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 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