Speciation and Unusual Reactivity in PuO2+x

• DOI: 10.1021/ic026044l
• Publication Date: 2003-06-09T04:39:41Z
• Authors: Steven D. Conradson; Bruce D. Begg; David L. Clark; Christophe Den Auwer; Francisco J. Espi...; Pamela L. Gordon; Nancy J. Hess; Ryan Hess; D. Webster Keogh; Luis A. Morales; Mary P. Neu; Wolfgang Runde; C. Drew Tait; D. Kirk Veirs; Phillip M. Villella
• Keywords: [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th]; 02 engineering and technology; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]; 0210 nano-technology

Pu L(3) XAFS measurements show that the excess oxygen in single phase PuO(2+)(x)() occurs as oxo groups with Pu-O distances of 1.83-1.91 A. This distance and the energy of the edge (via comparison with a large number of related compounds) are more consistent with a Pu(IV/V) than a Pu(IV/VI) mixture. Analogous to Pu(IV) colloids, although the Pu-Pu pair distribution remains single site even when it shows substantial disorder, the Pu-O distribution can display a number of additional shells at specific distances up to 3.4 A even in high fired materials when no oxo groups are present, implying intrinsic H(+)/OH(-)(/H(2)O). The number of oxo atoms increases when samples are equilibrated with humid air at ambient temperature, indicating that the Pu reactivity in this solid system differs notably from that of isolated complexes and demonstrating the importance of nanoscale cooperative phenomena and total free energy in determining its chemical properties.