Mechanical and thermal properties of δ‐RE4Hf3O12(RE = Yb, Lu)

Abstract

AbstractRare‐earth (RE) hafnates are promising thermal and environmental barrier coating (TEBC) materials for SiCf/SiC ceramic matrix composites. In this study, pure‐phase and dense δ‐RE4Hf3O12(RE = Yb, Lu) bulk ceramics have been fabricated via a hot‐pressing method. The crystal structure, microstructure, mechanical, and thermal properties of δ‐RE4Hf3O12were systematically investigated in order to probe their potential application as TEBCs. The high‐temperature elastic moduli of δ‐Yb4Hf3O12and δ‐Lu4Hf3O12are measured to be 185 and 188 GPa at 1673 K, respectively, which are over 85% values of room temperature. The coefficients of thermal expansion are 7.64 × 10−6and 7.46 × 10−6 K−1for δ‐Yb4Hf3O12and δ‐Lu4Hf3O12, respectively. The relatively low coefficient of thermal expansion and thermal conductivity as well as their excellent high‐temperature stability endow these hafnates as potential TEBC candidates.