Impedance investigation on porous Sr-doped LaMnO3 films onto Sr-Mg-doped LaGaO3 electrolyte

The use of Sr-Mg-doped LaGaO3 (LSGM), a highly conducting oxygen ion electrolyte, in intermediate temperature solid oxide fuel cells (IT-SOFC) technology requires suitable electrode materials. Because the Sr-doped LaMnO3 (LSM) cathode coupled with the YSZ electrolyte had shown relatively good performances, it has been also suggested for LSGM-based cells. As cathode overpotential is the main performance limitation, the optimization of the LSM/LSGM interface might be of fundamental relevance in the technology development of LSGM-based IT-SOFC. LSM films with different porosities were screen printed on both faces of the LSGM pellets; their morphology and electrical properties were investigated by scanning electron microscopy and impedance spectroscopy, respectively. Porosity was induced by the addition of icing sugar (3-5 wt%) to the LSM powder during ink preparation. Homogeneous electrode layers with a thickness of about 30 mu m were obtained. The higher the sugar amount, the higher the film porosity and the lower the LSM grain size. The Nyquist plots show two low frequency arcs to which the charge transfer and mass transfer process or oxygen dissociation process were associated, respectively. One can expect that the best electrochemical performances are obtained using highly porous electrode.