Impedance study of perovskite materials for IT-SOFCs: case of La0.8Sr0.2MnO3-d, La0.8Sr0.2Co0.2Fe0.8O3-d and Ba0.5Sr0.5Co0.8Fe0.2O3-d

Solid oxide fuel cells (SOFCs) are clean and efficient electrochemical devices, which can produce electricity from different practical fuels. Cathodes for SOFCs are generally based on perovskite-type oxides, such as La1-xSrxMnO3-d, La1-xSrxCo1-yFeyO3-d and Ba1-xSrxCo1-yFeyO3-d, whose electrocatalytical properties depend not only by the chemical composition of the materials but also by the operating conditions, such as the applied overpotentials. The aim of the present work is to discuss the behavior of different cathode systems investigated by the research group under practical SOFC conditions. The analysis was pursued with combinations of modeling and high quality impedance spectroscopy experiments. Electrochemical measurements were carried out on the following systems: La0.8Sr00.2MnO3-d/Y0.08Zr0.92O2-d, LSCF/Sm0.2Ce0.8O2-d and BSCF/Sm0.2Ce0.8O2-d. Furthermore, LSCF and BSCF cathodes infiltrated with an LSM nanosized discrete layer were also investigated. The effect of temperature and cathodic overpotential was observed on different kinds of microstructures. Different approaches for the analysis of the impedance spectra were used and the results combined, in order to understand and possibly correlate the electrochemical behavior with material parameters, with the aim of getting useful information for optimizing SOFC materials and devices.