Radiation-enhanced impurity aggregation in MgO

Electron irradiation at high temperatures of pure, Fe-, and Ni-doped MgO suppresses the ${\mathrm{Fe}}^{3+}$ and ${\mathrm{Ni}}^{2+}$ optical absorption bands, and leads to the production of precipitates containing Fe and Ni. The results suggest metallic precipitates. This process is due to radiation-induced reduction and precipitation, in which displacement damage and radiation-enhanced diffusion play an important role. In the case of Fe, the results indicate ${\mathrm{Fe}}^{2+}$ as the diffusing entity. Comparison between electron and γ-ray irradiations show that ${\mathrm{Fe}}^{2+}$ ions which are paired with other impurities do not readily diffuse under electron irradiation.