Sintering behavior and ionic conductivity of Ce_0.8Gd_0.2O_1.9with a small amount of MnO₂doping

A 20% GdO1.5doped ceria solid solution with a small amount of MnO2doping (≤ 5% molar ratio) was prepared via the mixed oxide method from high-purity commercial powders with grain size around 0.2-0.5 μm. X-ray diffraction analysis indicated that all the samples exhibited the fluorite structure, and no new phase was found. The data from dilatometeric measurements and scanning electron microscopy observations revealed that 1% Mn doping reduced the sintering temperature by over 150°C, and enhanced the densification and grain growth. Mn doping has little effect on grain interior conductivity, but a marked deterioration in grain boundary behavior is observed. This leads to a lower total conductivity in comparison with the undoped Ce0.8Gd0.2O2-δ. Therefore, for solid oxide fuel cells (SOFCs) with Mn-containing compounds as electrodes, optimization of electrode fabrication conditions is needed to prevent the formation of a lower conductivity layer at the electrode/electrolyte interface since Mn will diffuse from the electrode side to the electrolyte during fabrication and operation of SOFCs.