Enhanced ionic conductivity of Ce0.8Sm0.2O2−δ by Sr addition

► Sr addition has been executed with the aim of enhancing the ionic conductivity of Ce0.8Sm0.2O2−δ. ► The Sr addition greatly improves the microstructure of space charge layers. ► All of the total conductivities of Sm and Sr co-doped ceria are higher than those of Ce0.8Sm0.2O2−δ.