EARLY-STAGE MICROSTRUCTURE DEVELOPMENT IN BI-SR-CA-CU-O GLASSES

Amorphous samples of Bi2Sr2Ca1Cu2Ox were produced by quenching from th e melt. The early-stage microstructure development in these samples wa s monitored using XRD, DTA, and hot-stage TEM. It was observed that th e molten glass undergoes phase separation during initial quenching and that subsequent refinement of these features generates the initial DT A exotherm during heating. This exotherm has been found for many relat ed compositions, and has been shown not to correspond to crystallizati on. This initial phase separation strongly impacts the final microstru cture by providing copious nucleation sites for the R-phase that ultim ately crystallizes first.