Characterization of Fe- and Mn-doped GDC for low-temperature processing of solid oxide fuel cells

This study reports the development of a low-temperature solid oxide fuel cell (SOFC) based on gadolinium-doped-ceria (Gd0.1Ce0.9O1.95, GDC) electrolyte and copper anode. Single cells were fabricated by sintering of all three SOFC components - electrolyte, copper-based anode and composite cathode - in a single step at low temperature (900 degrees C). Low-temperature sintering was necessitated due to the low melting point of copper and was achieved by the addition of transition metal oxides (TMOs) (Fe and Mn) to the GDC electrolyte. The sinterability of TMO-doped GDC samples was evaluated over 900-1400 degrees C. Key functional properties - density, mechanical strength and electrical conductivity - of the doped GDC were determined. Acceptable levels of density (>95% of theoretical) and mechanical strength were achieved for the samples sintered at 900 degrees C. Scanning electron micrographs (SEMs) of the doped-GDC samples showed no open pores at the lowest sintering temperature of 900 degrees C. The electrical conductivities of the doped-GDC samples sintered at 900 degrees C at a test temperature of 650 degrees C were determined to be 0.0067 S cm(-1) and 0.009 S cm(-1) for Fe- and Mn-doped samples, respectively, but lower than that of undoped-GDC sintered at 1100 degrees C (sigma(650 degrees C)=0.027 S cm(-1)). Single cells were prepared by slurry painting of CuO-GDC anode on one side of TMO-doped GDC electrolyte and Gd0.1Ce0.9O1.95 (GDC)-La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) composite cathode on the other side of the electrolyte followed by co-sintering of all the three layers at 9001 degrees C. The performance of the single cells was evaluated over 650-7001 degrees C using humidified hydrogen as fuel and air as oxidant. (C) 2009 Elsevier B.V. All rights reserved.