Please use this identifier to cite or link to this item: http://hdl.handle.net/10995/27153
Title: Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy
Authors: Konysheva, E. Y.
Francis, S. M.
Issue Date: 2013
Citation: Konysheva E. Y. Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy / E. Y. Konysheva, S. M. Francis // Applied Surface Science. — 2013. — Vol. 268. — P. 278-287.
Abstract: X-ray photoelectron spectroscopy (XPS) has been used to explore the cation rearrangement between the surface and bulk of grains and the surface chemical states of Ce, Mn, Co, Sr, and O ions in the single phase CeO2-based solid solutions and in the two phase (100 - x)La0.6Sr 0.4CoO3-xCeO2 (LSCCx) and (100 - x)La 0.8Sr0.2MnO3-xCeO2 (LSMCx) composites. The well-resolved Ce 3d5/2 and Ce 3d3/2 spin-orbit components were determined to study the Ce4+ to Ce 3+ electronic transition at the surface. The surface of the LSCCx and LSMCx (x = 8-40 mol%) composites is depleted in cerium. Both Ce4+ and Ce3+ cations were revealed. The surface fraction of Ce 4+ cations increases with the rise in CeO2 content in both systems, but it is higher by about a factor of two in the LSCC composites. A strong enrichment of the surface by Co cations was observed for the composites LSCCx (x = 8-40 mol%), implying that the presence of cerium could facilitate the Co surface segregation. A slight Sr surface enrichment compared to the nominal stoichiometry was found for La0.6Sr0.4CoO3, CeO2-based solid solutions, LSCC57, and LSMCx (x = 10-57) composites. In contrast, the surface of the LSCCx (x = 10-37) composites is slightly depleted in strontium cations. The O 1s spectra of the LSCC and LSMC composites contain several contributions associated with the lattice oxygen related to the phases with the perovskite and fluorite structures as well as with different surface states. Their contributions vary with CeO2 content and a chemical origin of the transition metal cations on the B-site in the perovskite structure. The Ce2(CO3)3-based phase seems to exist at the surface of grains and crystallites in the LSCC57 and LSCM composites. © 2012 Elsevier B.V.
Keywords: BINDING ENERGY
COMPOSITES WITH PEROVSKITE AND FLUORITE STRUCTURES
OXIDATION STATE OF CERIUM CATIONS
SURFACE COMPOSITION
X-RAY PHOTOELECTRON SPECTROSCOPY (XPS)
ELECTRONIC TRANSITION
FLUORITE STRUCTURE
OXIDATION STATE
PEROVSKITE STRUCTURES
STRONTIUM CATIONS
SURFACE CHEMICAL STATE
SURFACE ENRICHMENT
TRANSITION METAL CATIONS
BINDING ENERGY
CERIUM
COBALT COMPOUNDS
FLUORSPAR
MANGANESE OXIDE
PEROVSKITE
PHOTOELECTRONS
SOLID SOLUTIONS
STOICHIOMETRY
SURFACE SEGREGATION
SURFACE STATES
SURFACE STRUCTURE
THREE DIMENSIONAL COMPUTER GRAPHICS
X RAY PHOTOELECTRON SPECTROSCOPY
POSITIVE IONS
URI: http://hdl.handle.net/10995/27153
SCOPUS ID: 84875412671
WOS ID: WOS:000315330300044
PURE ID: 930850
ISSN: 0169-4332
DOI: 10.1016/j.apsusc.2012.12.079
Appears in Collections:Научные публикации, проиндексированные в SCOPUS и WoS

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