1. Charge distribution and local structure and speciation in the UO2+ x and PuO2+ x binary oxides for x⩽0.25
- Author
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Conradson, Steven D., Begg, Bruce D., Clark, David L., den Auwer, Christophe, Ding, Mei, Dorhout, Peter K., Espinosa-Faller, Francisco J., Gordon, Pamela L., Haire, Richard G., Hess, Nancy J., Hess, Ryan F., Webster Keogh, D., Lander, Gerard H., Manara, Dario, Morales, Luis A., Neu, Mary P., Paviet-Hartmann, Patricia, Rebizant, Jean, Rondinella, Vincenzo V., and Runde, Wolfgang
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SPECTRUM analysis , *QUALITATIVE chemical analysis , *INTERFEROMETRY , *OPTICS - Abstract
Abstract: The local structure and chemical speciation of the mixed valence, fluorite-based oxides UO2+ x (0.00⩽x⩽0.20) and PuO2+ x /PuO2+ x−y (OH)2 y ·zH2O have been determined by U/Pu LIII XAFS spectroscopy. The U spectra indicate (1) that the O atoms are incorporated as oxo groups at short (1.75Å) U–O distances consistent with U(VI) concomitant with a large range of U displacements that reduce the apparent number of U neighbors and (2) that the UO2 fraction remains intact implying that these O defects interact to form clusters and give the heterogeneous structure consistent with the diffraction patterns. The PuO2+ x system, which does not show a separate phase at its endpoint, also displays (1) oxo groups at longer 1.9Å distances consistent with Pu(V+δ), (2) a multisite Pu–O distribution even when is close to zero indicative of the formation of stable species with H2O and its hydrolysis products with O2−, and (3) a highly disordered, spectroscopically invisible Pu–Pu component. The structure and bonding in AnO2+ x are therefore more complicated than have previously been assumed and show both similarities but also distinct differences among the different elements. [Copyright &y& Elsevier]
- Published
- 2005
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