Electrolyte-supported cells were made of a La0.8Sr0.2Ga0.85Mg0.15O3-delta (LSGM2015) electrolyte (200 mu m thickness) prepared by ethylene glycol complex solution synthesis, isostatic pressing and sintered at 1400 degrees C, a Ni-SDC anode, a Sm0.2Ce0.8O3-delta (SDC) buffer-layer between anode and electrolyte, and a La0.5Sr0.5CoO3-delta-SDC cathode. The cells were tested in single-chamber configuration using methane-air mixtures. The results of X-ray diffraction and SEM-EDS showed a single-phase in the electrolyte and conductivities (similar to 0.01 S cm(-1) at 650 degrees C) close to the typical values. Good cell power densities of 215 and 102 mW cm(-2) were achieved under CH4/O-2 = 1.4 of at 800 and 650 degrees C, respectively. However, the cell stability tests indicated that the operating temperature strongly influenced on the cell performance after 100 h. While no significant change in the power density was observed working at 650 degrees C, a clear performance degradation was evidenced at 800 degrees C. SEM-EDS revealed an appreciable degradation of the electrolyte and both the electrodes. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.