Oxygen vacancy ordering within anion-deficient Ceria
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)
- Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden)
- School of Chemistry, Edinburgh University, The King's Building, West Mains Road, Edinburgh EH9 3JJ (United Kingdom)
The structural properties of anion deficient ceria, CeO{sub 2-{delta}}, have been studied as a function of oxygen partial pressure, p(O{sub 2}), over the range 0>=log{sub 10p}(O{sub 2})>=-18.9 at 1273(2) K using the neutron powder diffraction technique. Rietveld refinement of the diffraction data collected on decreasing p(O{sub 2}) showed increases in the cubic lattice parameter, a, the oxygen nonstoichiometry, delta, and the isotropic thermal vibration parameters, u{sub Ce} and u{sub O}, starting at log{sub 10p}(O{sub 2}){approx}-11. The increases are continuous, but show a distinct kink at log{sub 10p}(O{sub 2}){approx}-14.5. Analysis of the total scattering (Bragg plus diffuse components) using reverse Monte Carlo (RMC) modelling indicates that the O{sup 2-} vacancies preferentially align as pairs in the <111> cubic directions as the degree of nonstoichiometry increases. This behaviour is discussed with reference to the chemical crystallography of the CeO{sub 2}-Ce{sub 2}O{sub 3} system at ambient temperature and, in particular, to the nature of the long-range ordering of O{sup 2-} vacancies within the crystal structure of Ce{sub 7}O{sub 12}. - Graphical abstract: Partial radial distribution function for oxygen vacancies within CeO{sub 1.710} at 1273 K (solid line) showing the increased tendency for local ordering in <111> directions compared to a random distribution (dashed line).
- OSTI ID:
- 21372351
- Journal Information:
- Journal of Solid State Chemistry, Vol. 182, Issue 10; Other Information: DOI: 10.1016/j.jssc.2009.07.044; PII: S0022-4596(09)00354-5; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AMBIENT TEMPERATURE
ANIONS
CERIUM OXIDES
CRYSTALLOGRAPHY
CUBIC LATTICES
DIFFUSE SCATTERING
MONTE CARLO METHOD
NEUTRON DIFFRACTION
OXYGEN
OXYGEN IONS
PARTIAL PRESSURE
SIMULATION
SPATIAL DISTRIBUTION
VACANCIES
CALCULATION METHODS
CERIUM COMPOUNDS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
CRYSTAL DEFECTS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIFFRACTION
DISTRIBUTION
ELEMENTS
IONS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POINT DEFECTS
RARE EARTH COMPOUNDS
SCATTERING
THERMODYNAMIC PROPERTIES