Effect of Sr on Sm-doped ceria electrolyte

The effect of Sr addition (0–10 mol%) on the densification, crystal structure, ionic conductivity, thermal expansion, and flexural strength of Ce0.8Sm0.2O1.9 (SDC) was studied. Sr addition promotes densification and reduces sintering temperature by ∼100 °C. X-ray diffraction analysis showed that all the samples exhibit a fluorite structure. Impedance spectroscopy measurements indicated that SDC incorporated with an appropriate ratio of Sr (4–10 mol%) has higher ionic conductivity and lower activation energy compared with those of SDC. As the added amount of Sr increases by up to 6 mol% (0.94SDC-0.06Sr), the sample attains the highest ionic conductivity, about 30% higher than that of SDC at 700 °C. Moreover, flexural strength increases with Sr content, with the addition of 10 mol% Sr increasing the flexural strength of SDC from 97 to 160 MPa. In addition, thermal expansion is linear for all the samples. The addition of Sr does not appreciably change thermal expansion coefficient.

► The addition of Sr promotes densification, and reduces sintering temperature of SDC by ∼100 °C.
► Impedance spectroscopy measurements indicated that SDC with appropriate ratio of Sr (4–10 mol%) addition has higher ionic conductivity and lower activation energy compared with that of SDC.
► As the addition amount of Sr increases up to 6 mol%, the sample attains the highest ionic conductivity, about 30% higher than that of SDC at 700 °C.
► The flexural strength increases with Sr content, and 10 mol% Sr added can make the flexural strength of SDC increase from 97 to 160 MPa.
► The results suggest that Sr is not only beneficial to the electrical properties, but also an effective sintering aid and reinforcement of flexural strength for the ceria-based electrolytes.