ELECTRODE KINETIC-BEHAVIOR OF (U0.4PR0.6)O-2+ -X/YSZ/U0.4PR0.6)O-2+/-X CELLS/

Results of kinetic studies on (U0.4Pr0.6)O-2+/-x/stabilised zirconia/( U0.4Pr0.6)O-2+/-x cells as a function of oxygen partial pressure (1-10 (-4)atm), temperature (500-900 degrees C) and electrode heat treatment have been described. Impedance spectroscopy was used for kinetic stud ies. At all temperatures and in various oxygen partial pressures a sin gle are, skewed on the high-frequency end of the impedance spectrum, w as observed. The data were deconvoluted into two electrode processes w ith relaxation times differing by about an order of magnitude. The ele ctrode process relaxing in the lower frequency range had an activation energy of 165+/-10 kJ mol(-1), a small angle of depression for the im pedance are, [p(O-2)](-0.5) dependence for the time constant and has b een attributed to an adsorption/dissociation of oxygen at the gas/elec trode interface. The activation energy associated with the high-freque ncy are was lower by ca. 35 kJ mol(-1) than that for the low-frequency are and this are appears to be associated with the charge-transfer re action.