Influence of Nd doping on the structural and electrochemical properties of uranium dioxide

The influence of the Nd-doping ratio and oxygen vacancies on the structural properties and electrochemical reactivity of U1-yNdyO2-x (x approximate to y/2, y = 0.02, 0.06, and 0.1) solid solutions was investigated using X-ray diffraction, Raman spectroscopy, and cyclic voltammetry. Defect structures induced by oxygen vacancies were observed with Raman spectroscopy, which showed that Raman modes shifted to higher wavenumbers with increasing doping ratio. This result is indicative of a crystal lattice disorder caused by oxygen vacancies. The wavenumber shifts and relative ratios of the Raman modes were indicators of the composition and oxygen vacancies, respectively, of the U1-yNdyO2-x solid solutions. The oxygen deficiencies of the solid solutions were estimated from the relation between the doping ratio and lattice parameter calculated from X-ray diffraction patterns. Cyclic voltammetry revealed that changes in the Nd content influenced the electrochemical reactivity of hypo-stoichiometric U1-yNdyO2-x, which increased with increasing Nd content. The results of this study provide fundamental data to improve the understanding of spent nuclear fuel.