Core-shell type La0.6Sr0.4Co0.2Fe0.8O3-d (LSCF)-Sm0.2Ce0.8O2-d (SDC) powders are synthesized to achieve a high-performance durable cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The SDC core size is controlled so that all core particles are surrounded by the LSCF particles with no unattached spots. Such a core-shell composite cathode develops an ideal microstructure with improved phase contiguity, homogeneity, and maximized triple-phase boundary density. The cathode that involves an SDC core of 500 nm exhibits the lowest interfacial polarization resistance (0.265 Omega cm(2) at 650 degrees C), as well as long-term stability during both thermo-cyclic and electrochemically accelerated tests. (C) 2009 Elsevier B.V. All rights reserved.