In Situ Observation of Phase Changes in Bi2212 Superconducting Tapes by High Temperature X-ray Diffraction

High-temperature X-ray diffraction has been used to investigate an aspect from partial melting state to crystallization for Bi2Sr2Ca1Cu2Oz tapes. When a sample having a nominal composition of Bi2Sr2Ca1Cu2Oz was heated in air, the simple XRD pattern that is, (Sr,Ca)1Cu1O2 and liquid, in partial melting state was observed and the XRD pattern nearest to single phase of 2212 was obtained. When the same sample was heated in oxygen, Bi-(Sr,Ca)-O and Bi-2201 phases additional to (Sr,Ca)1Cu1O2 largely remained in partial melting state. Such phases were hard to react and precipitated after transformation to the 2212 phase. The Ag addition was effective to reduce impurity phases in oxygen cooling.