CRITICAL-CURRENT DENSITY AND IRREVERSIBILITY BEHAVIOR IN AG-SHEATHED BI-BASED SUPERCONDUCTING WIRES FABRICATED USING A CONTROLLED MELT PROCEDURE

A phase formation-decomposition-recovery(PFDR) has been developed for fabrication of Ag/(Bi,Pb)2Sr2Ca2Cu3Oy(2223) wires which exhibit a sign ificant enhancement of the J(c). The irreversibility lines were determ ined using both AC susceptibility measurements under DC fields and mag netisation measurements. It was found that flux pinning was enhanced i n the PFDR processed samples over the normal processed samples, in par ticular at temperatures above 77 K. The PFDR process results in high m ass density, grain alignment, uniform distribution of impurity precipi tates and high density of defects. The irreversibility temperatures sc aled with the applied field according to the H-1/3, which is in contra st to H-2/3 law for YBa2Cu3O7-x and conventional superconductors. The irreversibility lines for PFDR processed tapes showed a crossover with those for normal processed tapes at temperatures below T(c) of the (B i,Pb)2Sr2CaCu2O8+x (2212) phase, suggesting that at temperatures above T(c) of the 2212 phase, the 2212 as nonsuperconducting region, may se rve as effective pinning sites for fluxoids.