The fabrication, microstructure and transport current study of BPSCCO 2223 multi-connected tapes

Abstract

The properties of BPSCCO-2223 tapes produced by the oxide powder in tube (OPIT) method with a “multi-connected” core configuration are presented. By using large silver particles (∼ 80 μm) up to 50 wt.% in the precursor BPSCCO powder, a multi-connected core with a homogeneous distribution of elongated and aligned silver platelets was obtained in the processed tapes. The samples were sintered at 832°C in air for different times with two intermediate cold-rolling processes and were characterised by transport critical current measurements at 77 K (0 T < B < 0.5 T), XRD, SEM, and optical microscopy. The effect of silver addition on the formation rate of the high-temperature BiPb(2223) phase is presented. The XRD analysis shows a saturation percentage of the BiPb(2223) phase within the core that is not affected by increased sintering time. Although the initial speed of conversion of the BiPb(2223) phase is seen to increase with increasing silver addition, the saturation percentage decreases. Local phase analysis shows a homogeneous distribution of the BiPb(2223) phase throughout the multi-connected tape, in contrast to the significant phase gradient observed in the control tapes without silver addition. For similar processing parameters, the critical current density increases with increasing silver addition ( J c = 20 kAcm −2 at 77 K ( B = 0) with 50 wt.% added Ag, compared to J c = 10 kA cm −2 without Ag).