Synthesis of Al2O3 - Y2O3 - SiO2 frit additives by combining sol-gel and coprecipitation methods for advanced ceramics SiAlON ☆

Advanced SiAlON ceramics play a crucial role in high-temperature industries, such as aluminum smelting, due to their superior properties, including high thermal stability, excellent thermal shock resistance, and anticorrosive behavior. In this study, Al₂O₃-Y₂O₃-SiO₂ frits (2A4Y3S and 2A5Y2S) were synthesized via sintering, and the dynamic phase formation of these materials was investigated. To lower the sintering temperature, Y₂O₃ and Al₂O₃ particles were synthesized using a co-precipitation method, employing Al(NO₃)₃•9H₂O and Y(NO₃)₃•6H₂O in an NH₄OH solution. Meanwhile, SiO₂ was prepared via the sol-gel method using Na₂SiO₃ as the precursor and HCl as a catalyst. The effects of synthesis conditions on the formation of 2A4Y3S and 2A5Y2S frits via sintering were systematically analyzed using X-ray diffraction (XRD), differential thermal analysis (DTA), and scanning electron microscopy (SEM). The optimal synthesis conditions for 2A4Y3S were achieved by melting at 1200°C for 5 hours. At 1000°C, 2A4Y3S exhibited a fully amorphous structure, with crystallization occurring in the temperature range of 1100°C to 1200°C. In contrast, the optimal synthesis conditions for 2A5Y2S were obtained by melting at 1300°C for 5 hours. This material remained fully amorphous at 1100°C, with crystallization occurring between 1200°C and 1300°C. Notably, the crystallization temperatures observed in this study were significantly lower than those required for conventional solid-state reaction methods used in the preparation of advanced ceramics.