title: Oxygen Insertion Reactions within the One-Dimensional Channels of Phases Related to FeSb2O4.
abstract: The structure of the mineral schafarzikite, FeSb2O4, has one-dimensional channels with walls comprising Sb3+cations; the channels are separated by edge-linked FeO6octahedra that form infinite chains parallel to the channels. Although this structure provides interest with respect to the magnetic and electrical properties associated with the chains and the possibility of chemistry that could occur within the channels, materials in this structural class have received very little attention. Here we show, for the first time, that heating selected phases in oxygen-rich atmospheres can result in relatively large oxygen uptakes (up to ∼2% by mass) at low temperatures (ca. 350 °C) while retaining the parent structure. Using a variety of structural and spectroscopic techniques, it is shown that oxygen is inserted into the channels to provide a structure with the potential to show high one-dimensional oxide ion conductivity. This is the first report of oxygen-excess phases derived from this structure. The oxygen insertion is accompanied not only by oxidation of Fe2+to Fe3+within the octahedral chains but also Sb3+to Sb5+in the channel walls. The formation of a defect cluster comprising one 5-coordinate Sb5+ion (which is very rare in an oxide environment), two interstitial O2-ions, and two 4-coordinate Sb3+ions is suggested and is consistent with all experimental observations. To the best of our knowledge, this is the first example of an oxidation process where the local energetics of the product dictate that simultaneous oxidation of two different cations must occur. This reaction, together with a wide range of cation substitutions that are possible on the transition metal sites, presents opportunities to explore the schafarzikite structure more extensively for a range of catalytic and electrocatalytic applications.
authors.affiliation: School of Chemistry, University of Birmingham , Birmingham B15 2TT, U.K.
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: de Laune
authors.affiliation: Department of Physics, University of Warwick , Coventry CV4 7AL, U.K.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Rees
authors.affiliation: School of Chemistry, University of Birmingham , Birmingham B15 2TT, U.K.
authors.forename: Mariana J
authors.initials: MJ
authors.lastname: Whitaker
authors.forename: Hien-Yoong
authors.initials: HY
authors.lastname: Hah
authors.forename: Charles E
authors.initials: CE
authors.lastname: Johnson
authors.forename: Jacqueline A
authors.initials: JA
authors.lastname: Johnson
authors.affiliation: Department of Physics, Northern Illinois University , DeKalb, Illinois 60115, United States.
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Brown
authors.affiliation: Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Tucker
authors.affiliation: Institut Laue Langevin , BP 156, F-38042 Grenoble 9, France.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Hansen
authors.affiliation: School of Chemistry, University of Birmingham , Birmingham B15 2TT, U.K.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Berry
authors.affiliation: Department of Physics, University of Warwick , Coventry CV4 7AL, U.K.
authors.forename: John V
authors.initials: JV
authors.lastname: Hanna
authors.affiliation: School of Chemistry, University of Birmingham , Birmingham B15 2TT, U.K.
authors.forename: Colin
authors.identifier: http://orcid.org/0000-0002-9568-3697
authors.initials: C
authors.lastname: Greaves