Phase equilibria in the system HfO2-ZrO2-CeO2 at 1500°C

Andrievskaya, E. R.; Gerasimyuk, G.I.; Kornienko, O. A.; Samelyuk, A. V.; Lopato, L. M.; Red’ko, V. P.

doi:10.1007/s11106-006-0105-y

Cited by 18 publications

(14 citation statements)

References 12 publications

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“…This finding is in agreement with previous work on the thermally induced transformations in the CeO 2 -Y 2 O 3 system[28], demonstrating that the maximum solubility of Y 2 O 3 in CeO 2 (sometimes called "hot spots" or "thermal spikes"[29]) occurred during highenergy ball milling provide important factors enhancing the reaction between CeO 2 and Y 2 O 3 reactants.Fig. 1 (bottom)shows the XRD pattern of the mechanosynthesized Ce 0.65 Y 0.35 O 2-δ phase after thermal treatment at 800°C for 4 h in ambient atmosphere.…”

supporting

confidence: 92%

Mechanosynthesis and structural characterization of nanocrystalline Ce1–Y O2– (x=0.1–0.35) solid solutions

Fábian

Antić

Girman

et al. 2015

Journal of Solid State Chemistry

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supporting

confidence: 92%

Mechanosynthesis and structural characterization of nanocrystalline Ce1–Y O2– (x=0.1–0.35) solid solutions

Fábian

Antić

Girman

et al. 2015

Journal of Solid State Chemistry

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“…It is also known that Ce may enhance the stability of the cubic phase [54,55]. However, the HfO2-CeO2-ZrO2 ternary phase diagram shows the three-phase region (monoclinic + tetragonal + cubic) for the equimolar composition at 1500°C [56]. It appears that the cubic stabilizers in this system affects the phase stability to a more considerable degree in this CCFO system than yttria does in the zirconia system.…”

Section: Phase Stabilitymentioning

confidence: 81%

“…All specimens were annealed at the respective temperatures for 24 h and subsequently quenched. The composition (Hf1/3Zr1/3Ce1/3)O2 exhibits three phases according to Andrievskaya et al[56]. (Legends: ▲ = 3 phase; • = tetragonal; ■ = cubic.)…”

mentioning

confidence: 99%

From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides

Wright

Wang

Huang

et al. 2020

Journal of the European Ceramic Society

219

125

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Using fluorite oxides as an example, this study broadens high-entropy ceramics (HECs) to compositionally-complex ceramics (CCCs) or multi-principal cation ceramics (MPCCs) to include medium-entropy and/or non-equimolar compositions. Nine compositions of compositionally-complex fluorite oxides (CCFOs) with the general formula of (Hf1/3Zr1/3Ce1/3)1x(Y1/2X1/2)xO2-δ (X = Yb, Ca, and Gd; x = 0.4, 0.148, and 0.058) are fabricated. The phase stability, mechanical properties, and thermal conductivities are measured. Compared with yttriastabilized zirconia, these CCFOs exhibit increased cubic phase stability and reduced thermal conductivity, while retaining high Young's modulus (~210 GPa) and nanohardness (~18 GPa).Moreover, the temperature-dependent thermal conductivity in the non-equimolar CCFOs shows an amorphous-like behavior. In comparison with their equimolar high-entropy counterparts, the medium-entropy non-equimolar CCFOs exhibit even lower thermal conductivity (k) while maintaining high modulus (E), thereby achieving higher E/k ratios. These results suggest a new direction to achieve thermally-insulative yet stiff CCCs (MPCCs) via exploring non-equimolar and/or medium-entropy compositions. Summary of Novel Conclusions:This study broadens "high-entropy ceramics" to "compositionally-complex ceramics". Using fluorite oxides as an example, we show that lower thermal conductivity and higher stiffness-toconductivity ratios are achieved in medium-entropy non-equimolar compositions. Highlights:• Nine compositionally-complex fluorite oxides (CCFOs) are made and investigated.• CCFOs exhibit reduced thermal conductivity and increased cubic phase stability.• Lower thermal conductivity is achieved in medium-entropy non-equimolar CCFOs.• High modulus and hardness retain in CCFOs with reduced thermal conductivity.• Non-equimolar CCFOs exhibit amorphous-like T-dependent thermal conductivity.

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“…the system appears to be fully miscible in the entire composition range as already reported by several authors. 27,29,31,55,56 In contrast, Sammes et al 57 found a local maximum of the cell parameter vs. x in the system (CeO 2 ) 1Àx (8YSZ) x for x E 0.5 and drew the conclusion that CeO 2 has a limited solubility in YSZ. Similar results from Hinatsu et al 58 and Sakai et al 53 indicate a miscibility gap for In addition to phase analysis by X-ray diffraction (XRD), Raman spectroscopy on small single crystals of each composition was performed (Fig.…”

Section: Phase Analysis and Compositionmentioning

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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Phase equilibria in the system HfO2-ZrO2-CeO2 at 1500°C

Cited by 18 publications

References 12 publications

Mechanosynthesis and structural characterization of nanocrystalline Ce1–Y O2– (x=0.1–0.35) solid solutions

Mechanosynthesis and structural characterization of nanocrystalline Ce1–Y O2– (x=0.1–0.35) solid solutions

From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides

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

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Phase equilibria in the system HfO2-ZrO2-CeO2 at 1500°C

Cited by 18 publications

References 12 publications

Mechanosynthesis and structural characterization of nanocrystalline Ce1–Y O2– (x=0.1–0.35) solid solutions

Mechanosynthesis and structural characterization of nanocrystalline Ce1–Y O2– (x=0.1–0.35) solid solutions

From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides

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

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