Mechanical Grinding and Reforming Process of the Pb-substituted 2223 Phase

Mechanical grinding and reforming process of the Pb-substituted 2223 phase has been studied for the monophasic samples with a composition of Bi_0.9Pb_0.2SrCaCu_1.6O₂. The 2223 phase changes to ultla-fine powder by full grinding, exhibiting no magnetic response, while the ultra-fine powder and the small 2223 crystals coexist in samples ground for short periods. Some second phases were formed in the ground powder subjected to heating at temperatures between 500° and 800°C. On the other hand, annealing of the bulk samples below 800°C leads to precipitation of the 3321 phase identified as Sr_2.5Bi_0.5Pb₃Ca₂CuO₂. Precipitation of second phases in the coexistent powder was interpreted by those in ultra-fine powder and bulk samples.