Evolution of the microstructure in (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x//Ag wires and its influence on the critical current density

Mono- and multifilamentary (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/-wire tapes were fabricated by the oxide-powder-in-tube-technique (OPIT) using precursors which were prepared by various methods. In order to get information about the kinetics of the BiPb-2223 phase formation, the microstructure and the phase composition evolution were investigated during annealing by SEM and XRD, respectively. In addition, DTA measurements were performed on precursor powder samples. From the results, it can be concluded that in dependence on the precursor parameters, the formation of BiPb-2223 can proceed by precipitation from a partial melted system as well as by formation from preexisting BiPb-2212 crystals. The microstructure and critical current densities j/sub c/ of the tapes seem to be dependent on its mechanism of formation. Maximum j/sub c/-values of 31 kA/cm/sup 2/ (77 K, 0 T) and about 22 kA/cm/sup 2/ were measured on multifilamentary wires with a length of 5 cm and 90 m, respectively, with precursors made by aerosol spray pyrolysis.