Liquid-phase separation and crystallization of high silicon canasite-based glass ceramic

•By SEM and SAXS, the L–L phase separation was observed in canasite glass ceramic.•The rate and activation energy of crystallization were calculated by XRD and DTA.•Give a complete image of the phase change during the heat treatment

The phase separation of high silicon composition 7.6Na2O·4K2O·8.4 CaO·70SiO2·8.9 CaF2·1.0 Al2O3 canasite-based glass ceramic during heat treatment was studied. The crystallization rate of calcium fluoride and canasite was estimated by using quantitative analysis of XRD. The non-isothermal DTA study shows that high silicon content increases the activation energy and restrains the crystallization of canasite appropriately. Through FE-SEM and SAXS, the early stage liquid–liquid phase separation was discovered in this kind of glass ceramic by long time heat treatment at 555 °C. Interestingly, the SAXS result shows that the small scale liquid–liquid phase separation has existed in the glass matrix intrinsically even after quenching.