A Review of the Synthesis of Compositionally Complex Ultra-High-Temperature Ceramics

Abstract

Ultra-high temperature ceramics (UHTC) are a class of ceramics that possess melting points greater than 3000 °C and can withstand temperatures higher than 2000 °C without structural failure. The need to increase the performance inherently leads to the implementation of extreme temperatures, leading to the search for a new class of materials with better thermal properties. Compositionally complex ultra-high temperature ceramics with the inclusion of additional elements, whether resulting in an equimolar or non-equimolar site occupation in the respective sublattices, can improve properties due to the contributions of the configurational entropy. The term compositional complexity can be used as an umbrella term for the class of compositions with 3 or more elements and also their non-equimolar parts. The current review paper is based on the classification of the different compositionally complex ultrahigh temperature ceramics as borides, carbides, nitrides, etc., and reviews the different procedures employed for the bulk or powder synthesis thereof.