Role of hydrogen and lithium impurities in radiation damage in neutron-irradiated MgO single crystals -: art. no. 224108

Radiation damage induced by neutron irradiation was studied by optical absorption measurements in undoped MgO crystals and in MgO crystals intentionally doped with either hydrogen or lithium impurities. The oxygen-vacancy concentration incurred by the neutron irradiation increases with neutron dose. Suppression of radiation damage as characterized by oxygen vacancies is observed in MgO:H crystals and attributed to migration of oxygen vacancies to microcavities filled with hydrogen gas. In MgO:Li crystals irradiated with neutron doses below 10(18) neutrons/cm(2), most of the oxygen vacancies are camouflaged as hydride ions formed by the capture of protons by the oxygen vacancies. Substitutional lithium ions are also displaced. We postulate that they aggregate at Li2O precipitates. Thermal annealing experiments demonstrate that protons are mobile at 700 K and lithium ions at 1100 K.