Title

Microstructural Evolution and Mechanical Properties of (Mg,Co,Ni,Cu,Zn)O High-Entropy Ceramics

Abstract

The reaction sequence and mechanical properties were studied for (Mg,Co,Ni,Cu,Zn)O high-entropy ceramics that were synthesized using field-assisted sintering technology. The evolution from binary oxide starting powders to a single-phase rock salt structure exhibited a distinct incorporation sequence. For the rock salt oxides, MgO and CoO had the lowest vacancy formation energies and were the first to be incorporated into the high-entropy ceramic followed by NiO, which had a higher vacancy formation energy. Both CuO and ZnO had different crystal structures, and were incorporated into the single phase structure after the rock salt oxides due to the additional energy barrier associated with the transformations from their original structures to the rock salt structure. Distinctive morphological features including Cu-rich regions and lattice distortion were observed in the high entropy ceramic. In addition, a trade-off between densification and grain growth resulted in a maximum in strength (323 MPa) and elastic modulus (108 GPa) after densification at 900°C. This study has revealed new information that can be used to design other high-entropy ceramics including selection criteria for constituent compounds based on crystal structure and defect formation energy as well as the effects of grain size and porosity on control strength and elastic modulus.

Department(s)

Materials Science and Engineering

Comments

This work was financially supported by the National Key Research and Development Program of China (No. 2018YFB0905600, 2017YFB0310400), the National Natural Science Foundation of China (No. 51472188, and 51521001), Natural Research Funds of Hubei Province (No. 2016CFB583), Fundamental Research Funds for the Central Universities in China, State Key Laboratory of Advanced Electromagnetic Engineering and Technology (Huazhong University of Science and Technology), and the "111" project (No. B13035). WGF acknowledges support from the Enabling Materials for Extreme Environments signature area at Missouri S&T.

Keywords and Phrases

Field-Assisted Sintering Technology; High-Entropy Ceramics; Mechanical Property; Phase Evolution

International Standard Serial Number (ISSN)

0002-7820; 1551-2916

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2019 The American Ceramic Society, All rights reserved.

Publication Date

01 Apr 2019

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