ENHANCEMENT OF TRANSPORT CURRENT DENSITY IN YBA2CU3O7-X SUPERCONDUCTORS USING DUAL-TEMPERATURE EXTRUSION PROCESSING

TREMENDOUS EXCITEMENT AND INTEREST HAS BEEN GENERATED IN RECENT MONTHS OVER THE DISCOVERY OF THE YBA(2)CU(3)O(7-X) (123) LIQUID NITROGEN SUPERCONDUCTORS. HOWEVER, THIS EXCITEMENT HAS BEEN TEMPERED BY THE INABILITY TO ACHIEVE LARGE TRANSPORT CURRENT DENSITIES (J(C)S) IN BULK-PROCESSED POLYCRYSTALLINE MATERIALS BECAUSE OF 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 CRITICAL TEMPERATURE SUPERCONDUCTORS. IN THIS PROJECT THE 123 POWDERS WILL BE PROCESSED AVOIDING THE PRESENCE OF A NON-SUPERCONDUCTING BACUO(2)-CUO EUTECTIC, WITH A MELTING TEMPERATURE OF ABOUT 900 DEGREES CENTIGRADE, AND DUAL-TEMPERATURE EXTRUSION TECHNIQUES WILL BE USED TO COLD WORK AND DENSIFY THE POWDERS. INITIAL EXPERIMENTS SHOW ENCOURAGING RESULTS, GIVING CERAMIC FIBERS WITH 90% GREEN DENSITY.