Electron microscopy study of the fluorite⇹rhombohedral (R III) transformation in the U-La-O system

Unit cell parameters of a rhombohedral fluorite-related superstructure formed in the U-La-O system, for which several sets of cell parameters have been proposed, have been uniquivocally determined by HRTEM. The calculated hexagonal parameters are a H=0.393 (1) nm, c H=1.890 (4) nm. Microstructural a...

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Bibliographic Details
Published in:Solid state ionics 1991-01, Vol.44 (3), p.263-266
Main Authors: Rojas, R.M., Garcia-Chain, P., Herrero, P.
Format: Article
Language:English
Subjects:
Condensed matter: structure, mechanical and thermal properties
Crystalline state (including molecular motions in solids)
Crystallographic aspects of phase transformations
pressure effects
Exact sciences and technology
Physics
Structure of solids and liquids
crystallography
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Summary:Unit cell parameters of a rhombohedral fluorite-related superstructure formed in the U-La-O system, for which several sets of cell parameters have been proposed, have been uniquivocally determined by HRTEM. The calculated hexagonal parameters are a H=0.393 (1) nm, c H=1.890 (4) nm. Microstructural aspects such as microdomains formation and twinning accompanying the reversible fluorite (disordered)⇹rhombohedral (ordered) transformation are revealed. The presence of twins, a characteristic feature of the rhombohedral phase, is evidently derived from the pre-existent disorder in the fluorite phase.
ISSN:0167-2738
1872-7689
DOI:10.1016/0167-2738(91)90016-5