Electrical and microstructural aging of porous lanthanum. Strontium manganite/yttria-doped cubic zirconia electrodes

The formation of insulating phases at the interface between cathode and ele ctrolyte materials during solid oxide fuel cell (SOFC) operation leads to d eleterious effects on SOFC properties. We report in situ impedance spectros copy measurements of the degradation process of porous La0.65Sr0.35MnO3/Zr0 .84Y0.16O1.92 electrodes submitted to annealing temperatures above normal S OFC operating temperature, which is around 1173 K, simulating longterm SOFC operation. To measure the remaining effects after high-temperature anneali ng, impedance diagrams were plotted during the entire heating process up to the annealing temperatures, and during the complete cooling process. These diagrams were also plotted during the aging periods to follow the overall degradation. It was possible to detect and quantify electrical and electroc hemical degradations, which are related to the formation of insulating phas es at the electrode/electrolyte interface. Samples were annealed for about 200 h in air at temperatures between 1373 and 1673 K. Scanning electron mic roscopy and energy-dispersive X-ray spectrometry were also used to detect m icrostructural changes at the electrode.