Powder production methods of Bi-Pb-Sr-Ca-Cu-O superconductors

Abstract

In this work the production of Bi-Pb-Sr-Ca-Cu-O powder precursors by three different chemical route techniques, namely freeze-drying, spray-drying and thermal co-decomposition methods, plus the two-powder oxide route method, were investigated experimentally. The most reactive precursor made by the chemical route was made by the freeze-drying method. The reactivity of the powders was related to the particle size and stoichiometric changes during heat treatment. Sintering for 60 h at was sufficient to form nearly pure single-phase (91%) Bi-2223 when the freeze-drying method was employed, whereas the maximum amount of Bi-2223 phase produced by the thermal co-decomposition method was 77% for 83 h sintering at in air, and the maximum amount of Bi-2223 phase produced by spray drying was 55% for 150 h sintering at in air. The two-powder oxide route was found to be intermediate in efficiency among the other techniques used here, i.e. it is worse than freeze drying and thermal co-decomposition but better than spray drying.