Maksimchuk P. Formation of luminescent centers in CeO2-x nanocrystals

The thesis is devoted to the study of the effect of oxygen stoichiometry and size of nanocrystals on the luminescence properties of CeO2-x nanocrystals. In the thesis it was shown that luminescence of CeO2-х is determined by two optical centres of different nature: the first one is Ce4+-O2- complex and the second one - Ce3+ ions. Investigation of splitting of Ce3+ 4f?5d luminescence excitation band has shown that reduction of Ce4+ occurred mainly by the mechanism of oxygen vacancy formation on the nearest-neighbour position to the cerium ion. The ratio of Се4+-О2- and Се3+-ions intensities of luminescence bands strongly depends on the oxygen non-stoichiometry. By means of two independent spectroscopic techniques (using intensity of 5d?4f luminescence of Ce3+ ions and 5D0?7F1/5D0?7F2 ratio of Eu3+ bands as indicators of the concentration of oxygen vacancies) the sufficient increase of vacancy concentration with decrease of the size of CeO2-x nanocrystals was determined.