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Electrical properties of bulk and grain boundaries of scandia-stabilized zirconia co-doped with yttria and ceria
Authors:W Preis  J WaldhäuslA Egger  W SitteE de Carvalho  JTS Irvine
Institution:
  • a Chair of Physical Chemistry, University of Leoben, A-8700 Leoben, Austria
  • b School of Chemistry, University of St. Andrews, St. Andrews, KY16 9ST, Scotland, UK
  • Abstract:The electrical properties of bulk and grain boundaries of scandia-stabilized zirconia co-doped with yttria and ceria have been determined as a function of temperature (300 < T/°C < 700) and oxygen partial pressure 10− 24 ≤ p(O2)/bar ≤ 1, T = 700 °C] by application of impedance spectroscopy. The yttria and ceria contents of CexY0.2 − xSc0.6Zr3.2O8 − δ (0 ≤ x ≤ 0.2) have been varied systematically. Homogeneous samples have been prepared by means of a sol-gel (glycine-nitrate) combustion process. The ionic conductivity in air is almost independent of composition with typical values around 0.03-0.04 S cm− 1 for the bulk at 700 °C. A significant decrease of the ionic conductivities of bulk and grain boundaries is found for samples co-doped with ceria at low oxygen partial pressures p(O2) < 10− 15 bar, T = 700 °C]. Activation energies for the ionic transport in oxidizing (air) and reducing (1%-H2/Ar) atmospheres have been extracted from Arrhenius-plots. The oxygen nonstoichiometry in 1%-H2/Ar has been investigated by employing thermogravimetry. The decrease of the ionic conductivity under reducing conditions is accompanied by an increase of the corresponding high temperature activation energy of the bulk, which is interpreted in terms of defect association or clustering.
    Keywords:Solid electrolyte  Oxide ion conductor  Impedance spectroscopy  Scandia-stabilized zirconia  IT-SOFC
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