Inorg. Chem. 2006, 45, 8408−8413
Neutron Diffraction Studies of U4O9: Comparison with EXAFS Results F. Garrido Centre de Spectrome´ trie Nucle´ aire et de Spectrome´ trie de Masse, CNRS-IN2P3, UniVersite´ Paris-Sud, F-91405 Orsay Campus, France A. C. Hannon and R. M. Ibberson ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, U.K. L. Nowicki The Andrzej Soltan Institute for Nuclear Studies, ul. Hoza 69, PL-00-681 Warsaw, Poland B. T. M. Willis* Chemistry Research Laboratory, UniVersity of Oxford, Mansfield Road, Oxford OX1 3TA, U.K. Received June 1, 2006
Conradson et al.1 have analyzed X-ray absorption fine-structure spectra of the UO2−U4O9 system and concluded that oxygen atoms are incorporated in U4O9 as oxo groups with U−O distances in the range 1.72−1.76 Å. They also found that the uranium sublattice consists of an ordered portion and an additional ‘spectroscopically silent’ glassy portion. We have carried out studies of powdered U4O9 by neutron diffraction which contradict these conclusions from EXAFS measurements. Our analysis shows that there are no U−O bonds shorter than 2.2 Å and that U4O9 is crystallographically ordered with no evidence of a glassy structure.
Introduction At high temperatures, excess oxygen is incorporated in uranium dioxide, UO2, to form UO2+x, and as oxidation proceeds, many crystallographically distinct phases are formed in the range 0 < x 1/2. and k, 1/2 ) 1/2) which are less than half our values for σ ()1/2 values and which are broadly consistent with the
