Novel Chemical Synthesis and Characterization of CeTi<sub>2</sub>O<sub>6</sub> Brannerite

Kong, Linggen; Gregg, Daniel J.; Karatchevtseva, Inna; Zhang, Zhaoming; Blackford, Mark G.; Middleburgh, Simon C.; Lumpkin, Gregory R.; Triani, Gerry

doi:10.1021/ic500563j

Cited by 30 publications

(39 citation statements)

References 34 publications

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“…The pelletized precursors U1 and U2 were then sintered in air at 1200/1300°C to produce samples U1B/U1C and U2B/U2C, respectively. The XRD patterns of samples U1B (Figure A) and U2B (Figure B) showed typical brannerite in good agreement with the XRD patterns of CeTi 2 O 6 and UTi 2 O 6 (JCPDS card No. 00‐012‐0477) in monoclinic C 2/ m space group.…”

Section: Resultsmentioning

confidence: 98%

“…The refined unit cell parameters are summarized in Table , together with those of CeTi 2 O 6 and some substituted UTi 2 O 6 and ThTi 2 O 6 brannerite phases available in the literature. The unit cell volume ( V ), the b ‐parameter and c ‐parameter show good linear relationships with the Shannon ionic radii of the A‐site cations in ATi 2 O 6 , while the a ‐parameter shows weak relationship with the ionic radii of the A‐site cations (Figure ).…”

Section: Resultsmentioning

confidence: 99%

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Uranium brannerite with Tb(III)/Dy(III) ions: Phase formation, structures, and crystallizations in glass

et al. 2019

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Uranium brannerite phases with terbium(III) or dysprosium(III) ions have been investigated. The precursors with molar ratio of 0.5:0.5:2 (Ln: U: Ti with Ln = Tb or Dy) were prepared and calcined at 750°C in argon. Sintering the pelletized samples in argon at 1200°C led to the formation of pyrochlore phases with TiO2 rutile and U‐rich oxides while sintering in air led to the formation of brannerite phases with the nominal composition close to Ln0.5U0.5Ti2O6 together with trace amounts of TiO2 rutile and LnUO4. Incorporating an excess of TiO2 (20 wt%) and sintering at higher temperature (1300°C) resulted in no obvious change to the phase equilibrium. As designed, pentavalent uranium has been proven to be dominant in these brannerite phases with diffuse reflectance spectroscopy. The relationships between the cell parameters and the ionic radii of the A‐site cations have been explored and rationalized from the structure point of view for a range of titanate brannerite phases (ATi2O6). In addition, the crystallization of Ln0.5U0.5Ti2O6 brannerite in glass has been achieved via heat treatment at 1200°C and confirmed with X‐ray diffraction, scanning electron microscopy‐energy dispersive spectroscopy and transmission electron microscopy–selected area electron diffraction.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Uranium brannerite with Tb(III)/Dy(III) ions: Phase formation, structures, and crystallizations in glass

et al. 2019

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“…00‐025‐0177) with trace amounts of UO 2 . The refined unit cell parameters for sample U1 (as same composition to sample U2) are summarized in Table , together with those for Ce 0.975 Ti 2 O 5.95 , UTi 2 O 6 , Y 0.15 Th 0.6 Pu 0.25 Ti 2 O 5.925 , and Y 0.15 Th 0.6 Np 0.25 Ti 2 O 5.925 for comparison. The refinement of sample U1 gives reasonably well R factor, 7.88 (Table ).…”

Section: Resultsmentioning

confidence: 99%

“…Earlier work demonstrated that end‐member CeTi 2 O 6 , ThTi 2 O 6 , and UTi 2 O 6 brannerite phases could be stabilized by high temperature (1200°C‐1400°C) sintering. However, brannerite phase crystallization in glass remains little studied.…”

Section: Methodsmentioning

confidence: 99%

Development of brannerite glass‐ceramics for the immobilization of actinide‐rich radioactive wastes

et al. 2017

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Brannerite‐based glass‐ceramics have been developed as potential waste forms for the immobilization of actinide‐rich radioactive wastes. For the first time, the formation of brannerite phases in glass has been demonstrated using uranium (U) and plutonium (Pu) with additions of gadolinium and hafnium as neutron absorbers. Both XRD and SEM‐EDS confirm that brannerite is the dominating phase with compositions close to Y0.5U0.5Ti2O6, Gd0.2Pu0.3U0.5Ti2O6, and Gd0.1Hf0.1Pu0.2U0.6Ti2O6 internally crystallized in the glass. TEM SAED and Raman spectroscopy reveal the typical structure and vibration modes for brannerite. In addition, the presence of U5+ species as designed in the formulations has been confirmed by diffuse reflectance spectroscopy. More importantly, the U and Pu were partitioned exclusively in the ceramic phases with no detectable actinide in the glass.

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“…The TiO 6 layers are connected along the c axis by corner-sharing with CeO 6 octahedra 41,42. CeTi 2 O 6 as well as anatase and rutile polymorphs of TiO 2 were observed as…”

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Flame-Made WO₃/CeO_x-TiO₂ Catalysts for Selective Catalytic Reduction of NO_x by NH₃

et al. 2015

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Materials based on combination of tungsten-cerium-titanium are potentially durable catalysts for selective catalytic NO x reduction using NH 3 (NH 3 -SCR). Flame spray synthesis is used here to produce WO 3 /CeO x -TiO 2 nanoparticles, which are characterized with respect to their phase composition, morphology and acidic properties and are evaluated for deNO x by NH 3 -SCR. HR-TEM and XRD revealed that flame-made WO 3 /CeO x -TiO 2 consists of mainly rutile TiO 2 , brannerite CeTi 2 O 6 , cubic CeO 2 and a minor fraction of anatase TiO 2 . These phases coexist with a large portion of amorphous mixed Ce-Ti phase. The lack of crystallinity and the presence of brannerite together with the evident high fraction of Ce 3+ are taken as evidence that cerium is also present as a dopant in TiO 2 and is well dispersed on the surface of the nano-particles. Clusters of amorphous WO 3 homogeneously cover all particles as observed by STEM. Such morphology and phase composition guarantee short range Ce-O-Ti and Ce-O-W interactions and thus the high surface concentration of Ce 3+ . The presence of the WO 3 layer and the close Ce-O-W interaction further increase the Ce 3+ content compared to binary Ce-Ti materials as shown by XPS and XANES. The acidity of the materials and the nature of the acid sites were determined by NH 3 temperature programmed desorption (NH 3 -TPD) and DRIFT spectroscopy, respectively. TiO 2 possesses mainly strong Lewis acidity; addition of cerium, especially the presence of surface Ce 3+ in close contact with titanium and tungsten, inducesBrønsted acid sites that are considerably increased by the amorphous WO 3 clusters. As a result of this peculiar element arrangement and phase composition, 10 wt% WO 3 /10 mol% CeO x -90 mol% TiO 2 exhibits the highest deNO x efficiency, which matches that of a V 2 O 5 -WO 3 /TiO 2 catalyst. Preliminary activity data indicate that the flame-made catalyst demonstrates much higher performance after thermal and hydrothermal aging at 700°C than the V-based analogue despite the presence of the rutile phase. Ce 3+ remains the dominating surface cerium species after both aging treatments thus confirming its crucial role in NH 3 -SCR by Ce-W-Ti based catalysts.

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Novel Chemical Synthesis and Characterization of CeTi₂O₆ Brannerite

Cited by 30 publications

References 34 publications

Uranium brannerite with Tb(III)/Dy(III) ions: Phase formation, structures, and crystallizations in glass

Uranium brannerite with Tb(III)/Dy(III) ions: Phase formation, structures, and crystallizations in glass

Development of brannerite glass‐ceramics for the immobilization of actinide‐rich radioactive wastes

Flame-Made WO₃/CeO_x-TiO₂ Catalysts for Selective Catalytic Reduction of NO_x by NH₃

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Novel Chemical Synthesis and Characterization of CeTi2O6 Brannerite

Cited by 30 publications

References 34 publications

Uranium brannerite with Tb(III)/Dy(III) ions: Phase formation, structures, and crystallizations in glass

Uranium brannerite with Tb(III)/Dy(III) ions: Phase formation, structures, and crystallizations in glass

Development of brannerite glass‐ceramics for the immobilization of actinide‐rich radioactive wastes

Flame-Made WO3/CeOx-TiO2 Catalysts for Selective Catalytic Reduction of NOx by NH3

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Novel Chemical Synthesis and Characterization of CeTi₂O₆ Brannerite

Flame-Made WO₃/CeO_x-TiO₂ Catalysts for Selective Catalytic Reduction of NO_x by NH₃