THE EFFECT OF SHEATH MATERIAL AND DEFORMATION METHOD ON THE OXIDE CORE DENSITY, FILAMENT UNIFORMITY, AND CRITICAL CURRENT DENSITY OF (Bi,Pb)2Sr2Ca2Cu3Ox TAPES

Many variables control the critical current density (Jc ) in BSCCO-2223 composites but not all of them are yet well understood, or even positively identified. One important factor is reported to be the density of the BSCCO filament, as measured by microhardness. Since different deformation processes may be used during fabrication, and each can have a different effect on the final BSCCO core density, we have made systematic investigations of the microhardness, filament uniformity, and final Jc as a function of sheath hardness and whether the tape is rolled or pressed between heat treatments. Results show a strong correlation between the after-heat-treatment-microhardness and Jc. Rolled tapes never achieved the hardness of pressed tapes, and their Jc was correspondingly lower. The degree of transformation of the BSCCO powder to the BSCCO-2223 phase was always lower in the rolled tapes than in the pressed tapes.