Abstract
The Ce 1− x Gd x O 2− δ (0.02 ≤ x ≤ 0.3) solid solutions with ∼30 ppm SiO 2 were prepared through the conventional mixed-oxide method from high-purity CeO 2 and Gd 2O 3 powders. The ionic conductivity (especially the grain boundary (GB) conduction) in this system was studied as a function of dopant content, over the temperature range of 250–750 °C in air, using an impedance spectroscopy. The GB 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 GB conductivities maximized at the composition x = 0.15, and this composition also had the lowest activation energies for the total and GB conduction. The maximum total conductivity at 700 °C, σ t = 4.07 (Ω m) −1 with the activation energy, E t = 0.77 eV, was found for the composition x = 0.15.
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