The electrochemical performances of Nd0.6Sr0.4Co0.5Fe0.5O3-delta Ag composite cathodes have been investigated in intermediate temperature solid oxide fuel cells. The Nd0.6Sr0.4Co0.5Fe0.5O3-delta-Ag cathodes prepared by ball milling followed by firing at 920 degrees C show the maximum performance (power density: 0.15 W cm(-2) at 800 degrees C) at 3 wt.% Ag. On the other hand, the Nd0.6Sr0.4Co0.5Fe0.5O3-delta-Ag composite cathodes with 0.1 Mg cm(-2) (similar to 0.5 wt.%) Ag that were prepared by an impregnation of Ag into Nd0.6Sr0.4Co0.5Fe0.5O3-delta followed by filing at 700 degrees C (but the electrolyte-Nd0.6Sr0.4Co0.5Fe0.5O3-delta assembly was prepared first by firing at 1100 degrees C) exhibit much better performance (power density: 0.27 W cm(-2) at 800 degrees C) than the composite cathodes prepared by ball milling, despite a much smaller amount of Ag due to a better dispersion and an enhanced adhesion. AC impedance analysis indicates that the Ag catalysts dispersed in the porous Nd0.6Sr0.4Co0.5Fe0.5O3-delta cathode reduce the ohmic and the polarization resistances due to an increased electronic conductivity and enhanced electrocatalytic activity. (c) 2006 Elsevier B.V. All rights reserved.