Influence of microstructure on oxide ionic conductivity in doped CeO2 electrolytes

Abstract

Doped ceria (CeO 2 ) compounds are fluorite type oxides, which show oxide ionic conductivity higher than yttria stabilized zirconia, in oxidizing atmospheres. As a consequence of this, considerable interest has been shown in application of these materials for 'low (500 • -650 • C)' temperature operation of solid oxide fuel cells (SOFCs). In this study, some rare earth (eg. Gd, Sm, and Dy) doped CeO 2 nanopowders were synthesized via a carbonate co-precipitation method. Fluorite-type solid solution were able to be formed at low temperature, such as 400 • C and dense sintered bodies were subsequently fabricated in the temperature ranging from 1000 • to 1450 • C by conventional sintering (CS) method. To develop high quality solid electrolytes, the microstructure at the atomic level of these doped CeO 2 solid electrolytes were examined using transmission electron microscopy (TEM). The specimens obtained by CS had continuous and large micro-domains with a distorted pyrochlore structure or related structure, within each grain. We conclude that the conducting properties in these doped CeO 2 systems are strongly influenced by the micro-domain size in the grain. To minimize the micro-domain size, spark plasma sintering (SPS) was examined. SPS has not been used to fabricate dense sintered bodies of doped CeO 2 electrolytes, previously; carbon from the graphite dies penetrates the specimens and inhibits densification. To overcome this challenge, and to be able to produce dense sintered bodies of doped CeO

Synthesis and Characterization of Nanosized Dy-Doped of Ceria Developed by Microwave Assisted Combustion Route

“…Our results conclude that the mobility of oxide ions is higher in small grains MS specimens (< 500 nm) than the bigger one CS (>1000 nm). These results very well agree with earlier reported work [29,30]. The sintered body with homogeneously grown grains develops order structure of oxygen vacancies within the whole grain.…”

Microstructural and chemical aspects of working-temperature aged Ca-doped CeO2

“…16,17 And it is generally accepted that lattice distortion, formed during doping (sintering) aliovalent elements into CeO 2 , is responsible for the appearance of the superstructure 9 ; the microdomain forms as a kind of compensation to this lattice distortion. 18 With longterm aging like the processing in the current study, the lattice distortion in grains can be relaxed, consequently leading to the weakening of the superstructures as well as the microdomains.…”

In situ compatibility studies of lanthanum nickelate with a ceria-based electrolyte for SOFC composite cathodes

“…Ceria is a well known redox catalyst with its activity attributed to its variable oxidation states, and fast oxide ion transport properties 28,29,[35][36][37][38] . Reduction of ceria results in the formation of oxygen vacancies and occurs by the process outlined below,…”

“…In IS-3, the capillary is sealed and it would therefore be expected that the oxygen pressure in the capillary would increase on heating, however from Rietveld refinement of the XRD data under these conditions it is apparent that LNO is reduced to form La 2 O 3 and Ni. This indicates that the reduction of LNO is not due to the ambient oxygen pressure in the capillary but is related to the nature of the composite material and the presence of the CGO.Ceria is a well known redox catalyst with its activity attributed to its variable oxidation states, and fast oxide ion transport properties 28,29,[35][36][37][38] . Reduction of ceria results in the formation of oxygen vacancies and occurs by the process outlined below,…”