A New Model for the Formation of the 110K BPSCCO Phase

Intermediate products obtained during the production of 2223 Bi(Pb)SrCaCuO superconductors typically consist of 2201, 2212, Ca2PbO4, CaO, CuO and alkaline earth cuprates. Through systematic investigations of mixtures of these phases by thermal analysis, the endothermic reactions leading to the formation of the 2223 phase were identified. Thus, a new model is proposed to explain the formation of the high Tc phase. The intermediate phases, mainly 2201, CaO, 2212 and CuO, produce a partial melt at a temperature below the melting point of the 2223 phase. The 2223 phase grows in the presence of this melt which serves as a materials reservoir and transport medium. The melt must contain the proper concentrations of cations and oxygen.