HIGH-TEMPERATURE X-RAY-DIFFRACTION ANALYSIS FOR BI2SR2CACU2OY

In the case of Bi-2212/Ag composite tapes, the partial-melting technique is useful to obtain a highly textured microstructure. The liquid phase plays an important role during this process. In this letter, we studied the phase transition of oxide phases in the Bi-2212/Ag composite tapes during partial melting and solidification by using the high-temperature x-ray diffraction technique. In the partially molten state, the liquid phase coexists with various kinds of (Ca,Sr)-Cu oxides whose Cu content decreases with increasing temperature. The Bi-2212 phase forms directly from the coexistent state of the liquid phase and the (Ca,Sr)2CuO3 compound. c-axis alignment of Bi-2212 phase starts subsequently to the beginning of precipitation. Bi-2212 phase decomposes and the Bi-2201 phase appears below 800-degrees-C. At lower temperature, the Bi-2201 phase is more stable than Bi-2212 phase and can easily form in the super-cooled liquid phase.