Structures and electrical conductivities of Gd3+ and Fe3+ co-doped cerium oxide electrolytes sintered at low temperature for ILT-SOFCs

Gd3+ and Fe3+ co-doped cerium oxide electrolytes, Ce0.9Gd0.1‐xFexO2-δ (x = 0.00, 0.01, 0.03, 0.05, 0.07, 0.10), were prepared by co-precipitation for ultrafine precursor powders and sintering for densified ceramic pellets. The crystal and microscopic structures were characterized by XRD, FESEM and Raman spectroscopy and their electrical properties were studied by AC impedance spectroscopy and the measurement of single cell's outputs. In comparison with Ce0.9Gd0.1O1.95, the ceramic pellets of Ce0.9Gd0.1‐xFexO2-δ with a relative density of 95% can be obtained after sintered at 1000 °C for 5 h, showing a remarkably enhanced sintering performance with a sintering temperature reduction of 500 °C, which might be ascribed to the highly activated migration of constituent species in the cerium oxide lattice doped with Gd3+ and Fe3+ions. Moreover, the electrical conductivity of Ce0.9Gd0.1‐xFexO2-δ can be significantly enhanced depending on the mole fraction x, with Ce0.9Gd0.07Fe0.03O1.95 exhibiting the highest electrical conductivity of 38 mS/cm at 800 °C, about 36% higher than that of Ce0.9Gd0.1O1.95 electrolyte sintered at 1500 °C for 5 h. So, The Gd3+ and Fe3+ co-doped cerium oxide would be an excellent candidate electrolyte for ILT SOFCs due to its prominent sintering performance and enhanced electrical conductivity.