Fully nanostructured La0.6Sr0.4Co0.2Fe0.8O3-delta/Gd0.2Ce0.8O1.9 [lanthanum strontium cobalt ferrite (LSCF)/gadolinium-doped ceria (GDC)] composite cathode is successfully demonstrated with conventional powder processing using nanocomposite particles, grown via a colloidal-processing-based bottom-up approach, as starting material. The cathode/electrolyte interface adheres well at a relatively low temperature of 900 degrees C because of the promoted surface diffusion of constituent elements by the higher surface energy of the nano-sized particles. By contrast, successful fabrication of a nanostructured porous cathode composed of uniformly distributing LSCF and GDC grains with a diameter of 50-70 nm strongly supports the prevented grain growth and pore closure by the co-existing hetero-phases in the composite particles acting as bulk diffusion barrier of each other's constituents during sintering. The nanocomposite cathode exhibits quite low area-specific polarization resistances for oxygen reduction reaction (ORR) of 0.127, 0.054, 0.032, 0.015 and 0.009 Omega cm(2) at 600, 650, 700, 750 and 800 degrees C, respectively. These are significantly lower than those reported in the literature. The highly accelerated ORR kinetics contribute directly to the very high power densities of the anode-supported cells of 0.40, 0.77, 1.40, 2.32, and 3.29 W cm(-2) at 600, 650, 700, 750, and 800 degrees C, respectively, with a cell voltage at 0.7 V.