Mixed conducting samaria-doped ceria (SDC) anode with highly dispersed Ni catalysts exhibited a stable high performance over 1100 h in solid oxide fuel cell (SOFC) operated at constant current density of 0.6 A cm(-2) at 800 degrees C. While the apparent average size of Ni particles was found to be increased, both the IR-free polarization performance (reflecting an effective reaction area) and the ohmic resistance (reflecting an electronic network) were not changed noticeably during the long-term operation. It was found by scanning electron microscope (SEM) and scanning transmission electron microscope (STEM) that Ni particles were rather stabilized by changing the morphology at the portion contacting with SDC surface presumably due to a strong interaction. (c) 2005 Elsevier B.V. All rights reserved.