The effect of TiO2 and ZrO2 addition on the crystallization of Ce3+ doped yttrium aluminum garnet from glasses in the system Y2O3/Al2O3/SiO2/AlF3

The crystallization of yttrium aluminum garnet (YAG) doped with Ce3+ from alkali free glasses in the system Y2O3/Al2O3/SiO2/AlF3 has been investigated with and without the addition of ZrO2 and/or TiO2 as nucleation agents. X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA) were used to characterize the crystallization process. Fluorescence microscopy and fluorescence spectroscopy were used to investigate optical properties. Thermal annealing of the glass was carried out at temperatures in the range from 1100 to 1400 °C. In all samples studied, crystallization at temperatures ≥1300 °C lead to the formation of YAG as the main crystalline phase. If the glass contained TiO2, the crystallization of YAG occurred at lower temperatures; here, already at 1150 °C, YAG was the main crystalline phase. After annealing at 1300 °C, the only crystalline phase formed was YAG. The fluorescence intensity showed a maximum at a wavelength of 532 nm and was largest in the sample solely doped with 5 mol% TiO2. This proves that Ce3+ was incorporated into the YAG crystals.

► Yttrium aluminum garnet was crystallized from an alkali free silicate glass.
► Titania acts as nucleating agent, while zirconia does not.
► Higher temperatures promote the crystallization of garnet.
► Optical microscopy proved that the garnet crystals show fluorescence.
► The fluorescence is due to Ce3+ which hence is incorporated into the crystals.