The effect of CeO2 on the crystallization of MgO-Al2O3-SiO2-ZrO2 glass

Glasses with the mol% composition of 21.2 MgO·21.2 Al2O3·51.9 SiO2·5.7 ZrO2 were doped with 0.5 mol% CeO2 and analysed concerning their crystal phases and microstructure after a one- as well as a two-step crystallization treatment. X-ray diffraction studies indicate the presence of tetragonal ZrO2, a high-/low-quartz solid solution and spinel which were also obtained in the glass-ceramics without CeO2 and are essential for the good mechanical properties of the glass-ceramics. However, the X-ray diffraction results show an increase of the concentration of the desired crystal phases low-quartz solid solution and spinel with the addition of CeO2 to the glass composition. As shown by X-ray absorption near edge spectroscopy and optical spectroscopy, Ce occurs mainly in the valence state +3. Only a very small concentration of Ce4+ exists which probably leads to the slight yellow or beige colour observed in the samples.