Crystallization Characteristics of SiO2-Al2O3-MgO-F-ZrO2 Glass-Ceramic

To explore the effects of the additions of ZrO2 on the crystallization in SiO2-Al2O3-MgO-F-ZrO2 glass, the base glasses with various ZrO2 contents were prepared by melt-quenching methods. The results indicate that the maximum solid solution of ZrO2 in the studied glass is around 5.0 wt%, above which the crystalline phase of zirconia (ZrO2) will be precipitated. The phase-separation is observed in the glass thermal treated at 700 degrees C, in which the accumulation of fluorine element instead of zirconium element is formed. It is found that the crystalline phases of fluormica as the major phase and zirconia and mullite as a minor phase are formed in the glass with different ZrO2 additives. The increase of ZrO2 contents is favor to decrease the crystallization temperature, but to inhibit the precipitation of fluormica. The morphology of fluormica crystals changes from "rose" shape to cluster shape.