Kazarinov Y. Influence of the structure defects and impurities on the optical and luminescence properties of the magnesium aluminate spinel crystals

The dissertation is devoted to the investigation of the influence of concentration and spatial distribution of structure defects and impurity ions on the optical and luminescence properties of magnesium aluminate spinel crystals. Changes in the concentration and spatial distribution of antisite defects of in spinel crystals and ceramics caused by molar composition and growth methods of nominally pure single crystals of spinel are studied. It was established that antisite defects form a spatially correlated pairs, which serve as UV luminescence centers. Deviation from the stoichiometric molar composition results in reduction of lattice parameter that affects the spectral characteristics of the absorption centers as well as luminescence centers. For crystals with the same composition, different growth conditions of crystals cause differences in the energy depth of the traps that affect the kinetic parameters of luminescence. It is shown that the concentration of antisite defects increases with the addition of impurities and under neutron irradiation. When using the spinel crystals for producing the optical devices applied under the irradiation conditions one can avoid undesirable decreasing of transparency and/or luminescence by maintaining the appropriate temperature of the crystals.