The nature of the current collector was shown to have a noticeable influence on the measured polarization resistances of functionally graded composite cathodes. A decrease by a factor 3 was detected around 600°C by using sputtered current collectors. The use of metallic grid as a current collector was proned when porous electrodes are characterized. Impedance measurements were performed on different cathode materials in contact with yttria stabilized zirconia during isothermal dwells and thermal cycles: conventionnal La_(0.65)Sr_(0.35)MnO_3 slurry painted electrodes and single graded LSM-YSZ composite cathodes. The electrode characteristic proper showed a marked degradation which increased with heating time. It mainly comes from an increasing amplitude of the low frequency side of the electrode diagram. The cathode/YSZ interface was also shown to degrade. Cooling down to medium temperatures results in irreversible effects.
展开▼
