Electrical properties of the ZrO2-CeO2 system

Chiodelli, Gaetano; Flor, Giorgio; Scagliotti, M.

doi:10.1016/s0167-2738(96)00382-7

Cited by 106 publications

(113 citation statements)

References 15 publications

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“…The k-CeZrO 4 prepared in this study involved negligible antiphase domain boundaries. Lattice parameter a and lattice volume V of the k phase were 1.05248 (2) nm and 1.1659 (1) nm 3 , respectively, and agreed excellently with those reported previously [8]; the number in the parentheses shows the standard deviation estimated in the last digit. Fig.…”

Section: Resultssupporting

confidence: 89%

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Electrical conductivity of metastable κ-CeZrO₄ phase possessing ordered arrangement of Ce and Zr ions

Izu

Kishimoto

Omata

et al. 2001

Science and Technology of Advanced Materials

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Electrical conductivity s t of metastable k-CeZrO 4 possessing ordered arrangement of Ce and Zr ions in a manner similar to a pyrochloretype was measured as a function of temperature and time, and compared with tetragonal metastable t 0 -(Ce 0.5 Zr 0.5 )O 2 and t 0 meta -(Ce 0.5 Zr 0.5 )O 2 phases possessing random arrangement of the cations. The k disk was prepared by reoxidizing a pyrochlore-type precursor in O 2 gas at 873 K. The s t as measured for the k-CeZrO 4 was reproducible as a function of temperatures between 957 and 1190 K. At increasing temperatures above 1233 K, the s t decreased gradually with time due to the phase transition: k ! t 0 , and became consistent with the t 0 . Although the k-CeZrO 4 phase is thermodynamically less stable than the t 0 -(Ce 0.5 Zr 0.5 )O 2 , it was virtually stable up to around 1233 K. It was found from the change in the s t due to the phase transition that the s t for the metastable k-CeZrO 4 was an order of magnitude higher than that for the t 0 and was similar to that for the t 0 meta . It was previously reported that a phase transition, t 0 meta ! t 0 , occurred above 1143 K. The phase transition, k ! t 0 , accompanied by redistribution of the cations appeared to occur at higher temperatures than that for t 0 meta ! t 0 leaving random cation arrangement. q

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Section: Resultssupporting

confidence: 89%

“…The electrical conductivity of xCeO 2 ±(1 2 x)ZrO 2 oxides has been investigated at intermediate temperatures as 1273 K over the wide composition range [3]. In the intermediate composition range of the CeO 2 ±ZrO 2 system, no compound exists in the equilibrium phase diagram, except for the CaF 2 -type cubic phase over 1823 K [4,5].…”

Section: Introductionmentioning

confidence: 99%

Electrical conductivity of metastable κ-CeZrO₄ phase possessing ordered arrangement of Ce and Zr ions

Izu

Kishimoto

Omata

et al. 2001

Science and Technology of Advanced Materials

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“…[17][18][19][20] In theoretical calculations the oxygen vacancy formation energy turns out to show a minimum at this ratio. [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.…”

Section: +mentioning

confidence: 91%

“…We suggest that structural effects similar to the mixed alkali effect may also contribute to the formation of the maximum. Additionally, the activation energy E a and the preexponential factor of the conductivity s 0 were evaluated from the temperature dependence according to eqn (24), where s denotes the total conductivity, k the Boltzmann factor and T the absolute temperature.…”

Section: Composition and Temperature Dependence Of The Total Conductimentioning

confidence: 99%

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.

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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.

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“…By doping with Zr, the resistivity becomes low. [13] The resistive sensors using CeO 2 ÀZrO 2 thick film and their sensor properties were investigated by Izu et al [14] It was reported that the thick film with 0.5À40 mol% ZrO 2 had a shorter response time, a lower resistivity and a better oxygen partial pressure dependence of resistivity compared to the ceria thick film without ZrO 2 . [ As mentioned above various applications of Zr-doped ceria which include promoters for catalytic reactions, resistive sensors, enhancement of thermal stability, etc.…”

Section: Introductionmentioning

confidence: 99%

Absorption and emission properties of Zr-doped nanoceria synthesised by co-precipitation-hydrothermal treatment route

Sahoo

Mohapatra

Anand

2014

Journal of Experimental Nanoscience

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A series of nanoceria samples doped with zirconium (nil to 2 mol%) and a typical sample doped with 1 mol% each of Zr and Eu were synthesised following coprecipitation-hydrothermal treatment route. The main peaks in X-ray diffraction (XRD) patterns of all the samples corresponded to (111), (200), (220) and (311) planes of cubic ceria. The Fourier transform infrared spectra showed bands which were indicative of formation of nanoceria with intercalated/adsorbed water. In Raman spectra, a sharp and intense Raman shift at around 460À462 cm ¡1 was observed for all the samples and the peak intensity decreased with increase in mol% doping of Zr. In case of ZrÀEu-doped sample the peak intensity was similar to the undoped ceria. The decrease in intensity could be due to accumulation/precipitation of more numbers of Zr ions on the surface rather than incorporation into ceria lattice. The indirect band gaps estimated from ultravioletÀvisible absorption spectra were smaller when compared to the direct ones. The smaller indirect band gaps indicate that Zr-doped nanoparticles with a higher fraction of atoms residing at the surface were available to assist the indirect electron transition from the valence band to the conduction band. Emission spectra obtained by exciting at 300 and 500 nm for all samples are discussed in details. Transmission electron microscope image of a typical sample showed mono-dispersed uniform sized single crystalline doped ceria.

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Electrical properties of the ZrO2-CeO2 system

Cited by 106 publications

References 15 publications

Electrical conductivity of metastable κ-CeZrO₄ phase possessing ordered arrangement of Ce and Zr ions

Electrical conductivity of metastable κ-CeZrO₄ phase possessing ordered arrangement of Ce and Zr ions

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

Absorption and emission properties of Zr-doped nanoceria synthesised by co-precipitation-hydrothermal treatment route

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Electrical properties of the ZrO2-CeO2 system

Cited by 106 publications

References 15 publications

Electrical conductivity of metastable κ-CeZrO4 phase possessing ordered arrangement of Ce and Zr ions

Electrical conductivity of metastable κ-CeZrO4 phase possessing ordered arrangement of Ce and Zr ions

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

Absorption and emission properties of Zr-doped nanoceria synthesised by co-precipitation-hydrothermal treatment route

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Electrical conductivity of metastable κ-CeZrO₄ phase possessing ordered arrangement of Ce and Zr ions

Electrical conductivity of metastable κ-CeZrO₄ phase possessing ordered arrangement of Ce and Zr ions

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