Microstructural Evolution in a CeO2-Gd2O3 System
Abstract Microstructural evolution in a CeO2-Gd2O3 system at atomic and nanoscale levels with increasing Gd concentration has been comprehensively investigated by transmission electron microscopy. When the Gd concentration was increased from 10 to 80 at.%, the phase transformation from ceria with fluorite structure to solid solution with C-type structure was not a sudden change but an evolution in the sequence of clusters, domains, and precipitates with C-type structure in the fluorite-structured matrix. Moreover, the ordering of aggregated Gd cations and oxygen vacancies in these microstructural inhomogeneities developed continuously with increasing Gd concentration. This microstructural evolution can be further described based on the development of defect clusters containing Gd cations and oxygen vacancies.
Ionic Conductivities and Microstructures of Ytterbium-Doped Ceria
The ionic conductivities and microstructures of Ce1-xYbxO2-x/2 ( x = 0.10, 0.15, 0.20, and 0.25 ) with average grain sizes in a range of 0.2 - 3.7 mu m were studied systematically. Nanosized domains were confirmed through detailed studies of transmission electron microscopy. The relationships of the domains, doping concentration, and grain size were determined, and their effects on the ionic conductivities were examined. It was concluded that the domains were formed via the segregation of Yb cations so that they could trap the oxygen vacancies and lower the conductivity. Furthermore, the development of the domains, which depends on the doping concentration and grain size, can affect the doping concentration and grain-size dependencies of the conductivity. (c) 2006 The Electrochemical Society.
Electrochemical removal of NO and CH4 in the presence of excess O2, H2O and CO2 using Sm2O3-doped CeO2 as a solid electrolyte
Electrochemical removal of NO and CH4 from a gas stream containing excess O2, H2O and CO2 has been carried out between 400 and 800 °C using a single-compartment reactor, which is constructed from CeO2-based solid electrolyte with two palladium electrodes. At all temperatures studied, both NO and CH4 were decomposed by applying a direct current to the reactor. NO was decomposed to N2 in two different ways depending on the applied current. At low currents, NO was electrolysed together with O2 at the palladium cathode; and, at high currents, NO was catalytically reduced over the palladium surface free from adsorbed oxygen. By investigating the influences of the concentration of NO, H2O, CO2, CH4 or C3H8 contained in the reactant gas to these two decompositions, their mechanisms are discussed in detail.