Junjie Shi

The phase equilibria of the MgO-Al2O3-V2O5 system with CaO additions of 5-10 wt.% were systematically investigated at 1700 °C in air using high-temperature equilibrium experiments combined with XRD and SEM-EPMA analyses. Based on experimentally determined phase assemblages and equilibrium phase compositions, reliable isothermal sections were constructed for both CaO-containing systems. At 1700 °C, the system containing 5 wt.% CaO exhibits one single-phase liquid region, three two-phase fields (L+MgAl2O4, L+MgO, and L+Al2O3), and two three-phase equilibrium regions (L+MgAl2O4+MgO and L+MgAl2O4+Al2O3). The liquid phase is confined to V2O5-rich compositions, while a broad stability field of MgAl2O4 solid solution is observed under oxidizing conditions. Increasing the CaO content to 10 wt.% does not introduce new equilibrium phases nor alter the overall types of phase fields. Only marginal changes in the extent of the liquid region are observed. The obtained phase equilibrium data provide fundamental insight into slag phase stability and offer guidance for composition control in aluminothermic ferrovanadium smelting.

The phase equilibria of the CaO–SiO ₂ –TiO ₂ ternary system were experimentally investigated at 1300 and 1400°C in air using high‐temperature equilibration followed by quenching, combined with phase identification via x‐ray diffraction and electron probe microanalysis. Based on the identified phase assemblages, isothermal sections at both temperatures were constructed. Comparisons with the calculated diagrams from the FactSage thermodynamic software and previous reported data revealed notable discrepancies, particularly in the SiO ₂ ‐rich region and the extent of rutile primary phase field. These findings provide reliable experimental constraints for thermodynamic model optimization and offer a solid foundation for the design and performance tuning of Ti‐bearing oxide ceramics.

This study presents the first systematic experimental determination of phase equilibria in the Er ₂ O ₃ –Al ₂ O ₃ –SiO ₂ system at 1600°C in air, employing the high‐temperature isothermal equilibration method followed by rapid drop‐quenching to preserve high‐temperature phase assemblages. The mineralogy and chemical compositions of the equilibrated samples were analyzed by x‐ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe x‐ray microanalysis (EPMA). One single liquid equilibria, five two‐phase equilibria (liquid–SiO ₂ , liquid–Er ₂ Si ₂ O ₇ , liquid–Er ₃ Al ₅ O ₁₂ , liquid–Al ₂ O ₃ , and liquid–mullite) and seven three‐phase equilibria (liquid–SiO ₂ –Er ₂ Si ₂ O ₇ , liquid–Er ₂ Si ₂ O ₇ –Er ₂ SiO ₅ , liquid–Er ₂ SiO ₅ –Er ₃ Al ₅ O ₁₂ , liquid–Er ₃ Al ₅ O ₁₂ –Al ₂ O ₃ , liquid–Al ₂ O ₃ –mullite, Er ₂ O ₃ –Er ₂ SiO ₅ –Er ₄ Al ₂ O ₉ , Er ₃ Al ₅ O ₁₂ –Er ₂ SiO ₅ –Er ₄ Al ₂ O ₉ ) were observed in the equilibrium ternary system. The 1600°C isothermal section of the Er ₂ O ₃ –Al ₂ O ₃ –SiO ₂ phase diagram in air ( p O ₂ = 0.21 atm) was constructed based on the present experimentally determined equilibrium phase compositions. The liquid area and the primary fields of SiO ₂ , Er ₂ Si ₂ O ₇ , Er ₃ Al ₅ O ₁₂ , Al ₂ O ₃ , and mullite were constructed. The comparison of the present experimental results deviate significantly from the modelling by FactSage (version 8.3) using its “ FactPS ” and “ FToxid ” databases, suggesting that FactSage underestimated the stability of the liquid phase under the present experimental conductions.

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.