Uncovering the effects of chemical disorder on the irradiation resistance of high-entropy carbide ceramics

Ultra-high temperature ceramics (UHTCs) hold great potential as structural materials in advanced nuclear reactors that operate in harsh environments characterized by high temperatures and irradiation doses. In this study, we explore the accumulation and evolution of irradiation-induced defects in high-entropy ceramics composed of multiple principal components derived from binary UHTCs, aiming to optimize their irradiation performance. Our results based on ab initio calculations reveal that high-entropy mixing of different transition metals within the cation sublattice only has a minor impact on the irradiation defect evolution compared with ZrC. However, significant improvement in defect recovery is observed when chemical disorder is introduced to the anion sublattice to form high-entropy carbonitride ceramics. By examining the defect energetics and kinetics, we propose a parameter, that is, the recombination energy barrier of the Frenkel pair defects, to dictate the irradiation tolerance of rocksalt high-entropy ceramics, which is in stark distinction with other ceramics such as MAX phases, pyrochlores, and spinels. We further establish a correlation between the recombination barrier and formation enthalpy, suggesting that formation enthalpy can be used as a key indicator in rocksalt ceramics for composition design to improve their irradiation tolerance.