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Oxygen Vacancy Migration in Disordered Gd2(ZrxTi1-x)2O7

Published online by Cambridge University Press:  10 February 2011

R.E. Williford,
W.J. Weber,
R. Devanathan and
J.D. Gale
R.E. Williford
Affiliation:
Materials Department, Pacific Northwest National Laboratory, Richland, WA 99352
W.J. Weber
Affiliation:
Materials Department, Pacific Northwest National Laboratory, Richland, WA 99352
R. Devanathan
Affiliation:
Materials Department, Pacific Northwest National Laboratory, Richland, WA 99352
J.D. Gale
Affiliation:
Department of Chemistry, Imperial College, South Kensington, London, UK, SW7 2AY
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Abstract

Oxygen vacancy formation and migration energies in the pyrochlores Gd2(ZrxTi1-x)2O7 were computed using atomistic energy minimization methods, with particular attention to the role of cation antisite disorder. The interatomic potentials recognize oxygens in distinct crystallographic sites (polarizations) as distinct species, and permit assessment of the directional anisotropy in vacancy migration energies. Oxygen vacancy migration is determined by O48f - O48f transitions along the shortest edges of the TiO6 octahedra, in agreement with previous results. Oxygen vacancies migrate towards disorder to reduce local stresses. In contrast to previous work, the VO8a and VO8a + IO8b Frenkel defects are favored over the VO8f and VO48f + IO8b Frenkel. The transition VO8a -> VO48f is energetically favored for the ordered structure, and activates the three dimensional O48f - O48f vacancy migration network by filling empty 8a sites with 48f oxygens. Local regions of order and moderate disorder must both be present for optimum oxygen conductivity. High disorder retards vacancy migration.

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Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 538: Symposium J – Multiscale Modelling of Materials , 1998, 235
Copyright
Copyright © Materials Research Society 1999

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