Ionic conductivity of Nd3+ and Y3+ co-doped ceria solid electrolytes for intermediate temperature solid oxide fuel cells

Nanocrystalline co-doped ceria powders having composition, Ce0.80Nd0.20-xYxO1.90 has been prepared via citrate/nitrate gel auto-combustion method. Phase identification, surface morphology and electrical measurements have been made using X-ray diffraction, scanning electron microscope and two probe complex plane impedance analysis respectively. X-ray diffraction patterns show formation of the single phase having fluorite structure similar to ceria. More than 92% of the theoretical density has been obtained after sintering at 1350 °C. AC impedance measurements have been carried out to separate the contributions of grains, grain boundaries and electrode/specimen interface to the total observed resistance in the temperature range 200-600 °C. Enhancement in the ionic conductivity has been observed due to substitution of Nd3+ and Y3+ in ceria. The composition, Ce0.80Nd0.18Y0.02O1.90 shows the maximum conductivity 1.28 × 10−2 S/cm at 600 °C. This value is about 40% higher than that reported for the composition Ce0.80Nd0.20O1.90.