High temperature X-ray diffractometric studies on the lattice thermal expansion behaviour of UO2, ThO2 and (U0.2Th0.8)O2 doped with fission product oxides

Momin, A.C.; Mirza, E. B.; Mathews, M.D.

doi:10.1016/0022-3115(91)90521-8

Cited by 48 publications

(13 citation statements)

References 6 publications

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“…It appears that the strain associated with the Pbnm -Ibmm transition in BaThO 3 is reflected in the thermal expansion of the ThO 2 impurity phase. The average linear TEC � for ThO 2 is derived as 1.01 x 10 -5 ºC -1 , in reasonable agreement with the earlier studies 34,35 and are similar to values reported for other fluorite type materials 36 .…”

Section: Resultssupporting

confidence: 90%

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Structure and phase transition in BaThO3: A combined neutron and synchrotron X-ray diffraction study

Murphy

Kennedy

Zhang

et al. 2017

Journal of Alloys and Compounds

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The structure of BaThO 3 , obtained by solid state synthesis, was refined for the first time by the Rietveld method using a combination of synchrotron X-ray and neutron powder diffraction data. BaThO 3 has an orthorhombic structure at room temperature, in space group Pbnm with a = 6.3491(5), b = 6.3796(4) and c = 8.9907(7) Å. Heating BaThO 3 to above 700 °C results in a continuous transition to a second orthorhombic structure, in space group Ibmm, demonstrated by both in situ neutron and synchrotron X-ray powder diffraction measurements. The coefficient of volumetric thermal expansion for BaThO 3 is determined to be 1.04 x 10 -5 o C -1 from 50 to 625 o C (Pbnm phase), and 9.43 x 10 -6 o C -1 from 800 to 1000 o C (Ibmm phase) . BaThO 3 was found to decompose upon exposure to atmospheric moisture resulting in the formation of ThO 2 . The thermal expansion of ThO 2 , which invariably coexists with BaThO 3 , is also described.

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Section: Resultssupporting

confidence: 90%

“…So the validly of the actual SrThO 3 structure formation is questionable, especially considering that the average linear thermal expansion coefficient (1.049 x 10 -5 ºC -1 ) reported by Purohit et al 41 is very close to our value for ThO 2 (1.01 x 10 -5 ºC -1 ) and also to other previous ThO 2 investigations. 34,35…”

Section: Resultsmentioning

confidence: 99%

Structure and phase transition in BaThO3: A combined neutron and synchrotron X-ray diffraction study

Murphy

Kennedy

Zhang

et al. 2017

Journal of Alloys and Compounds

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“…However, the most recent diffraction studies contributing to the Martin-Fink model are from a 1991 study employing a laboratory based x-ray diffractometer and only reaching 1600 K in temperature [5]. In the 25 years since then, there have been significant technological advances.…”

Section: Introductionmentioning

confidence: 99%

Thermal expansion in UO2 determined by high-energy X-ray diffraction

Guthrie

Benmore

Skinner

et al. 2016

Journal of Nuclear Materials

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Here we present crystallographic analyses of high-energy x-ray diffraction data on polycrystalline UO 2 up to the melting temperature. The Rietveld refinements of our x-ray data are in agreement with previous measurements, but are systematically located around the upper bound of their uncertainty, indicating a slightly steeper trend of thermal expansion compared to established values. This observation is consistent with recent first principles calculations.

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“…A robust energy cut off up to 700 eV with the convergence precision of 10 −6 eV was used in all the calculations, and the Brillouin zone was sampled using a 6×6×6 k-point mesh. Atomic positions were optimized with the lattice parameters fixed at its observed value (a=5.469 Å) [80]. Among the points that we explore in detail below are (A) the evaluation of interaction parameters U and J using the cRPA, (B) magnetically constrained DFT calculations, (C) spin adiabatic occupation matrix analysis of the magnetic energy landscape, (D) parametrization of the multipolar pseudospin Hamiltonian and exchange coupling, and (E) evaluation of the strength of SOC.…”

Section: Ab Initio Methodologymentioning

confidence: 99%

Parametrization of LSDA+U for noncollinear magnetic configurations: Multipolar magnetism in UO2

Dudarev

Liu

Andersson

et al. 2019

Phys. Rev. Materials

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To explore the formation of noncollinear magnetic configurations in materials with strongly correlated electrons, we derive a noncollinear LSDA+U model involving only one parameter U, as opposed to the difference between the Hubbard and Stoner parameters U − J. Computing U in the constrained random phase approximation, we investigate noncollinear magnetism of uranium dioxide UO 2 and find that the spin-orbit coupling (SOC) stabilizes the 3k ordered magnetic ground state. The estimated SOC strength in UO 2 is as large as 0.73 eV per uranium atom, making spin and orbital degrees of freedom virtually inseparable. Using a multipolar pseudospin Hamiltonian, we show how octupolar and dipole-dipole exchange coupling help establish the 3k magnetic ground state with canted ordering of uranium f -orbitals. The cooperative Jahn-Teller effect does not appear to play a significant part in stabilizing the noncollinear 3k state, which has the lowest energy even in an undistorted lattice. The choice of parameter U in the LSDA+U model has a notable quantitative effect on the predicted properties of UO 2 , in particular on the magnetic exchange interaction and, perhaps trivially, on the band gap: The value of U = 3.46 eV computed fully ab initio delivers the band gap of 2.11 eV in good agreement with experiment, and a balanced account of other pertinent energy scales. * sergei.dudarev@ukaea.uk † cesare.franchini@univie.ac.at. (6) Here,N = m,σĉ † m,σĉm,σ is the operator of the total number of electrons on a site,n kl = σĉ † k,σĉ l,σ , and M = m,ξ,ξ ′ĉ † m,ξ σ ξξ ′ĉ m,ξ ′

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High temperature X-ray diffractometric studies on the lattice thermal expansion behaviour of UO2, ThO2 and (U0.2Th0.8)O2 doped with fission product oxides

Cited by 48 publications

References 6 publications

Structure and phase transition in BaThO3: A combined neutron and synchrotron X-ray diffraction study

Structure and phase transition in BaThO3: A combined neutron and synchrotron X-ray diffraction study

Thermal expansion in UO2 determined by high-energy X-ray diffraction

Parametrization of LSDA+U for noncollinear magnetic configurations: Multipolar magnetism in UO2

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