Electronic and ionic conductivity of Eu0.2Ce0.8O2 − δ

•The ionic and electronic conductivity of 20 mol% Eu substituted ceria was investigated.•Conductivity exhibited behavior similar to acceptor doped ceria with no evidence found for multivalency of Eu cations.•Grain and grain boundary conductivity was extracted using impedance spectroscopy.

Eu-doped cerium oxide was synthesized and its crystal structure was analyzed by X-ray diffraction. The electrical conductivity was measured by impedance spectroscopy at 350–900 °C over a wide range of controlled oxygen partial pressures, from H2 to O2, using gas mixtures. In the high pO2 region, ionic conductivity is predominant, and the activation energy for total conductivity is 0.8 ± 0.01 eV. In low pO2, the conductivity is found to obey a − 1/4 power law dependence on pO2, with an enthalpy of reduction of 4.2 ± 0.16 eV. These results demonstrate that Eu has a similar effect on electrical properties as Gd or Sm acceptor dopants in ceria, namely, that Eu shows no evidence for multivalent behavior; rather, it appears to be a fixed valent dopant in the fluorite structured ceria, in contrast to prior studies finding multivalency of Eu in perovskite oxides under similar conditions.