Nanocrystalline La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) and La0.25Ba0.25Sr0.5Co0.2Fe0.8O3-delta (LBSCF) with a high specific surface area (similar to 40 m(2)/g) were synthesized by spray pyrolysis. The as prepared powder was characterized by X-ray diffraction. nitrogen adsorption, and high-resolution electron microscopy. Water-based dispersions of pure LSCF, LBSCF and mixtures containing gadolinium doped ceria (GDC) with agglomerate sizes of approx. 50 nm were prepared by application of ultrasonic energy. Spin coating was employed to prepare porous thin films. The thickness of the films (<= 1 mu m) was more than 10-20 times lower than conventional cathode layers. The interfacial polarization resistances of LBSCF cathodes are 19.38, and 101 m Omega cm(2) at 650, 600, and 550 degrees C, respectively. The high performance is attributed to the nanometer-sized grain dimensions, the nanoporosity,and the large specific surface area within the cathode layer. The novel approach of preparing nanoparticulate thin film cathodes suggests strong benefit for Micro Solid Oxide Fuel Cells operating below 500 degrees C. (C) 2009 Elsevier B.V. All rights reserved.