Characterization of Sb-doped Bi2UO6 Solid Solutions by X-ray Diffraction and X-ray Absorption Spectroscopy

The preparation and characterization of Sb-doped Bi2UO6 solid solutions, in a limited composition range, is reported for the first time. The solid solutions were prepared by solid-state reactions of Bi2O3, Sb2O3 and U3O8 in the required stoichiometry. The reaction products were characterized by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) measurements at the Bi and U L-3 edges. The XRD patterns indicate the precipitation of additional phases in the samples when Sb doping exceeds 4 at%. The chemical shifts of the Bi absorption edges in the samples, determined from the XANES spectra, show a systematic variation only up to 4 at% of Sb doping and support the results of XRD measurements. These observations are further supported by the local structure parameters obtained by analysis of the EXAFS spectra. The local structure of U is found to remain unchanged upon Sb doping indicating that Sb+3 ions replace Bi+3 during the doping of Bi2UO6 by Sb.