Anisotropy of local electrical conductivity of hyper-stoichiometric uranium dioxide revealed by current-sensing atomic force microscopy (CS-AFM)

• Published in: Electrochemistry communications Vol. 10; no. 11; pp. 1805 - 1808
• Main Authors: O’Neil, Kevin D., He, Heming, Keech, Peter, Shoesmith, David W., Semenikhin, Oleg A.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.11.2008; Amsterdam Elsevier; New York, NY
• Subjects: Analysis methods; Applied sciences; Current-sensing atomic force microscopy; Exact sciences and technology; Hyper-stoichiometric uranium dioxide; Local conductivity; Local corrosion; Nuclear waste disposal; Pollution; Radioactive wastes; Wastes; Current-sensing atomic force microscopy; Hyper-stoichiometric uranium dioxide; Local conductivity; Nuclear waste disposal; Local corrosion; Radioactive waste; Atomic force microscopy; Scanning electron microscopy; Stoichiometry; Electrical conductivity; Electrochemical detector; Surface structure; Corrosion; Actinide Compounds; Anisotropy; Conductometry; Morphology; Raman spectrometry; Uranium dioxide
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2008.09.009

The local electrical conductivity and chemical composition of hyper-stoichiometric uranium dioxide were studied using localized Raman and current-sensing AFM techniques. Distinct types of surface features, representative of either stoichiometric or hyper-stoichiometric uranium dioxide, and remarkably different in their electrical conductivity, were identified. Stoichiometric UO 2 formed smooth featureless grains and showed little or no electrical conductivity, while considerably more conducting hyper-stoichiometric UO 2+ x formed characteristic ridges and/or facetted structures. Surprisingly, such hyper-stoichiometric regions also showed anisotropic electrical conductivity and combined relatively non-conducting flat terraces with a highly conducting inclined facets. Our CS-AFM measurements clearly indicate that the highly conducting grain boundaries, as well as facetted grains and grain regions, are the prime locations for local corrosion.