Radiation-induced swelling and softening in magnesium aluminate spinel irradiated with high-flux Cu− ions

Magnesium aluminate spinel of single crystal was irradiated with 60 keV Cu− at a flux up to 6.2 × 1018 ions/m2 s, to a total fluence of 3 × 1020 ions/m2, in order to study changes in hardness and step-height swelling by high-flux implantation. Hardness determined by nano-indentation measurements steeply decreased with implantation. There is a strong negative correlation between flux dependences of the hardness and the step-height swelling: the former decreases as the latter increases. The Rutherford backscattering spectrometry (RBS)/channeling measurements showed that the spinel is not completely amorphized over the flux range in this study, and the radiation-induced softening observed is not due to amorphization. Results of optical absorbance suggested that radiation-induced point defects and their clusters on the anion sublattices of the spinel played an important role in the radiation-induced swelling under high-flux ion implantation.