Effect of La2O3 on the physical and crystallization properties of Co2+-doped MgO–Al2O3–SiO2 glass

The physical and crystallization properties of MgO–Al2O3–SiO2 glasses with various La2O3 additions (0–10 wt.%) were studied by means of density, hardness and coefficient of thermal expansion (CTE), differential thermal analysis (DTA), in situ high temperature XRD, room temperature XRD, and absorption spectrum. Density, hardness and CTE were found to increase with adding La2O3 content. The slight variation of transformation temperature (Tg) observed between different LMAS glass compositions can be attributed to the relatively strong LaO bonds. La2O3 was found to hardly influence the nucleation and crystallization processes of Co2+-doped MgO–Al2O3–SiO2 glasses when lower than 5 wt.%, while the nucleation of the glass was hindered and MgAl2O4 spinel cannot be formed with the La2O3 content greater than 5 wt.%. Transparent glass-ceramics were synthesized by heat-treating glasses with 0–5 wt.% La2O3 at 760 °C/12 h + 930 °C/4 h; the changes in absorption spectra reflected that Co2+ ions entered into MgAl2O4 nanocrystals precipitated in the glass-ceramics and occupied tetrahedral coordinated site.