YBaCo3ZnO7 + Gd0.2Ce0.8O1.9 (GDC) composites with various GDC contents (0-70 wt.%) have been investigated as cathode materials for intermediate temperature solid oxide fuel cells (SOFC). The effect of GDC incorporation on the microstructure, electrochemical properties, and thermal expansion behavior of the YBaCo3ZnO7 + GDC composites has been studied. The composite cathodes consist of smaller particles with larger surface area compared to the pure YBaCo3ZnO7 cathode, which is beneficial for providing extended triple-phase boundary (TPB) where the oxygen reduction reaction (ORR) occurs. Among the various compositions investigated, the YBaCo3ZnO7 + GDC (50:50 wt.%) composite is found to be optimum with the lowest polarization resistance (0.28 Omega cm(2) at 600 degrees C) compared to that of pure YBaCo3ZnO7 (0.62 Omega cm(2) at 600 degrees C). Anode-supported single cell SOFC fabricated with the YBaCo3ZnO7 + GDC (50:50 wt.%) composite cathode also exhibits excellent performance with a maximum power density of 743 mW/cm(2) at 750 degrees C. Additionally, the YBaCo3ZnO7 + GDC (50:50 wt.%) composite shows a low thermal expansion coefficient (TEC) of 10.7 x 10(-6)degrees C-1, which provides good compatibility with those of standard SOFC electrolytes. (C) 2010 Elsevier Ltd. All rights reserved.