Radiation resistance of the oxide spinel: The role of stoichiometry on damage response

Stoichiometric and non-stoichiometric magnesio-aluminate spinel single crystals (compositions MgO . Al2O3 and MgO . 3Al(2)O(3), respectively) were irradiated with both 400 keV and 1.5 MeV Xe ions under cryogenic and room temperature conditions, in order to compare the irradiation damage response of these isostructural compounds. Overall, stoichiometric spinel was found to be more resistant to irradiation damage (microstructural alterations) than the non-stoichiometric compound. At room temperature, non-stoichiometric spinel transforms to a metastable crystalline structure at an ion dose representing 1 to 2 displacements per atom (dpa), while this transformation is not observed in stoichiometric spinel to a dose of 10 dpa. Furthermore, under cryogenic conditions, both stoichiometric and non-stoichiometric spinel undergo a metastable phase transformation, followed by a transformation to an aperiodic structure, and they do so at similar ion doses.