Preparation and fluorite–pyrochlore phase transformation in Gd2Zr2O7

Lee, Y.H.; Sheu, Hwo‐Shuenn; Deng, Junru; Kao, H.-C.I.

doi:10.1016/j.jallcom.2009.08.021

Cited by 88 publications

(28 citation statements)

References 17 publications

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“…It has been recently demonstrated that the degree of disorder in Gd 2 Zr 2 O 7 is sensitive to the thermal history of the material. When prepared at low temperatures Gd 2 Zr 2 O 7 adopts a defect fluorite structure and this transforms to disordered pyrochlore at temperatures higher than 1200 1C in static air environment [27]. It seems a reasonable postulate that x $ 0.346 in well ordered Gd 2 Zr 2 O 7 ( Table 2).…”

Section: Resultsmentioning

confidence: 99%

Neutron diffraction studies of Gd2Zr2O7 pyrochlore

Kennedy

Zhou

Avdeev

2011

Journal of Solid State Chemistry

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Section: Resultsmentioning

confidence: 99%

Neutron diffraction studies of Gd2Zr2O7 pyrochlore

Kennedy

Zhou

Avdeev

2011

Journal of Solid State Chemistry

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“…As the ionic radii ratio (r A /r B ) approaches $1.46, the A-site and B-site cations may undergo anti-site disorder which can result in a phase transition from the pyrochlore to the defect fluorite structure [5,7,22,59]. The super structural peaks (odd planes) from the XRD patterns were used to differentiate the pyrochlore-phase materials from the defect-fluorite phase materials [59][60][61][62]. A decrease in the intensity of the superstructural peaks is generally indicative of cation anti-site disorder; however, the intensities of these peaks relative to the other peaks are also affected by the differences in the scattering power between the A-and B-site cations [33,63].…”

Section: Powder X-ray Diffraction Before and After Ion Implantationmentioning

confidence: 99%

An investigation of the electronic structure and structural stability of RE2Ti2O7 by glancing angle and total electron yield XANES

Aluri

Grosvenor

2014

Journal of Alloys and Compounds

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a b s t r a c tPyrochlore-type oxides (A 2 B 2 O 7 ) have been investigated for nuclear waste sequestration applications due to their overall resistance to radiation-induced structural damage. This damage can be simulated by implanting the materials with high-energy ions to aid in understanding how the structure of a crystalline material responds to radioactive decay of incorporated nuclear waste elements. RE 2 Ti 2 O 7 (RE = La-Lu), Yb 1.85 Ca 0.15 Ti 2 O 7Àd , and Yb 2 Ti 1.85 Fe 0.15 O 7Àd were synthesized by the ceramic method and investigated by Ti K-edge X-ray absorption near edge spectroscopy (XANES) and powder X-ray diffraction before and after being implanted by 2 MeV Au À ions. Surface sensitive total electron yield (TEY) XANES spectra and glancing-angle (GA) XANES spectra were collected to study the ion-implanted materials. It was necessary to use these surface sensitive detection methods because the 2 MeV Au À ions only implant to $450 nm into the surface of the materials. An effective sample mounting procedure has been developed that uses conductive silver paint to collect high quality TEY-XANES spectra from the damaged surface layer of the implanted pellets so as to minimize charging effects. This investigation has shown that the local coordination number of Ti decreased after implantation, and that the degree of damage observed decreases with decreasing radius of the RE cation. The study has also shown that the oxygen vacancies generated by a slight substitution of Yb 3+ for Ca 2+ or Ti 4+ for Fe 3+ does not considerably affect the resistance of Yb 2 Ti 2 O 7 to radiation-induced damage.

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“…[10][11][12] From a crystallographic point of view, it is known to exist in two different space groups depending on the conditions of preparation. 13 If annealed at a temperature above 1773 K, it attains an anion-deficient fluorite structure with space group Fm3m, whereas below 1773 K, it normally exists as a ordered pyrochlore with space group Fd3m. 13 An investigation into the effect of Eu 3+ substitution in place of Gd 3+ carried out by Xia et al 10 showed that the ionic conductivity of Gd 2 Zr 2 O 7 increases with an increase in Eu 3+ content.…”

Section: Introductionmentioning

confidence: 99%

Induced oxygen vacancies and their effect on the structural and electrical properties of a fluorite-type CaZrO₃–Gd₂Zr₂O₇ system

2015

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Solid oxide materials were prepared via a solid state reaction route with a stoichiometry composition: x% of CaZrO 3 and (100 À x)% of Gd 2 Zr 2 O 7 (x = 10, 20, 33.3, 40). Powder X-ray diffraction under ambient and high-temperature conditions, scanning electron microscopy, transmission electron microscopy and ac impedance spectroscopy techniques were used to analyze and correlate the structural and electrical properties of the materials. The aliovalent substitution of Gd 3+ by Ca 2+ allowed the creation of more oxygen vacancies in the lattice of these compositions. This resulted in a progressive decrease in the lattice parameter and an increase in the thermal expansion coefficient. The induced oxygen vacancies provided a lower energy barrier for ionic diffusion and hence led to an increase in conductivity which was found to show a maximum value of 3.59 Â 10 À3 S cm À1 at 1023 K for x = 33.3. The high ionic conductivity value measured in this study indicates that solid solutions of this kind are promising as good ionic conductors.

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Preparation and fluorite–pyrochlore phase transformation in Gd2Zr2O7

Cited by 88 publications

References 17 publications

Neutron diffraction studies of Gd2Zr2O7 pyrochlore

Neutron diffraction studies of Gd2Zr2O7 pyrochlore

An investigation of the electronic structure and structural stability of RE2Ti2O7 by glancing angle and total electron yield XANES

Induced oxygen vacancies and their effect on the structural and electrical properties of a fluorite-type CaZrO₃–Gd₂Zr₂O₇ system

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Preparation and fluorite–pyrochlore phase transformation in Gd2Zr2O7

Cited by 88 publications

References 17 publications

Neutron diffraction studies of Gd2Zr2O7 pyrochlore

Neutron diffraction studies of Gd2Zr2O7 pyrochlore

An investigation of the electronic structure and structural stability of RE2Ti2O7 by glancing angle and total electron yield XANES

Induced oxygen vacancies and their effect on the structural and electrical properties of a fluorite-type CaZrO3–Gd2Zr2O7 system

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Induced oxygen vacancies and their effect on the structural and electrical properties of a fluorite-type CaZrO₃–Gd₂Zr₂O₇ system