Hardening of MgO single crystals by electron and neutron irradiation

Measurements of the flow stress and optical coloration have been made at room temperature on a number of MgO single crystals as a function of neutron and electron irradiation. The flow stress increase due to electron irradiation is found to be proportional to the square root of the concentration of negative-ion vacancies produced by the irradiation. In the case of neutron irradiation the incremental increase in flow stress is proportional to the square root of the neutron dose. A comparison of these data with hardening due to impurity-vacancy pairs in Fe and Cr-doped MgO indicates that the radiation hardening is due to interstitial type defects.