Reduced He ion irradiation damage in ZrC-based high-entropy ceramics

Excellent irradiation resistance is the basic property of nuclear materials to keep nuclear safety. The high-entropy design has great potential to improve the irradiation resistance of the nuclear materials, which has been proven in alloys. However, whether or not high entropy can also improve the irradiation resistance of ceramics, especially the mechanism therein still needs to be uncovered. In this work, the irradiation and helium (He) behaviors of zirconium carbide (ZrC)-based high-entropy ceramics (HECs), i.e., (Zr_0.2Ti_0.2Nb_0.2Ta_0.2W_0.2)C, were investigated and compared with those of ZrC under 540 keV He ion irradiation with a dose of 1×10¹⁷ cm⁻² at room temperature and subsequent annealing. Both ZrC and (Zr_0.2Ti_0.2Nb_0.2Ta_0.2W_0.2)C maintain lattice integrity after irradiation, while the irradiation-induced lattice expansion is smaller in (Zr_0.2Ti_0.2Nb_0.2Ta_0.2W_0.2)C (0.78%) with highly thermodynamic stability than that in ZrC (0.91%). After annealing at 800 ℃, ZrC exhibits the residual 0.20% lattice expansion, while (Zr_0.2Ti_0.2Nb_0.2Ta_0.2W_0.2)C shows only 0.10%. Full recovery of the lattice parameter (a) is achieved for both ceramics after annealing at 1500 ℃. In addition, the high entropy in the meantime brings about the favorable structural evolution phenomena including smaller He bubbles that are evenly distributed without abnormal coarsening or aggregation, segregation, and shorter and sparser dislocation. The excellent irradiation resistance is related to the high-entropy-induced phase stability, sluggish diffusion of defects, and stress dispersion along with the production of vacancies by valence compensation. The present study indicates a high potential of high-entropy carbides in irradiation resistance applications.