Modifications on bulk crystallization of glasses belonging to M₂O-CaO-SiO₂-ZrO₂ system in a 2.45 GHz microwave field

The potential for microwave processing of a single phase material is often limited due to the dependence of dielectric losses upon the chemical bonding and temperature of the material. We will present results showing the effect of microwave absorption on bulk crystallization of glasses belonging to M₂O-CaO-SiO₂-ZrO₂ system (where M = Li, Na, K). The glass samples were devitrified using both microwave and conventional heating. The effect of Li⁺, Na⁺, K⁺ on crystallization is quite remarkable and is a function of ion size. This is true especially in the microwave heating where the important dielectric losses observed in silicate glasses are related to the motion of alkali cations throughout the glass matrix. X-ray diffraction analysis was performed on the powdered samples to determine crystalline phases. Results of microstructure and microanalysis on these glass-ceramic samples will also be presented.