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

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.