title: Spinel-rock salt transformation in LiCoMnO4-δ.
abstract: The transformation on heating LiCoMnO4, with a spinel structure, to LiCoMnO3, with a cation-disordered rock salt structure, accompanied by loss of 25% of the oxygen, has been followed using a combination of diffraction, microscopy and spectroscopy techniques. The transformation does not proceed by a topotactic mechanism, even though the spinel and rock salt phases have a similar, cubic close-packed oxygen sublattice. Instead, the transformation passes through two stages involving, first, precipitation of Li2MnO3, leaving behind a Li-deficient, Co-rich non-stoichiometric spinel and, second, rehomogenization of the two-phase assemblage, accompanied by additional oxygen loss, to give the homogeneous rock salt final product; a combination of electron energy loss spectroscopy and X-ray absorption near edge structure analyses showed oxidation states of Co2+and Mn3+in LiCoMnO3. Subsolidus phase diagram determination of the Li2O-CoOx-MnOysystem has established the compositional extent of spinel solid solutions at approximately 500°C.
authors.affiliation: Department of Materials Science and Engineering , University of Sheffield , Sheffield S1 3JD, UK.
authors.forename: Nik
authors.initials: N
authors.lastname: Reeves-McLaren
authors.affiliation: Department of Materials Science and Engineering , University of Sheffield , Sheffield S1 3JD, UK.
authors.forename: Joanne
authors.initials: J
authors.lastname: Sharp
authors.affiliation: Departamento de Química Inorgánica y Orgánica , Universidad Jaume I , Avda. Sos Baynat s/n, Castellón 12071, Spain.
authors.forename: Héctor
authors.initials: H
authors.lastname: Beltrán-Mir
authors.affiliation: Department of Materials Science and Engineering , University of Sheffield , Sheffield S1 3JD, UK.
authors.forename: W Mark
authors.initials: WM
authors.lastname: Rainforth
authors.affiliation: Department of Materials Science and Engineering , University of Sheffield , Sheffield S1 3JD, UK.
authors.forename: Anthony R
authors.initials: AR
authors.lastname: West
keywords: LiCoMnO4; Raman; Rietveld; X-ray absorption near edge structure; electron energy loss spectroscopy; oxygen loss