Polycrystalline pyrochlore Lu 2 Ti 2 O 7 pellets are irradiated with 600-keV Kr 3+ ions up to a fluence of 1.45 × 10 16 Kr 3+ /cm 2 . 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 × 10 15 Kr 3+ /cm 2 , and the results are explained with a direct-impact model. However, when the irradiation fluence is higher than 2 × 10 15 Kr 3+ /cm 2 , 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 × 10 15 Kr 3+ /cm 2 . No full amorphization is achieved even at the highest fluence of 1.45 × 10 16 Kr 3+ /cm 2 (∼36 displacement per atom). The high irradiation resistance of pyrochlore Lu 2 Ti 2 O 7 at higher fluence is explained on the basis of enhanced radiation tolerance of nano-crystal structure.

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