Structural study of the rhombohedral fluorite-related R{sub III} phase U{sub 1-y}La{sub y}O{sub 2{+-}x{prime}} 0.56 {le} y {le} 0.67

Journal Article · Sat Oct 01 04:00:00 EDT 1994 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1994.1312· OSTI ID:508693

Rojas, R M; Herrero, P; Garcia Chain, P J ^[1]

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1. CSIC, Madrid (Spain); and others

The structural relationships between the R{sub III} phase, existing in the UO{sub 3}-UO{sub 2}-LaO{sub 1.5} system for the compositional range U{sub 1-y}La{sub y}O{sub 2{+-}x} (0.56 {le} y {le} 0.67), and the fluorite structure have been definitely established by means of electron diffraction. The determination of the structure has been carried out using both X-ray and neutron powder diffraction. The R{sub III} phase constitutes a partially cation-ordered fluorite-related structure, where La and U/La layers alternate along [111]c. The rhombohedral lattice, in its hexagonal setting, is related to the cubic fluorite substructure by the relations a{sub H} = {1/2}a{sub C} - {1/2}b{sub C}, b{sub H} = {1/2}b{sub C} - {1/2}c{sub C}, c{sub H} = 2(a{sub C} + b{sub C} + c{sub C}). The space group (R3m), cell parameters a{sub H} {approx} 3.9 {Angstrom} and C{sub H} {approx} 18.9 {Angstrom}, and the refined structure show that the R{sub III} phase can be considered as isomorphous to the CaUO{sub 4} structure.

• OSTI ID: 508693
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 112; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
40 CHEMISTRY
ELECTRON DIFFRACTION
LANTHANUM OXIDES
NEUTRON DIFFRACTION
PHASE STUDIES
STOICHIOMETRY
TRIGONAL LATTICES
URANIUM OXIDES
X-RAY DIFFRACTION