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Impedance spectroscopy of mixed conductors
modelling and experiments J. Jamnik National
Institute of Chemistry, Hajdrihova 19, Ljubljana,
Slovenia Max-Planck Institut für
Festkörperforschung, Heisenbergstr. 1, Stuttgart,
Germany
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Polycrystalline mixed conductors with blocking
grain boundaries Electrochemical parameters of
interest Parameters of no interest? Grains G
rain boundaries Electrodes
Energy dissipation Energy storage
Different parametrisation possible, for example
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• Impedance spectroscopy theory
• Local description ? generalised equivalent
  circuits derived from
• Nernst-Planck-Poisson equations
• (J. Jamnik J. Maier, PCCP 3, 1668 (2001)) .
• Assumptions
• continuum model
• 2-mobile charge carriers
• internal reactions in local equilibrium
• Microstructure ? Brick layer model

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Introductory remarks An important strength of IS
is that the electrode effects appear separated
from the bulk and grain boundary response!??
Pure ionic or electronic conductors
Mixed conductors Single crystals first
Completely blocking or completely reversible
electrodes
Ideal selectively blocking electrodes
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Electrode effects in single crystals Résumé
electrode effects in single crystals ? grain
boundary effects in polycrystals but
J. Jamnik, SSI 157, 19, 2003
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Experiment bicrystal

• ?13 grain boundary
• strongly blocking for ions
• weakly blocking for holes

J. Jamnik, X. Guo, J. Maier, APL, in press.
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Consistency test