Polycrystalline pyrochlore Lu2Ti2O7 pellets are irradiated with 600-ke V Kr3+ions up to a fluence of 1.45 ×1016Kr3+/cm2. Irradiation induced structural modifications are examined by using grazing incidence x-ray diffraction(GIXRD) and cross-sectional transmission electron microscopy(TEM). The GIXRD reveals that amorphous fraction increases with the increase of fluences up to 2 × 1015Kr3+/cm2, and the results are explained with a direct-impact model.However, when the irradiation fluence is higher than 2 × 1015Kr3+/cm2, the amorphous fraction reaches a saturation of^80%. Further TEM observations imply that nano-crystal is formed with a diameter of ~10 nm within the irradiation layer at a fluence of 4 × 1015Kr3+/cm2. No full amorphization is achieved even at the highest fluence of 1.45 × 1016Kr3+/cm2(~36 displacement per atom). The high irradiation resistance of pyrochlore Lu2Ti2O7 at higher fluence is explained on the basis of enhanced radiation tolerance of nano-crystal structure.
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