Thermodynamic insights into the Yb2O3–Al2O3–SiO2 system: A focus on the phase equilibria at 1600°C

Phase relationships in the Yb 2 O 3 –Al 2 O 3 –SiO 2 system are critical for the design and corrosion protection of environmental barrier coatings (EBCs), the available data remain scarce and primarily limited to studies from the 1990s. The isothermal phase diagram of the Yb 2 O 3 –Al 2 O 3 –SiO 2 system at 1600°C was conducted using a classical high-temperature equilibrium quenching technique, followed by XRD, SEM, and EPMA phase analysis. The data were reported in the form of liquidus projections and an isothermal phase diagram at 1600°C, with one single-phase region, six two-phase regions, and seven three-phase regions. A comparison of the liquid phase regions at 1550°C and 1600°C revealed a systematic expansion with increasing temperature, consistent with thermodynamic expectations. The experimental results from the present work are essential for the development of a thermodynamic database for rare earth oxides, providing vital guidance for designing next-generation EBCs.