Formation of the High-t_c Phase in Bi-2223 System in Various Atmospheres —Effect of o₂-Partial Pressure—

The effects of O₂-partial pressure on formation of the Bi-2223 phase. The samples were heated at 807°C∼850°C under various O2 atmospheres after calination in air or Ar flow. Single phase products of the 2223 phase were obtained by heating in 20%O₂ both in Ar and air. The Pb-substituted 2212^* phase, (Ca, Sr)₂CuO₃ and CuO coexist in samples calcined in Ar. The 2223 phase forms at a markedly lower temperature (807°C) in samples calcined in Ar than in those in air. In samples calcined in Ar the 2223 phase forms without formation of (Ca, Sr)2PbO4. These results reveal that the formation process of the 2223 phase in samples calcined in Ar is different from that in those in air.