LAUSR

Currently, high-entropy ceramics have become a research hotspot in the field of ceramics because of their unique compositions, microstructures, and notable properties.1-4 Similar to high-entropy alloys, they dissolve five or more elements together with a solid ratio of nearly equal atoms to form individual solid-solutions.5 Owing to the high-entropy effect, compared with individual ceramics, high-entropy ceramics have higher mechanical properties and better oxidation resistance.6-8 According to Boltzmann's hypothesis on the relationship between the entropy and the complexion of a system,9 for the as-defined high-entropy ceramics, the configurational entropy (∆Sconf) of equimolar ceramic compounds with five or more principal metal elements is ≥1.5R. Three-element and four-element equimolar ceramic compounds have the configurational entropy of 1.1R and 1.39R, respectively. They can be classified as medium-entropy ceramics because their configurational entropy (1R ≤ ∆Sconf ≤ 1.5R) is lower than that of high-entropy cases. Recently, medium-entropy carbide ceramics have attracted considerable attention because of their extremely Received: 5 November 2020 | Revised: 26 December 2020 | Accepted: 26 December 2020 DOI: 10.1111/jace.17677