Microstructure evolution of the 5 MeV Xe20+-implanted α-MoSi₂ before and after annealing

MoSi₂ is widely used in environmental barrier coatings of high-temperature alloys and ceramic matrix composites due to its excellent high-temperature oxidation resistance and mechanical properties, making it a promising candidate for advanced nuclear energy systems. However, its irradiation behavior has not been thoroughly investigated. In this study, we explored the microstructural evolution of MoSi₂ under irradiation at room temperature (RT) and 700 °C. MoSi₂ was fully amorphized after irradiation at RT, but remained mostly crystalline at 700 °C, with rich-Mo second phases formed only in Xe-enriched regions—— these second phases had an average size of 8.09 nm. After annealing, MoSi₂ irradiated at RT recrystallized, the average size of Xe bubbles was 9.81 nm, and the striped-like structure in damage peaks contributed to the "a(amorphous phase)→β→α" phase transformation, while Xe inhibited the β→α transition. Under 700 °C irradiation condition, annealing resulted in Xe bubbles with an average size of 6.34 nm, and the (110) plane (with low surface energy and depth-parallel orientation) of MoSi₂ provided a pathway for Xe, facilitating its diffusion to the near-surface. This research provides a guidance for the use of MoSi₂ in advanced nuclear reactors.