title: Two Charge Ordering Patterns in the Topochemically Synthesized Layer-Structured Perovskite LaCa2Fe3O9with Unusually High Valence Fe3.67.
abstract: A-site-ordered layer-structured perovskite LaCa2Fe3O9with unusually high valence Fe3.67+was obtained by low-temperature topochemical oxidation of the A-site layer-ordered LaCa2Fe3O8. The unusually high valence Fe3.67+in LaCa2Fe3O9shows charge disproportionation of Fe3+and Fe5+first along the layer-stacking ⟨010⟩ direction below 230 K. Fe3+is located between the La3+and Ca2+layers, while Fe5+is between the Ca2+layers. The two-dimensional electrostatic potential due to the A-site layered arrangement results in the quasi-stable ⟨010⟩ charge ordering pattern. Below 170 K, the charge ordering pattern changes, and the 2:1 charge-disproportionated Fe3+and Fe5+ions are ordered along the ⟨111⟩ direction. The ground-state charge ordering pattern is stabilized primarily by the electrostatic lattice energy, and the Fe5+ions are arranged to make the distances between the nearest neighboring Fe5+as large as possible.
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji, Kyoto 611-0011, Japan.
authors.forename: Haichuan
authors.initials: H
authors.lastname: Guo
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji, Kyoto 611-0011, Japan.
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Hosaka
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji, Kyoto 611-0011, Japan.
authors.forename: Fabio Denis
authors.initials: FD
authors.lastname: Romero
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji, Kyoto 611-0011, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Saito
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji, Kyoto 611-0011, Japan.
authors.forename: Noriya
authors.initials: N
authors.lastname: Ichikawa
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji, Kyoto 611-0011, Japan.|Integrated Research Consortium on Chemical Sciences , Uji, Kyoto 611-0011, Japan.
authors.forename: Yuichi
authors.identifier: http://orcid.org/0000-0003-1019-2512
authors.initials: Y
authors.lastname: Shimakawa