Towards the rapid synthesis of pure 2223 powders with Bi_2-xPb_xSr₂Ca₂Cu₃O_y compositions by semi-wet methods II. Optimization of Pb content using PB---Sr---Ca carbonate precursors

Abstract

The effect of Pb content on the formation of the 2223 phase in stoichiometric compositions Bi_2-xPb_xSr₂Ca₂Cu₃O_y (0.1 ≤ x ≤ 0/4) is reported for a semi-wet route using [xPbCO₃+2SrCO₃+2CaCO₃] precursors. Synthesis of high-purity 2223 phase free from Ca₂PbO₄ is reported for x=0.3 within a total heat treatment duration of 44 h with several intermediate crushings and grindings. By studying the sequence of solid state thermochemical reactions, it is shown that in the absence of Ca₂PbO₄, which plays a crucial role in accelerating the formation of 2223 phase, the conversion of 2212 into 2223 gets slowed down unless one resorts to intermediate crushing and grinding. The optimum Pb content for the formation of 2223 phase in Bi_2-xPb_xSr₂Ca₂Cu₃O_y compositions has been estimated to be in the range of 0.3 ≤ x < 0.4.