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Issue 38, 2006
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Impedance spectroscopy of reduced monoclinic zirconia

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Abstract

Zirconia doped with low-valent cations (e.g. Y3+ or Ca2+) exhibits an exceptionally high ionic conductivity, making them ideal candidates for various electrochemical applications including solid oxide fuel cells (SOFC) and oxygen sensors. It is nevertheless important to study the undoped, monoclinic ZrO2 as a model system to construct a comprehensive picture of the electrical behaviour. In pure zirconia a residual number of anion vacancies remains because of contaminants in the material as well as the thermodynamic disorder equilibrium, but electronic conduction may also contribute to the observed conductivity. Reduction of zirconia in hydrogen leads to the adsorption of hydrogen and to the formation of oxygen vacancies, with their concentration affected by various parameters (e.g. reduction temperature and time, surface area, and water vapour pressure). However, there is still little known about the reactivities of defect species and their effect on the ionic and electronic conduction. Thus, we applied electrochemical impedance spectroscopy to investigate the electric performance of pure monoclinic zirconia with different surface areas in both oxidizing and reducing atmospheres. A novel equivalent circuit model including parallel ionic and electronic conduction has previously been developed for titania and is used herein to decouple the conduction processes. The concentration of defects and their formation energies were measured using volumetric oxygen titration and temperature programmed oxidation/desorption.

Graphical abstract: Impedance spectroscopy of reduced monoclinic zirconia

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Publication details

The article was received on 27 Mar 2006, accepted on 14 Aug 2006 and first published on 24 Aug 2006


Article type: Paper
DOI: 10.1039/B604396H
Citation: Phys. Chem. Chem. Phys., 2006,8, 4476-4483
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    Impedance spectroscopy of reduced monoclinic zirconia

    D. Eder and R. Kramer, Phys. Chem. Chem. Phys., 2006, 8, 4476
    DOI: 10.1039/B604396H

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