High-entropy(Nd_(0.2)Sm_(0.2)Eu_(0.2)Y_(0.2)Yb_(0.2))_(4)Al_(2)O_(9) with good high temperature stability,low thermal conductivity,and anisotropic thermal expansivity

作     者：Zifan ZHAO Huimin XIANG Heng CHEN Fu-Zhi DAI Xiaohui WANG Zhijian PENG Yanchun ZHOU 

作者机构：Science and Technology on Advanced Functional Composite LaboratoryAerospace Research Institute of Materials&Processing TechnologyBeijing 100076China School of Engineering and TechnologyChina University of GeosciencesBeijing 100083China Shenyang National Laboratory for Materials ScienceInstitute of Metal ResearchChinese Academy of SciencesShenyang 110016China 

出 版 物：《Journal of Advanced Ceramics》 (先进陶瓷（英文）)

年 卷 期：2020年第9卷第5期

页      面：595-605页

核心收录：

学科分类：0808[工学-电气工程] 0809[工学-电子科学与技术（可授工学、理学学位）] 08[工学] 0817[工学-化学工程与技术] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 

基　　金：financial support from the National Natural Science Foundation of China(Grant Nos.51672064 and 51972089). 

主　　题：(Nd_(0.2)Sm_(0.2)Eu_(0.2)Y_(0.2)Yb_(0.2))_(4)Al_(2)O_(9) high-entropy ceramics(HECs) environmental barrier coatings phase stability thermal properties 

摘      要：The critical requirements for the environmental barrier coating(EBC)materials of silicon-based ceramic matrix composites(CMCs)include good tolerance to harsh environments,thermal expansion matches with the interlayer mullite,good high-temperature phase stability,and low thermal conductivity.Cuspidine-structured rare-earth aluminates RE_(4)Al_(2)O_(9) have been considered as candidates of EBCs for their superior mechanical and thermal properties,but the phase transition at high temperatures is a notable drawback of these materials.To suppress the phase transition and improve the phase stability,a novel cuspidine-structured rare-earth aluminate solid solution(Nd_(0.2)Sm_(0.2)Eu_(0.2)Y_(0.2)Yb_(0.2))_(4)Al_(2)O_(9) was designed and successfully synthesized inspired by entropy stabilization effect of high-entropy ceramics(HECs).The as-synthesized HE(Nd_(0.2)Sm_(0.2)Eu_(0.2)Y_(0.2)Yb_(0.2))_(4)Al_(2)O_(9) exhibits a close thermal expansion coefficient(6.96×10^(-6) K^(-1) at 300-1473 K)to that of mullite,good phase stability from 300 to 1473 K,and low thermal conductivity(1.50 W·m^(-1)·K^(-1) at room temperature).In addition,strong anisotropic thermal expansion has been observed compared to Y_(4)Al_(2)O_(9) and Yb_(4)Al_(2)O_(9).The mechanism for low thermal conductivity is attributed to the lattice distortion and mass difference of the constituent atoms,and the anisotropic thermal expansion is due to the anisotropic chemical bonding enhanced by the large size rare-earth cations.