Towards the rapid synthesis of pure 2223 powders with Bi_2-xPb_xSr₂Ca₂Cu₂O_y compositions by semi-wet methods III. Role of sintering temperature and duration

Abstract

The role of the sintering temperature and duration in the formation of 2223 phase in stoichiometric compositions, Bi_2-xPb_xSr₂Ca₂Cu₃O_y for x = 0.35 and 0.4, is reported for a semi-wet route using (xPbCO₃ + 2SrCO₃ + 2CaCO₃) precursors. By studying the sequence of solid-state thermochemical reactions it is shown that the impurity phase Ca₂PbO₄ can appear and disappear at the same temperature with respect to the sintering time. The synthesis of very high purity 2223 phase, free from Ca₂PbO₄, 2212 and 2201 impurity phases, is reported for the x = 0.4 composition within a total heat-treatment duration of 38 h (including 24 h of calcination). The single-phase 2223 samples so prepared are shown to have a good compositional homogeneity. The intergranular critical current density of the single-phase pellets, (J^j_c) as obtained from AC susceptibility measurements, is compared with those obtained for samples prepared by a conventional dry route.