How relative defect migration energies drive contrasting temperature-dependent microstructural evolution in irradiated ceramics

Abstract

Ceramic materials have become widely used in various fields of material science, and ceramic oxides such as cubic zirconia (c-${\mathrm{ZrO}}_{2})$ and magnesia (MgO) are candidate materials for nuclear energy applications. For the corresponding in-service conditions of these materials, there is a crucial need in studies at moderate or high temperatures of the physical phenomena underlying the damage buildup under irradiation. In the present work, we show, using x-ray diffraction, that these two materials exhibit a similar damage accumulation process under ion irradiation at fixed temperature. However, they display an unexpected opposite damaging rate to changes in the irradiation temperature. In fact, as the temperature is increased, the final damage state is reached earlier in c-${\mathrm{ZrO}}_{2}$ while it is delayed in MgO. Rate equation cluster dynamics simulations show that defect clustering is favored over defect recombination in c-${\mathrm{ZrO}}_{2}$, but the situation is reversed for MgO, explaining the observed opposite response to temperature of the two materials. This contrasting behavior can be rationalized in terms of nonequivalent interstitial versus vacancy defect migration energies in MgO. We finally demonstrate that these results allow for a qualitative prediction of the evolution of the experimental irradiation-induced disorder with temperature, henceforth potentially reducing the cost in selecting and developing ad hoc materials.