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Title: Incorporation of uranium in pyrochlore oxides and pressure-induced phase transitions
Authors: Zhang, FX
Lang, M
Tracy, C
Ewing, RC
Gregg, DJ
Lumpkin, GR
Keywords: Zirconates
Rare earths
X-ray diffraction
Raman spectroscopy
Issue Date: 1-Nov-2014
Publisher: Elsevier - ScienceDirect
Citation: Zhang, F. X., Lang, M., Tracy, C., Ewing, R. C., Gregg, D. J., & Lumpkin, G. R. (2014). Incorporation of uranium in pyrochlore oxides and pressure-induced phase transitions. Journal of Solid State Chemistry, 219(0), 49-54. doi:10.1016/j.jssc.2014.07.011
Abstract: Uranium-doped gadolinium zirconates with pyrochlore structure were studied at ambient and high-pressure conditions up to 40 GPa. The bonding environment of uranium in the structure was determined by x-ray photoelectron and Raman spectroscopies and x-ray diffraction. The uranium valence for samples prepared in air is mainly U6+, but U4+ is present in pyrochlores fabricated in an argon atmosphere. Rietveld refinement of the XRD pattern suggests that uranium ions in pyrochlores are on the 16d site in 6-fold coordination with oxygen. At pressures greater than 22 GPa, the pyrochlore structure transformed to a cotunnite-type phase. The cotunnite high-pressure phase transformed to a defect fluorite structure on the release of pressure. © 2014 Elsevier Inc.
Gov't Doc #: 7579
ISSN: 0022-4596
Appears in Collections:Journal Articles

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