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Planar cells incorporating a microelectrode as the working electrode were prepared using materials and techniques commonly employed in fabrication of planar solid oxide fuel cells. Initial results of ac and dc polarization measurements suggest that these cells potentially offer excellent isolation of working electrode frequency response (impedance), and quantification of steady-state current-overpotential relationships. The success of the technique relies heavily on how precisely the geometry of the microelectrode pattern is defined and characterized. Some of the challenges in implementing this technique are discussed.

Abstract. The structural refinements of CaTil.xFexO3_ ~ (x = 0 -0.4) were performed by means of the X-ray data full-profile analysis method on the basis of the orthorhombic perovskite structure (space group Pbnm). The lattice parameters, atomic coordinates, occupancies and equivalent isotropic temperature factors were refined. The characteristic Debye temperature value was determined for the composition x = 0.25 by analysis of the temperature dependence of X-ray reflections intensity. Using the structural refinement results, the model of oxygen vacancy formation, ordering and transport under acceptor doping was proposed. The dependence of the ionic conductivity on the iron concentration in CaTil_xFexO3_ ~ calculated in the frame of proposed model describes well the experimental data.

The effect of Sr-nonstoichiometry on phase composition, microstructure, defect chemistry and electrical conductivity of SrxZrO3−δ and SrxZr0.95Y0.05O3−δ ceramics (SZx and SZYx, respectively; x = 0.94–1.02) was investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and impedance spectroscopy followed by distribution of relaxation times analysis of impedance data. It was shown that at low Sr deficiency (x > 0.96 and 0.98 for SZx and SZYx, respectively) a solid solution of strontium vacancies in strontium zirconate crystal structure forms, whereas at higher Sr deficiency the secondary phase, zirconium oxide or yttrium zirconium oxide, is precipitated. Yttrium solubility limit in strontium zirconate was found to be close to 2 mol%. Y-doped strontium zirconates possess up to two orders of magnitude higher total conductivity than SZx samples. A-site nonstoichiometry was shown to have a significant effect on the electrical conductivity of SZx and SZYx. The highest total and bulk conductivity were observed at x = 0.98 for both systems. Increasing the conductivity with a rise in humidity indicates that proton conduction appears in the oxides in wet conditions. A defect model based on consideration of different types of point defects, such as strontium vacancies, substitutional defects and oxygen vacancies, and assumption of Y ions partitioning over Zr and Sr sites was elaborated. The proposed model consistently describes the obtained data on conductivity.