Preparation and Characterization of Solid Oxide Fuel Cells Cathode Films
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0928-GG16-03
Preparation and Characterization of Solid Oxide Fuel Cells Cathode Films Laura Baqué1,2, Adriana Serquis1,2, Nicolás Grunbaum1, Fernando Prado1,2, and Alberto Caneiro1,2 1 Instituto Balseiro - Centro Atomico Bariloche, Bariloche, 8400, Argentina 2 CONICET, Bariloche, 8400, Argentina
ABSTRACT Perovskite oxide cobaltites with composition La0.4Sr0.6Co0.8Fe0.2O3-δ were prepared by an acetic acid-based gel route. Then, cathodes were deposited onto porous ceramic substrates, like the usual electrolytes Cerium Gadolinium Oxide (CGO), by spray, spin coating and dip-coating. The structure and morphology of the layers were characterized by XRD and SEM, respectively. Electrical properties were characterized by complex impedance measurements. The correlation between structural characteristics and electrical properties is discussed. INTRODUCTION In recent years, perovskite oxide mixed conductors (La, Sr)MO3-δ (M= transition metal) have attracted much attention because of their potential applications, including oxygen separation membranes and solid oxide fuel cell (SOFC) cathodes. The electronic conductor (La, Sr)MnO3-δ (LSM) is widely used in commercial SOFC at temperatures higher than 900°C. A decrease of working temperature of SOFCs, in the range of 600–800 °C, is necessary to allow both the use of cost-effective interconnects and the decrease in the thermal degradation of cells. However, in this range of temperature, SOFCs performances are principally limited by cathode overpotential. Even if the influence of cathode film microstructure was recognized to be a key parameter, most of studies have just dealt with the influence of cathode film composition. One proposed solution was to add an ionically conducting second phase to the electronically conducting electrode material. For example, yttria-stabilized zirconia YSZ is often mixed with strontium-doped lanthanum manganite LSM, resulting in polarization resistance values significantly lower than single-phase LSM cathodes [1-3]. Other composite cathodes consisting of LSM and Ce0.8Gd0.2O2-δ (GDC) on yttria-stabilized zirconia YSZ and GDC electrolytes were also reported [4]. On the other hand, the cobaltites La1−xSrxCo1-yFeyO3-δ (LSCF) are good candidates for SOFC cathodes because these materials present high ionic and electronic conductivity, allowing a lower temperature of operation [5,6]. Therefore, efforts have to be done on the synthesis processes of these materials in order to prepare cathodes with different microstructures. In the literature, most of the composite films have been synthesized by the slurry deposition techniques such as spraying [7], painting [8], or spin coating [4,9]. In order to increase SOFCs performances further, it is necessary to understand how the microstructure of the composites electrodes affects the performance of the system. The aim of this work is to study the electrode resistance of porous electrodes of the same composition films (La0.4Sr0.6Co0.8Fe0.2O3-δ) deposited by different methods and to identify the
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