Rapid one-powder process to synthesize phase assemblage composed of (Bi,Pb)₂Sr₂CaCu₂O_x, Ca₂CuO₃ and CuO

Ultrafine (200 nm) BiPbSrCaCuO powder with phase assemblage of (Bi,Pb)₂Sr₂CaCu₂O_x, (Bi,Pb)₂Sr₂CaCu₂O_x, Ca₂CuO₃ and CuO is synthesized by our recently developed coprecipitation-based micro-reactor process (CMP) in one-step, based on the study of the effects of atmosphere in each step of CMP on phase assemblages. The phase assemblages are mainly determined by the atmosphere in the ramp step. The O₂-containing atmosphere leads to the phase assemblages of (Bi,Pb)₂Sr₂CaCu₂O_x (2212), Ca₂PbO₄, Ca₂CuO₃, CuO and (Bi,Pb)₂ Sr₂CuO_x(2201) at 800°C. The inert (N₂) atmosphere results in the phase assemblages of (Bi,Pb)₂Sr₂CaCu₂O_x, Ca₂CuO₃ and CuO at 800°C. This variation leads to the quicker formation of (Bi,Pb)₂Sr₂Ca₂Cu₃O_x at higher temperature in the latter process. The results show that the phase assemblage composed of (Bi,Pb)₂Sr₂CaCu₂O_x, Ca₂CuO₃ and CuO is the best candidate for the synthesis of highly pure (Bi,Pb)₂Sr₂Ca₂Cu₃O_x in less than 50 h. The Pb in 2223 phase seems to enter the BiO plane of the 2212 structure and thereby stabilizes the parent structure of 2223 phase for further insertion of Ca/CuO₂ layers.