High Entropy & Compositionally Complex Ceramics (HECs/CCCs): A Review on Design, Processing, Properties and Emerging Applications

Abstract

High Entropy Ceramics (HECs) and Compositionally Complex Ceramics (CCCs) are new class of advanced ceramic materials derived from the concept of high entropy alloys. Instead of one or two principal elements, these ceramics consist of multiple principal cations in near equal proportion forming single phase solid solutions. Such unusual composition leads to exceptional thermal stability, mechanical strength, and oxidation resistance and radiation tolerance. In recent years, researchers are showing interest towards HECs because of their promising applications in extreme environments such as aerospace, nuclear reactors, cutting tools and thermal barrier coatings. This review paper discusses the fundamental concept, thermodynamic principles, synthesis methods, microstructural characteristics, mechanical and functional properties and recent applications of HECs/CCCs. Also challenges in fabrication and future research direction are highlighted. Although this field is still developing, HECs are expected to play an important role in next generation structural and functional ceramics.

KEYWORDS: High Entropy Ceramics, Compositionally Complex Ceramics, Solid Solution, Thermal Stability, Ultra-High Temperature Ceramics, Advanced Materials