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Microstructural evolution and mechanical properties of (Mg,Co,Ni,Cu,Zn)O high‐entropy ceramics
Author(s) -
Hong Weichen,
Chen Fei,
Shen Qiang,
Han YoungHwan,
Fahrenholtz William G.,
Zhang Lianmeng
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16075
Subject(s) - materials science , sintering , ceramic , elastic modulus , grain size , vacancy defect , mineralogy , crystal structure , grain growth , porosity , configuration entropy , crystallography , metallurgy , composite material , thermodynamics , geology , chemistry , physics
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.