Pulsed Cathodoluminescence Spectra of Solid Oxides with Low   Concentrations of Optically-Active Impurities
  Pulsed cathodoluminescence (PCL) spectra of ultra-pure SiO2, GeO2, SnO2, TiO2, La2O3, Y2O3, Sc2O3, CaCO3 powders and {\alpha}-quartz, Ca:YVO4, LiNbO3 and Sc:LiNbO3 crystals were studied under the same experimental conditions. It was found that PCL spectra of SiO2, SnO2, GeO2, TiO2, La2O3 and CaCO3 powders contain a common band with maximum intensity at 500 nm, PCL spectra of samples Y2O3, Sc2O3, PbWO4 and Ca:YVO4 contain a common band at 490 nm and PCL spectra of LiNbO3 and Sc:LiNbO3 crystals contain a common band at 507 nm. It was found that the average intensity of the PCL spectra and position of the maximum intensity of these common bands depend on the type of a band gap transition of the material. We suppose that these common bands have the same origin in PCL spectra of all the materials studied and are related to recombination of O2--O-oxygen complexes. These complexes appear in the vicinities of anionic and cationic vacancies, where the geometry and orientation of coordination polyhedrons are violated due to the stress in the lattice. 
V.A. Kozlov, S.A. Kutovoi, N.V. Pestovskii, A.A. Petrov, S.Yu.   Savinov, Yu.D. Zavartsev, M.V. Zavertyaev and A.I. Zagumenniy
physics.optics cond-mat.mtrl-sci