Phase relations in the system Ta-Rh-O and thermodynamic properties of TaRhO4

The limited experimental thermodynamic data for Rh-rich alloys available in the literature are in fair accord with Miedema's model. The Gibbs energies of formation of the different phases in the binary system Ta-Rh were estimated based on these inputs, consistent with the binary phase diagram. Based on the thermodynamic information on the stability of various phases, an oxygen potential diagram for the system Ta-Rh-O at 1273 K was constructed. Also presented are temperature-composition diagrams for the ternary system at constant oxygen partial pressures (pO2/po=0.212and 10−6) calculated form the basic data.