Abstract: The effect of components of ceramics in the Sm₂O₃–Y₂O₃–HfO₂ system on their thermophysical properties was studied. It was shown that the most stable materials at 1400°C are ternary ceramics in the system under investigation that contain ≤12.5 mol % Sm₂O₃; the thermal conductivity of these materials does not exceed 1.3 W/(m K). Increasing samarium oxide content in samples in the Sm₂O₃–Y₂O₃–HfO₂ system was found to lead to significant changes in phase equilibria at temperatures ≥1000°C. The effect of the contents of individual components of the studied ceramics on the thermal conductivity and the linear thermal expansion coefficient, which largely determine the suitability of a ceramic material for using in a thermal barrier coating. It was shown that the addition to 12.5 mol % samarium oxide ensures the stability of the linear thermal expansion coefficient at acceptable values of the thermal conductivity of 0.8–1.6 W/(m K).