The effects of heat treatment on phase separation, crystallisation, and microwave dielectric properties of the 1MgO.1.2Al2O3.2.8SiO2.1.4TiO2.O.2La2O3 (in molar ratio) glass and glass-ceramic were investigated. The results show that the parent glass has a two-liquid phase separation structure, with a droplet phase rich in Al & Ti embedded in the matrix rich in Si. Heat treatment of the glass at 770 deg C leads to the enlargement of the liquid droplets and promotes the formation of crystals from the droplets. The initial crystalline phase perrierite appears after heat treatment of the parent glass at 850 deg C, and it is analysed to precipitate from the Al&Ti-rich droplet phase. With increasing heat-treatment temperature from 850 deg C, to 1250 deg C, the crystallization degree of the glass increases as the other main crystal phases rutile, cordierite and magnesium aluminotitanate precipitate successively from the material.
