Effect of phase structure on electrical conductivity of CexGd1−xO2−δ solid electrolytes

A series of CexGd1−xO2−δ samples were prepared by a citrate method. Phase structure and AC impedance spectroscopy of these electrolytes were studied. It was found that doping of Gd3+ into CeO2 could help to form solid solutions, which is beneficial to the formation of more oxygen vacancies and consequently improves electrical conductivity of the electrolytes. The highest conductivity was obtained on a Ce0.6Gd0.4O2−δ electrolyte. Arrhenius plot of the Ce0.6Gd0.4O2−δ electrolyte shows an inflexion at 600 °C, implying that the electrolyte has dual mechanisms of electrical conductivity. It was also found that the phase transition has influence on the electrical conductivity, as the activation energy increases when the electrolytes transit from a mixed CeO2-based and Gd2O3-based solid solution phases to only CeO2-based solid solution phase.