A chemical diffusion-controlled electrode reaction at the compact La1-xSrxMnO3/stabilized zirconia interface in oxygen atmospheres

In order to elucidate how the oxide-ion electron mixed conduction in an oxide cathode affects the kinetics of the cathode reaction in solid oxide fuel cells, a compact La0.63Sr0.27MnO3 layer was prepared as a working electrode on the electrolyte of 3 mole percent Y2O3 doped ZrO2 by a laser flash evaporation method, and electrochemical measurements were made as a function of oxygen partial pressures, P(O-2), at 700 to 900 degrees C. Contrary to the case of a porous electrode system, the electrode interface conductivity was found to increase with decreasing P(O-2). With large anodic polarization, the oxide layer was found to be peeled off by oxygen evolution at the electrode/stabilized zirconia interface. The kinetics controlled by chemical diffusion of oxygen in the oxide layer were observed under cathodic polarization with P(O-2) < 10(4) Pa at 900 degrees C. The oxide ion conductivity in La0.63Sr0.27MnO3 was found to be proportional to a(o)(-1/2), where a(o) is the oxygen activity in the oxide.