Anode-supported solid oxide fuel cells (SOFCs) with lanthanum-doped ceria (LDC)/Sr-, Mg-doped LaGaO3 (LSGM) bilayered or LDC/LSGM/LDC trilayered electrolyte films were fabricated with a pure La0.6Sr0.4CoO3 (LSC) cathode. The behaviors of the two electrolytes in cells were investigated by using scanning electron microscopy, impedance spectroscopy and cell performance measurements. The reactions between LSGM and anode material can be suppressed by applying a ca. 15 mu m LDC film. Due to the Co diffusion from the LSC cathode to the LSGM electrolyte during high temperature sintering, the electronic conductivity of the LDC electrolyte cannot be completely blocked with an LSGM layer below 50 mu m, which leads to open-circuit potentials of these cells of ca. 0.988 V at 800 degrees C. The electrical conductivities of LDC and LSGM electrolytes in the cells under operation conditions are obtained from the dependence of the cell ohmic resistance on the electrolyte thickness. The electrical conductivity of LDC electrolyte is ca. 0.117 S cm(-1) at 800 degrees C on the bilayered electrolyte cells with a 50 mu m LSGM layer. The bilayer electrolyte cells with a 25 mu m LDC layer at 800 degrees C, had a cell ohmic resistance two-stage linear dependence on the LSGM layer thickness, which showed the electrical conductivity of ca. 1.9 S cm(-1) for the LSGM layer below 50 mu m and 0.22 S cm(-1) for the LSGM layer above 100 mu m. With a LDC/LSGM/LDC trilayered electrolyte film for the anode-supported cell, an open-circuit potential of 1.043 V was achieved. (c) 2006 Elsevier B.V. All rights reserved.