Study of the crystallization process in Bi_2-xPb _xSr₂Ca₂Cu₃O_10-y glass systems: Optical polarized light microscopy, electrical and magnetic properties

Synthesis of Bi_2-xPb_xSr₂Ca ₂Cu₃O_10-y (x=0 and x=0.3) has been performed using the glass recrystallization route technique. After splat quenching, the samples were annealed at 820, 850 or 870 degrees C for 96 or 144 h (with one intermediary grinding). High-resolution polarization micrographs and electrical (and magnetic susceptibility) measurements have been taken. Various growth mechanisms can thus be checked, and the physical properties are studied in relation to the microstructure. It is found that the 2223 phase does not crystallize directly from the amorphous one but results from a dissolution-reprecipitation process. The stability of the 2212 phase is emphasized. The 2201 phase precipitates at high temperature and rapidly reacts with the melt to form the 2223 phase. The kinetics of the lead-substituted sample seems to be controlled by the Ca₂PbO₄ phase, which acts as a flux.