Sm3+ and Sr2+ co-doped ceria prepared by citrate–nitrate auto-combustion method

• The system Ce1 − x − ySmxSryO1.90 prepared by auto-combustion has been investigated for the first time.
• In present study, number of oxygen vacancies is kept constant in all compositions.
• Composition Ce0.82Sm0.16Sr0.02O1.90 has maximum conductivity at 600 °C.
• Its conductivity is more than the highest value reported for 0.94SDC–0.06Sr at 600 °C.

A few compositions in the system, Ce1 − x − ySmxSryO1.90 have been prepared by citrate–nitrate auto-combustion method. X-ray diffraction data show that all the compositions are solid solution having cubic fluorite structure. Density of the samples sintered at 1350 °C has been found to be more than 95% of the theoretical value. Surface morphology has been studied by scanning electron microscope. AC impedance spectroscopy measurements have been carried out to study the grains, grain boundaries and total ionic conductivity of the samples in the temperature range 200–600 °C. The composition, Ce0.82Sm0.16Sr0.02O1.90 shows the maximum conductivity i.e. 2.67 × 10−2 S-cm−1 at 600 °C among all the compositions investigated. This is about two times higher than that of Ce0.80Sm0.20O1.90.