Differential impedance study of solid oxide fuel cell composite cathodes

A comparative impedance study of pure ff{ G,a-r=,Sr".)rMnO3_5 rvith x : 0.25 and y :0.95) and composite LSM/YSZ {Zroz-8 mol.Yo YzO:) cathode materials for SOFC is performed. The technique of ihe Differential Impeiance Analysis (DIA), which ensures structural identihcation without any preliminary hypothesis, is applied to the data analysis. It identifies three steps, determines quantitatively their parricipition and ihus iecognizes the iate-limiting step. It is found that the main conhibution to the polarization resistance is due to transport limiltions. The results obtained by DIA show that the improvement of the LSM/YSZ material for low temp€rafure applications should concern both the ionic and the electronic conductivity.