High entropy(Y_0.2Yb_0.2Lu_0.2Eu_0.2Er_0.2)₃Al₅O₁₂:A novel high temperature stable thermal barrier material

Heng Chen^1,2，Zifan Zhao¹，Huimin Xiang¹，Fu-Zhi Dai¹，Jiachen Liu⁴，Yanchun Zhou¹

1. Science and Technology on Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials & Processing Technology2. Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education,School of Materials Science and Engineering, Tianjin University4. Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials Science and Engineering, Tianjin University

摘 要：Ytterbium aluminum garnet(Yb₃Al₅O₁₂) is considered as a promising thermal barrier material. However, the main limitations of Yb₃Al₅O₁₂ for thermal barrier applications are relative low thermal expansion coefficient and high thermal conductivity. In order to overcome these obstacles, herein, a new high entropy(Y_0.2Yb_0.2Lu_0.2Eu_0.2Er_0.2)₃Al₅O₁₂ ceramic was designed, and then powders and bulk were prepared through solid-state reaction method and spark plasma sintering（SPS）, respectively.The thermal expansion coefficient of HE(Y_0.2Yb_0.2Lu_0.2Eu_0.2Er_0.2)₃Al₅O₁₂ is（8.54 ± 0.29） × 10^-6 K^-1 at 673 K–1273 K, which is about 9% higher than that of Yb₃Al₅O₁₂. The thermal conductivity of HE(Y_0.2Yb_0.2Lu_0.2Eu_0.2Er_0.2)₃Al₅O₁₂ ceramic is 3.81 W·m^-1 K^-1 at 300 K, which is about 18% lower than that of Yb₃Al₅O₁₂. Moreover, there is no reaction between HE(Y_0.2Yb_0.2Lu_0.2Eu_0.2Er_0.2)₃Al₅O₁₂ and thermally grown（TG） Al₂O₃ even at 1600℃. After annealing at 1590℃ for 18 h, the average grain size of HE(Y_0.2Yb_0.2Lu_0.2Eu_0.2Er_0.2)₃Al₅O₁₂ increases only from 1.56 μm to 2.27 μm. Close thermal expansion coefficient to TG Al₂O₃, low thermal conductivity, good phase stability, excellent chemical compatibility with TG Al₂O₃ and slow grain growth rate make HE(Y_0.2Yb_0.2Lu_0.2Eu_0.2Er_0.2)₃Al₅O₁₂ promising for thermal barrier applications.

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