Irradiation-induced amorphization accelerated by elemental migration near the surface of fluorapatite

SM Jiang and R Yin and XT Hu and JM Zhu and SH Liu and MZ Ma and SG Dong and J Zhang, APPLIED SURFACE SCIENCE, 701, 163287 (2025).

DOI: 10.1016/j.apsusc.2025.163287

The free surface, acting as a sink, invariably exerts an impact on the evolution of irradiation damage in the near-surface region, though its mechanism in multi-component compounds remains unclear. This study investigates fluorapatite, a potential nuclear waste form, through ex- situ and in-situ irradiation experiments, and MD simulations. Results show that the near-surface region tends to be amorphous preferentially due to the unbalanced elements diffusion, with effects extending over 400 nm at 493 K. Directional irradiation induces displacement atoms inward, increasing surface vacancy accumulation. Higher defect concentrations enhance element diffusion coefficients. Once amorphized, defects diffuse rapidly and are pinned by sinks, such as the free surface and numerous vacancy-type defects. Studying the amorphization of the near-surface region is helpful for grasping the weaknesses of irradiation resistance, and is crucial for evaluating the long-term service performance of nuclear waste forms.

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