Oxygen nonstoichiometry and cobalt valence in misfit-layered cobalt oxides

Y. Morita; J. Poulsen; K. Sakai; T. Motohashi; T. Fujii; I. Terasaki; H. Yamauchi; M. Karppinen

doi:10.1016/j.jssc.2004.05.023

Oxygen nonstoichiometry and cobalt valence in misfit-layered cobalt oxides

Y. Morita, J. Poulsen, K. Sakai, T. Motohashi, T. Fujii, I. Terasaki, H. Yamauchi, M. Karppinen^*

^*Corresponding author for this work

Department of Chemistry and Materials Science

Research output: Contribution to journal › Article › Scientific › peer-review

65 Citations (Scopus)

Abstract

The hexagonal CoO₂ layer is the main building unit of the newly established category of misfit-layered and related oxides showing - as a general feature - excellent thermoelectric characteristics. Here we use high-quality samples of the three prototype phases, Na_0.77CoO_2+δ, Ca₃Co_3.95O_9+δ and (Bi,Pb) ₂Sr₂Co₂O_8+δ, and apply both precise wet-chemical redox analysis techniques and thermogravimetric annealing experiments to approach the not-yet-addressed questions concerning oxygen nonstoichiometry and the valence of Co in these phases. In terms of the oxygen-stoichiometry tunability, substantial variation in the overall oxygen content upon reducing/oxidizing annealing is observed only for Ca ₃Co_3.95O_9+δ. The valence of Co in all the samples is found to lie in a range of 3.0-3.3, being significantly lower than the commonly believed values of 3.3-3.5.

Original language	English
Pages (from-to)	3149-3155
Number of pages	7
Journal	Journal of Solid State Chemistry
Volume	177
Issue number	9
DOIs	https://doi.org/10.1016/j.jssc.2004.05.023
Publication status	Published - Sept 2004
MoE publication type	A1 Journal article-refereed

Keywords

Cobalt valence
Misfit-layered cobalt oxides
Oxygen content
Thermogravimetry
Wet-chemical analysis

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10.1016/j.jssc.2004.05.023

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title = "Oxygen nonstoichiometry and cobalt valence in misfit-layered cobalt oxides",

abstract = "The hexagonal CoO2 layer is the main building unit of the newly established category of misfit-layered and related oxides showing - as a general feature - excellent thermoelectric characteristics. Here we use high-quality samples of the three prototype phases, Na0.77CoO2+δ, Ca3Co3.95O9+δ and (Bi,Pb) 2Sr2Co2O8+δ, and apply both precise wet-chemical redox analysis techniques and thermogravimetric annealing experiments to approach the not-yet-addressed questions concerning oxygen nonstoichiometry and the valence of Co in these phases. In terms of the oxygen-stoichiometry tunability, substantial variation in the overall oxygen content upon reducing/oxidizing annealing is observed only for Ca 3Co3.95O9+δ. The valence of Co in all the samples is found to lie in a range of 3.0-3.3, being significantly lower than the commonly believed values of 3.3-3.5.",

keywords = "Cobalt valence, Misfit-layered cobalt oxides, Oxygen content, Thermogravimetry, Wet-chemical analysis",

author = "Y. Morita and J. Poulsen and K. Sakai and T. Motohashi and T. Fujii and I. Terasaki and H. Yamauchi and M. Karppinen",

year = "2004",

month = sep,

doi = "10.1016/j.jssc.2004.05.023",

language = "English",

volume = "177",

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T1 - Oxygen nonstoichiometry and cobalt valence in misfit-layered cobalt oxides

AU - Morita, Y.

AU - Poulsen, J.

AU - Sakai, K.

AU - Motohashi, T.

AU - Fujii, T.

AU - Terasaki, I.

AU - Yamauchi, H.

AU - Karppinen, M.

PY - 2004/9

Y1 - 2004/9

N2 - The hexagonal CoO2 layer is the main building unit of the newly established category of misfit-layered and related oxides showing - as a general feature - excellent thermoelectric characteristics. Here we use high-quality samples of the three prototype phases, Na0.77CoO2+δ, Ca3Co3.95O9+δ and (Bi,Pb) 2Sr2Co2O8+δ, and apply both precise wet-chemical redox analysis techniques and thermogravimetric annealing experiments to approach the not-yet-addressed questions concerning oxygen nonstoichiometry and the valence of Co in these phases. In terms of the oxygen-stoichiometry tunability, substantial variation in the overall oxygen content upon reducing/oxidizing annealing is observed only for Ca 3Co3.95O9+δ. The valence of Co in all the samples is found to lie in a range of 3.0-3.3, being significantly lower than the commonly believed values of 3.3-3.5.

AB - The hexagonal CoO2 layer is the main building unit of the newly established category of misfit-layered and related oxides showing - as a general feature - excellent thermoelectric characteristics. Here we use high-quality samples of the three prototype phases, Na0.77CoO2+δ, Ca3Co3.95O9+δ and (Bi,Pb) 2Sr2Co2O8+δ, and apply both precise wet-chemical redox analysis techniques and thermogravimetric annealing experiments to approach the not-yet-addressed questions concerning oxygen nonstoichiometry and the valence of Co in these phases. In terms of the oxygen-stoichiometry tunability, substantial variation in the overall oxygen content upon reducing/oxidizing annealing is observed only for Ca 3Co3.95O9+δ. The valence of Co in all the samples is found to lie in a range of 3.0-3.3, being significantly lower than the commonly believed values of 3.3-3.5.

KW - Cobalt valence

KW - Misfit-layered cobalt oxides

KW - Oxygen content

KW - Thermogravimetry

KW - Wet-chemical analysis

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U2 - 10.1016/j.jssc.2004.05.023

DO - 10.1016/j.jssc.2004.05.023

M3 - Article

AN - SCOPUS:4444267365

SN - 0022-4596

VL - 177

SP - 3149

EP - 3155

JO - Journal of Solid State Chemistry

JF - Journal of Solid State Chemistry

IS - 9

ER -

Oxygen nonstoichiometry and cobalt valence in misfit-layered cobalt oxides

Abstract

Keywords

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