Long-range charge transfer and oxygen vacancy interactions in strontium ferrite

    Research output: Contribution to journalArticle

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    Abstract

    The high oxygen non-stoichiometry (δ) in many mixed ionic conductors does not translate into high ionic conductivity due to strong interactions between oxygen vacancies. In this study, the charge states of Fe in various phases of SrFeO3-δ were determined by interpreting the density functional theory (DFT) predicted magnetic moment on Fe. The charge on Fe in square pyramidal (SP) was shown to always remain +4 while the Fe in distorted octahedral (Oh) varied from +4 to +3 with δ, due to the different d-orbital splitting of SP and Oh Fe. Furthermore, a new 'long-range charge transfer' mechanism was observed where the electrons left by the charge-neutral oxygen vacancy were transferred to the second nearest neighbor Fe (instead of the Fe directly connected to the vacancy) and resulted in extended lattice distortions that promoted strong oxygen vacancy interactions. A DFT-based thermodynamics model for interacting vacancies was also developed to predict the δ and oxygen vacancy site fraction (X) at high temperatures. The δ and X values calculated with this model showed good agreement with experiments. These calculations resolve a long-standing debate in the literature on the mixed charge states of Fe in SrFeO3-δ and identify a new mechanism for oxygen vacancy interactions.

    Original languageEnglish (US)
    Pages (from-to)4493-4506
    Number of pages14
    JournalJournal of Materials Chemistry A
    Volume5
    Issue number9
    DOIs
    StatePublished - 2017

    Profile

    Osteoradionecrosis
    Oxygen vacancies
    Ostertagiasis
    Anthralin
    Density functional theory
    Charge transfer
    Vacancies
    Magnetics
    Common Bile Duct Diseases
    Acetanilides
    Erythrocebus patas
    Community Psychiatry
    Physiological Adaptation
    Alkynes
    Magnetic moments
    Ferrite
    Electrons
    Ionic conductivity
    Strontium
    Crystal lattices

    ASJC Scopus subject areas

    • Chemistry(all)
    • Renewable Energy, Sustainability and the Environment
    • Materials Science(all)

    Cite this

    Long-range charge transfer and oxygen vacancy interactions in strontium ferrite. / Das, Tridip; Nicholas, Jason D.; Qi, Yue.

    In: Journal of Materials Chemistry A, Vol. 5, No. 9, 2017, p. 4493-4506.

    Research output: Contribution to journalArticle

    Das, Tridip; Nicholas, Jason D.; Qi, Yue / Long-range charge transfer and oxygen vacancy interactions in strontium ferrite.

    In: Journal of Materials Chemistry A, Vol. 5, No. 9, 2017, p. 4493-4506.

    Research output: Contribution to journalArticle

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    abstract = "The high oxygen non-stoichiometry (δ) in many mixed ionic conductors does not translate into high ionic conductivity due to strong interactions between oxygen vacancies. In this study, the charge states of Fe in various phases of SrFeO3-δ were determined by interpreting the density functional theory (DFT) predicted magnetic moment on Fe. The charge on Fe in square pyramidal (SP) was shown to always remain +4 while the Fe in distorted octahedral (Oh) varied from +4 to +3 with δ, due to the different d-orbital splitting of SP and Oh Fe. Furthermore, a new 'long-range charge transfer' mechanism was observed where the electrons left by the charge-neutral oxygen vacancy were transferred to the second nearest neighbor Fe (instead of the Fe directly connected to the vacancy) and resulted in extended lattice distortions that promoted strong oxygen vacancy interactions. A DFT-based thermodynamics model for interacting vacancies was also developed to predict the δ and oxygen vacancy site fraction (X) at high temperatures. The δ and X values calculated with this model showed good agreement with experiments. These calculations resolve a long-standing debate in the literature on the mixed charge states of Fe in SrFeO3-δ and identify a new mechanism for oxygen vacancy interactions.",
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