Effect of BaO on the crystallization kinetics of glasses along the Diopside-Ca-Tschermak join

We report on the effect of BaO on the crystallization kinetics of glasses in the diopside (CaMgSi2O6)-Ca-Tschermak (CaAl2SiO6) system. Partial substitution (i.e. 5%, 10% and 20%) of Ba2+ for Ca2+ was attempted in composition CaMg0.8Al0.4Si1.8O6, in three different glasses while partial substitution of B3+ for Al3+ was made in the fourth glass. Structural investigations on the glasses have been made by density measurements, molar volume and Infra-red spectroscopy (FTIR). Non-isothermal crystallization kinetic studies have been employed to study the mechanism of crystallization in all the four glasses. The Avrami parameter for the glass powders is ∼2, indicating the existence of intermediate mechanism of crystallization. Crystallization sequence in the glasses has been followed by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and FTIR. Augite crystallized out being the dominant phase in all the glass-ceramics, while different polymorphs of BaAl2Si2O8 were present as secondary or minor phases.