Charge and mass transfer involving hydrogen in MgO crystals thermochemically reduced at high temperatures

Optical-absorption measurements show that H^- ions are thermally much more stable than anion vacancies when thermochemically reduced MgO samples are annealed in a reducing atmosphere. At 1900 K all anion vacancies are annihilated, but the concentration of H^- ions remains unchanged. Results of electron irradiations on a crystal annealed at 1900 K demonstrate unambiguously that the infrared-absorption peaks previously attributed to H^- ions are indeed due to protons in anion sublattice sites. H^- concentrations can be obtained from the infrared absorbance of the H^- ions. The lifetime of the 2.3-eV F-center phosphorescence is shown to be affected by the relative concentrations of H^- ions to anion vacancy. Decreasing the anion-vacancy concentration by thermal annealing, thereby increasing the relative concentration of H^- ions to anion vacancies, leads to an enhancement of the lifetime of the phosphorescence.