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Layered cobalt oxide epitaxial films exhibiting thermoelectric ZT = 0.11 at room temperature

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Title: Layered cobalt oxide epitaxial films exhibiting thermoelectric ZT = 0.11 at room temperature
Authors: Yugo, Takashima Browse this author
Yu-qiao, Zhang Browse this author
Jiake, Wei Browse this author
Feng, Bin Browse this author
Ikuhara, Yuichi Browse this author
Cho, Hai Jun Browse this author
Ohta, Hiromichi Browse this author →KAKEN DB
Issue Date: 7-Jan-2021
Publisher: Royal Society of Chemistry
Journal Title: Journal of Materials Chemistry A
Volume: 9
Issue: 1
Start Page: 274
End Page: 280
Publisher DOI: 10.1039/d0ta07565e
Abstract: Among many thermoelectric materials, oxide-based materials draw significant interest due to their environmental compatibility. In particular, layered cobaltite, Na0.75CoO2, shows a large thermoelectric power factor parallel to the layers. However, the thermal conductivity (k) is rather high (5-7 W m(-1) K-1), and therefore, its thermoelectric figure of merit ZT is small (similar to 0.03) at room temperature. Here we show that substituting the Na+ ion with the Ba2+ ion in NaxCoO2 drastically reduces the kappa while keeping the large power factor, resulting in a large enhancement in ZT. We fabricated epitaxial films of Na0.75CoO2 by the reactive solid-phase epitaxy method and performed ion-exchange treatment from Na+ to Ba2+ to synthesize Ba0.27CoO2 films. The room temperature electrical conductivity (s), thermopower (S), and power factor of the c-axis oriented Ba0.27CoO2 films along the in-plane direction were 2310 S cm(-1), +72 mV K-1, and 1.2 mW m(-1) K-2, respectively, while the k along the in-plane, which was clarified by measuring the k of the c-axis inclined (55 degrees) film, was 3.3 W m(-1) K-1. This yields a ZT (= S-2 sigma T/kappa) value along the in-plane as high as 0.11 at room temperature, which is the highest among those reported for oxide thermoelectric materials except oxychalcogenide (BiO)(CuSe).
Type: article (author version)
Appears in Collections:電子科学研究所 (Research Institute for Electronic Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 太田 裕道

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