Thermodynamic assessment of the system La-W-O with focus on the core oxide system La2O3-WO3

The binary system La 2 O 3 -WO 3 was thermodynamically assessed using the available experimental information on phase equilibria and thermodynamic properties of binary lanthanum tungstates. The Gibbs energies of eight compounds (La 2 O 3 ) m (WO 3 ) n were for the first time generated based on thermal (Differential Thermal Analysis-DTA), calorimetrical and EMF (Electro-motive force) measurements from the literature. The melting temperature of the compound La 6 W 2 O 15 was determined by high-temperature dilatometry. The modified associate species model was successfully applied for description of the liquid phase. The solid solution based on the compound La 10 W 2 O 21 (called LaWO) with defective fluorite type structure shows promising conductive properties and can be applied as proton conductor in various electrochemical devices. Therefore, this phase was included in the dataset and modelled using a multi-sublattice model. The calculations on phase equilibria and thermodynamic properties are in good agreement with the available experimental data. The dataset obtained can be used for calculations of the thermodynamic stability of the relevant ceramic phases in order to predict the properties of the complex systems containing functional materials and environmental conditions (temperature, chemical compositions). • Oxide system La 2 O 3 -WO 3 was thermodynamically assessed for the first time. • Modified associate species model was used for the liquid phase. • Gibbs energy of eight binary compounds was generated based on the experimental data from the literature. • Solid solubility based on the compound La 10 W 2 O 21 was successfully described using the multi-sublattice model. • Calculated thermodynamic properties are in good agreement with the experiments.