Comparison conductivity between Yb and Dy co-doped CeO2-Gd2O3 systems for IT-SOFCs

The effect of co-doping with Dy and Yb elements on electrical properties of grain and grain boundary in Gd0.15Dy0.05Ce0.8O1.9 and Gd0.15Yb0.05Ce0.8O1.9 solid electrolytes was studied. In order to investigate the electrical properties of the series of ceria co-doped with Gd3+ and Dy3+ (Yb3+), the effects of co-doping and sintering conditions on grain and grain boundary conductivity are discussed in detail. The phase identification, ionic conductivity and microstructures of samples were studied by X-ray diffraction (XRD), AC impedance spectroscopy (IS) and scanning electron microscopy (SEM). Impedance spectroscopy measurements indicated that GDC doped by Dy and Yb electrolytes have higher grain conductivity in air at 400-700 ˚C compared with those of GDC. The addition of Dy and grain size together are influenced on grain boundary conductivity, however, the segregation amount of Yb3+ to the grain boundaries lead to increase grain boundary activation energy and higher schottcy barrier in Gd0.15Yb0.05Ce0.8O1.9 sample. It is verified that Dy and Gd co-doped CeO2 show acceptable conductivities especially in the intermediate temperature region compared with singly doped CeO2 ceramics