Isothermal Phase Relations in the SiO2-Al2O3-MgO-5wt.% CaO System at 1400°C: Implications for Refractory Material Design

Understanding the phase equilibrium relationships in multi-component oxide systems is essential for the design and performance optimization of advanced refractory materials used in high-temperature industrial processes. In this study, the equilibrium phase relations of the SiO₂-Al₂O₃-MgO-5wt.% CaO system at 1400°C were experimentally determined in ambient air using the high temperature equilibration-quenching technique. The solid phases of Mg₂SiO_4, MgSiO_3, Mullite, MgAl₂O₄ and SiO₂ were found to be coexisting with liquid phase. Furthermore, it was concluded that additional optimization is necessary to update the existing oxide thermodynamic database, which was proved by the comparison of the current results with thermodynamic calculations by FactSage. The findings of this study provide critical phase equilibrium data for the SiO₂-Al₂O₃-MgO-CaO system, thereby contributing to the accurate modeling and rational design of refractory materials under high-temperature conditions.