Authors: Cheng Peng, Zhen Zhang, Dong Lin Huang, Yan Li Liu
Abstract: Pr2O3-doped ceria nanopowders were synthesized by a nitrate-citrate combustion process. This
route is based on the gelling of nitrate solutions by the addition of citric acid and ammonium hydroxide,
followed by an intense combustion process due to an exothermic redox reaction between nitrate and
citrate ions. XRD analysis showed that no impurity were observed up to x=0.3 in Ce1-xPrxO2-δ systems.
The influence of ignition temperature on the characteristics of the powders was studied. The change of the
crystal structure with the content of doped Pr was investigated. The highest ionic conductivity,
σ600°C=2.45×10-3S/cm, was found for the composition of x=0.15.
253
Authors: Alexander Rodrigo Arakaki, Walter Kenji Yoshito, Valter Ussui, Dolores Ribeiro Ricci Lazar
Abstract: One of the main applications of ceria-based (CeO2) ceramics is the manufacturing of Intermediate Temperature Solid Oxide Fuel Cells electrolytes. In order to improve ionic conductivity and densification of these materials various powder synthesis routes have been studied. In this work powders with composition Ce0.8(SmGd)0.2O1.9 have been synthesized by coprecipitation and hydrothermal treatment. A concentrate of rare earths containing 90wt% of CeO2 and other containing 51% of Sm2O3 and 30% of Gd2O3, both prepared from monazite processing, were used as precursor materials. The powders were characterized by X-ray diffraction, scanning and transmission electron microscopy, agglomerate size distribution by laser scattering and specific surface area by gas adsorption. Ceramic sinterability was evaluated by dilatometry and density measurements by Archimedes method. High specific surface area powders (~100m2/g) and cubic fluorite structure were obtained after hydrothermal treatment around 200°C. Ceramic densification was improved when compared to the one prepared from powders calcined at 800°C.
959
Authors: Yang Feng Huang, Ye Bin Cai, Hao Liu
Abstract: In this work, synthesis of the nanocrystalline Ce0.8Nd0.2O1.9 Solid solution Powders by a nitrate-glycine gel-combustion process was investigated. The effects of glycine/metal ratio and calcination temperature on the powders phase structure, morphology and particle were investigated. TG-DSC curves and XRD peak of different glycine/metal ratio show that smaller particle size can be obtained with a slightly fuel-deficient ratio. XRD results indicate that the as-prepared powders are crystallinzed in a single fluorrite structure. The crystalline size ranges from 9 nm to 24 nm, which increases with the increase of calcination temperature. The SEM results imply some organic agent may be eliminated by high temperature calcination process.
860
Authors: Li Li Zhu, Xiao Min Lin, Li Jing Qi
Abstract: Ce0.8Pr0.2–xNdxO2-δ(x = 0.02, 0.05, 0.1) solid solutions were synthesized by the sol-gel method. The XRD results show that all powders calcined at 800 °C are crystallized in a single cubic fluorite structure. The average grain sizes are between 20 nm and 25 nm. The Raman spectra analysis reveals that the solid solution Ce0.8Pr0.2–xNdxO2-δ has a cubic fluorite structure with oxygen vacancies. The oxygen vacancy concentration is increased by doping Nd in Ce0.8Pr0.2–xNdxO2-δ. Impedance spectra shows that the conductivity of rare earth co-doped ceria Ce0.8Pr0.18Nd0.02O2-δ is higher than that of single rare earth doped ceria Ce0.83Sm0.17O2−y. The results also show that Ce0.8Pr0.18Nd0.02O2-δ possess maximum conductivity. At 600 °C, the conductivity is 1.85×10-2S/cm, which is assigned to the higher oxygen vacancy concentration and the hopping electron transition of small polarons in the sample Ce0.8Pr0.18Nd0.02O2-δ.
1921
