Electrical properties of ceria/carbonate nanocomposites

Ceria-based composites are developed as potential electrolytes for intermediate solid oxide fuel cell applications and a better understanding of the ionic conduction mechanism serves this purpose. Ceria-based composites were produced by several processing routes using a ceria-based ceramic host (Sm, Gd doped ceria) and various Na and Li carbonates. Simple ceria/carbonate two-phase nanocomposites were synthesized by the carbonate precipitation method followed by a thermal treatment. The decomposition course of the precursor, the thermal stability, morphology and the composite formation mechanism were studied by thermogravimetric-differential thermal analyses (TG-DTA), IR, UV, SEM and XRD analyses. The conductivity temperature dependence in the 300-800 degrees C temperature range, performed on composite pellets, exhibits conductivity values one-two higher magnitude order and a lower activation energy of 0.809 +/- 0.001 eV, with respect to 1.693 +/- 0.005 eV for pure ceria obtained under the same conditions. This enhancement of the composite conductivity, corroborated with the blue shift of the gap energy, as deduced from the UV spectra, was attributed to the oxygen ion transport through an interface mechanism between the two phases of the ceria/carbonate composite. (C) 2012 Elsevier B.V. All rights reserved.