EFFECT OF THERMOMECHANICAL TREATMENT ON THE CRITICAL CURRENT-DENSITY OF AG-SHEATHED B(PB)SCCO TAPES

The critical current density of Ag-sheathed Bi-Pb-Sr-Ca-Cu-O tapes was significantly improved by thermomechanical treatment. After the Ag tube filled with oxide powder was reduced in diameter by swaging, the wire was pressed and heat treated at different temperatures above 830 degrees C. The pressing and heat treatment processes were repeated. High densification and a high laminated structure have been achieved, where the c axis of elongated grains is almost parallel to the surface normal and both 2223 and 2212 phases coexist. At present the best value of the transport critical current densities obtained at 4.2 K was 2.5*105 A cm-2 at zero field and 5.3*104 A cm-2 at 10 T. For this specimen, hysteresis was still observed in the plot of magnetic field against Jc. © 1990 IOP Publishing Ltd.