The effect of double stage cold rolling treatment on the microstructure and the critical current of silver clad (Bi,Pb)2Sr2Ca2Cu3Ox superconducting tapes

The transport critical current densities (Jc) of silver clad (Bi,Pb)2Sr2Ca2Cu3Ox tapes prepared by repetition of the cold rolling and the sintering processes were found to be affected by three factors: the densification and grain-alignment of the superconductor and the morphology of the superconductor-silver interface. the first two factors tended to improve Jc, but a rough superconductor-silver interface caused a non-uniform superconductor distribution, which limited the improvements in Jc. In order to optimise the Jc values through cold rolling treatments, it is suggested that the reduction in the cross-sectional area of the tape during the first rolling should not exceed 50%, and that during the second rolling the reduction in the tape thickness should exceed 50%