Oxygen reaction on strontium-doped lanthanum cobaltite dense electrodes atintermediate temperatures

La0.7Sr0.3CoO3-delta (LSC) powder was characterized by thermogravimetry. Th in, dense layers of LSC were deposited by RF magnetron sputtering on YSZ pe llets. The electrochemical behavior was studied as functions of temperature (300-530 degreesC) and oxygen partial pressure (0.21-2 X 10(-5) bar) by im pedance spectroscopy. Impedance diagrams were decomposed into two elements, characteristic of the electrode polarization. The low frequency contributi on can be described either as a limiting Warburg diffusion loop or as a sem i-circle. These results can be interpreted in terms of a progressive evolut ion of the limiting process as functions of oxygen pressure and temperature , i.e. a finite diffusion process in series with dissociative sorption proc ess. Under low oxygen pressure, at temperatures higher than 475 degreesC, g as-phase diffusion polarization becomes significant. (C) 2001 Published by Elsevier Science B.V.