The influence of filament size and atmosphere on the microstructure and J/sub c/ of round multifilament Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ wires

摘要

Round multifilament Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ wires having 37 and 259 filaments fabricated by the oxide-powder-in-tube method were given a step solidification partial melt heat treatment in air and oxygen atmospheres. Significant improvement in the critical current density (J/sub c/), as high as 1.65/spl times/10/sup 5/ A/cm/sup 2/ at 4.2 K zero field, was obtained for samples treated in pure oxygen versus air anneals. Moreover, as the filament size decreased the J/sub c/ increased. We discuss the development of 2212 microstructure and its dependence on filament size and heat treatment atmosphere in round multifilament 2212 wires.