ENHANCEMENT OF TRANSPORT CURRENT DENSITY IN YBA2CU3O7-X SUPERCONDUCTORS USING LOW TEMPERATURE DENSIFICATION

THE DISCOVERY OF THE YBA(2)CU(3)O(7)-(X)(123) SUPERCONDUCTORS WITH A CRITICAL TEMPERATURE (T(C)) WELL ABOVE LIQUID NITROGEN TEMPERATURES BROUGHT THE LEVEL OF INTEREST AND EXCITEMENT IN SUPERCONDUCTIVITY TO UNPRECEDENTED HEIGHTS. UNFORTUNATELY, THE TRANSPORT CURRENT DENSITY (J(C)) OF THIS MATERIAL, ESPECIALLY IN BULK-PROCESSED POLYCRYSTALLINE POWDERS, IS NOT HIGH ENOUGH. THIS IS BELIEVED TO BE DUE TO WEAK-LINK BEHAVIOR. THESE WEAK-LINKS HAVE TWO POSSIBLE ORIGINS: FIRSTLY, THE PRESENCE OF NON-SUPERCONDUCTING PHASES AT THE GRAIN BOUNDARIES AND, SECONDLY, THE INTRINSIC ANISOTROPY OF THE SUPERCONDUCTIVITY IN THE HIGH T(C) SUPERCONDUCTORS. IN THIS RESEARCH PROJECT THE EFFECTS OF LOW TEMPERATURE DENSIFICATION PROCESSES ON THE TRANSPORT CRITICAL CURRENTS IN 123 SUPERCONDUCTING COMPOSITES WILL BE STUDIED. THE LOW TEMPERATURE DENSIFICATION PROCESSES, ROOM TEMPERATURE SWAGING, AND ROOM TEMPERATURE ROLLING, WILL ALLOW AVOIDANCE OF THE PRESENCE OF A NONSUPERCONDUCTING BACUO(2)-CUO EUTECTIC, WITH A MELTING TEMPERATURE OF APPROXIMATELY 900 DEGREES CENTIGRADE. ALSO, THE COLD WORK IN THESE PROCESSES WILL DENSIFY AND TEXTURE THE POWDERS. INITIAL EXPERIMENTS SHOW ENCOURAGING RESULTS, GIVING CERAMIC FIBERS WITH 90% GREEN DENSITY.