The microstructure changes of Bi-2212/Ag composite tapes processed under a temperature gradient

摘要

The microstructure changes of Bi-2212/Ag tapes during melt-solidification under a temperature gradient have been investigated by using an oil-quenching technique. The cross-sections and oxide layers at the oxide/silver interfaces of the tapes quenched from several temperatures were examined by using SEM observation and X-ray diffraction analysis. At maximum processing temperature T_(max), impurity phases such as Bi-free and Cu-free solid phases exist in the liquid. When the solidification of the Bi-2212 phase started at the low-temperature region, most of the Bi-free and Cu-free phases at the region near the oxide/silver interface disappeared. A large grain size of Bi-2212 near the oxide/silver interface was obtained by the heat treatment under the temperature gradient. Large in-plane textured domains were obtained by the growth of Bi-2212 grains whose a- and/or b-axes were aligned. This in-plane texturing can basically be explained by the unidirectional solidification.