Abstract
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.
| Original language | English |
|---|---|
| Article number | 182110 |
| Journal | Applied Physics Letters |
| Volume | 109 |
| Issue number | 18 |
| DOIs | |
| Publication status | Published - Oct 31 2016 |
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All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)
Cite this
High power factor in thiospinels Cu2 T r Ti3S8 (T r = Mn, Fe, Co, Ni) arising from TiS6 octahedron network. / Hashikuni, Katsuaki; Suekuni, Koichiro; Usui, Hidetomo; Ohta, Michihiro; Kuroki, Kazuhiko; Takabatake, Toshiro.
In: Applied Physics Letters, Vol. 109, No. 18, 182110, 31.10.2016.Research output: Contribution to journal › Article
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TY - JOUR
T1 - High power factor in thiospinels Cu2 T r Ti3S8 (T r = Mn, Fe, Co, Ni) arising from TiS6 octahedron network
AU - Hashikuni, Katsuaki
AU - Suekuni, Koichiro
AU - Usui, Hidetomo
AU - Ohta, Michihiro
AU - Kuroki, Kazuhiko
AU - Takabatake, Toshiro
PY - 2016/10/31
Y1 - 2016/10/31
N2 - 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.
AB - 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.
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U2 - 10.1063/1.4966955
DO - 10.1063/1.4966955
M3 - Article
AN - SCOPUS:84994285909
VL - 109
JO - Applied Physics Letters
JF - Applied Physics Letters
SN - 0003-6951
IS - 18
M1 - 182110
ER -