1994 年 41 巻 4 号 p. 388-391
Thermal behavior of the Bi-2223 phase in the Bi, Pb-Sr-Ca-Cu-O system, especially segregation and dissolution reaction of the "3321" phase which was identified as Sr2.5Bi0.5Pb3Ca2CuO2, has been studied by XRD, SQUID and resistivity measurements. On annealing below 830°C in air, the "3321" phase precipitated from the 2223 crystals. When the 2223 phase was annealed at 750°C in O2stream, the precipitation of the "3321 " phase increased. On annealing at 750°C in Ar stream, however, no precipitation of the "3321" phase was detected. By reheateing at 850°C even for 1min, the "3321" phase was almost dissolved into the mother 2223 crystals. When the 2223 phase was reheated at 750°C in Ar stream after annealing at 750°C in air, the "3321 " phase disappeared. On the contrary, the "3321" phase was stable on reheating at 870°C in O2 stream. Therefore, it seems that the "3321" and the 2223 phase coexist in epuilibrium in a high oxygen partial pressure.