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

The use of Sr-Mg-doped LaGaO3 (LSGM ), high conducting oxygen ion electrolyte, in IT-SOFC technology requires suitable electrode materials. Because Sr-doped LaMnO3 (LSM) cathode coupled with YSZ electrolyte had showed relatively good performances, it has been also suggested for LSGM based cells. As cathode overpotential is the main performance limitation, the optimization of LSM/LSGM interface might be of fundamental relevance in the technology development of LSGM based IT SOFC. LSM films with different porosity were screen printed on both the faces of LSGM pellets; their morphology as well as electrical properties were investigated by Scanning Electrode Microscopy and Impedance Spectroscopy, respectively. The porosity was induced by addition of icing sugar (3-5% wt.) to LSM powder during ink preparation. Homogeneous electrode layers having thickness of about 30 m was obtained. Higher is the sugar amount, higher the film porosity and 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 aspect the best electrochemical performances are obtained using high porous electrode.