniform current densities in the range of 104 have been achieved in PIT tapes in lengths of several meters. Novel processing techniques have also been developed for the fabrication of thick film Tl-1223 conductors in lengths of several meters.
9:50 am Invited
PHASE ASSEMBLAGES AND TRANSIENT PHASES FOR GROWTH OF THE (Tl,Bi)-1223 SUPERCONDUCTOR: D. J. Miller, Y. S. Sung, K. C. Richter, M. T. Lanagan, Energy Technology Division; N. J. Zaluzec, Materials Science Division, Argonne National Laboratory, Argonne, IL 60439; Z. F. Ren, C. A. Wang, J. H. Wang, Dept. of Chemistry and Einstein Chair Dept., State University of New York, Buffalo, NY
Various phase assemblages and transient phases involved during the growth of (Tl,Bi)-1223 have been explored by quenching powder-in-tube as well as film samples. In particular, we have looked for evidence of fluxing liquids and explored the role of Ag in samples in which it has been added intentionally as well as samples in which Ag is introduced only during growth through the external container. Selected intermediate phases have been synthesized for additional characterization. The evolution of superconducting phases and influence of the initial and intermediate phase assemblages will be discussed. Work supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, as part of a DOE program to develop electric power technology, and Basic Energy Sciences (Materials Sciences), under Contract W31-109-Eng-38.
10:10 am BREAK
10:20 am Invited
FABRICATION OF BIAXIALLY ALIGNED POLYCRYSTALLINE HTSC CONDUCTORS: A. Goyal, D. P. Norton, E. D. Specht, D. M. Kroeger, M. Paranthaman, Q. He, J.-D. Budai, D. K. Christen, Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
Measurements of grain boundary misorientations between hundreds of contiguous grains in well-linked, high-Jc Bi-2223 powder-in-tube, Bi-2212 thick films and Tl-1223 thick films using Electron Backscatter Diffraction indicate the presence of a connected network of low energy (low angle and low sigma) boundaries. The observed grain boundary texture in the samples was used in limiting path calculations to determine the effective critical current density. Good agreement with the observed Jc was observed. These results suggest that to further increase the Jc, macroscopic biaxial texture in the superconductor is required. Several research groups have now demonstrated that ion-beam-assisted deposition (IBAD) can be used to deposit biaxially aligned ceramic buffer layers on metal substrates. Subsequent deposition of YBa2Cu3Ox results in biaxially aligned films with high-Jc's. We have developed a new method "RABIT" for fabricating biaxially textured substrates. In-plane aligned HTSC films have been grown on these substrates using several methods. Microstructure and properties of these films will be discussed. Research sponsored by U.S. Department of Energy under contract DE AC05840R21400.
10:40 am
TBCCO HTS THIN FILMS AND PASSIVE MICROWAVE DEVICES: K. Kale, A. P. Jenkins, J. D. O'Connor, D. Dew-Hughes, D. J. Edwards, Dept. of Engineering Science, Univ. of Oxford, Oxford OX1 3PJ,UK; A. P. Bramley, C. R. M. Grovenor, S. M. Morley, Dept. of Materials, Univ. of Oxford, Oxford, OX1 3PJ,UK
Thin films of Tl-based HTS have been deposited on various substrates, with and without buffer layers. A variety of microwave devices have been fabricated from such films (both single sided and double sided). These include delay lines, planar filters and low phase noise oscillators. Experimental results for such devices will be presented that demonstrate performance enhancements over similar copper implementations of the devices. In addition preliminary details will be given for the integration of these individual components into a complete microwave sub-system.
11:00 am Invited
ON THE DEVELOPMENT OF ADVANCED SENSORS TO MONITOR HIGH TEMPERATURE SUPERCONDUCTOR (HTS) MANUFACTURING PROCESSES: S. Parhasarathi, M. D. Aesoph, J. Kajuch, Concurrent Technologies Corporation Johnstown, PA 15904
Silver sheathed, ceramic HTS wire and tape manufacturing processes are currently being scaled up for long length applications. In this context there is an urgent need for improved quality management and control of these processes. The development of advanced sensing techniques for process and quality control through variuos stages of HTS manufacturing promises to reduce manufacturing costs and enhance HTS quality. Uniformity of conductor dimensions and ceramic core density are of critical importance to the inservice performance of HTS wires and tapes. This paper reports on the development of advanced sensors based on nondestructive techniques to monitor conductor dimensions and core density in HTS wires and tapes. Preliminary results from sensor testing for on-line, real-time monitoring of HTS manufacturing processes are also presented. This work was conducted by the National Center for Excellence in Metalworking Technology, operated by Concurrent Technologies Corporation, under contract to the U.S. Navy as part of the U. S. Navy Manufacturing Science and Technology Program.
11:20 am Invited
FREEZE DRYING SYNTHESIS OF HIGH Tc SUPERCONDUCTORS: O. A. Shlyakhtin, Yu. D. Tretyakov, Dept. of Chemistry, Moscow State University, 119899 Moscow, Russia
Freeze drying (FD) method has been successfully applied in the synthesis of the main groups of high Tc phases. Melt processing of FD powders to obtain dense ceramics needs special procedures to avoid encapsulation of air in micropores. The application of FD in the synthesis of melt grown composites of Y-123 and Bi-2212 with nonsuperconductive dopants allows to reduce the size of dopant particles up to submicron level. Due to easily controlled grain size, phase composition and reactivity of precursor powders FD has a good perspective in the Ag-BSCCO tapes preparation. The most effective way of FC precursors application is Tl and, especially, Hg-HTSC's preparation due to extensive porous structure of particles promoting vapour transport of volatile components.
11:40 am
MICROSTRUCTURE OF Tl-1223 TAPES PREPARED BY PIT TECHNIC: P. Diko, S. Fox, Institute of Experimental Physics, SAS, Watsonova 47, 04353 Kosice, Slovakia; J. C. Moore, C. Grovenor, M. J. Gorringe, Department of Materials, Oxford University, Parks Road, Oxford OX1 3PH, UK
The microstructure of Ag and Ag alloy sheathed Tl-1223 tapes prepared by PIT
technic was studied by polarized light microscopy. The porosity, 1223 platelet
size and alignment, secondary phase content and defects were given into the
relationship with the annealing time at 840deg.C and cold rolling thickness
reduction.
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