Local Defect Structures and Ion Transport Mechanisms in the Oxygen-Excess Apatite La-9.67(SiO4)(6)O-2.5

Alison Jones, P Slater, M S Islam

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104 Citations (Scopus)

Abstract

Apatite-type oxides of general formula La9.33+x(SiO4)(6)O-2 + (3x/2) have been attracting considerable interest recently because of their observed high oxide-ion conductivity and potential use in solid oxide fuel cells (SOFCs), oxygen sensors, and ceramic membranes. In this paper, computer modeling techniques are used to investigate, at the atomic level, the energetics of defect formation, oxide-ion migration, and cation migration in the oxygen-excess apatite silicate, La-9.67(SiO4)(6)O-2.5. Recent research has suggested that oxide-ion conduction in these apatite systems proceeds by an interstitial mechanism. Our results support this view and have revealed how the flexibility of the SiO4 substructure plays a crucial role in facilitating oxide-ion migration: the presence of interstitial oxide ions creates pseudo-"SiO5" units, which can effectively pass along the c direction by oxygen transfer. La vacancy migration is also examined and, as expected, found to have a high energy barrier.
Original languageEnglish
Pages (from-to)5055-5060
Number of pages6
JournalChemistry of Materials
Volume20
Issue number15
DOIs
Publication statusPublished - 2008

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  • Projects

    DAPHNE JACKSON FELLOWSHIP

    Jones, A. & Islam, S.

    The Daphne Jackson Trust

    1/02/0631/01/08

    Project: UK charity

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