Effect of Mg and Sr co-doping on the electrical properties of ceria-based electrolyte materials for intermediate temperature solid oxide fuel cells

Highlights: •The system Ce0.90Mg0.10−xSrxO1.90 has been investigated for the first time. •In present study, number of oxygen vacancies is kept constant in all composition. •Composition Ce0.90Mg0.06Sr0.04O1.90 has much higher conductivity in comparison to singly magnesium doped ceria. •Ce0.90Mg0.06Sr0.04O1.90 may be a potential candidate as a solid electrolyte for IT-SOFCs. -- Abstract: Attempts have been made to synthesize a few compositions in the system Ce0.90Mg0.10−xSrxO1.90 (x = 0.00, 0.02, 0.04 and 0.06) by citrate–nitrate auto-combustion method. XRD patterns reveal that all the samples have fluorite crystal structure similar to ceria. Microstructures of samples have been studied by scanning electron microscope. Ionic conductivity of singly doped and co-doped ceria has been investigated as a function of temperature by AC impedance spectroscopy in the temperature range 200–700 °C. Impedance plots show a significant decrease in grain boundary resistance after partial substitution of Sr in Mg-doped ceria in the intermediate temperature range. Composition with x = 0.04 shows the highest ionic conductivity (2.0 × 10−2 S/cm at 700 °C) among all the samples studied