The Ce1−xGdxO2−δ (0.02 ≤ x ≤ 0.3) solid solutions with about 30ppmSiO2 were prepared through the conventional mixed-oxide method from high-purity CeO2 and Gd2O3 powders. The ionic conductivity (especially the grain boundary conduction) in this system was studied as a function of dopant content, at 250 to750C in air, using impedance spectroscopy. The grain boundary impedance played an important role in the total conduction in the samples with low Gd content (usually x ≤ 0.1), but decreased sharply with increasing Gd content. Both the total and grain boundary conductivities maximized at the composition, x = 0.15, and this composition also had the lowest activation energies for total and grain boundary conduction. The maximum total conductivity at 700C was 4.07S/m, with an activation energy of 0.77eV being found for the composition x = 0.15.

Ionic Conductivity of High-Purity Gd-Doped Ceria Solid Solutions. T.S.Zhang, J.Ma, H.Cheng, S.H.Chan: Materials Research Bulletin, 2006, 41[3], 563-8