Characterization of LSM-YSZ composite electrode by ac impedance spectroscopy

The characteristics of La1-xSrxMnO3 perovskite (LSM)-yttria-stabilized zirconia (YSZ) composite electrodes were studied over a range of compositions by ac impedance spectroscopy. The transfer and surface diffusion of oxygen ions were found to be rate-determining steps. The polarization resistance of oxygen ion transfer was found to be independent of the partial pressure of oxygen and proportional to the length of the three-phase boundary. The capacitance of oxygen ion transfer was approximately 10(-4) F/cm(2). The polarization resistance of O- surface diffusion was determined to be proportional to P-O2(1/4), with a minimum at 40-50 wt.% YSZ. The polarization resistance of oxygen ion transfer was observed to remain largely unaffected by variations in cathodic potential, whereas that of O- surface diffusion decreased with increasing cathodic potential, At low partial oxygen pressure, the arc due to gas phase diffusion was observed in the low frequency region, with proportion to P-O2 and having low activation energy. (C) 2001 Elsevier Science B.V. All rights reserved.