Monitoring F, F+ and F22+ related intense defect emissions from nanocrystalline MgO

MgO contains several oxygen defect related absorption peaks in the UV as well as in the visible region. The emission spectra are obtained at three different excitations, 6.02 eV (206 nm), 4.59 eV (270 nm) and 3.75 eV (330 nm) respectively. Each excitation results in an intense emission associated with F+, F22+ and F-type oxygen defect centers. These intense defect emissions mostly appear in the UV and visible region of the energy spectrum. Since the emission peaks are associated with oxygen vacancies, annealing at 800 °C reduces the intensity of these peaks. The ratio of the emission intensity of F+/F and F+/F22+ decreases at 800 °C, whereas F/F22+ intensity ratio increases at 800 °C. It is anticipated that thermal conversion of F+ and F22+ to F centers at 800 °C results in the enhancement of F/F22+ emission intensity ratio at high temperature.