TA of non-stoichiometric ceria obtained via hydrothermal synthesis

Doped ceria was studied in the last 20 years as a solid electrolyte capable of replacing stabilized zirconia in fuel cells. Nevertheless, one of the problems concerned with the application of this material is the joint presence of the Ce(III) and Ce(IV) in the ceria sublattice, mainly under low partial pressure of oxygen. TG and DTA measurements were performed in order to verify non-stoichiometric character for cerias hydrothermally treated under reflux and in autoclave. X-ray powder diffraction was used to observe long-range structural evolution varying time and temperature of reaction and the type of hydrothermal synthesis. Finally, scanning electron microscopy (SEM) gave the temperature influence for powder morphology. Those techniques pointed out that: i) reaction temperature is not important for converting Ce³⁺ to Ce⁴⁺; ii) testing the reaction time parameter, it is observed quite complete oxidation for the 2-12 h range; and iii) the type of hydrothermal synthesis parameter influences the crystallinity and non-stoichiometric character of products. This revised version was published online in August 2006 with corrections to the Cover Date.