Nonstoichiometry of Ce1−XYXO2−0.5X−δ (X=0.1, 0.2)

Otake, Takanori; Yugami, Hiroo; Yashiro, Keiji; Nigara, Yutaka; Kawada, Tatsuya; Mizusaki, Junichiro

doi:10.1016/s0167-2738(02)00873-1

Cited by 61 publications

(51 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At a first glance, the calculated non-stoichiometry appears to be overestimated but able to describe the observed deviation quite well. 35 We tried to adapt this approach to the present data but did not achieve a satisfying agreement between model and experimental data. Taking a closer look to published data for the nonstoichiometry of nominally pure CeO 2 and solid solutions of (Ce, M)O 2Àd (M = Zr, Y, Gd) we find that the maximum d value with respect to the Ce content was not reached in any study.…”

Section: Non-stoichiometry and Oxygen Storage Capacity (Osc)mentioning

confidence: 93%

“…[21][22][23] As well shown by Chiodelli et al, 24 Lee et al 25 and Kuhn et al, 26 defect chemical modelling is essential for the fundamental understanding of the OSC and for further improvement. The solid solution system CeO 2 -ZrO 2 -Y 2 O 3 has already been examined in polycrystalline form with regard to total conductivity, 25,[27][28][29][30][31][32][33] partial electronic conductivity 34 and nonstoichiometry 26,35 as a function of temperature and oxygen partial pressure. Reviewing these studies, three questions remain open: (a) it was observed by Cales and Baumard, 31 Lee et al 32 and Xiong et al 34 that the course of the total and the partial electronic conductivity as a function of oxygen partial pressure deviates strongly from the ''classical'' point defect model for acceptor doping (see Section 2), especially at low pO 2 .…”

Section: +mentioning

confidence: 99%

“…(b) The non-stoichiometry d of the systems CeO 2 , Ce-Zr-O and Ce-Zr-Y-O was measured isothermally as a function of pO 2 in the temperature range between 700 r y/1C r 1500 by Panlener et al, 6 Kuhn et al 26 and Otake et al 35 In particular at low temperatures the reduction of cerium appears to be hindered, and a much smaller non-stoichiometry than expected is observed. 3 With decreasing pO 2 , d even attains a plateau.…”

Section: +mentioning

confidence: 99%

See 2 more Smart Citations

The model case of an oxygen storage catalyst – non-stoichiometry, point defects and electrical conductivity of single crystalline CeO₂–ZrO₂–Y₂O₃solid solutions

Eufinger

Daniels

Schmale

et al. 2014

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

The ternary solid solution CeO 2 -ZrO 2 is known for its superior performance as an oxygen storage catalyst in exhaust gas catalysis (e.g. TWC), although the defect chemical background of these outstanding properties is not fully understood quantitatively. Here, a comprehensive experimental study is reported regarding defects and defect-related transport properties of cubic stabilized single crystalline (Ce x Zr 1Àx ) 0.8 Y 0.2 O 1.9Àd (0 r x r 1) solid solutions as a model system for CeO 2 -ZrO 2 . The constant fraction of yttria was chosen in order to fix a defined concentration of oxygen vacancies and to stabilize the cubic fluorite-type lattice for all Ce/Zr ratios. Measurements of the total electrical conductivity, the partial electronic conductivity, the ionic transference number and the non-stoichiometry (oxygen deficiency, oxygen storage capacity) were performed in the oxygen partial pressure range À25 o lg pO 2 /bar o 0 and for temperatures between 500 1C and 750 1C. The total conductivity at low pO 2 is dominated by electronic transport.A strong deviation from the widely accepted ideal solution based point defect model was observed.An extended point defect model was developed using defect activities rather than concentrations in order to describe the point defect reactions in CeO 2 -ZrO 2 -Y 2 O 3 properly. It served to obtain good quantitative agreement with the measured data. By a combination of values for non-stoichiometries and for electronic conductivities, the electron mobility could be calculated as a function of pO 2 , ranging between 10 À2 cm 2 V À1 s À1 and 10 À5 cm 2 V À1 s À1. Finally, the origin of the high oxygen storage capacity and superior catalytic promotion performance at a specific ratio of n(Ce)/n(Zr) E 1 was attributed to two main factors: (1) a strongly enhanced electronic conductivity in the high and medium pO 2 range qualifies the material to be a good mixed conductor, which is essential for a fast oxygen exchange and (2) the equilibrium constant for the reduction exhibits a maximum, which means that the reduction is thermodynamically most favoured just at this composition.

show abstract

Section: Non-stoichiometry and Oxygen Storage Capacity (Osc)mentioning

confidence: 93%

Section: +mentioning

confidence: 99%

Section: +mentioning

confidence: 99%

See 1 more Smart Citation

The model case of an oxygen storage catalyst – non-stoichiometry, point defects and electrical conductivity of single crystalline CeO₂–ZrO₂–Y₂O₃solid solutions

Eufinger

Daniels

Schmale

et al. 2014

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…The assumption of ideal solution behaviour required for ready application of equation (2.4) is equivalent to the statement that the oxidation enthalpy is, to a first approximation, independent of defect concentration, and that the configurational entropy describes a solution with random and non-interacting defects. It has been shown that ideal solution behaviour is obeyed in 15-20% samarium-, gadolinium-and yttrium-doped ceria for d as large as 0.03-0.05 (Wang et al 1997;Kobayashi et al 1999;Otake et al 2003). In contrast, undoped ceria deviates from ideal solution behaviour for d greater than 0.01 (Panlener et al 1975;Duncan et al 2007;Bishop et al 2009).…”

Section: Characteristics Of Ceria Relevant For Thermochemical Fuel Prmentioning

confidence: 99%

A thermochemical study of ceria: exploiting an old material for new modes of energy conversion and CO ₂ mitigation

Chueh

Haile

2010

Phil. Trans. R. Soc. A.

386

399

View full text Add to dashboard Cite

We present a comprehensive thermodynamic and kinetic analysis of the suitability of cerium oxide (ceria) for thermochemical fuel production. Both portions of the two-step cycle, (i) oxygen release from the oxide at 1773 and 1873 K under inert atmosphere, and (ii) hydrogen release upon hydrolysis at 1073 K, are examined theoretically as well as experimentally. We observe gravimetric fuel productivity that is in quantitative agreement with equilibrium, thermogravimetric studies of ceria. Despite the non-stoichiometric nature of the redox cycle, in which only a portion of the cerium atoms change their oxidation state, the fuel productivity of 8.5-11.8 ml of H 2 per gram of ceria is competitive with that of other solid-state thermochemical cycles currently under investigation. The fuel production rate, which is also highly attractive, at a rate of 4.6-6.2 ml of H 2 per minute per gram of ceria, is found to be limited by a surface-reaction step rather than by ambipolar bulk diffusion of oxygen through the solid ceria. An evaluation of the thermodynamic efficiency of the ceria-based thermochemical cycle suggests that, even in the absence of heat recovery, solar-to-fuel conversion efficiencies of 16 to 19 per cent can be achieved, assuming a suitable method for obtaining an inert atmosphere for the oxygen release step.

show abstract

“…The Yttria-stabilized Zirconia (YSZ) was used as electrolyte in solid oxide fuel cell (SOFC), and drawbacks such as high operating temperature in using YSZ as electrolyte can be eliminated by replacing it with cerium materials. Ceria is being used extensively because of its ability to store and release oxygen ion vacancies due to its easily accessible oxidation states from Ce 3þ Ce 4þ and hence has high ionic conductivity due to oxygen vacancies (Zivkovic et al 2011;Otake et al 2003). …”

Section: Introductionmentioning

confidence: 99%

Effect of Mg doping and sintering temperature on structural and morphological properties of samarium-doped ceria for IT-SOFC electrolyte

et al. 2017

View full text Add to dashboard Cite

Samples of Sm and Mg co-doped ceria electrolyte of Ce 1-x Sm x-y Mg y O 2-d (x = 0.2; y = 0.00, 0.05, 0.1, 0.15, and 0.175) were synthesized by sol-gel process. The prepared samples were sintered at 1100 and 1400°C for 4 h. The bulk densities were measured by Archimedes method. XRD measurements indicate that the synthesized samples were in single-phase cubic fluorite structure (space group Fm3m). The cell parameters decrease with the concentration of Mg, and 2h values slightly shift towards right. The particle sizes obtained were between 7.14 and 17.44 nm. The sintered sample achieved 95% of theoretical density. FTIR spectra of samples sintered at 1400°C indicates weak interactions between 3550-3400 cm -1 and 1600-1300 cm -1 are attributed to O-H stretching modes and strong bonds 850-450 cm -1 are assigned to characteristic Ce-O vibrations. The surface morphology and chemical composition were analyzed by SEM and EDS, SEM micrographs show spherical faceted grains, and the samples were crack free, dense material with some pores on surface which are inconsistent with density results. The average grain size obtained was 0.5 lm. Particle size obtained by TEM was in agreement with that obtained by XRD. The high-density ceria co-doped ceramic can be used as electrolyte in SOFC.

show abstract

Nonstoichiometry of Ce1−XYXO2−0.5X−δ (X=0.1, 0.2)

Cited by 61 publications

References 5 publications

The model case of an oxygen storage catalyst – non-stoichiometry, point defects and electrical conductivity of single crystalline CeO₂–ZrO₂–Y₂O₃solid solutions

The model case of an oxygen storage catalyst – non-stoichiometry, point defects and electrical conductivity of single crystalline CeO₂–ZrO₂–Y₂O₃solid solutions

A thermochemical study of ceria: exploiting an old material for new modes of energy conversion and CO ₂ mitigation

Effect of Mg doping and sintering temperature on structural and morphological properties of samarium-doped ceria for IT-SOFC electrolyte

Contact Info

Product

Resources

About

Nonstoichiometry of Ce1−XYXO2−0.5X−δ (X=0.1, 0.2)

Cited by 61 publications

References 5 publications

The model case of an oxygen storage catalyst – non-stoichiometry, point defects and electrical conductivity of single crystalline CeO2–ZrO2–Y2O3solid solutions

The model case of an oxygen storage catalyst – non-stoichiometry, point defects and electrical conductivity of single crystalline CeO2–ZrO2–Y2O3solid solutions

A thermochemical study of ceria: exploiting an old material for new modes of energy conversion and CO 2 mitigation

Effect of Mg doping and sintering temperature on structural and morphological properties of samarium-doped ceria for IT-SOFC electrolyte

Contact Info

Product

Resources

About

The model case of an oxygen storage catalyst – non-stoichiometry, point defects and electrical conductivity of single crystalline CeO₂–ZrO₂–Y₂O₃solid solutions

The model case of an oxygen storage catalyst – non-stoichiometry, point defects and electrical conductivity of single crystalline CeO₂–ZrO₂–Y₂O₃solid solutions

A thermochemical study of ceria: exploiting an old material for new modes of energy conversion and CO ₂ mitigation