Pressure crystallization of SiO2-Al2O3-MgO-F glass ceramics

The crystallization behaviors of SiO2-Al2O3-MgO-F glass under applied pressures were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The base glass was prepared by melting-quenching method and the glass-ceramic was obtained by thermal treatment, at the same time the different pressures were applied. The results indicate that mica phase is the mainly crystals in the crystallizing process and the pressures have little effects on the types of crystal precipitated. But the pressure, applied at different stage, has a significant impact on the morphology of the crystals. Applying pressure in the nucleating stage may lead to the mica crystal oriented crystallization, and applying pressure in the crystallization stage promotes the preferential growth of crystals. However, the tendency with the preferential-growth of mica crystal was decreased when the pressure was applied only in the nucleating stage.