The process of phase formation in the synthesis of Al2O3 - Y2O3 - SiO2 frit by sol-gel and coprecipitation method

Frits are utilized in various high-temperature and structural applications due to their exceptional properties. However, most frits are fabricated via solid-state reactions, which require high sintering temperatures and extended time to achieve homogeneity. Therefore, this study investigates the phase transition in the Al2O3 -Y2O3 -SiO2 frit using sol-gel method, which enables lower synthesis temperature and achieves higher purity. The energy dispersive X-ray spectroscopy (EDX) results confirm the successful fabrication of Al2O3 -Y2O3 -SiO2 frits. The effect of the sintering conditions on the phase transition was studied. The X-ray diffraction patterns revealed that the frit remained completely amorphous up to 1000 °C. Although the crystalline phases Y2O3·2SiO2, Y2O3·SiO2, and α-Al2O3 begin to appear around 1100 °C, the overall degree of crystallinity increases with temperature, indicating a gradual transformation from an amorphous to a more crystalline structure. A fully crystallized structure of the Al2O3 -Y2O3 -SiO2 frit is observed at 1400 oC. The differential thermal analysis (TGA) results confirm the glass transition, crystallization and eutectic temperature of the Al2O3 -Y2O3 -SiO2 frit. The optimized sintering condition was determined to be 1400 oC for 5 hours.