2016年10月
High power factor in thiospinels Cu2TrTi3S8 (Tr = Mn, Fe, Co, Ni) arising from TiS6 octahedron network
APPLIED PHYSICS LETTERS
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- 巻
- 109
- 号
- 18
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1063/1.4966955
- 出版者・発行元
- AMER INST PHYSICS
Thermoelectric properties and electronic structures of n-type thiospinels Cu2TrTi3S8 composed of CuS4 tetrahedron and (Tr/Ti)S-6 octahedron network have been studied for Tr = Mn, Fe, Co, and Ni. The samples with Tr = Mn, Co, and Ni exhibit metallic behaviors in the electrical resistivity (rho) and rather large and negative thermopower (S), leading to a high power factor (S-2/rho) of 0.4-0.6 mW/K-2 m at 650 K. In addition to the superior electrical properties, relatively low thermal conductivity of similar to 2 W/Km gives rise to a dimensionless figure of merit ZT reaching 0.16-0.18 at 650 K. The analysis of the temperature dependent magnetic susceptibility indicates that the Mn, Fe, and Ni ions are in high-spin divalent states while the Co2+ ion is in a low-spin nonmagnetic state. This electronic state for the Co2+ in Cu2CoTi3S8 is consistent with our first-principles electronic structure calculation indicating that the Fermi level lies in the conduction bands composed mainly of Ti-3d, Co-3d, and S-3p orbitals. The Ti-3d and S-3p orbitals forming the octahedron network likely results in high power factors irrespective of Tr elements. The addition of Co-3d orbitals makes a peak with steep slope in the density of states near the Fermi level, leading to the further enhanced power factor. Published by AIP Publishing.
- リンク情報
- ID情報
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- DOI : 10.1063/1.4966955
- ISSN : 0003-6951
- eISSN : 1077-3118
- Web of Science ID : WOS:000387900600018