Defect chemistry, thermomechanical and transport properties of (RE2−xSrx)0.98(Fe0.8Co0.2)1−yMgyO4−δ (RE = La, Pr)

Christodoulos Chatzichristodoulou, Jens Christian Sidney Schönbeck, Anke Hagen, Peter Vang Hendriksen

    Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

    Resumé

    The oxygen nonstoichiometry of Ruddlesden-Popper compounds with chemical composition (RE2 − xSrx)0.98(Fe0.8Co0.2)1 − yMgyO4 − δ (RE = La, Pr, x = 0.9–1.2 and y = 0, 0.2) was measured as a function of temperature and oxygen activity (aO2) by coulometric titration and thermogravimetry. All compositions were found to be approximately stoichiometric in air (δ ≈ 0). The oxidation state of Fe and Co was determined by XANES. Fe retains an oxidation state of + 3 upon reduction of the sample, whereas Co is reduced to an oxidation state of + 2. A model of the defect chemistry is proposed that can account well for the measured oxygen activity dependence of the oxygen nonstoichiometry at all temperatures investigated. The studied compositions exhibit remarkable thermodynamic stability under reducing conditions. Decomposition was only observed for temperatures above 800 °C in a hydrogen water vapor gas mixture ([H2]/[H2O] = 50). The thermal and chemical expansion coefficients of these compounds are significantly decreased compared to those of (La0.6Sr0.4)0.99Fe0.8Co0.2O3 − δ, a well studied perovskite with related composition. The transport properties were investigated by conductivity relaxation and the potential of using these materials as oxygen separation membranes was assessed by calculating the oxygen flux that can be delivered through a 30 μm thick membrane.
    OriginalsprogEngelsk
    TidsskriftSolid State Ionics
    Vol/bind232
    Sider (fra-til)68-79
    ISSN0167-2738
    DOI
    StatusUdgivet - 7 feb. 2013

    Citer dette

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    title = "Defect chemistry, thermomechanical and transport properties of (RE2−xSrx)0.98(Fe0.8Co0.2)1−yMgyO4−δ (RE = La, Pr)",
    abstract = "The oxygen nonstoichiometry of Ruddlesden-Popper compounds with chemical composition (RE2 − xSrx)0.98(Fe0.8Co0.2)1 − yMgyO4 − δ (RE = La, Pr, x = 0.9–1.2 and y = 0, 0.2) was measured as a function of temperature and oxygen activity (aO2) by coulometric titration and thermogravimetry. All compositions were found to be approximately stoichiometric in air (δ ≈ 0). The oxidation state of Fe and Co was determined by XANES. Fe retains an oxidation state of + 3 upon reduction of the sample, whereas Co is reduced to an oxidation state of + 2. A model of the defect chemistry is proposed that can account well for the measured oxygen activity dependence of the oxygen nonstoichiometry at all temperatures investigated. The studied compositions exhibit remarkable thermodynamic stability under reducing conditions. Decomposition was only observed for temperatures above 800 °C in a hydrogen water vapor gas mixture ([H2]/[H2O] = 50). The thermal and chemical expansion coefficients of these compounds are significantly decreased compared to those of (La0.6Sr0.4)0.99Fe0.8Co0.2O3 − δ, a well studied perovskite with related composition. The transport properties were investigated by conductivity relaxation and the potential of using these materials as oxygen separation membranes was assessed by calculating the oxygen flux that can be delivered through a 30 μm thick membrane.",
    author = "Christodoulos Chatzichristodoulou and Sch{\"o}nbeck, {Jens Christian Sidney} and Anke Hagen and Hendriksen, {Peter Vang}",
    year = "2013",
    month = "2",
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    doi = "10.1016/j.ssi.2012.10.026",
    language = "English",
    volume = "232",
    pages = "68--79",
    journal = "Solid State Ionics",
    issn = "0167-2738",
    publisher = "Elsevier BV * North-Holland",

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    Defect chemistry, thermomechanical and transport properties of (RE2−xSrx)0.98(Fe0.8Co0.2)1−yMgyO4−δ (RE = La, Pr). / Chatzichristodoulou, Christodoulos; Schönbeck, Jens Christian Sidney; Hagen, Anke; Hendriksen, Peter Vang.

    I: Solid State Ionics, Bind 232, 07.02.2013, s. 68-79.

    Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

    TY - JOUR

    T1 - Defect chemistry, thermomechanical and transport properties of (RE2−xSrx)0.98(Fe0.8Co0.2)1−yMgyO4−δ (RE = La, Pr)

    AU - Chatzichristodoulou, Christodoulos

    AU - Schönbeck, Jens Christian Sidney

    AU - Hagen, Anke

    AU - Hendriksen, Peter Vang

    PY - 2013/2/7

    Y1 - 2013/2/7

    N2 - The oxygen nonstoichiometry of Ruddlesden-Popper compounds with chemical composition (RE2 − xSrx)0.98(Fe0.8Co0.2)1 − yMgyO4 − δ (RE = La, Pr, x = 0.9–1.2 and y = 0, 0.2) was measured as a function of temperature and oxygen activity (aO2) by coulometric titration and thermogravimetry. All compositions were found to be approximately stoichiometric in air (δ ≈ 0). The oxidation state of Fe and Co was determined by XANES. Fe retains an oxidation state of + 3 upon reduction of the sample, whereas Co is reduced to an oxidation state of + 2. A model of the defect chemistry is proposed that can account well for the measured oxygen activity dependence of the oxygen nonstoichiometry at all temperatures investigated. The studied compositions exhibit remarkable thermodynamic stability under reducing conditions. Decomposition was only observed for temperatures above 800 °C in a hydrogen water vapor gas mixture ([H2]/[H2O] = 50). The thermal and chemical expansion coefficients of these compounds are significantly decreased compared to those of (La0.6Sr0.4)0.99Fe0.8Co0.2O3 − δ, a well studied perovskite with related composition. The transport properties were investigated by conductivity relaxation and the potential of using these materials as oxygen separation membranes was assessed by calculating the oxygen flux that can be delivered through a 30 μm thick membrane.

    AB - The oxygen nonstoichiometry of Ruddlesden-Popper compounds with chemical composition (RE2 − xSrx)0.98(Fe0.8Co0.2)1 − yMgyO4 − δ (RE = La, Pr, x = 0.9–1.2 and y = 0, 0.2) was measured as a function of temperature and oxygen activity (aO2) by coulometric titration and thermogravimetry. All compositions were found to be approximately stoichiometric in air (δ ≈ 0). The oxidation state of Fe and Co was determined by XANES. Fe retains an oxidation state of + 3 upon reduction of the sample, whereas Co is reduced to an oxidation state of + 2. A model of the defect chemistry is proposed that can account well for the measured oxygen activity dependence of the oxygen nonstoichiometry at all temperatures investigated. The studied compositions exhibit remarkable thermodynamic stability under reducing conditions. Decomposition was only observed for temperatures above 800 °C in a hydrogen water vapor gas mixture ([H2]/[H2O] = 50). The thermal and chemical expansion coefficients of these compounds are significantly decreased compared to those of (La0.6Sr0.4)0.99Fe0.8Co0.2O3 − δ, a well studied perovskite with related composition. The transport properties were investigated by conductivity relaxation and the potential of using these materials as oxygen separation membranes was assessed by calculating the oxygen flux that can be delivered through a 30 μm thick membrane.

    U2 - 10.1016/j.ssi.2012.10.026

    DO - 10.1016/j.ssi.2012.10.026

    M3 - Journal article

    VL - 232

    SP - 68

    EP - 79

    JO - Solid State Ionics

    JF - Solid State Ionics

    SN - 0167-2738

    ER -