Grain size-dependent electrical conductivity of polycrystalline cerium oxide I. Experiments

Citation
A. Tschope et al., Grain size-dependent electrical conductivity of polycrystalline cerium oxide I. Experiments, SOL ST ION, 139(3-4), 2001, pp. 255-265
Citations number
40
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
SOLID STATE IONICS
ISSN journal
01672738 → ACNP
Volume
139
Issue
3-4
Year of publication
2001
Pages
255 - 265
Database
ISI
SICI code
0167-2738(200102)139:3-4<255:GSECOP>2.0.ZU;2-L
Abstract
The electrical conductivity of polycrystalline cerium oxide was investigate d in the nanometer and micrometer size range. Nanocrystalline samples of di fferent grain size were prepared by uniaxial hot-pressing of nanocrystallin e powder at various temperatures and pressures. Additional annealing at hig h temperatures was employed in order to obtain microcrystalline samples. An equivalent-circuit analysis of ac-impedance spectra based on the brick-lay er model was performed and the apparent bulk conductivity determined. The e ffect of a variation in temperature or oxygen partial pressure revealed the rather different nature of the electrical transport properties in the nano - and microcrystalline materials. Nanocrystalline cerium oxide exhibited el ectronic conductivity under conditions at which, microcrystalline samples s howed impurity-controlled ionic conductivity. The electronic conductivity o f nanocrystalline samples was larger than the intrinsic electronic conducti vity of pure single crystalline cerium oxide and was increasing with decrea sing grain size. The experimental results: were analyzed according to the d efect chemistry of cerium oxide and consequences of a space charge effect o n the partial electronic and ionic conductivity in polycrystalline cerium o xide will be discussed. (C) 2001 Elsevier Science B.V. All rights reserved.