Microstructure of Sol-gel Derived Nanoscaled La0.6Sr0.4CoO3-δ Cathodes for Intermediate-Temperature SOFCs

Nanocrystalline La1-xSrxCoO3-delta (LSC) thin films with a nominal Sr-content of x = 0.4 were deposited on Ce0.9Gd0.1O1.95 electrolyte substrates by low-temperature sol-gel processing. Microstructure, element distribution and electrochemical properties of the LSC thin films were studied after thermal treatment, which included calcination and extended annealing at 700 degrees C or 800 degrees C. Transmission electron microscopy combined with Debye electron diffraction and electron tomography was applied for the investigation of the grain-size distribution and porosity. The local chemical composition and element distribution was analyzed by energy-dispersive X-ray spectrometry on the nanoscale. Area specific polarization resistances as low as 0.023 Omega cm(2) at 600 degrees C were measured applying electrochemical impedance spectroscopy. These low resistance values are facilitated by a substantial increase of the inner surface area of the porous thin-film cathode and amplified by an enhanced surface exchange, resulting from precipitation of Co3O4.