Coupled phase diagram study and thermodynamic modeling of R2O (R = Li, Na, K, Rb, and Cs) and V2O5 ternary systems and their applications

Phase equilibria and thermodynamic properties of alkali metal oxides R2O (R = Li, Na, K, Rb, and Cs) and vanadium pentoxide (V2O5) ternary systems are essential for various industrial applications and materials synthesis. In this study, an experimental study on the LiVO3-KVO3 isopleth under an air atmosphere was conducted in Pt capsules using X-ray diffraction and differential thermal analysis. The results confirmed the absence of any intermediate compounds in the LiVO3-KVO3 isopleth. Furthermore, the eutectic temperature corresponding to the liquid, LiVO3, and KVO3, was determined to be 410 ± 5 ℃. Building on these experimental findings, thermodynamic modeling of the MVO3-NVO3 (M, N = Li, Na, K, Rb, and Cs) system was performed. Modeling for the target ternary systems incorporated crystal structure, phase relations, and available thermodynamic data. Subsequently, the M2O-N2O-V2O5 (M, N = Li, Na, K, Rb, and Cs) ternary systems were modeled using the CALculation of PHAse Diagrams (CALPHAD) methodology, based on a critical evaluation of all available phase diagram data. The ternary phase diagrams were reasonably predicted using the geometry-based interpolation method based on binary system descriptions. The developed database was applied to thermodynamically simulate materials synthesis and vanadium extraction processes, with in-depth discussions provided on these applications.