Defect segregation facilitates oxygen transport at fluorite UO2 grain boundaries

A. R. Symington, M. Molinari, N. A. Brincat, N. R. Williams, S. C. Parker

Research output: Contribution to journalArticle

Abstract

An important challenge for modelling transport in materials for energy applications is that in most applications they are polycrystalline, and hence it is critical to understand the properties in the presence of grain boundaries. Moreover, most grain boundaries are not pristine stoichiometric interfaces and hence dopants are likely to play a significant role. In this paper, we describe our recent work on using atomistic molecular dynamics simulations to model the effect of doped grain boundaries on oxygen transport of fluorite structured UO2. UO2, much like other fluorite grain boundaries, are found to be sinks for oxygen vacancy segregation relative to the grain interior, thus facilitating oxygen transport. Fission products further enhance diffusivity via strong interactions between the impurities and oxygen defects. Doping produces a striking structural alteration in the Σ5 class of grain boundaries that enhances oxygen diffusivity even further.

LanguageEnglish
Article number20190026
Number of pages16
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Volume377
Issue number2152
DOIs
Publication statusPublished - 8 Jul 2019

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Fluorspar
Grain Boundary
fluorite
Segregation
Oxygen
Grain boundaries
grain boundaries
Defects
defects
oxygen
Diffusivity
diffusivity
Doping (additives)
fission products
Fission products
Vacancy
Oxygen vacancies
sinks
Impurities
Molecular Dynamics Simulation

Cite this

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title = "Defect segregation facilitates oxygen transport at fluorite UO2 grain boundaries",
abstract = "An important challenge for modelling transport in materials for energy applications is that in most applications they are polycrystalline, and hence it is critical to understand the properties in the presence of grain boundaries. Moreover, most grain boundaries are not pristine stoichiometric interfaces and hence dopants are likely to play a significant role. In this paper, we describe our recent work on using atomistic molecular dynamics simulations to model the effect of doped grain boundaries on oxygen transport of fluorite structured UO2. UO2, much like other fluorite grain boundaries, are found to be sinks for oxygen vacancy segregation relative to the grain interior, thus facilitating oxygen transport. Fission products further enhance diffusivity via strong interactions between the impurities and oxygen defects. Doping produces a striking structural alteration in the Σ5 class of grain boundaries that enhances oxygen diffusivity even further.",
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Defect segregation facilitates oxygen transport at fluorite UO2 grain boundaries. / Symington, A. R.; Molinari, M.; Brincat, N. A.; Williams, N. R.; Parker, S. C.

In: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 377, No. 2152, 20190026, 08.07.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Defect segregation facilitates oxygen transport at fluorite UO2 grain boundaries

AU - Symington, A. R.

AU - Molinari, M.

AU - Brincat, N. A.

AU - Williams, N. R.

AU - Parker, S. C.

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KW - MO-doped UO

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KW - Oxygen diffusion

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KW - Space charge in UO

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