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    Oxygen Incorporation and Release Behaviors in Perovskite-Structure Oxides
    Yuichi Shimakawa1;
    1KYOTO UNIVERSITY, Uji, Japan;
    PAPER: 157/Chemistry/Plenary (Oral)
    SCHEDULED: 14:00/Thu. 24 Oct. 2019/Aphrodite A (100/Gr. F)



    ABSTRACT:
    Oxygen ions are incorporated in and released from transition-metal oxides when the valence states of the transition-metal ions change [1]. In topotactic changes of perovskite-structure oxides like SrFe<sup>2+</sup>O<sub>2</sub> - SrFe<sup>3+</sup>O<sub>2.5</sub> - SrFe<sup>4+</sup>O<sub>3</sub>, we found that the oxygen incorporation and release behaviors are strongly influenced by the structural factors. The A-site disordered perovskite (La<sub>1/3</sub>Ca<sub>2/3</sub>)FeO<sub>3</sub> with unusually high valance Fe<sup>3.67+</sup> releases oxygen gradually above 500°C, whereas the A-site-layer-ordered perovskite LaCa<sub>2</sub>Fe<sub>3</sub>O<sub>9</sub> with the identical chemical composition of (La<sub>1/3</sub>Ca<sub>2/3</sub>)FeO<sub>3</sub> readily releases oxygen around 400°C [2,3]. From the B-site-layer-ordered double perovskite Ca<sub>2</sub>FeMnO<sub>6</sub> with Mn<sup>4+</sup> and unusual high valence Fe<sup>4+</sup>, oxygen is released only form the two-dimensional Fe-O layers according to the successive changes of Ca<sub>2</sub>Fe<sup>4+</sup>Mn<sup>4+</sup>O<sub>6</sub> - Ca<sub>2</sub>Fe<sup>3.5+</sup>Mn<sup>4+</sup>O<sub>5.75</sub> - Ca<sub>2</sub>Fe<sup>3+</sup>Mn<sup>4+</sup>O<sub>5.5</sub>. The B-site-disordered Ca<sub>2</sub>(FeMn)O<sub>6</sub>, on the other hand, oxygen appears to be released at about 390°C by a single change of Ca<sub>2</sub>(Fe<sup>4+</sup>Mn<sup>4+</sup>)O<sub>6</sub> - Ca<sub>2</sub>(Fe<sup>3+</sup>Mn<sup>4+</sup>)O<sub>5.5</sub> [4,5]. Thus, the oxygen release behaviors differ depending on both A-site and B-site cation order. An important point for the behaviors of oxides with unusually high valence cations like Fe<sup>4+</sup> is that the incorporation and the release of oxygen can occur at much lower temperatures than those with typical valence transition-metal ions. We will discuss the details of such behaviors from temperature-dependent structure analysis.

    References:
    [1] Y. Shimakawa, <i>Bull. Chem. Soc. Jpn.</i> <b>86</b>, 299-311 (2013).<br />[2] H. Guo, Y. Hosaka, H. Seki, T. Saito, N. Ichikawa, and Y. Shimakawa, <i>J. Solid State Chem.</i> <b>246</b>, 199-202 (2017).<br />[3] H. Guo, Y. Hosaka, F. D. Romero, T. Saito, N. Ichikawa, and Y. Shimakawa, <i>Inorg. Chem.</i> <b>56</b>, 3695-3701 (2017).<br />[4] Y. Hosaka, N. Ichikawa, T. Saito, P. Manuel, D. Khalyavin, J. Paul Attfield, and Y. Shimakawa, <i>J. Am. Chem. Soc.</i> <b>137</b>, 7468-7473 (2015).<br />[5] H. Hosaka, N. Ichikawa, T. Saito, J. P. Attfield, and Y. Shimakawa, <i>Phys. Rev. B</i> <b>94</b>, 104429 (2016).