Phase equilibria in the Li ₂ O‒MnO _x system

Abstract Phase equilibria in the Li 2 O‒MnO x system was experimentally investigated under air condition and inert atmosphere (Ar). The experimental investigations for selected compositions of isothermally heat‐treated samples were performed using X‐ray diffraction and scanning electron microscopy/energy dispersive X‐ray spectroscopy. Differential thermal analysis was used to determine the temperature of phase transformations. The thermodynamic parameters were optimized using the CALPHAD approach. Homogeneity ranges for cubic and tetragonal phases were reproduced and modeled in the framework of the compound energy formalism, while LiMnO 2 and Li 2 MnO 3 phases were treated as stoichiometric. Two‐sublattice partially ionic liquid model was employed to describe the liquid. Available thermodynamic properties were accounted during the optimization and the results reproduce them well. The calculated phase diagram agrees with the experimental data and it reproduces the equilibria within uncertainties.