Abstract
We used cathodoluminescence (CL) spectroscopy to characterize the oxygen vacancies (VO) in ceria (CeO2). The effects of the processing atmosphere and thermal quenching temperature on the nature and distribution of the intrinsic defects and on the spectroscopic behavior were investigated. The presence of polarons and associates of the polarons with the oxygen vacancies such as (VO••–CeCe′)• is demonstrated. CL intensity quenching above a critical concentration of VO has been shown. Even though the emission centers in all samples are the same, their concentration changes with the oxygen partial pressure of the processing atmosphere. Deconvolution of the observed CL spectra shows that the emissions originating from the F0 centers prevail over those of F+ centers of VO when the defect concentration is high.
Highlights
Because of its fundamental ability to accommodate a large number of defects without destabilizing the crystal structure, cerium oxide has become a technologically important material that finds its use in many areas
Samples CeO2 nanopowder sintered in oxygen (C-O), C for h in air (C-A), and CeO2 sintered in nitrogen (C-N) have been sintered in oxygen, air, and nitrogen atmospheres, respectively, with the scope of obtaining CeO2 samples having an increasing concentration of oxygen vacancies because of processing in higher to lower oxygen partial pressure atmospheres
The oxygen vacancy-related CL emission from pure CeO2 heat-treated in different atmospheres was presented here
Summary
Because of its fundamental ability to accommodate a large number of defects without destabilizing the crystal structure, cerium oxide (ceria, CeO2) has become a technologically important material that finds its use in many areas. From a crystallographic point of view, this means that the ceria crystal structure can tolerate a high density of oxygen vacancies and reduced cerium ions, Ce3+. The density of these defects is associated with the external oxygen partial pressure. There have been extensive studies on defects in ceria, which focused on their formation by doping, treatment in reductive or oxidative atmosphere,[3,4] and the dependence on a crystal size[5,6] and atomic surface structures.[7,8]
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