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A Formalism to Describe Demixing of Mixed Oxides of Large and Small Grain Size in an Electric Field

Published online by Cambridge University Press:  15 March 2011

Irina V. Belova
Affiliation:
Diffusion in Solids Group, School of Engineering, The University of Newcastle, Callaghan, New South Wales 2308, AUSTRALIA
Mandy J. Brown
Affiliation:
Diffusion in Solids Group, School of Engineering, The University of Newcastle, Callaghan, New South Wales 2308, AUSTRALIA
Graeme E. Murch
Affiliation:
Diffusion in Solids Group, School of Engineering, The University of Newcastle, Callaghan, New South Wales 2308, AUSTRALIA
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Abstract

In this paper, we address the theory of electric field demixing of the cations in semi-conducting and initially homogeneous mixed ceramic oxides. We include the off-diagonal phenomenological transport coefficients by assuming a random distribution of cations and making use of an exact sum-rule expression. The steady state atomic composition profiles are shown to be quite different when different assumptions are made about vacancy equilibration. We show that in the case of large grained material (where vacancies in the interior do not equilibrate easily to the external oxygen partial pressure), a maximum develops in the steady state vacancy composition profiles. This behaviour is verified by independent Monte Carlo simulations.

Type
Research Article
Copyright
Copyright © Materials Research Society 2004

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