The interpretation of surface damages in Al2O3, MgAl2O4 and MgO irradiated with energetic iodine ions

Samples of polycrstalline sintered ceramics of Al2O3, MgAl2O4 and MgO were irradiated at room temperature with 85 MeV I7+ ions to doses up to 1.2×1019 m2. Both MgAl2O4 and Al2O3 samples are observed to be amorphized up to depths of approximately 5–6 μm for a dose of 1.2×1019/m2, through a cross-sectional transmission electron microscopy (XTEM). No defected clusters are observed at approximately 7.5–8.5 μm, where displacement damage due to the nuclear energy deposition is predicted to peak at 1 dpa (displacement per atom). No amorphization is observed for the MgO sample irradiated with the same dose. Instead, X-ray diffractometry (XRD) revealed an enhancement of the diffraction peaks for the (200), and (400) reflections and a reduction of peak intensities from other reflections, as compared with those before irradiation. This indicates that an atomistic rearrangement may occur along an ion path to form a new surface with the lower energy.