Abstract
Melt-solidification technique brings a textured microstructure and an excellent critical current density (Jc) value on Bi2Sr2CaCu2Ox(Bi2212)/Ag composite tape. However, the optimum condition of the heat treatment is tight, and the highest Jc value can not always be obtained so far. In order to improve the reproducibility of sample with excellent Jc value, we applied the melt-solidification treatment combined with a bismuth vapor atmosphere to Bi2212/Ag tape. In this paper, dependence of Jc value on the maximum temperature in the heat treatment and microstructural study on the tape surface are reported. Reproducibility in Jc value is extraordinarily improved by the bismuth vapor treatment in contrast with the case of the conventional one, although the highest Jc values are still comparable for both cases. Microstructural observation reveals that, in the case of the bismuth treatment, the Bi-free phase particles are much smaller than those in the usual air treatment, and that the flatness of the tape surface is improved. The grain size and distribution of Bi-free phase particles plays an important role in the formation of Bi2212 textured structure and controls its Jc value.
