Oxygen Nonstoichiometry and Thermodynamic Explanation of Large Oxygen-Deficient Ruddlesden–Popper Oxides LaxSr3−xFe2O7−δ

Yihan Ling, Fang Wang, Yusuke Okamoto, Takashi Nakamura, Koji Amezawa, A. Belik

    Research output: Contribution to journalArticlepeer-review

    7 Citations (Scopus)

    Abstract

    The oxygen nonstoichiometry of large oxygen-deficient Ruddlesden–Popper oxides LaxSr3−xFe2O7−δ (LSFO7-x) (x = 0, 0.25, 0.5) was measured by the high-temperature gravimetry and the coulometric titration. In the composition series, the P(O2) dependencies exhibited typical plateaus at δ = (2−[LaSr])/2. Meanwhile, La0.5Sr2.5Fe2O7−δ showed the smallest oxygen nonstoichiometry and was the most thermochemically stable compound against P(O2), temperature, and the La content. Based on the defect equilibrium model and the statistical thermodynamic calculation derived oxygen nonstoichiometric data, the substitution of La for Sr-site can promote the forward reaction of oxygen incorporation, the backward reaction of the disproportionation of the charge carriers, and oxygen redistribution between the O1 and O3 sites, resulting in the reduction of oxygen-deficient and the lower decomposition P(O2). The obtained thermodynamic quantities of the partial molar enthalpy of oxygen, hO – h°O, and the partial molar entropy of oxygen, sO – s°O, calculated from the statistical thermodynamic calculation are in good agreement with those using the Gibbs–Helmholtz equation.

    Original languageEnglish
    Pages (from-to)3792-3801
    Number of pages10
    JournalJournal of the American Ceramic Society
    Volume99
    Issue number11
    DOIs
    Publication statusPublished - 2016 Nov 1

    Keywords

    • defect equilibrium model
    • oxygen nonstoichiometry
    • statistical thermodynamic calculation
    • thermodynamic quantities

    ASJC Scopus subject areas

    • Ceramics and Composites
    • Materials Chemistry

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