Evolution of core density of Ag-clad Bi-2223 tapes during process

The porosity and its effect on critical current density J/sub c/ of Ag-clad (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ (Bi-2223) tapes throughout important steps in their thermomechanical treatment was investigated by using mass density measurement, microstructural observation, and superconducting property characterization. The relative mass density of the final filament for 19 filament tape was less than 75%, even though the J/sub c/ is /spl sim/50 kA/cm/sup 2/ (77 K, 0 T). The mass density in monofilaments reached 90%, because retrograde densification during the first heat treatment (HT1) was less or even absent. Well textured Bi-2223 grain growth could result in a significant densification during the first HT in the monofilament composite. Our results hint at considerable variability in this important property of Bi-2223 tape.