Ion irradiation temperature effect on HfO2/MgO multi-layer structures

Properties of nuclear materials may be improved by employing composite materials. However, these properties usually degrade during the operation in a nuclear reactor environment due to radiation damage accumulation. For this study we fabricated a multi-layer structure composed of MgO and HfO2 thin films on a sapphire substrate. This multi-layer structure was designed to mimic a CERCER (ceramic–ceramic) composite fuel form. The goal of this study was to investigate features of radiation damage evolution cause by ion beam irradiation in a wide temperature range. We observed phase transformation in HfO2 from monoclinic to the tetragonal polymorph and no changes in MgO. Formation of thin amorphous regions adjacent to the MgO/HfO2 and HfO2/sapphire substrate interfaces was identified in both cases. Phase and microstructural changes demonstrated pronounced dependence on irradiation temperature, which we attributed to either enhanced annihilation of irradiation induced point defects or intermixing between the components of our multi-layered structure.