High entropy (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12: A novel high temperature stable thermal barrier material

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 (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)(3)Al5O12 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 (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)(3)Al5O12 is (8.54 +/- 0.29) x 10(-6) K-1 at 673 K-1273 K, which is about 9% higher than that of Yb3Al5O12. The thermal conductivity of HE (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)(3)Al5O12 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 (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)(3)Al5O12 and thermally grown (TG) Al2O3 even at 1600 degrees C. After annealing at 1590 degrees C for 18 h, the average grain size of HE (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)(3)Al5O12 increases only from 1.56 mu m to 2.27 mu m. 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 (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)(3)Al5O12 promising for thermal barrier applications. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.