SOFC cathode/YSZ - Non-stationary TPB effects

The origin of the dynamic nature of (La0.85Sr0.15)(0.95)MnO3 +/-delta (LSM) cathodes with activation and deactivation processes was studied by comparison between measurements on and electrode/YSZ interfacial changes of Au, LSM point electrodes and thin 1/2-1 mu m thick LSM film electrodes on YSZ. The techniques used in the study were linear potential sweeps and long term (250-300 h) step polarization. After experiments the electrodes were removed by dissolution and the YSZ contact areas were studied by SEM and EDS. The results show current induced YSZ morphological changes, which lead to an increase in the Three-Phase-Boundary (TPB) length and consequently an activation of the electrode. In the case of LSM electrodes a current enhanced formation of La2Zr2O7 that can result in deactivating phenomena of LSM electrodes was observed. The interplay between these processes can to a large extent explain the dynamic nature of LSM electrodes. (C) 2008 Elsevier B.V. All rights reserved.