Structure and electronic states of defects in spinel of different compositions MgO center dot nAl(2)O(3): Me

This paper reviews the nature of defects and optical centers in magnesium a luminate spinel. The identification of absorption and luminescence bands wa s used to investigate the influence of UV and electron irradiation on optic al center formation. Crystals examined were nominally pure MgO-nAl(2)O(3) c rystals with compositions in the series n=1.0, 1.5, 2.0, and 2.5, MgO . Al2 O3 crystals doped with transition-metal ion dopants were also studied to de termine the influence of impurities on the nature and concentration of latt ice defects in spinel. Results strongly suggest that absorption bands at 3. 78 and 4.15 eV, and luminescence bands near 5 eV, may be attributed to opti cal centers on antisite defects. It is also apparent that through the intro duction of specific amounts of Mn and Cr ions, the concentration of optical centers (which are related to defects such as cation antisites in the spin el structure) can be considerably changed.