Feasibility Synthesis and Characterisation of Gadolinia Doped Ceria Coatings Obtained By Cathodic Arc Evaporation

Abstract

The SOFC/SOEC community is now convinced that it is necessary to reduce the operating temperature of fuel cells to make the systems more robust, more reliable and thus to consider large-scale development. At the material level, the change of the reference electrolyte (YSZ) by a cerium compounds allows a significant performance gain for lower temperatures of use. It is obviously necessary to keep in mind the constraints related to the electrolyte application in solid electrolyte device, namely: good ionic conductivity unlike the electrical conductivity which must be low, electrochemical compatibility with the electrodes, be dense and covering on porous substrates.In this study, Gadolinia doped ceria coatings were deposited by cathodic arc evaporation from a metallic Ce-Gd (90/10 at%) target inserted into a conventional multiarc Ti evaporation target in the presence of a reactive argon-oxygen gas mixture. The structural and chemical features of these films were determined by X-ray diffraction and scanning electron microscopy. Their electrical properties were characterised using impedance spectroscopy measurements. It is shown that the as-deposited coatings crystallise in the fluorite type fcc structure of ceria and that their composition is the same than that of the target. The morphology of the coatings is influenced by the evaporation parameter (stress and droplet). The electrical measurements showed two contributions in Nyquist representation (figure1) and the activation energy is slightly higher than that given in the literature data for the bulk material.Figure 1 : Nyquist impedance plots of GDC coating, registered at 400°C, for two a.c. signal amplitudes. Logarithms of frequencies are indicated in the figure. Figure 1