High power factor in thiospinels Cu2 T r Ti3S8 (T r = Mn, Fe, Co, Ni) arising from TiS6 octahedron network

Katsuaki Hashikuni, Koichiro Suekuni, Hidetomo Usui, Michihiro Ohta, Kazuhiko Kuroki, Toshiro Takabatake

    研究成果: ジャーナルへの寄稿学術誌査読

    18 被引用数 (Scopus)


    Thermoelectric properties and electronic structures of n-type thiospinels Cu2TrTi3S8 composed of CuS4 tetrahedron and (Tr/Ti)S6 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 (ρ) and rather large and negative thermopower (S), leading to a high power factor (S2/ρ) of 0.4-0.6 mW/K2 m at 650 K. In addition to the superior electrical properties, relatively low thermal conductivity of ∼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.

    ジャーナルApplied Physics Letters
    出版ステータス出版済み - 10月 31 2016

    !!!All Science Journal Classification (ASJC) codes

    • 物理学および天文学(その他)


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