High entropy defective fluorite structured rare-earth niobates and tantalates for thermal barrier applications

By Zifan Zhao, Heng Chen, Huimin Xiang, Fu‐Zhi Dai, Xiaohui Wang, Wei Xu, Kuang Sun, Zhijian Peng, Yanchun Zhou. Journal of Advanced Ceramics, 2020

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Rare-earth tantalates and niobates (RE 3 TaO 7 and RE 3 NbO 7 ) have been considered as promising candidate thermal barrier coating (TBC) materials in next generation gas-turbine engines due to their ultra-low thermal conductivity and better thermal stability than yttria-stabilized zirconia (YSZ). However, the low Vickers hardness and toughness are the main shortcomings of RE 3 TaO 7 and RE 3 NbO 7 that limit their applications as TBC materials. To increase the hardness, high entropy (Y 1/3 Yb 1/3 Er 1/3 ) 3 TaO 7 , (Y 1/3 Yb 1/3 Er 1/3 ) 3 NbO 7 , and (Sm 1/6 Eu 1/6 Y 1/6 Yb 1/6 Lu 1/6 Er 1/6 ) 3 (Nb 1/2 Ta 1/2 )O 7 are designed and synthesized in this study. These high entropy ceramics exhibit high Vickers hardness (10.9–12.0 GPa), close thermal expansion coefficients to that of single-principal-component RE 3 TaO 7 and RE 3 NbO 7 (7.9×10 −6 -10.8×10 −6 C −1 at room temperature), good phase stability, and good chemical compatibility with thermally grown Al 2 O 3 , which make them promising for applications as candidate TBC materials.

Subfields: Aerospace Engineering, Materials Chemistry, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/72edd339ecb223c9561895cb2b5843cc6bf0f2f7