Effect of Y2O3 content on the crystallization behaviors and physical properties of glasses based on MgO-Al2O3-SiO2 system

Different concentrations of Y2O3 doped MgO-Al2O3-SiO2 system glasses were prepared by melting method. The effects of Y2O3 content on the physical properties, crystallizability, and the resultant microstructures of the glass samples were investigated. With the increase of Y2O3 content, the glass transition temperature, dilatometric softening temperature and micro hardness all increased. Low concentrations of Y2O3 (0-1.0 mol%) favored the formation of quartz solid solution at 840 °C for 1.5 h, and phase transformation from β- to α-quartz solid solution happened after heat treatment at 1000 °C with subsequent cooling process. While high concentration of Y2O3 (1.5 mol%) inhibited the crystallization process, and quartz solid solution formed at a high temperature ~ 940 °C. The phase transformation from β- to α-quartz solid solution happened after heat treatment at 1060 °C with subsequent cooling process. Average crystal sizes were increased significantly with the crystallization temperature increasing from 940 °C to 1120 °C. The coefficient of thermal expansion of the glass treated at 1120 °C decreased obviously around temperature ~ 300 °C, which indicated that the phase transformation from α- to β-quartz solid solution happened in the heating process.