ELECTRODE POLARIZATION AND ELECTRICAL-PROPERTIES OF THE LA(0.6)SR(0.4)CO(0.8)FE(0.2)0(3-DELTA), O-2 YTTRIA STABILIZED ZIRCONIA INTERFACE - EFFECT OF GAS-PHASE COMPOSITION AND TEMPERATURE/

The steady-state current-overpotential characteristics of the O-2,La0. 6Sr0.4Co0.8Fe0.2O3-delta/YSZ interface have been studied as a function of oxygen partial pressure and temperature. Ideal Nernst behaviour is observed in the temperature range between 400-900 degrees C and oxyge n pressure range between 0.5-100 kPa. The results of I-eta measurement s indicate that in the potential range 0.05-0.25 V, the apparent anodi c and cathodic charge transfer coefficients are close to unity: alpha( a) = alpha(c) = 1. The logarithm of the equilibrium exchange current d ensity (I,) shows a positive dependence on the logarithm of the oxygen partial pressure with a slope m = 0.25+/-0.05. These observations are in agreement with a proposed reaction model in which the diffusion of singly ionized oxygen adatoms (O-ads(-)) on the oxide surface is assu med to be the rate determining step of the electrode reaction.