A detailed Raman and X-ray study of UO2+x oxides and related structure transitions. Issue 40 (3rd October 2016)

• Record Type: Journal Article
• Authors: Elorrieta, J. M.; Bonales, L. J.; Rodríguez-Villagra, N.; Baonza, V. G.; Cobos, J.
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 40(2016)
• Page Start: 28209
• Page End: 28216
• Publication Date: 2016-10-03
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp03800j
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Quantitative analysis of hyperstoichiometric UO2+ x oxides by means of Raman and X-ray diffraction techniques. Abstract : This work presents a detailed study of hyperstoichiometric UO2+ x (0 < x < 0.25) oxides and an assessment of the structural evolution taking place as oxidation proceeds. For this purpose, different UO2+ x powder samples with controlled degree of non-stoichiometry have been identified by thermogravimetric analysis and characterized by X-ray diffraction (XRD) and Raman spectroscopy. XRD analysis reflects that the commonly assumed Vegard's law is not applicable over the whole hyperstoichiometry range, since a slight increase of the lattice constant is observed for 0.13 < x < 0.20. A quantitative Raman analysis of the UO2+ x spectra as a function of the oxidation degree is also shown. A new method to characterize any UO2+ x sample (for x < 0.20), based on the shift of the 630 cm −1 band observed in the Raman spectrum, is proposed here for the first time. Moreover, three structure transitions have been detected at x = 0.05, 0.11 and 0.20, giving rise to four distinct regions associated with consecutive structural rearrangements over the hyperstoichiometry range: x < 0.05, 0.05 < x < 0.11, 0.11 < x < 0.20 and 0.20 < x < 0.25.