PHASE-EQUILIBRIA NEAR (BI,PB)-2223, AS A FUNCTION OF OXYGEN PARTIAL-PRESSURE

The phase equilibria near (Bi,Pb)(2)Sr2Ca2Cu3O10+delta ((Bi,Pb)-2223) was studied in the temperature range of 750 degrees-820 degrees C in a ir and in reducing atmospheres. In air, (Bi,Pb)-2223 was in equilibriu m with one or more of the following phases: (Bi,Pb)(2)Sr2CaCu2O8+delta ((Bi,Pb)-2212), (Sr,Ca)(14)Cu24O41 (14:24), (Ca,Sr)(2)CuO3, (Bi,Pb)(4 )(Sr,Ca)(5)-CuOx (451), Ca2PbO4, and CuO, Ca2PbO4 and the 451 phase we re not in equilibrium with (Bi,Pb)-2223 at an oxygen partial pressure (p(O2)) of 10(-3) atm, which is indicative of higher lead solubility i n (Bi,Pb)-2223 under more-reducing conditions. In a second set of expe riments, the lead content in both (Bi,Pb)-2212 single crystals and (Bi ,Pb)-2223 powders was investigated as a function of p(O2) at a constan t temperature of 750 degrees C, Lead solubility in (Bi,Pb)-2212 and (B i,Pb)-2223 increased as p(O2) decreased.