Theoretical analysis of thermal and mechanical properties of Eu₂Hf₂O₇ and Gd₂Hf₂O₇ pyrochlores

Abstract

First-principles calculations were used to analyze relationship between elastic stiffness and thermal conductivity of Eu₂Hf₂O₇ and Gd₂Hf₂O₇ pyrochlore oxides. Eu₂Hf₂O₇ demonstrated mechanical properties inferior to Gd₂Hf₂O₇. Eu₂Hf₂O₇ and Gd₂Hf₂O₇ belong to quasi-ductile ceramic materials because their G/B ratios are below 0.571 and because of their positive Cauchy pressure values. Thermal conductivity values of Eu₂Hf₂O₇ and Gd₂Hf₂O₇, equal to 1.66 and 1.62 W/(m·K) are below that of yttria stabilized zirconia. Thus, Eu₂Hf₂O₇ and Gd₂Hf₂O₇ pyrochlores are promising as thermal barrier coatings for high-temperature applications, for example, in gas turbine engines.