Phase Separation and Crystallization of Li2O·Al2O3·4SiO2―Ta2O5 Glass―ceramics

Li2O·Al2O3·4SiO2―Ta2O5 glass―ceramics were prepared with Ta2O5 as nucleating agent, and the phase separation and crystallization mechanism were investigated. The results show that addition of Ta2O5 promotes internal crystallization effectively, which result in fine―grained microstructure with dimension of 50nm. The non―isothermal crystallization kinetics indicates that the crystallization activation energy decrease and crystallization index increase apparently with increasing amount of Ta2O5, the parameter of K(Tp) is recommended as a better crystallization criterion. It is considered that spinodal decomposition occur primarily and result in an interlocking phase separation on cooling of glass, metastable droplet phase separate by nucleation and growth mechanism upon reheating process, then, anhedral crystallization takes place and inherits the morphology of the original phase separation. Consequently, the crystallization model of LAST glass―ceramics is put forward successfully.