TOWARDS THE RAPID SYNTHESIS OF PURE 2223 POWDERS WITH BI2-XPBXSR2CA2CU3OY COMPOSITIONS BY SEMI-WET METHODS .2. OPTIMIZATION OF PB CONTENT USING PB-SR-CA CARBONATE PRECURSORS

摘要

The effect of Pb content on the formation of the 2223 phase in stoichiometric compositions Bi2-xPbxSr2Ca2Cu3Oy (0.1 less than or equal to x less than or equal to 0.4) is reported for a semi-wet route using [xPbCO(3) + 2SrCO(3) + 2CaCO(3)] 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 Bi2-xPbxSr2Ca2Cu3Oy compositions has been estimated to be in the range 0.3 less than or equal to x less than or equal to 0.4. [References: 27]