Preparation and Electrochemical Characterization of Perovskite/YSZ Ceramic Films

Perovskite-type La0.8Sr0.2Co0.8Fe0.2O32d powders were prepared using a complex polymeric precursor method. Thermal analysis was carried out on the perovskite precursor to investigate the oxide-phase formation. The structural phase of the powders was determined by X-ray diffraction. These results showed that the decomposition of the precursors occurs in a two-step reaction and temperatures higher that 1000°C are required for these decomposition reactions. For the electrochemical characterization, La0.8Sr0.2Co0.8Fe0.2O32d electrodes were deposited by a wet spray technique on dense yttria-stabilized zirconia ~YSZ! layers. The morphology of the deposited perovskite thick films (;50 mm) was investigated by field emission scanning electron microscopy and showed a porous microstructure. Electrochemical impedance spectroscopy ~EIS! measurements were carried out under synthetic air flux at temperatures ranging from 200-600°C in the 10 mHz-10 MHz frequency range showing an interfacial electrical resistance related to the La0.8Sr0.2Co0.8Fe0.2O32d electrodes. EIS measurements were also performed in the same frequency range at different oxygen partial pressures (1025-1 atm) at 600°C. At this temperature and frequencies below 0.1 MHz, the electrical response to the applied signal of the electrode material is best fitted by two semicircles, which can be related to charge-transfer processes. The activation energy for the limiting step ~adsorption/desorption! was found to be 1.6 eV. © 2004 The Electrochemical Society