Magnetic Properties and Irreversibility Behavior in Ag-Sheathed Bi-Based Superconducting Wires Fabricated Using a Controlled Melt Procedure

Abstract

A significant enhancement of the in-field Jc of Ag-clad (Bi,Pb)-Sr-Ca-C"u-O (BPSCCO:2223) wires has been achieved using a controlled melt procedure. The greatly reduced weak linking has resulted in an extended plateau regime in the Jc-H curve. Jcs of 40,000 A/cre 2 at 77 K (self field) and 9,000 A/cre 2 at 77 K (1 "lr) have been achieved. The improved Jc-H characteristics may I_e attributed to microstructures consisting of uniform grain alignment throughout the entire cross section, intimate connection between grains, impurities within the grains, and an optimal level of 6ispersed 2212 phase. Irreversibility line measurements using both AC susceptibility in DC fields (reported elsewhere), and magnetization measurements, have indicated that flux pinning can be enhanced in the melt-processed samples over the results of normal solid-state processing with its less-than optimal 2212-phase content. But sufficiently long annealing times during the "normal" route may achieve 2212-phase content and Jes which are comparable to those of melt-processed samples.