The Phase Transformation of R2O-CaO-SiO2-F Glass-ceramics

The phase transformation of R2O-CaO-SiO2-F system glass-ceramics with various additions of K2O and F was investigated by DTA, XRD, SEM and other techniques. The crystallization and the microstructure of the obtained glass-ceramics were also evaluated. The phase separation occurred in CN1 specimen after being quenched in water, but phase separation did not appear in other quenched specimens with the content of K2O and F increasing obviously, showing K2O and F modified the structure of the glass-forming melts. The increase of K2O and F resulted in the reduction of phase separation and the enhancement of crystallization. The main crystalline phase formed after heat-treatment was canasite and CaF2. The microstructures of the crystalline specimens consisted of interlocking radial and granular crystals. Moreover, the crystallinity was increased as the content of K2O was increased from 0.07 mol to 0.08 mol.