Synthesis and characterization of Pr/Gd co-doped ceria by using the citric acid-nitrate combustion method

A series of Ce0.8Gd0.2−xPrxO1.90 (x = 0-0.10) compositions have been synthesized by citric acid-nitrate combustion method for intermediate temperature solid oxide fuel cells (ITSOFCs). Characterization studies were carried out with X-ray diffraction (XRD), scanning electron microscopy (SEM) and AC impedance spectroscopy. X-ray diffraction results showed that a single-phase fluorite structure formed at a relatively low calcination temperature which is 600 °C. Dense Ce0.8Gd0.2−xPrxO1.90 pellets were successfully prepared by sintering at 1400 °C for 6 h. The relative density of Ce0.8Gd0.2−xPrxO1.90 samples was over 94% of the theoretical density. The two-probe AC impedance spectroscopy was used to study the ionic conductivity of co-doped ceria samples. According to the electrochemical impedance spectroscopy results, the conductivity of the Ce0.8Gd0.10Pr0.10O1.90 (σTotal,750 °C = 5.1 × 10−2 S/cm) composition was found to be higher than that of gadolinia-doped ceria (Ce0.8Gd0.20O1.90 (σTotal,750 °C = 3.4 × 10−2 S/cm). Due to higher ionic conductivity, it is thought that this composition can be a potential candidate to be used as an electrolyte material in ITSOFCs applications.