MICROSTRUCTURE AND DEFECTS IN AG-CLAD BI-PB-SR-CA-CU-O WIRES PREPARED THROUGH A CONTROLLED MELT PROCESS

Microstructure and defects in Ag-sheathed (Bi, Pb)2Sr2Ca2Cu3O10+y (2223) wires prepared through a high-T(c) phase formation-decomposition-recovery (PFDR) process have been investigated using SEM, TEM and XRD. PFDR-processed tapes contain varying percentage of highly dispersed, elongated low-T(c) (Bi, Pb)2Sr2CaCu2O8+y (2212) phase in the 2223 matrix and a variety of defects. The PFDR-processed samples contain massive interfacial dislocations with density up to 10(11) cm-2. These interfacial defects, fine precipitates and 2212 phase in the basal plane with thickness or core diameter comparable to the dimension of flux vortices are considered to be desirable pinning sites for fluxoids. For the PFDR processed wires, the normalized J(c) at 77 K and 1 T correlates the fraction of 2212 in the super-conductor core with optimal pinning within 5% to 10% of 2212 A J(c) of 40 000 A cm-2 at 77 K and 0 T and 9000 A cm-2 at 77 K and 1 T has been achieved for the PFDR-processed tapes.