title: Assessment of the U3O7Crystal Structure by X-ray and Electron Diffraction.
abstract: Polycrystalline U3O7powder was synthesized by oxidation of UO2powder under controlled conditions using in situ thermal analysis, and by heat treatment in a tubular furnace. The O/U ratio of the U3O7phase was measured as 2.34 ± 0.01. The crystal structure was assessed from X-ray diffraction (XRD) and selected-area electron diffraction (SAED) data. Similar to U4O9-ε(more precisely U64O143), U3O7exhibits a long-range ordered structure, which is closely related to the fluorite-type arrangement of UO2. Cations remain arranged identical to that in the fluorite structure, and excess anions form distorted cuboctahedral oxygen clusters, which periodically replace the fluorite anion arrangement. The structure can be described in an expanded unit cell containing 15 fluorite-like subcells (U15O35), and spanned by basis vectors A = ap- 2bp, B = -2ap+ bp, and C = 3cp(lattice parameters of the subcell are ap= bp= 538.00 ± 0.02 pm and cp= 554.90 ± 0.02 pm; cp/ap= 1.031). The arrangement of cuboctahedra in U3O7results in a layered structure, which is different from the well-known U4O9-εcrystal structure.
authors.affiliation: Belgian Nuclear Research Centre (SCK·CEN), Institute for Nuclear Materials Science , Boeretang 200, B-2400 Mol, Belgium.|Department of Chemistry, KU Leuven , Celestijnenlaan 200F, P.O. Box 2404, B-3001 Heverlee, Belgium.
authors.forename: Gregory
authors.initials: G
authors.lastname: Leinders
authors.affiliation: Belgian Nuclear Research Centre (SCK·CEN), Institute for Nuclear Materials Science , Boeretang 200, B-2400 Mol, Belgium.
authors.forename: Rémi
authors.initials: R
authors.lastname: Delville
authors.affiliation: Belgian Nuclear Research Centre (SCK·CEN), Institute for Nuclear Materials Science , Boeretang 200, B-2400 Mol, Belgium.
authors.forename: Janne
authors.initials: J
authors.lastname: Pakarinen
authors.affiliation: Belgian Nuclear Research Centre (SCK·CEN), Institute for Nuclear Materials Science , Boeretang 200, B-2400 Mol, Belgium.|Department of Chemistry, KU Leuven , Celestijnenlaan 200F, P.O. Box 2404, B-3001 Heverlee, Belgium.
authors.forename: Thomas
authors.initials: T
authors.lastname: Cardinaels
authors.affiliation: Department of Chemistry, KU Leuven , Celestijnenlaan 200F, P.O. Box 2404, B-3001 Heverlee, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Binnemans
authors.affiliation: Belgian Nuclear Research Centre (SCK·CEN), Institute for Nuclear Materials Science , Boeretang 200, B-2400 Mol, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: Verwerft