Effect of rolling reduction on the transport property, microstructure, phase formation and fill factor of high- Tc superconducting Bi-(Pb)-Sr-Ca-Cu-O tapes

Abstract

Well-controlled intermediate deformation between sintering stages of (Bi,Pb) 2Sr 2Ca 2Cu 3O x tapes is crucial in achieving high critical current density. This deformation, whether by rolling or pressing, depends on factors such as the compositional phase, the degree of microcracks, sintering periods or duration and sintering temperature. For rolling, additional factors such as roller size and rolling speed might also need to be taken into consideration. These factors together might then give an indication as to how much reduction is best between sintering stages. Here, it is shown that there is indeed an optimal ‘window’ of reduction for intermediate rolling (at room temperature) between sintering stages. For a particular temperature of sintering, this window varies depending on the time of sintering and phase composition after a certain sintering period. It is found that the degree of intermediate deformation does certainly dictate the transformation rate of the high- T c phase as well as determine the tape's final microstructure and fill factor.