The local structure of iron and uranium ions in a series of iron phosphate glasses with the general composition (40 - x)Fe2O3-xUO2-60P2O5 and (1-x-y)(40Fe2O3-60P2O5)-xUO2-y(Na2O or CaO) was investigated using Fe K-edge and U LIII-edge x-ray absorption fine structure spectroscopy. Replacing Fe2O3 by UO2 in the glass caused more distortion in the coordination environment of Fe(III) ions. Extended x-ray absorption fine structure fits revealed that the Fe-P bonds observed in the base glass also existed in all the waste-loaded glasses. X-ray absorption near-edge structure showed that the uranium ions were predominantly present as U(IV) in the glasses. Uranium ions were coordinated to approximately 8 ± 1 oxygen atoms and 2.5 ± 0.6 phosphorus atoms at an average distance of 2.47 ± 0.02 and 3.8 ± 0.02 Å, respectively. There were no Fe-U or U-Fe neighbors observed, indicating that uranium ions occupied voids in the glass away from the PO4 units. These conclusions were supported by Mössbauer, x-ray photoelectron, and Raman spectroscopic data.
M. Karabulut and G. K. Marasinghe and C. S. Ray and D. E. Day and G. D. Waddill and P. G. Allen and C. H. Booth and J. J. Bucher and D. L. Caulder and D. K. Shuh and M. Grimsditch and M. Saboungi, "Local Environment of Iron and Uranium Ions in Vitrified Iron Phosphate Glasses Studied by Fe K and ULIII-edge X-Ray Absorption Fine Structure Spectroscopy," Journal of Materials Research, Materials Research Society, Jan 2000.
The definitive version is available at http://dx.doi.org/10.1557/JMR.2000.0284
Materials Science and Engineering
United States. Department of Energy
Article - Journal
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