Enhanced ionic conductivity of Ce _0.8Sm _0.2O _2-δ by Sr addition

Sm and Sr co-doped ceria-based electrolyte with compositions of Ce _0.8(Sm _1-xSr _x) _0.2O _2-δ (x = 0, 0.3, 0.5, 0.7) are synthesized and investigated with the aim of improving the electrical properties of Ce _0.8Sm _0.2O _2-δ. X-ray diffraction (XRD) and electron microscope (SEM and TEM) techniques are employed to characterize the microstructure of powders and sintered pellets. The ionic conductivity has been examined by the A.C. impedance spectroscopy in air. The Ce _0.8(Sm _0.7Sr _0.3) _0.2O _2-δ exhibits the highest bulk conductivity among the series, which can be mainly ascribed to the increase of oxygen vacancy concentration. The specific grain-boundary conductivities are observed to increase with the Sr doping content up to x = 0.5. Further increase in Sr concentration will lead to reduced specific grain-boundary conductivities. The total conductivities of all Sm and Sr co-doped ceria are higher than that of Ce _0.8Sm _0.2O _1.9. The results indicate that Sr co-doping opens a new avenue to improve ionic conductivity in Ce _0.8Sm _0.2O _1.9.