Study on Sm³⁺ and Er³⁺ co-doped CeO₂-based electrolytes

Ceria doped with aliovalent cations, such as rare earth oxides, has been considered as one of the most promising candidate electrolyte materials for intermediate temperature solid oxide fuel cells. In this study, high purity cerium nitrate, samarium nitrate and erbium nitrate salts were used to obtain ceria-based solid solutions Ce_{0.80}Sm_{0.20}O_{1.90} (SDC), Ce_{0.80}Sm_{0.15}Er_{0.05}O_{1.90} (ESDC5), Ce_{0.80}Sm_{0.10}Er_{0.10}O_{1.90} (ESDC10) through the cellulose templating method. Crystal structure and microstructure were characterized by means of X-ray diffraction and scanning electron microscopy, respectively. X-ray diffraction results indicate that a single-phase fluorite structure formed at a relatively low calcination temperature, 500°C. The relative densities of the sintered pellets were higher than 93%. The electrical properties of doped and co-doped ceria electrolytes in the temperature range 300-750°C were analyzed by using electrochemical impedance spectroscopy. The singly doped ceria at 750°C showed the highest ionic conductivity with less activation energy.