Valence compensation of thermally generated[Li]0defects in MgO

The creation of thermally generated ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ defects (configuration: ${\mathrm{O}}^{2-}$-${\mathrm{Li}}^{+}$-${\mathrm{O}}^{-}$) and other lithium-associated centers in MgO is attended by valence changes of transition-metal impurities, such as Fe and Cr. The electron-paramagnetic-resonance (EPR) technique was used to monitor the concentrations of these impurities and the ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ defects as a function of the incubating temperature in static air. Although near the threshold temperature for ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ production the impurities may contribute a significant portion of the holes needed for the valence compensation of stabe ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ defects, at higher temperatures (∼1600 K) they can supply only a small percentage of the holes required. Since oxygen was found to be necessary for the formation of ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ defects, the primary source of holes at these high temperatures is attributed to the surface reaction: ${\mathrm{O}}_2$→${2\mathrm{O}}^{2-}$+4 holes. The effects of optical bleaching and ionizing radiation at 77 K on the concentrations were studied as a function of incubating temperatures. Electron-nuclear double resonance (ENDOR) was used to probe the local environments of the ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ defects and other lithium-associated centers.