Synthesis of Gd- and (Gd, Sr)-Doped Ceria Ceramics and Their Characterizations

Abstract

Singly-doped and doubly-doped CeO₂ with nominal compositions of Gd_0.2Ce_0.8O_1.9 and (Gd_0.9Sr_0.1)_0.175Ce_0.825O_1.9, respectively, have been synthesized via a simple and effective carbonate coprecipitation method, employing nitrates as the starting salts and ammonium hydrogen carbonate as the precipitant. The AHC/RE³⁺ molar ratio (R) and the reaction temperature (T) affect significantly the final yield and precursor properties, including chemical composition and particle morphology. The precursors and the resultant oxides are characterized by elemental analysis, differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffractometry (XRD) and high resolution scanning electron microscopy (HRSEM). Oxide solid-solutions are formed directly upon thermal decomposition at a very low temperature of ~400^oC, and can be further densified at a low temperature of ~1000^oC by pressureless sintering. The effects of additional Sr-doping on the particle morphology of the precursor, the densification behavior of the solid solution oxides as well as the bulk electrical conductivity were also investigated.