| Abstract Scope |
This talk will first review our recent studies of high-entropy ceramics (HECs), including high-entropy borides [Scientific Reports 2016], perovskite [Scripta 2018] and fluorite [JECS 2018] oxides, and silicides [J. Materiomics 2019], as well as single-phase high-entropy intermetallic compounds (aluminides) that bridge high-entropy metals and ceramics [Science Bulletin 2019]. Up to 2020, nearly all work of HECs has focused on five-component, equimolar compositions. We proposed a step forward to expand HECs to compositionally complex ceramics (CCCs) to include medium-entropy and non-equimolar compositions; see a perspective in J. Mater. Sci. 55:9812 (2020). For example, we found better thermally-insulating yet stiff CCCs in non-equimolar YSZ-like fluorite CCCs [JECS 2020] and in ordered pyrochlores with substantial size disorder [Scripta 2020]. It is demonstrated that medium-entropy ceramics can prevail over their high-entropy counterparts. The diversifying classes of CCCs provide even more possibilities than HECs to tailor the composition, defects, disorder/order, and, consequently, various properties. |