Effect of Dy on the properties of Sm-doped ceria electrolyte for IT-SOFCs

Research highlights: → The results showed that the samples of co-doping with Sm and Dy can result in higher ionic conductivity and lower activation energy in comparison with Sm singly doped ceria Ce0.8Sm0.2O2-δ (SDC) in the temperature range of 300-800 deg. C. As the addition amount of Dy increased up to 2 mol%, the sample attained the highest ionic conductivity, about 50% higher than that of SDC at 500 deg. C. The addition of Dy did not change the thermal expansion coefficient (TEC) significantly. - Abstract: Co-doped ceria-based electrolytes of Ce0.8Sm0.2-xDyxO2-δ (x = 0, 0.02, 0.06, 0.10, 0.14) were sintered from powders obtained by solid state reaction method. The phase identification, thermal expansion, ionic conductivities and microstructures of samples were studied by X-ray diffraction (XRD), dilatometry, AC impedance spectroscopy (IS) and scanning electron microscopy (SEM). The results showed that the addition of Dy led to higher ionic conductivity and lower activation energy in comparison with Sm singly doped ceria Ce0.8Sm0.2O2-δ (SDC) in the temperature range of 300-800 deg. C. As the addition amount of Dy increased up to 2 mol% (Ce0.8Sm0.18Dy0.02O2-δ), the sample attained the highest ionic conductivity, about 50% higher than that of SDC at 500 deg. C. The effect of Dy on the grain boundary conductivity was more apparent than that of the bulk conductivity. XRD measurements indicated that all the samples were single phase. The thermal expansion was linear for all the samples. The addition of Dy did not change the thermal expansion coefficient (TEC) significantly.