Mechanical and thermal properties of δ‐RE <sub>4</sub> Hf <sub>3</sub> O <sub>12</sub> (RE = Yb, Lu)
Wanpeng Hu, Guangheng Zhang, Yiming Lei, Luchao Sun, Jie Zhang, Jingyang Wang
Abstract
Abstract Rare‐earth (RE) hafnates are promising thermal and environmental barrier coating (TEBC) materials for SiC f /SiC ceramic matrix composites. In this study, pure‐phase and dense δ‐RE 4 Hf 3 O 12 (RE = Yb, Lu) bulk ceramics have been fabricated via a hot‐pressing method. The crystal structure, microstructure, mechanical, and thermal properties of δ‐RE 4 Hf 3 O 12 were systematically investigated in order to probe their potential application as TEBCs. The high‐temperature elastic moduli of δ‐Yb 4 Hf 3 O 12 and δ‐Lu 4 Hf 3 O 12 are 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 −6 and 7.46 × 10 −6 K −1 for δ‐Yb 4 Hf 3 O 12 and δ‐Lu 4 Hf 3 O 12 , 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.