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

1983; American Physical Society; Volume: 27; Issue: 2 Linguagem: Inglês

10.1103/physrevb.27.1276

1095-3795

Y. Chen, R. González, O. E. Schow, G.P. Summers,

Photorefractive and Nonlinear Optics

Optical-absorption measurements show that ${\mathrm{H}}^{\ensuremath{-}}$ 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 ${\mathrm{H}}^{\ensuremath{-}}$ ions remains unchanged. Results of electron irradiations on a crystal annealed at 1900 K demonstrate unambiguously that the infrared-absorption peaks previously attributed to ${\mathrm{H}}^{\ensuremath{-}}$ ions are indeed due to protons in anion sublattice sites. ${\mathrm{H}}^{\ensuremath{-}}$ concentrations can be obtained from the infrared absorbance of the ${\mathrm{H}}^{\ensuremath{-}}$ ions. The lifetime of the 2.3-eV $F$-center phosphorescence is shown to be affected by the relative concentrations of ${\mathrm{H}}^{\ensuremath{-}}$ ions to anion vacancy. Decreasing the anion-vacancy concentration by thermal annealing, thereby increasing the relative concentration of ${\mathrm{H}}^{\ensuremath{-}}$ ions to anion vacancies, leads to an enhancement of the lifetime of the phosphorescence.