Abstract
This work considers the effect of fission-energy ion irradiation on the electronic structure at the surface of bulk and thin film samples of CeO2 as a simulant for UO2 nuclear fuel. For this purpose, thin films of CeO2 grown on Si substrates and bulk CeO2 samples were irradiated by Xe ions (92 MeV, 4.8 × 1015 ions/cm2) to simulate the fission damage that occurs within nuclear fuels. The irradiated and unirradiated samples were characterized by X-ray photoelectron spectroscopy. A technique of the quantitative evaluation of cerium ionic composition on the surface of the samples has been successfully applied to the obtained XPS spectra. This technique is based on the intensity of only one of the reliably identifiable high-energy peak at 916.6 eV in the Ce 3d XPS spectra. The as-produced samples were found to contain mostly the Ce4+ ions with a small fraction of Ce3+ ions formed on the surface in the air or under X-rays. The core-electron XPS structure of CeO2 was associated with the complex final state with vacancies (holes) resulting from the photoemission of an inner electron. The Xe ion irradiation was found to increase the Ce3+ content in the samples of CeO2, with the thin films being more sensitive than the bulks samples.
Highlights
Cerium dioxide, CeO2, is a fluorite structure ceramic widely used as an inactive structural surrogate to UO2 and PuO2 to avoid difficulties associated when working with radioactive materials [1,2]
Thin films of CeO2 on Si substrates and bulk CeO2 samples were irradiated with 129Xe23+ ions of 92 MeV to a fluence of 4.8 Â 1015 ions/cm2 to simulate the damage produced by fission fragments in nuclear fuel
The Kratos charge neutraliser system was used and BEs were measured relative to the BE of the C 1s were used: 1.00 (C 1s) electrons from hydrocarbons adsorbed on the sample surface that was accepted to be equal to 285.0 eV on the gold plate Eb(Au 4f7/2) = 84.0 eV and Eb(C 1s) =
Summary
CeO2, is a fluorite structure ceramic widely used as an inactive structural surrogate to UO2 and PuO2 to avoid difficulties associated when working with radioactive materials [1,2]. Showed on the basis of the calculations that CeO2 contains only Ce4+ ions, and the Ce 3d structure appears due to the complex final state containing the ground state Ce 3d94f0 and two exited final states 3d94f1OVMOÀ1 and 3d95p5np1 These results agree with the experimental data of Ref. This work considers the explicit effect of radiation damage by fission-energy ions on non-stoichiometry in CeO2 as an inactive analogue to the UO2 matrix of nuclear fuel and outlines a methodology developed for determining the degree of non-stoichiometry in CeO2-x. For this purpose, thin films of CeO2 on Si substrates and bulk CeO2 samples were irradiated with 129Xe23+ ions of 92 MeV to a fluence of 4.8 Â 1015 ions/cm to simulate the damage produced by fission fragments in nuclear fuel. A similar work has been done using UO2 thin films in Ref. [48]
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