Peculiarities of mechanically activated synthesis of homologous Bi2+xSr2Can-1CunO4+2n+D compounds

A (BiPb)(2)Sr2Ca2Cu3O10+d-2223(Pb) compound which has the highest temperature of transition to the superconducting state (T-c similar to 110 K) in the homologous series considered is synthesized employing mechanical activation of a starting oxide-nitrate mixture containing lead oxide. The synthesis process is multi-stage and involves Bi2Sr2CuO6-2201 and (BiPb)(2)(SrO8+d)-O-2-2212(Pb) structural homologs. Mechanical activation of the stating mixture is shown to favor formation predominantly of phase 2201(Pb) - the basic compound through which the end product, 2223(Pb) forms. The rate of 2212(Pb) and 2223(Pb) homologs reduces with increasing n, which apparently is associated with the kinetic hindrance of ordering the intercalation layers in multilayer structures. Contribution of the liquid phase accelerating this process increases with n. It is revealed that in the Bi2+xSr2Can-1CunO4+2n+d homologous series, as in similar HgCan-1Ba2CunO2n+4+d and Tl2Can-1Ba2CunO2n+4+d series, the high-temperature superconducting compounds with n = 2,3,4 contain defects which are fragments of the structural homologs with n = n-1 and n = n+1.