Crystal structure of U1-yLnyO2-x (Ln = Gd, Er) solid solution

[摘要] The crystal structure was evaluated for U(1-y)Ln(y)O(2-x) (Ln = Gd, Er; y = 0-0.4) samples sintered at 1973 K for 8 h under Ar and Ar-10% H-2 atmospheres. The effect of LnO(1.5) doping on the crystal structure was investigated by X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The structures were refined by Rietveld analysis of the XRD patterns. LnO(1.5) doping into UO2 reduced the lattice parameter of UO2-LnO(1.5) solid solutions up to 40 mol % LnO(1.5). The lattice parameters of these samples were comparable to those of stoichiometric (U,Ln)O-2.00 solid solutions, that is, the O/M ratios were close to 2.00. XAFS spectra in the X-ray absorption near edge structure region showed that higher U oxidation states of + 5 or + 6 formed, in addition to + 4. Extended XAFS indicated that the interatomic distances of U-O and Gd-O decreased with increasing y , whereas those of Er-O may not decrease monotonically. (C) 2021 Elsevier B.V. All rights reserved.

[发布日期] 2021-12-01

[关键词] UO2;Burnable poisons;Crystal structure;XRD;XAFS;Synchrotron radiation