Opposite trends in the microstructural evolution of irradiated ceramics driven by asymmetric defect migration energies

Abstract : X-ray diffraction experiments complemented with numerical simulations reveal that two ceramic oxide materials, c-ZrO$_2$ and MgO, under similar ion irradiation conditions, exhibit an unexpected, opposite response with varying the irradiation temperature. In fact, the final damage state is reached faster in c-ZrO$_2$ with increasing temperature than in MgO. Rate equation cluster dynamics simulations show that defect clustering is favored in c-ZrO$_2$ while defect annealing is enhanced in MgO. This contrasting behavior can be rationalized in terms of the asymmetry in the interstitial vs. vacancy defect migration energies. We demonstrate that these trends allow qualitatively reproducing the evolution with temperature of the experimental disorder.