Role of Structure and Defect Chemistry in High-Performance Thermoelectric Bismuth Strontium Cobalt Oxides

Jakub D. Baran, Demie Kepaptsoglou, Marco Molinari, Nuth Kulwongwit, Feridoon Azough, Robert Freer, Quentin Mathieu Ramasse, Stephen C. Parker

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

[Bi0.87SrO2]2[CoO2]1.82 (BSCO) is one of the best p-type thermoelectric oxides but its structural and electronic properties are still poorly understood. BSCO is a misfit-layered compound consisting of an incommensurate stacking of hexagonal CoO2 and double rock-salt BiSrO2 layers. Here we combine experimental and computational approaches to investigate its crystallographic and electronic structure as well as thermoelectric transport properties. Considering different approximations for the subsystems stacking, we present a structural model that agrees well with both bulk and atomic-scale experimental data. This model, which suggests a level of Bi deficiency in the rock-salt layers, is then used to discuss the material's electronic, magnetic, and transport properties. We show that Bi deficiency leads to a band gap opening and increases p-type electronic conductivity due to the formation of Co4+ species that serve as itinerant holes within the predominantly Co3+ framework of the CoO2 layer. We validate these predictions using electron energy loss spectroscopy in the scanning transmission electron microscope. The relationship between the hole-doping mechanism and the changes of the local structure (in particular the level of Bi deficiency) is evaluated. The reliability of the simulations is supported by the calculated temperature dependence of the Seebeck coefficient, in good agreement with experimental measurements.

Original languageEnglish
Pages (from-to)7470-7478
Number of pages9
JournalChemistry of Materials
Volume28
Issue number20
Early online date26 Sep 2016
DOIs
Publication statusPublished - 25 Oct 2016
Externally publishedYes

Fingerprint

Bismuth
Strontium
Electronic properties
Cobalt
Salts
Rocks
Electron transport properties
Defects
Oxides
Seebeck coefficient
Electron energy loss spectroscopy
Transport properties
Electronic structure
Structural properties
Magnetic properties
Energy gap
Electron microscopes
Doping (additives)
Scanning
Temperature

Cite this

Baran, Jakub D. ; Kepaptsoglou, Demie ; Molinari, Marco ; Kulwongwit, Nuth ; Azough, Feridoon ; Freer, Robert ; Ramasse, Quentin Mathieu ; Parker, Stephen C. / Role of Structure and Defect Chemistry in High-Performance Thermoelectric Bismuth Strontium Cobalt Oxides. In: Chemistry of Materials. 2016 ; Vol. 28, No. 20. pp. 7470-7478.
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Baran, JD, Kepaptsoglou, D, Molinari, M, Kulwongwit, N, Azough, F, Freer, R, Ramasse, QM & Parker, SC 2016, 'Role of Structure and Defect Chemistry in High-Performance Thermoelectric Bismuth Strontium Cobalt Oxides', Chemistry of Materials, vol. 28, no. 20, pp. 7470-7478. https://doi.org/10.1021/acs.chemmater.6b03200

Role of Structure and Defect Chemistry in High-Performance Thermoelectric Bismuth Strontium Cobalt Oxides. / Baran, Jakub D.; Kepaptsoglou, Demie; Molinari, Marco; Kulwongwit, Nuth; Azough, Feridoon; Freer, Robert; Ramasse, Quentin Mathieu; Parker, Stephen C.

In: Chemistry of Materials, Vol. 28, No. 20, 25.10.2016, p. 7470-7478.

Research output: Contribution to journalArticle

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T1 - Role of Structure and Defect Chemistry in High-Performance Thermoelectric Bismuth Strontium Cobalt Oxides

AU - Baran, Jakub D.

AU - Kepaptsoglou, Demie

AU - Molinari, Marco

AU - Kulwongwit, Nuth

AU - Azough, Feridoon

AU - Freer, Robert

AU - Ramasse, Quentin Mathieu

AU - Parker, Stephen C.

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PY - 2016/10/25

Y1 - 2016/10/25

N2 - [Bi0.87SrO2]2[CoO2]1.82 (BSCO) is one of the best p-type thermoelectric oxides but its structural and electronic properties are still poorly understood. BSCO is a misfit-layered compound consisting of an incommensurate stacking of hexagonal CoO2 and double rock-salt BiSrO2 layers. Here we combine experimental and computational approaches to investigate its crystallographic and electronic structure as well as thermoelectric transport properties. Considering different approximations for the subsystems stacking, we present a structural model that agrees well with both bulk and atomic-scale experimental data. This model, which suggests a level of Bi deficiency in the rock-salt layers, is then used to discuss the material's electronic, magnetic, and transport properties. We show that Bi deficiency leads to a band gap opening and increases p-type electronic conductivity due to the formation of Co4+ species that serve as itinerant holes within the predominantly Co3+ framework of the CoO2 layer. We validate these predictions using electron energy loss spectroscopy in the scanning transmission electron microscope. The relationship between the hole-doping mechanism and the changes of the local structure (in particular the level of Bi deficiency) is evaluated. The reliability of the simulations is supported by the calculated temperature dependence of the Seebeck coefficient, in good agreement with experimental measurements.

AB - [Bi0.87SrO2]2[CoO2]1.82 (BSCO) is one of the best p-type thermoelectric oxides but its structural and electronic properties are still poorly understood. BSCO is a misfit-layered compound consisting of an incommensurate stacking of hexagonal CoO2 and double rock-salt BiSrO2 layers. Here we combine experimental and computational approaches to investigate its crystallographic and electronic structure as well as thermoelectric transport properties. Considering different approximations for the subsystems stacking, we present a structural model that agrees well with both bulk and atomic-scale experimental data. This model, which suggests a level of Bi deficiency in the rock-salt layers, is then used to discuss the material's electronic, magnetic, and transport properties. We show that Bi deficiency leads to a band gap opening and increases p-type electronic conductivity due to the formation of Co4+ species that serve as itinerant holes within the predominantly Co3+ framework of the CoO2 layer. We validate these predictions using electron energy loss spectroscopy in the scanning transmission electron microscope. The relationship between the hole-doping mechanism and the changes of the local structure (in particular the level of Bi deficiency) is evaluated. The reliability of the simulations is supported by the calculated temperature dependence of the Seebeck coefficient, in good agreement with experimental measurements.

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DO - 10.1021/acs.chemmater.6b03200

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JF - Chemistry of Materials

SN - 0897-4756

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