skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Direct proof of mesoscopic misfit in nanoscale islands by x-ray absorption spectroscopy

Authors:
; ; ; ; ; ; ;  [1];  [2]
  1. (MXPL-MW)
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
DOE - BASIC ENERGY SCIENCES
OSTI Identifier:
1088542
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. B; Journal Volume: 85; Journal Issue: (12) ; 03, 2012
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Meyerheim, H.L., Crozier, E.D., Gordon, R.A., Xiao, Q.F., Mohseni, K., Negulyaev, N.N., Stepanyuk, V.S., Kirschner, J., and Simon). Direct proof of mesoscopic misfit in nanoscale islands by x-ray absorption spectroscopy. United States: N. p., 2013. Web. doi:10.1103/PhysRevB.85.125405.
Meyerheim, H.L., Crozier, E.D., Gordon, R.A., Xiao, Q.F., Mohseni, K., Negulyaev, N.N., Stepanyuk, V.S., Kirschner, J., & Simon). Direct proof of mesoscopic misfit in nanoscale islands by x-ray absorption spectroscopy. United States. doi:10.1103/PhysRevB.85.125405.
Meyerheim, H.L., Crozier, E.D., Gordon, R.A., Xiao, Q.F., Mohseni, K., Negulyaev, N.N., Stepanyuk, V.S., Kirschner, J., and Simon). Tue . "Direct proof of mesoscopic misfit in nanoscale islands by x-ray absorption spectroscopy". United States. doi:10.1103/PhysRevB.85.125405.
@article{osti_1088542,
title = {Direct proof of mesoscopic misfit in nanoscale islands by x-ray absorption spectroscopy},
author = {Meyerheim, H.L. and Crozier, E.D. and Gordon, R.A. and Xiao, Q.F. and Mohseni, K. and Negulyaev, N.N. and Stepanyuk, V.S. and Kirschner, J. and Simon)},
abstractNote = {},
doi = {10.1103/PhysRevB.85.125405},
journal = {Phys. Rev. B},
number = (12) ; 03, 2012,
volume = 85,
place = {United States},
year = {Tue Jul 30 00:00:00 EDT 2013},
month = {Tue Jul 30 00:00:00 EDT 2013}
}
  • Cited by 6
  • Polycrystalline Ca{sub 3}Co{sub 4−x}Fe{sub x}O{sub 9+δ} ceramics (x=0, 0.01, 0.03, 0.05) were fabricated using a simple thermal hydro-decomposition method and a spark plasma sintering technique. Thermoelectric property measurements showed that increasing Fe concentration resulted in a decrease in electrical resistivity, thermopower and thermal conductivity, leading to an improvement in the dimensionless figure-of-merit, >35% for x=0.05 at 1073 K. An X-ray absorption spectroscopy technique was used to investigate the local structure of Fe ions in the Ca{sub 3}Co{sub 4−x}Fe{sub x}O{sub 9+δ} structure for the first time. By fitting data from the extended X-ray absorption fine structure (EXAFS) spectra and analyzing themore » X-ray absorption near-edge structure (XANES) spectra incorporated with first principle simulation, it was shown that Fe was substituted for Co in the the Ca{sub 2}CoO{sub 3} (rocksalt, RS) layer rather than in the CoO{sub 2} layer. Variation in the thermoelectric properties as a function of Fe concentration was attributed to charge transfer between the CoO{sub 2} and the RS layers. The origin of the preferential Fe substitution site was investigated considering the ionic radii of Co and Fe and the total energy of the system. - Graphical abstract: The Fe K-edge XANES spectra of: (a) experimental result in comparison to the simulated spectra when Fe atoms were substituted in the RS layer; (b) with magnetic moment; (c) without magnetic moment, and in the CoO{sub 2} layer; (d) with magnetic moment and (e) without magnetic moment. Highlights: • Synthesis, structural studies, and thermoelectric properties of Ca{sub 3}Co{sub 4−x}Fe{sub x}O{sub 9+δ}. • Direct evidence for the local structure of the Fe ions in the Ca{sub 3}Co{sub 4−x}Fe{sub x}O{sub 9+δ} using XAS analysis. • EXAFS and XANES analysis showed that Fe was likely to be situated in the RS layer structure. • Changes in TE property with Fe content was due to charge transfer between the CoO{sub 2} and the RS layers. • Total energy calculation showed energetically favorable Fe substitution in the RS layer.« less
  • Here we present a comprehensive X-ray absorption spectroscopy study carried out at Co-L₂,₃, Co-K, O-K and Sr-K edges for the parent misfit-layered cobalt oxide phase [Sr₂O₂]₀.₅₂CoO₂; comparison is made to another misfit-layered oxide [CoCa₂O₃]₀.₆₂CoO₂ and the perovskite oxide LaCoO₃. A high-quality sample of [Sr₂O₂]₀.₅₂CoO₂ was obtained through ultra-high-pressure synthesis using Sr₃Co₂O₆ and Sr(OH)₂∙8H₂O as starting materials. Different dosages of KClO₃ were mixed with the raw materials as an oxygen source and tested, but it was found that the window for the redox control of [Sr₂O₂]₀.₅₂CoO₂ is rather narrow. From Co-K and Co-L₂,₃ spectra a mixed III/IV valence state is revealedmore » for cobalt in [Sr₂O₂]₀.₅₂}CoO₂, but the average valence value is a little lower than in [CoCa₂O₃]₀.₆₂CoO₂. Then, Sr-K spectrum indicates that the [Sr₂O₂] double-layer block in [Sr₂O₂]₀.₅₂CoO₂ clearly deviates from the cubic SrO rock-salt structure, suggesting a more complicated coordination environment for strontium. This together with a somewhat low Co-valence value and the fact that the phase formation of [Sr₂O₂]₀.₅₂CoO₂ required the presence of Sr(OH)₂∙8H₂O in the high-pressure synthesis suggest that the [Sr₂O₂] block contains ---OH groups, i.e. [Sr₂(O,OH)₂]₀.₅₂CoO₂. - Graphical abstract: [Sr₂O₂]₀.₅₂CoO₂ obtained through high-pressure synthesis is a parent of misfit-layered cobalt oxides, such as [CoCa₂O₃]₀.₆₂CoO₂ or [M mA₂O 2+m] qCoO₂ in general. Our comprehensive X-ray absorption spectroscopy study shows that both [Sr₂O₂]₀.₅₂CoO₂ and [CoCa₂O₃]₀.₆₂CoO₂ possess mixed III/IV valence cobalt, but the average Co-valence is a little lower in the former. This is tentatively believed to be due to OH --- groups replacing part of O²⁻ ions in the [Sr₂O₂] layer block. Highlights: • [Sr₂O₂]₀.₅₂CoO₂ is a parent of misfit-layered cobalt oxides. • It is obtained by ultra-high-pressure synthesis from Sr₃Co₂O₆, Sr(OH)₂∙6H₂O and KClO₃. • Co-K and Co---L XANES spectra reveal lower than expected Co-valence value. • Sr-K XANES spectrum indicates that the [Sr₂O₂] block is not of simple rock-salt structure. • This block most probably contains ---OH --- groups, i.e. [Sr₂(O,OH)₂]₀.₅₂CoO₂.« less