Preparation and Characterization of La0.4Sr0.6Co0.8Fe0.2O3-d

L. BAQUÉ; A. SERQUIS; A. CANEIRO

Campinas, Brasil

Workshop; , Latin American Workshop on Applications of Powder Diffraction; 2007

LNLS

The cobaltites La1-xSrxCo1-yFeyO3 (LSCF) are good candidates for solid oxidefuel cell (SOFC) cathodes because these materials present high ionic and electronicconductivity, allowing a lower temperature of operation [Y. Teraoka et al, Mater.Res. Bull. 23, 51 (1988); F. Prado et al, Sol. State Ion. 167, 147 (2004)]. Most ofreported LSFC films have been synthesized by slurry deposition techniques such asspraying [N. Grunbaum et al, Sol. State Ion. 177, 907 (2006)], painting [V. Dusastreet al, Sol. State Ion. 126, 163 (1999)], or spin coating [E. P. Murray, M. J. Severand S. A. Barnett, Sol. State Ion. 148, 148 (2002)]. In order to increase SOFCsperformances further, it is necessary to understand how the microstructure of thecomposites electrodes a®ects the performance of the system. The aim of this workis to study the microstructure and electrode resistance of porous electrodes of thesame composition films (La0:4Sr0:6Co0:8Fe0:6O3) deposited by di®erent methodsand to identify the sintering conditions to obtain low cathode overpotential values.The influence of the microstructure on the transport properties (ionic and electronicconductivity) is evaluated by means of impedance spectroscopy. The perovskite ox-ide cobaltites powders have been prepared by an acetic acid-based gel and HTMAroutes to obtain nanopowders. Then, cathodes films were deposited onto ceramicsubstrates of the usual electrolytes Cerium Gadolinium Oxide (CGO), by serigra-phy, spin coating and dip-coating. The structure, morphology and composition ofthe powders and films were characterized by XRD, SEM and EDS, respectively.The grain size and strain of initial powders and films prepared through differentroutes is analyzed by Rietveld analysis. We found that the electrochemical proper-ties of LSFC cathodes films strongly depend on the microstructure that is mainlydetermined by synthesis parameters and technique used for the deposition of thefilms.