Luminescence of F0 centers in CeO2 nanocrystals

Abstract

In the paper luminescent properties of CeO2-x (ceria) nanocrystals are discussed. Ceria nanocrystals with different oxygen non-stoichiometry were obtained using sol-gel method and subsequent annealing in oxidizing or reducing atmosphere. Luminescence spectra of ceria nanocrystals reveal three types of luminescent centers. Beyond previously observed 4f-5d luminescence of Ce3+ ions and charge transfer (CT) luminescence determined by radiative relaxation in Ce4+-O2- complexes, wide luminescence band formed by F0 centers was revealed. Ratio between luminescent centers of different types can be varied by variation of treatment atmosphere. Luminescence of Ce3+ ions is the most intensive in reducing atmosphere due to highest content of oxygen vacancies, and, correspondingly, of Ce3+ ions. As CT luminescence of Ce4+-O2- complexes, so luminescence of F0 centers demonstrate strong quenching with temperature increase; however CT luminescence quenching is more pronounced than quenching of luminescence for F0 centers.