Microstructure and J/sub c/ improvements in overpressure processed Ag-sheathed Bi-2223 tapes

Overpressure (OP) processing influences the microstructure and critical current density (J/sub c/) of Ag sheathed Bi-2223 tapes. SEM and mass density measurements show higher core density and fewer micro-cracks in OP tape than in 1 atm tape. The self-field critical current density, J/sub c/ (0 T, 77 K) in multifilamentary tapes was increased from 33.5 kA/cm/sup 2/ with 1 atm processing (1 atm IR) to 48 kA/cm/sup 2/ with OP processing (OP pressure = 148 atm) after the first heat treatment (OP HT1), and to 58.7 kA/cm/sup 2/ with OP processing after intermediate rolling (OP IR). The corresponding values for J/sub c/ (0.1 T, 77 K) are 12.3 kA/cm/sup 2/ (1 atm IR) to 18.2 kA/cm/sup 2/ for OP HT1 and to 22.4 kA/cm/sup 2/ for OP IR.