Raman spectrum of U4O9: a new interpretation of damage lines in UO2

Desgranges, Lionel; Baldinozzi, Gianguido; Simon, Patrick; Guimbretière, Guillaume; Canizarès, A.

doi:10.1002/jrs.3054

Cited by 134 publications

(118 citation statements)

References 19 publications

(37 reference statements)

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“…We suggest that this mode at 719 cm -1 is related to oxygen defects in the structure. Similar behavior has been observed in fluorite structure having punctual defects [29][30][31] , i.e. interstitial oxygens as in case of UO 2+x 31 or oxygen vacancies as in UO 2 doped trivalent metals 29,30 .…”

Section: Table4: Main Interatomic Distances (å) Angles (°) and Bond supporting

confidence: 75%

Chemically stabilized δ-Bi2O3 phase: Raman scattering and X-ray diffraction studies

Loubbidi¹,

Naji²,

Orayech³

et al. 2016

Orient. J. Chem

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Thanks to its peculiar structural properties, the high temperature ä-phase of Bi 2 O 3 is considered as the best oxide ion conductor. Many efforts to stabilize this structure at room temperature have been deployed. In the present study, we have successfully stabilized the ä-phase by chemically introducing tetra-Te 4+ and pentavalent Ta 5+ cations into the structure. A series of compounds with different percentage of Te 4+ / Ta 5+ were obtained. Their structural and vibrational properties were investigated. From the Rietveld refinement of X Ray diffraction pattern we show that the composition x = 0.2 crystallizes in the cubic symmetry, space group Fm 3m (ITA No. 225) with a lattice parameter a =5.49 Å. The reliability factors are: R F =2.151 % and R Bragg =2.545 % confirm the goodness of the refinement. From the evolution of Raman bands, we confirm the existence of the solid solution features. Furthermore, comparing the spectra of ä-Bi 2 O 3 with the alpha phase, we comfortably suggest that the decrease of the number of Raman bands is a consequence of an increase in the lattice symmetry. Similarly to other fluorite compounds, we show that the structure presents oxygen defects clearly identified in the Raman spectra.

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Section: Table4: Main Interatomic Distances (å) Angles (°) and Bond supporting

confidence: 75%

Chemically stabilized δ-Bi2O3 phase: Raman scattering and X-ray diffraction studies

Loubbidi¹,

Naji²,

Orayech³

et al. 2016

Orient. J. Chem

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“…The position of the latter is shown in more detail in figure 5. This is followed by modes at about 535 cm À1 (characteristic for hypostoichiometry [21]), around 575 cm À1 (TO mode) and at about 630 cm À1 . The last was attributed in the case of uranium oxides to a U 4 O 9 phase [21].…”

Section: Raman Spectroscopymentioning

confidence: 97%

“…This is followed by modes at about 535 cm À1 (characteristic for hypostoichiometry [21]), around 575 cm À1 (TO mode) and at about 630 cm À1 . The last was attributed in the case of uranium oxides to a U 4 O 9 phase [21]. Part II and III show peaks which were also observed by Sarsfield et al for pure PuO 2 [22].…”

Section: Raman Spectroscopymentioning

confidence: 97%

“…These observed peaks therefore indicate defects in the lattice, which can be linked to energetically favourable oxygen Frenkel defects or oxygen losses, possibly quenched to room temperature. Also the peaks at 535 and 630 cm À1 can be related to a disorder in the lattice, while a formation of M 4 O 9 with these compounds, as in uranium compounds [21], seems unlikely. The origin of the band around 335 cm À1 remains unclear.…”

Section: Raman Spectroscopymentioning

confidence: 98%

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High temperature phase transition of mixed (PuO 2 + ThO 2 ) investigated by laser melting

Böhler

Cakir

Beneš

et al. 2015

The Journal of Chemical Thermodynamics

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a b s t r a c tA laser heating approach combined with fast pyrometry in a thermal arrest method was used to provide new data for the melting/solidification phase transition in mixed (PuO 2 + ThO 2 ) at high temperature. At low concentration of ThO 2 in PuO 2 a minimum in the solidification temperature in the pseudo binary (PuO 2 + ThO 2 ) was observed. The minimum was found around a composition with 5 mol% ThO 2 . Phase transition temperatures of other compositions are closer to an ideal solution behaviour. To detect changes in the material a complete investigation with electron microscopy, Raman spectroscopy and powder X-ray diffraction was done. Raman vibration modes were found, that are characteristic for materials containing PuO 2 , and high temperature segregation effects during solidification were described. The results obtained in the present work are compared to other mixed actinide dioxides and compared to the ideal solution case for this system. The presented results show the importance of the hightemperature oxygen chemistry in this actinide oxide phase.

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“…This peak has been related to the change in unit cell size in U 4 O 9 9 and, by comparison to ZrO 2 spectra, to a distortion of the U sublattice associated with the transition to tetragonal U 3 O 7 . 8 Some XRD evidence was offered in support of this claim.…”

Section: Sem/edx Analysis-mentioning

confidence: 98%

Influence of Trivalent-Dopants on the Structural and Electrochemical Properties of Uranium Dioxide (UO₂)

Razdan

Shoesmith

2013

J. Electrochem. Soc.

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The influence of trivalent dopants (rare-earths, RE) on the structure, composition and electrochemical reactivity of UO 2 has been investigated using scanning electron microscopy (SEM/XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and cyclic voltammetry (CV). This was achieved by comparing the behavior of undoped UO 2.002 , a slightly doped 1.5 at% SIMFUEL, and two rare-earth doped UO 2 (6 wt% Gd-UO 2 and 12.9 wt% Dy-UO 2 ) specimens. The reactivity decreased in the order UO 2.002 > SIMFUEL > Dy-UO 2 > Gd-UO 2 , showing that this decrease is a consequence of RE III doping. Raman spectroscopy showed this could be attributed to the formation of RE III -oxygen vacancy clusters whose formation decreases the availability of the vacancies required to accommodate the injection of oxygen interstitials during anodic oxidation. The behavior of SIMFUEL is complicated by the simultaneous formation of RE III -oxygen vacancy clusters and Zr-O 8 clusters.The safe disposal of spent nuclear fuel (SNF) is one of the key issues facing the modern nuclear power industry, and a major international effort is underway to develop safe management and disposal procedures. One potential management strategy in Canada is permanent disposal in a deep geologic repository. 1 The spent fuel would be sealed in metallic containers, emplaced in a repository and surrounded with compacted clay. The prospects for long term containment using copper containers are very good and corrosion models predict only minimal corrosion damage should be sustained. 2,3 However, if failure were to occur, contact of the fuel wasteform (uranium dioxide (UO 2 )) with groundwater would become possible. Although the solubility of UO 2 is very low under the anticipated anoxic conditions, radiolysis of the groundwater, due to the inherent radioactivity of the spent fuel, could lead to fuel corrosion, the U(IV) in the fuel being oxidized to the significantly more soluble U(VI) state. 4 This would make radionuclide release to the groundwater possible.Spent fuel is mainly UO 2 (> 95%), the remainder being the radioactive fission products and actinides produced during the in-reactor process. The inventory of radionuclides within the fuel depends on in-reactor burn-up and the linear power rating of the fuel. 5 Formation of these products leads to many physical and chemical changes within the fuel, 5 and post irradiation inspection of the fuel shows the presence of both volatile and non-volatile fission products. While volatile products may escape to the fuel-cladding gap, the non volatile products remain fixed within the fuel matrix in three distinct phases: the lanthanides in the fcc-fluorite lattice; the noble metals in metallic precipitates; and radionuclides unstable in the fluorite matrix in mixed metal oxides (perovskites). 6 The key changes likely to influence the chemical reactivity of the UO 2 matrix are the rare earth (RE) doping of the matrix and the development of non-stoichiometry. 7 Micro Raman spectroscopic studies show that non-stoichiometry lead...

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Raman spectrum of U₄O₉: a new interpretation of damage lines in UO₂

Cited by 134 publications

References 19 publications

Chemically stabilized δ-Bi2O3 phase: Raman scattering and X-ray diffraction studies

Chemically stabilized δ-Bi2O3 phase: Raman scattering and X-ray diffraction studies

High temperature phase transition of mixed (PuO 2 + ThO 2 ) investigated by laser melting

Influence of Trivalent-Dopants on the Structural and Electrochemical Properties of Uranium Dioxide (UO₂)

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Raman spectrum of U4O9: a new interpretation of damage lines in UO2

Cited by 134 publications

References 19 publications

Chemically stabilized δ-Bi2O3 phase: Raman scattering and X-ray diffraction studies

Chemically stabilized δ-Bi2O3 phase: Raman scattering and X-ray diffraction studies

High temperature phase transition of mixed (PuO 2 + ThO 2 ) investigated by laser melting

Influence of Trivalent-Dopants on the Structural and Electrochemical Properties of Uranium Dioxide (UO2)

Contact Info

Product

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Raman spectrum of U₄O₉: a new interpretation of damage lines in UO₂

Influence of Trivalent-Dopants on the Structural and Electrochemical Properties of Uranium Dioxide (UO₂)