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Gd2Zr2O7 ceramics with different grain sizes ranging from nanoscale to submicron scale (91, 204, and 634 nm) were irradiated at room temperature using 190 keV He ions with doses ranging from 5 × 1016 to 5 × 1017 ions/cm2. We fully characterized the pre‐ and post‐irradiation samples using grazing‐incidence X‐ray diffraction (GIXRD), scanning electron microscope (SEM), and atomic force microscope (AFM) as the grain size and degree of irradiation vary. The results suggested that all three Gd2Zr2O7 samples demonstrate outstanding radiation tolerance to displacement damage by retaining their crystallinity after irradiation at 5 × 1017 ions/cm2. which is equal to 16 displacement per atom (dpa) at peak positions. Although lattice expansion was observed at a He irradiation at 5 × 1016 ions/cm2 and beyond, the lattice remained stable for the nanograin ceramic, while the degree of distortion for the sample with the largest grain size (634 nm) continuously increased. Moreover, a delayed He bubble evolution process was seen for the nanograin ceramic, which did not appear for the submicron‐grained sample. Interestingly, the grain size‐dependent surface blistering was also found to be a function of ion fluence. After He irradiation at 5 × 1017 ions/cm2 the AFM root‐mean‐square(RMS) roughness variation for Gd2Zr2O7 ceramics of 91, 204, and 634 nm were 4.8, 7.0, and 11.1 nm, respectively.

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