Heat Capacity Measurements and Thermodynamic Assessment of the Y ₂ O ₃ –Ta ₂ O ₅ System

ABSTRACT Phase equilibria in the Y 2 O 3 –Ta 2 O 5 system play an important role in the development of new materials for thermal barrier coating (TBC) applications, with higher thermal stability resulting in more efficient gas turbines with reduced exhaust gas emissions. Therefore, the development of a consistent thermodynamic database for this oxide system is invaluable for faster and more sustainable material development. In this work, four different sample compositions were prepared by co‐precipitation reactions, and the heat capacities of the orthorhombic Y 3 TaO 7 (Y 1‐ x Ta x O 1.5+ x with x = 0.26 and x = 0.29) and the hexagonal YTa 7 O 9 phases, both with homogeneity ranges, were experimentally measured in the temperature range from 200 to 1373 K using differential scanning calorimetry (DSC). The obtained results, together with literature data on phase equilibria and experimental thermodynamic values, have been used to assess the thermodynamic description of the Y 2 O 3 –Ta 2 O 5 system applying the CALPHAD approach.