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Y2O3 is regarded as one of the potential environmental barrier coating (EBC) materials for Al2O3f/Al2O3 ceramic matrix composites owing to its high melting point and close thermal expansion coefficient to Al2O3. However, the relatively high thermal conductivity and unsatisfactory calcium–magnesium–aluminosilicate (CMAS) resistance are the main obstacles for the practical application of Y2O3. In order to reduce the thermal conductivity and increase the CMAS resistance, four cubic bixbyite structured high-entropy oxides RE2O3, including (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3, (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3, (Sm0.2Eu0.2Er0.2Y0.2Yb0.2)2O3, and (Sm0.2Eu0.2Lu0.2Y0.2Yb0.2)2O3 were designed and synthesized, among which (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 and (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 bulks were prepared by spark plasma sintering (SPS) to investigate their mechanical and thermal properties as well as CMAS resistance. The mechanical properties of (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 and (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 are close to those of Y2O3 but become more brittle than Y2O3. The thermal conductivities of (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 and (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 (5.1 and 4.6 W·m-1·K-1) are only 23.8% and 21.5% respectively of that of Y2O3 (21.4 W·m-1·K-1), while their thermal expansion coefficients are close to those of Y2O3 and Al2O3. Most importantly, HE RE2O3 ceramics exhibit good CMAS resistance. After being attacked by CMAS at 1350 ℃ for 4 h, the HE RE2O3 ceramics maintain their original morphologies without forming pores or cracks, making them promising as EBC materials for Al2O3f/Al2O3 composites.


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Preparation and properties of CMAS resistant bixbyite structured high-entropy oxides RE2O3 (RE = Sm, Eu, Er, Lu, Y, and Yb): Promising environmental barrier coating materials for Al2O3f/Al2O3 composites

Show Author's information Yanan SUNa,bHuimin XIANGbFu-Zhi DAIbXiaohui WANGcYan XINGdXiaojun ZHAOa( )Yanchun ZHOUb( )
School of Materials Science and Engineering, Central South University, Changsha 410083, China
Science and Technology on Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials & Processing Technology, Beijing 100076, China
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
New Energy Technology Engineering Laboratory of Jiangsu Province, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

Abstract

Y2O3 is regarded as one of the potential environmental barrier coating (EBC) materials for Al2O3f/Al2O3 ceramic matrix composites owing to its high melting point and close thermal expansion coefficient to Al2O3. However, the relatively high thermal conductivity and unsatisfactory calcium–magnesium–aluminosilicate (CMAS) resistance are the main obstacles for the practical application of Y2O3. In order to reduce the thermal conductivity and increase the CMAS resistance, four cubic bixbyite structured high-entropy oxides RE2O3, including (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3, (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3, (Sm0.2Eu0.2Er0.2Y0.2Yb0.2)2O3, and (Sm0.2Eu0.2Lu0.2Y0.2Yb0.2)2O3 were designed and synthesized, among which (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 and (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 bulks were prepared by spark plasma sintering (SPS) to investigate their mechanical and thermal properties as well as CMAS resistance. The mechanical properties of (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 and (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 are close to those of Y2O3 but become more brittle than Y2O3. The thermal conductivities of (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 and (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 (5.1 and 4.6 W·m-1·K-1) are only 23.8% and 21.5% respectively of that of Y2O3 (21.4 W·m-1·K-1), while their thermal expansion coefficients are close to those of Y2O3 and Al2O3. Most importantly, HE RE2O3 ceramics exhibit good CMAS resistance. After being attacked by CMAS at 1350 ℃ for 4 h, the HE RE2O3 ceramics maintain their original morphologies without forming pores or cracks, making them promising as EBC materials for Al2O3f/Al2O3 composites.

Keywords:

high-entropy ceramics, rare earth oxides, low thermal conductivity, thermal expansion coefficient, CMAS resistance
Received: 04 November 2020 Revised: 13 January 2021 Accepted: 17 January 2021 Published: 01 March 2021 Issue date: June 2021
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Publication history

Received: 04 November 2020
Revised: 13 January 2021
Accepted: 17 January 2021
Published: 01 March 2021
Issue date: June 2021

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© The Author(s) 2021

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China under Grant Nos. 51972089, 51672064, and U1637210.

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