Charge distribution and local structure and speciation in the UO{sub 2+x} and PuO{sub 2+x} binary oxides for x=<0.25
- Los Alamos National Laboratory, Chemistry Division, Materials Science and Technology Division and Nuclear Materials Technology Division, Los Alamos, NM 87545 (United States)
- Australian Nuclear Science and Technolgy Organisation, Menai, NSW 2234 (Australia)
- Los Alamos National Laboratory, Chemistry Division, Materials Science and Technology Division and Nuclear Materials Technology Division, Los Alamos, NM 87545 (United States); and others
The local structure and chemical speciation of the mixed valence, fluorite-based oxides UO{sub 2+x} (0.00=<x=<0.20) and PuO{sub 2+x}/PuO{sub 2+x-y}(OH){sub 2y}.zH{sub 2}O have been determined by U/Pu L{sub III} XAFS spectroscopy. The U spectra indicate (1) that the O atoms are incorporated as oxo groups at short (1.75A) 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 UO{sub 2} fraction remains intact implying that these O defects interact to form clusters and give the heterogeneous structure consistent with the diffraction patterns. The PuO{sub 2+x} system, which does not show a separate phase at its x=0.25 endpoint, also displays (1) oxo groups at longer 1.9A distances consistent with Pu(V+{delta}), (2) a multisite Pu-O distribution even when x is close to zero indicative of the formation of stable species with H{sub 2}O and its hydrolysis products with O{sup 2-}, and (3) a highly disordered, spectroscopically invisible Pu-Pu component. The structure and bonding in AnO{sub 2+x} are therefore more complicated than have previously been assumed and show both similarities but also distinct differences among the different elements.
- OSTI ID:
- 20721762
- Journal Information:
- Journal of Solid State Chemistry, Vol. 178, Issue 2; Other Information: DOI: 10.1016/j.jssc.2004.09.029; PII: S0022-4596(04)00515-8; Copyright (c) 2004 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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