Phases in Ce0.5Zr0.5O2−x system

Kang, Zhaofeng

doi:10.1016/j.jallcom.2004.12.154

Cited by 15 publications

(15 citation statements)

References 13 publications

(14 reference statements)

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“…CeO 2 -ZrO 2 solid solution phases exhibit cubic (c-), monoclinic (m-), and tetragonal (t-) polymorphism with a number of metastable tetragonal form t9, t99, t999 and t* etc. 17,18 Due to the structural complexity, it is still very challenging to synthesize nanoscale compositionally homogeneous CeO 2 -ZrO 2 mixed oxides, as the mixed oxides need to accommodate the discrepancy in crystal structure, ionic size, oxidation states, and oxygen-metal coordination numbers of cubic CeO 2 and monoclinic ZrO 2 . In this paper, we report a facile one-step hydrothermal synthesis method to prepare compositionally homogeneous Ce x Zr 12x O 2 (0 ¡ x ¡ 1) solid solution nanocrystals and the thermal stability of the prepared nanocrystals under oxidation and reduction atmosphere at high temperatures.…”

Section: Introductionmentioning

confidence: 99%

One-pot hydrothermal synthesis and high temperature thermal stability of CexZr1−xO2 nanocrystals

2013

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We report a facile one-pot synthesis of Ce x Zr 12x O 2 (0 ¡ x ¡ 1) solid solution nanocrystals using hydrothermal reactions. A direct formation of oxide solid solutions in aqueous solution under pressure at low temperatures was clearly revealed by X-ray diffraction, Raman spectroscopy, and chemical composition analysis of individual nanocrystals using energy dispersive X-ray spectroscopy in scanning transmission electron microscopy mode. Chemisorption behavior of the synthesized nanocrystals was characterized using a hydrogen temperature programmed reduction, which showed a superior lowtemperature activity in Ce x Zr 12x O 2 (0 , x , 1) compared to pure CeO 2 . Furthermore, we investigated the thermal stability of the prepared Ce 0.5 Zr 0.5 O 2 at high temperatures (900 uC-1400 uC) under oxidation and reduction atmosphere. The effect of varying conditions of heat-treatment has given information on the phase transformation in Ce 0.5 Zr 0.5 O 2 from pseudocubic to tetragonal structure under oxidation atmosphere, and to pyrochlore structure under reduction atmosphere.High surface area Ce x Zr 12x O 2 (0 ¡ x ¡ 1) samples were synthesized using a hydrothermal method. Typically, 0.1 M Ce(NO 3 ) 3 ?6H 2 O (Alfa Aesa, 99.99%) and 0.1 M ZrO(NO 3 ) 2 ?xH 2 O

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Section: Introductionmentioning

confidence: 99%

One-pot hydrothermal synthesis and high temperature thermal stability of CexZr1−xO2 nanocrystals

2013

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“…Montini et al 22 subjected ceria zirconia to redox cycles under high-temperature reducing conditions and found evidence for cation ordering at least on the surface of their material from Raman spectroscopy. Using transmission electron microscopy (TEM), Kang 23 showed the presence of cubic, tetragonal, and pyrochlore-type phases in material subjected to high-temperature reduction. Even though most of the recent results reported above were for samples of average composition Ce 0.5 Zr 0.5 O 2 , Aneggi et al 24 pointed out that the samples came from different synthesis and treatment procedures, which complicates the interpretation.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale Heterogeneity in Ceria Zirconia with Low-Temperature Redox Properties

et al. 2006

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We have investigated nanoscale compositional and structural variations in Ce(0.5)Zr(0.5)O(2) samples with different redox properties. Different samples were prepared using a spray freezing technique, and the synthesis conditions were varied to yield materials with reduction temperatures in the range of 400-750 degrees C. X-ray diffraction and thermal gravimetric analysis were used to characterize the average structures and redox properties of these materials. The nanoscale structural and compositional variations in individual nanoparticles of high activity were determined with atomic-scale electron imaging and nanometer-resolution electron energy loss spectroscopy. During the early stage of particle formation, the crystallization process is initiated via the nucleation of ceria-rich nanodomains. This results in the formation of high-surface-area materials that exhibit nanoscale compositional heterogeneity consisting of Ce-rich cores surrounded by Zr-rich shells. The effect of high-temperature redox cycling on the nanoscale structure, composition, and low-temperature redox properties was also determined. Our analysis suggests that our most active material exhibits significant compositional and structural heterogeneity at the nanometer level.

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“…In the ceria rich region (57-81%) the pyrochlore is in equilibrium with a cubic phase. The cubic phase is stable from 81-85% CeO 1.5 [59]. Yttria in higher concentrations can suppress the formation of the pyrochlore phase from the cubic phase on reduction [60].…”

Section: Ceria and Mixed Metal Cerium Oxidesmentioning

confidence: 99%