The role of dopant segregation on the oxygen vacancy distribution and oxygen diffusion in CeO2 grain boundaries

Adam Symington, Marco Molinari, Joel Statham, Ji Wu, Stephen Charles Parker

Research output: Contribution to journalArticle

Abstract

An important challenge when attempting to identify the role of microstructure and the effect of dopant concentration on the properties of energy materials is to distinguish the behaviour of each grain boundary. In this paper we describe our recent work using atomistic simulations to investigate the structure, composition and oxygen transport of gadolinium doped cerium dioxide tilt grain boundaries. We find that energy minimisation can be systematically employed to screen grain boundary structures and dopant segregation. When dopants are distributed equally across grains, molecular dynamics simulations reveal oxygen vacancies reside near dopants, resulting in higher oxygen diffusivity. Once the dopants accumulate at the grain boundaries these grain boundaries become saturated with oxygen vacancies. We see fast oxygen diffusion within the grain boundary plane, although the depletion layer, as shown via the electrostatic potential appears to block transport across the grain boundary. However, this is highly dependent on the grain boundary structure as we find striking differences of the potential and the segregation behaviour between each of interface studied.
LanguageEnglish
JournalJournal of Physics: Energy
Early online date11 Jun 2019
DOIs
Publication statusE-pub ahead of print - 11 Jun 2019

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grain boundaries
oxygen
gadolinium
cerium
dioxides
diffusivity
depletion
simulation
electrostatics
molecular dynamics
microstructure
optimization
energy

Cite this

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abstract = "An important challenge when attempting to identify the role of microstructure and the effect of dopant concentration on the properties of energy materials is to distinguish the behaviour of each grain boundary. In this paper we describe our recent work using atomistic simulations to investigate the structure, composition and oxygen transport of gadolinium doped cerium dioxide tilt grain boundaries. We find that energy minimisation can be systematically employed to screen grain boundary structures and dopant segregation. When dopants are distributed equally across grains, molecular dynamics simulations reveal oxygen vacancies reside near dopants, resulting in higher oxygen diffusivity. Once the dopants accumulate at the grain boundaries these grain boundaries become saturated with oxygen vacancies. We see fast oxygen diffusion within the grain boundary plane, although the depletion layer, as shown via the electrostatic potential appears to block transport across the grain boundary. However, this is highly dependent on the grain boundary structure as we find striking differences of the potential and the segregation behaviour between each of interface studied.",
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The role of dopant segregation on the oxygen vacancy distribution and oxygen diffusion in CeO2 grain boundaries. / Symington, Adam; Molinari, Marco; Statham, Joel; Wu, Ji; Parker, Stephen Charles.

In: Journal of Physics: Energy, 11.06.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The role of dopant segregation on the oxygen vacancy distribution and oxygen diffusion in CeO2 grain boundaries

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AU - Molinari, Marco

AU - Statham, Joel

AU - Wu, Ji

AU - Parker, Stephen Charles

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AB - An important challenge when attempting to identify the role of microstructure and the effect of dopant concentration on the properties of energy materials is to distinguish the behaviour of each grain boundary. In this paper we describe our recent work using atomistic simulations to investigate the structure, composition and oxygen transport of gadolinium doped cerium dioxide tilt grain boundaries. We find that energy minimisation can be systematically employed to screen grain boundary structures and dopant segregation. When dopants are distributed equally across grains, molecular dynamics simulations reveal oxygen vacancies reside near dopants, resulting in higher oxygen diffusivity. Once the dopants accumulate at the grain boundaries these grain boundaries become saturated with oxygen vacancies. We see fast oxygen diffusion within the grain boundary plane, although the depletion layer, as shown via the electrostatic potential appears to block transport across the grain boundary. However, this is highly dependent on the grain boundary structure as we find striking differences of the potential and the segregation behaviour between each of interface studied.

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