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The order-disorder transition (ODT) of A2B2O7 compounds obtained enormous attention owing to the potential application for thermal barrier coating (TBC) design. In this work, the influence of ODT on the mechanical and thermophysical properties of dual-phase A2B2O7 high-entropy ceramics was investigated by substituting Ce4+ and Hf4+ with different ionic radii on B-sites (Zr4+). The X-ray diffraction (XRD), Raman, and transmission electron microscopy (TEM) results show that rA3+/rB4+ = 1.47 is the critical value of ODT phase boundary with different doping B-site ion contents, and the energy dispersive spectroscopy (EDS) results further indicate the uniform distribution of elements. Interestingly, owing to the high intrinsic disorder derived from high-entropy effect, the A2B2O7 high-entropy ceramics exhibit unreduced modulus (E0 ≈ 230 GPa) and enhanced mechanical properties (HV ≈ 10 GPa, KIC ≈ 2.3 MPa·m0.5). A2B2O7 high-entropy ceramics exhibit excellent thermal stability with relatively high thermal expansion coefficients (TECs) (Hf0.25, 11.20×10-6 K-1, 1000 ℃). Moreover, the matching calculation implied that the ODT further enhances the phonon scattering coefficient, leading to a relatively lower thermal conductivity of (La0.25Eu0.25Gd0.25Yb0.25)2(Zr0.85Ce0.15)2O7 (1.48-1.51 W/(m·K), 100-500 ℃) compared with other components. This present work provides a novel composition design principle for high-entropy ceramics, as well as a material selection rule for high-temperature insulation applications.


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Influence of order-disorder transition on the mechanical and thermophysical properties of A2B2O7 high-entropy ceramics

Show Author's information Jiatong ZHUaMingyue WEIaJie XUa,b( )Runwu YANGaXuanyu MENGaPing ZHANGaJinlong YANGcGuangzhong LId( )Feng GAOa,b
State Key Laboratory of Solidification Processing, MIIT Key Laboratory of Radiation Detection Materials and Devices, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China
NPU-QMUL Joint Research Institute of Advanced Materials and Structure, Northwestern Polytechnical University, Xi’an 710072, China
State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
State Key Laboratory of Porous Metal Materials, Northwest Institute for Nonferrous Metal Research, Xi’an 710016, China

Abstract

The order-disorder transition (ODT) of A2B2O7 compounds obtained enormous attention owing to the potential application for thermal barrier coating (TBC) design. In this work, the influence of ODT on the mechanical and thermophysical properties of dual-phase A2B2O7 high-entropy ceramics was investigated by substituting Ce4+ and Hf4+ with different ionic radii on B-sites (Zr4+). The X-ray diffraction (XRD), Raman, and transmission electron microscopy (TEM) results show that rA3+/rB4+ = 1.47 is the critical value of ODT phase boundary with different doping B-site ion contents, and the energy dispersive spectroscopy (EDS) results further indicate the uniform distribution of elements. Interestingly, owing to the high intrinsic disorder derived from high-entropy effect, the A2B2O7 high-entropy ceramics exhibit unreduced modulus (E0 ≈ 230 GPa) and enhanced mechanical properties (HV ≈ 10 GPa, KIC ≈ 2.3 MPa·m0.5). A2B2O7 high-entropy ceramics exhibit excellent thermal stability with relatively high thermal expansion coefficients (TECs) (Hf0.25, 11.20×10-6 K-1, 1000 ℃). Moreover, the matching calculation implied that the ODT further enhances the phonon scattering coefficient, leading to a relatively lower thermal conductivity of (La0.25Eu0.25Gd0.25Yb0.25)2(Zr0.85Ce0.15)2O7 (1.48-1.51 W/(m·K), 100-500 ℃) compared with other components. This present work provides a novel composition design principle for high-entropy ceramics, as well as a material selection rule for high-temperature insulation applications.

Keywords:

high-entropy ceramics, A2B2O7, order-disorder transition (ODT), mechanical properties, thermal conductivity
Received: 20 December 2021 Revised: 13 April 2022 Accepted: 27 April 2022 Published: 25 July 2022 Issue date: August 2022
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Publication history

Received: 20 December 2021
Revised: 13 April 2022
Accepted: 27 April 2022
Published: 25 July 2022
Issue date: August 2022

Copyright

© The Author(s) 2022.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 52072301), State Key Laboratory of New Ceramics and Fine Processing Tsinghua University (No. KFZD202102), State Key Laboratory of Solidification Processing (NPU) (No. 2021-TS-08), the China-Poland International Collaboration Fund of the National Natural Science Foundation of China (No. 51961135301), the Fundamental Research Funds for the Central Universities (No. D5000210722), and State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology (No. P2020-009). We would like to acknowledge the Analytical & Testing Center of Northwestern Polytechnical University for the XRD, SEM, and other analyses.

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