Abstract
High-resolution x-ray photoemission spectroscopy (XPS) was used to examine the surface composition and chemical bonding of calcined UO2 powders as a function of process parameters. It is believed that the surface composition of the powder grains ultimately affects packing density. XPS quantitative analysis revealed O/U ratios indicative of mixed uranium valences. In addition, high-resolution U 4f7/2,5/2 core-level spectra revealed reoxidation of U4+ to U6+ for the lower temperatures, and a reduction of U6+ to U4+ for the higher temperatures using 4% H2/Ar. Reoxidation can also be affected by the presence of water or OH, and the powder samples calcined at the lower temperatures have the highest OH−/O2− peak area ratio. The valence-band electronic structure for the higher-temperature calcinations clearly shows a stronger 5f emission peak near the Fermi edge, a feature that is indicative of a highly localized state. Bulk structural analysis using x-ray diffraction also indicates a number of uranium oxide pha...
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Schedule a callMore From: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films
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