Microstructural characterization of the fluorite phase in the U-La-O system. I. Rhombohedral microdomain formation in (U sub 1 minus y La sub y )O sub 2+x , 0. 56 le y le 0. 67

Journal Article · Wed Aug 01 00:00:00 EDT 1990 · Journal of Solid State Chemistry; (USA)

DOI:https://doi.org/10.1016/0022-4596(90)90035-V· OSTI ID:6446982

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

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1. CSIC, Madrid (Spain)

A series of hyperstoichiometric, stoichiometric, and hypostoichiometric U-La mixed oxides with fluorite-type structures has been prepared in air at 1,673 K in the composition range (U{sub 1{minus}y}La{sub y})O{sub 2{plus minus}x}, 0.33 {le} {le} 0.67, by a mixed organic precursor/ceramic procedure. The oxidation state of uranium in these materials has been examined by XPS and near FT-IR spectroscopy, uranium ions existing within each sample either as U{sup 5+} and U{sup 6+} (0.33 {le} y {le} 0.50) or U{sup 6+} and U{sup 4+} (0.56 {le} y {le} 0.67). Electron diffraction studies reveal two sets of patterns with diffuse scattering phenomena depending on composition. The diffuse scattering for specimens with 0.56 {le} y {le} 0.67 is discussed in terms of microdomain formation of a rhombohedral R{sub III} phase, that is obtained as a single phase when samples with these compositions were annealed at 1,373 K for 100 hr.

• OSTI ID: 6446982
• Journal Information: Journal of Solid State Chemistry; (USA), Vol. 87:2; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
LANTHANUM OXIDES
MICROSTRUCTURE
URANIUM OXIDES
ELECTRON DIFFRACTION
EXPERIMENTAL DATA
MEASURING INSTRUMENTS
MEASURING METHODS
SYNTHESIS
ACTINIDE COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL STRUCTURE
DATA
DIFFRACTION
INFORMATION
LANTHANUM COMPOUNDS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
SCATTERING
URANIUM COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies