Structures and electrical conductivities of Gd 3+ and Fe 3+ co-doped cerium oxide electrolytes sintered at low temperature for ILT-SOFCs

Abstract Gd 3+ and Fe 3+ co-doped cerium oxide electrolytes, Ce 0.9 Gd 0.1‐x Fe x O 2-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 Ce 0.9 Gd 0.1 O 1.95 , the ceramic pellets of Ce 0.9 Gd 0.1‐x Fe x O 2-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 Gd 3+ and Fe 3+ ions. Moreover, the electrical conductivity of Ce 0.9 Gd 0.1‐x Fe x O 2-δ can be significantly enhanced depending on the mole fraction x, with Ce 0.9 Gd 0.07 Fe 0.03 O 1.95 exhibiting the highest electrical conductivity of 38 mS/cm at 800 °C, about 36% higher than that of Ce 0.9 Gd 0.1 O 1.95 electrolyte sintered at 1500 °C for 5 h. So, The Gd 3+ and Fe 3+ co-doped cerium oxide would be an excellent candidate electrolyte for ILT SOFCs due to its prominent sintering performance and enhanced electrical conductivity.