Microdomains in urania-yttria and urania-ceria

Journal Article · Sat Jun 01 00:00:00 EDT 1991 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1016/0022-4596(91)90361-K· OSTI ID:6115519

Pienkowski, M C; Jenkins, M L ^[1]; Moseley, P T ^[2]

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1. Univ. of Oxford (England)
2. Harwell Lab., Didcot (England)

The mixed uranium oxides (U{sub 0.4}, Y{sub 0.6})O{sub 2{plus minus}} and (U{sub 1-y}, Ce{sub y})O{sub 2{plus minus}x}, where y = 0.2, 0.4, 0.6 have been studied using selected-area electron diffraction (SAD) and high-resolution electron microscopy (HREM). Electron diffraction patterns from cubic solid solutions of urania-yttria contained diffuse features in addition to the strong reflections expected from the fluorite structure type. These SAD observations were consistent with HREM experiments which showed subtle modulations of contrast in the matrix planes. It is suggested that these diffuse features arise from small domains of size {approximately} {angstrom} embedded coherently in a number of orientations within the cubic matrix. Although there were some similarities between the diffuse scattering observed in this material and that observed for the case of yttria-doped zirconia, attempts to identify the structures of the microdomains explicitly were unsuccessful. Ordered domains have also been seen in (U{sub 1-y},Ce{sub y})O{sub 2{plus minus}x} solid solutions, having values of y = 0.4 and 0.6, using the technique of lattice imaging. It is concluded that these domains are likely to have adopted a partially ordered pyrochlore structure. In contrast, single crystals of urania-ceria having a ceria content of y = 0.2 showed no evidence of cation ordering. Instead, the most common features observed were dislocations having a Burgers vector consistent with the type 1/2 <110>f in projection.

• OSTI ID: 6115519
• Journal Information: Journal of Solid State Chemistry; (United States), Vol. 92:2; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CERIUM OXIDES
MICROSTRUCTURE
URANIUM OXIDES
YTTRIUM OXIDES
CATIONS
CHEMICAL PREPARATION
CRYSTAL LATTICES
CUBIC LATTICES
ELECTRON DIFFRACTION
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
LATTICE PARAMETERS
MILLER INDICES
PYROCHLORE
SOLID SOLUTIONS
X-RAY DIFFRACTION
ACTINIDE COMPOUNDS
CERIUM COMPOUNDS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
CRYSTAL STRUCTURE
DATA
DIFFRACTION
DISPERSIONS
INFORMATION
IONS
MICROSCOPY
MINERALS
MIXTURES
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
SCATTERING
SOLUTIONS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
URANIUM COMPOUNDS
YTTRIUM COMPOUNDS
360202* - Ceramics
Cermets
&amp; Refractories- Structure &amp; Phase Studies