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Title: New misfit-layered cobalt oxide (CaOH){sub 1.14}CoO{sub 2}

Abstract

We synthesized a new cobalt oxide (CaOH){sub 1.14}CoO{sub 2} by utilizing a high-pressure technique. X-ray and electron diffraction studies revealed that the compound has a layered structure that consists of CdI{sub 2}-type CoO{sub 2} layers and rock-salt-type double CaOH atomic layers. The two subcells have incommensurate periodicity along the a-axis, resulting in a misfit-layered structure. From resistivity and Seebeck coefficient measurements, we have shown that the two-dimensional (2-D) variable-range hopping (VRH) regime with hole conduction is dominant at low temperature for this compound. As temperature increases, the conduction mechanism undergoes crossover from the 2-D VRH regime to a thermal activation-energy-type regime. - Graphical abstract: Crystal-structure model of the misfit-layered cobalt oxide (CaOH){sub 1.14}CoO{sub 2}. The rectangles indicate unit cells of the two subsystems. The open circles and squares represent the cobalt atoms situated at different positions along the projected coordinate.

Authors:
 [1];  [2];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)
  2. National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan), E-mail: ISOBE.Masaaki@nims.go.jp
Publication Date:
OSTI Identifier:
21015644
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 1; Other Information: DOI: 10.1016/j.jssc.2006.10.014; PII: S0022-4596(06)00556-1; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACTIVATION ENERGY; COBALT OXIDES; CRYSTAL STRUCTURE; ELECTRON DIFFRACTION; ELECTRON MICROSCOPY; LAYERS; X RADIATION

Citation Formats

Shizuya, Mitsuyuki, Isobe, Masaaki, Baba, Yuji, Nagai, Takuro, Osada, Minoru, Kosuda, Kosuke, Takenouchi, Satoshi, Matsui, Yoshio, and Takayama-Muromachi, Eiji. New misfit-layered cobalt oxide (CaOH){sub 1.14}CoO{sub 2}. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2006.10.014.
Shizuya, Mitsuyuki, Isobe, Masaaki, Baba, Yuji, Nagai, Takuro, Osada, Minoru, Kosuda, Kosuke, Takenouchi, Satoshi, Matsui, Yoshio, & Takayama-Muromachi, Eiji. New misfit-layered cobalt oxide (CaOH){sub 1.14}CoO{sub 2}. United States. doi:10.1016/j.jssc.2006.10.014.
Shizuya, Mitsuyuki, Isobe, Masaaki, Baba, Yuji, Nagai, Takuro, Osada, Minoru, Kosuda, Kosuke, Takenouchi, Satoshi, Matsui, Yoshio, and Takayama-Muromachi, Eiji. Mon . "New misfit-layered cobalt oxide (CaOH){sub 1.14}CoO{sub 2}". United States. doi:10.1016/j.jssc.2006.10.014.
@article{osti_21015644,
title = {New misfit-layered cobalt oxide (CaOH){sub 1.14}CoO{sub 2}},
author = {Shizuya, Mitsuyuki and Isobe, Masaaki and Baba, Yuji and Nagai, Takuro and Osada, Minoru and Kosuda, Kosuke and Takenouchi, Satoshi and Matsui, Yoshio and Takayama-Muromachi, Eiji},
abstractNote = {We synthesized a new cobalt oxide (CaOH){sub 1.14}CoO{sub 2} by utilizing a high-pressure technique. X-ray and electron diffraction studies revealed that the compound has a layered structure that consists of CdI{sub 2}-type CoO{sub 2} layers and rock-salt-type double CaOH atomic layers. The two subcells have incommensurate periodicity along the a-axis, resulting in a misfit-layered structure. From resistivity and Seebeck coefficient measurements, we have shown that the two-dimensional (2-D) variable-range hopping (VRH) regime with hole conduction is dominant at low temperature for this compound. As temperature increases, the conduction mechanism undergoes crossover from the 2-D VRH regime to a thermal activation-energy-type regime. - Graphical abstract: Crystal-structure model of the misfit-layered cobalt oxide (CaOH){sub 1.14}CoO{sub 2}. The rectangles indicate unit cells of the two subsystems. The open circles and squares represent the cobalt atoms situated at different positions along the projected coordinate.},
doi = {10.1016/j.jssc.2006.10.014},
journal = {Journal of Solid State Chemistry},
number = 1,
volume = 180,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • The crystal structure of our newly discovered Sr-Co-O phase is investigated in detail through high-resolution electron microscopy (HREM) techniques. Electron diffraction (ED) measurement together with energy dispersive X-ray spectroscopy (EDS) analysis show that an ampoule-synthesized sample contains an unknown Sr-Co-O ternary phase with monoclinic symmetry and the cation ratio of Sr/Co=1. From HREM images a layered structure with a regular stacking of a CdI{sub 2}-type CoO{sub 2} sheet and a rock-salt-type Sr{sub 2}O{sub 2} double-layered block is observed, which confirms that the phase is the parent of the more complex 'misfit-layered (ML)' cobalt oxides of [M{sub m}A{sub 2}O{sub m+2}]{sub q}CoO{submore » 2} with the formula of [Sr{sub 2}O{sub 2}]{sub q}CoO{sub 2}, i.e. m=0. It is revealed that the misfit parameter q is 0.5, i.e. the two sublattices of the CoO{sub 2} sheet and the Sr{sub 2}O{sub 2} block coexist to form a commensurate composite structure. We propose a structural model with monoclinic P2{sub 1}/m symmetry, which is supported by simulations of ED patterns and HREM images based on dynamical diffraction theory.« less
  • Calcium-for-strontium substituted samples of the misfit-layered cobalt-oxide system, [(Sr{sub 1-x}Ca{sub x}){sub 2}(O,OH){sub 2}]{sub q}[CoO{sub 2}], were successfully synthesized up to x=0.2 with a sample-encapsulation technique originally developed for the x=0 end phase. While the x=0 sample has a commensurate match between the two layer blocks (i.e. q=0.5), isovalent Ca-for-Sr substitution induces lattice misfit (i.e. q>0.5). At the same time the Seebeck coefficient gets increased, but the increase in resistivity results in suppressing the thermoelectric power factor. The magnetic anomaly in the x=0 sample gets released upon the Ca substitution for the x=0.2 sample to exhibit an almost Curie-Weiss behavior. Itmore » is concluded that with increasing x in [(Sr{sub 1-x}Ca{sub x}){sub 2}(O,OH){sub 2}]{sub q}[CoO{sub 2}] the properties smoothly evolve towards those previously reported for the x=1.0 end member, [Ca{sub 1.7}O{sub 2.1}H{sub 2.4}]{sub 0.58}[CoO{sub 2}]. -- Graphical abstract: In the misfit-layered [(Sr{sub 1-x}Ca{sub x}){sub 2}(O,OH){sub 2}]{sub q}[CoO{sub 2}] (0.0{<=}x{<=}0.2) system the x=0 phase has a commensurate match between the two layer blocks (i.e. q=0.5), while isovalent Ca-for-Sr substitution induces lattice misfit (i.e. q>0.5). At the same time Seebeck coefficient gets increased. Simultaneous increase in resistivity however outweighs this benefit, and accordingly the thermoelectric power factor is decreased. Display Omitted« less
  • Fifty-three new misfit layered compounds within the [(BiSe){sub 1.10}]{sub m}[NbSe{sub 2}]{sub n,} [(PbSe){sub 1.10}]{sub m}[NbSe{sub 2}]{sub n}, [(CeSe){sub 1.14}]{sub m}[NbSe{sub 2}]{sub n}, and [(PbSe){sub 1.12}]{sub m}[TaSe{sub 2}]{sub n} families of compounds were successfully synthesized. This is the first report of compounds with n and m larger than 3, as self-assembly from designed precursors allows compounds with particular n and m values to be selectively prepared. The compounds form as crystallographically aligned films, with the c-axis perpendicular to the substrate. The compounds are well ordered along the c-axis and in the ab plane, with shorter coherence lengths between the constituent layers.more » All 18 compounds that were measured were found to be metallic. - Graphical abstract: The synthesis and characterization of new [(BiSe){sub 1.10}]{sub m}[NbSe{sub 2}]{sub n}, [(PbSe){sub 1.10}]{sub m}[NbSe{sub 2}]{sub n}, [(CeSe){sub 1.14}]{sub m}[NbSe{sub 2}]{sub n}, and [(PbSe){sub 1.12}]{sub m}[TaSe{sub 2}]{sub n} misfit layered compounds.« less
  • A monoclinic phase of the misfit-layered cobalt oxide (Ca{sub 0.85}OH){sub 1.16}CoO{sub 2} was successfully synthesized and characterized. It was found that this new material is a poly-type phase of the orthorhombic form of (CaOH){sub 1.14}CoO{sub 2}, recently discovered by the present authors. Both the compounds consist of two interpenetrating subsystems: CdI{sub 2}-type CoO{sub 2} layers and rock-salt-type double-atomic-layer CaOH blocks. However, these two phases exhibit a different stacking structure. By powder X-ray and electron diffraction (ED) studies, it was found that the two subsystems of (Ca{sub 0.85}OH){sub 1.16}CoO{sub 2} have c-centered monoclinic Bravais lattices with common a=4.898 A, c=8.810 Amore » and {beta}=95.8{sup o} lattice parameters, and different b parameters: b {sub 1}=2.820 A and b {sub 2}=4.870 A. Chemical analyses revealed that the monoclinic phase has a cobalt valence of +3.1-3.2. Resistivity of the monoclinic phase is approximately 10{sup 1}-10{sup 5} times lower than that of the orthorhombic phase. This suggests that the monoclinic phase is a hole-doped phase of the insulating orthorhombic phase. Furthermore, large positive Seebeck coefficients ({approx}100 {mu}V/K) were observed near room temperature. - Graphical abstract: Crystal structure of two kinds of poly-type phases of the misfit-layered cobalt oxides (Ca{sub 1-} {sub {delta}} OH) {sub x} CoO{sub 2}: (a) projection along the a-axis of the orthorhombic structure; (b) projection along the b-axis of the monoclinic structure; and (c) projection along the [-1 0 0] direction of the clinic structure. In each case, the rectangle is the unit cell.« 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