Thermoelectric Properties and Electronic Structures of CuTi 2 S 4 Thiospinel and Its Derivatives

Structural Design for Spinel-Related Thermoelectric Materials

Katsuaki Hashikuni, Koichiro Suekuni, Hidetomo Usui, Raju Chetty, Michihiro Ohta, Kazuhiko Kuroki, Toshiro Takabatake, Kosuke Watanabe, Michitaka Ohtaki

Research output: Contribution to journalArticle

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Abstract

We report the preparations, thermoelectric and magnetic properties, and electronic structures of Cu-Ti-S systems, namely, cubic thiospinel c-Cu 1-x Ti 2 S 4 (x ≤ 0.375), a derivative cubic and Ti-rich phase c-Cu 1-x Ti 2.25 S 4 (x = 0.5, 0.625), and a rhombohedral phase r-CuTi 2 S 4 . All samples have the target compositions except for r-CuTi 2 S 4 , whose actual composition is Cu 1.14 Ti 1.80 S 4 . All of the phases have n-type metallic character and exhibit Pauli paramagnetism, as proven by experiments and first-principles calculations. The Cu and Ti deficiencies in c-Cu 1-x Ti 2 S 4 and r-CuTi 2 S 4 , respectively, decrease the electron-carrier concentration, whereas the "excess" of Ti ions in c-Cu 1-x Ti 2.25 S 4 largely increases it. For r-CuTi 2 S 4 , the reduced carrier concentration increases the electrical resistivity and Seebeck coefficient, leading to the highest thermoelectric power factor of 0.5 mW K -2 m -1 at 670 K. For all of the Cu-Ti-S phases, the thermal conductivity at 670 K is 3.5-5 W K -1 m -1 , where the lattice part of the conductivity is as low as 1 W K -1 m -1 at 670 K. As a result, r-CuTi 2 S 4 shows the highest dimensionless thermoelectric figure of merit ZT of 0.2. The present systematic study on the Cu-Ti-S systems provides insights into the structural design of thermoelectric materials based on Cu-M-S (M = transition-metal elements).

Original languageEnglish
Pages (from-to)1425-1432
Number of pages8
JournalInorganic Chemistry
Volume58
Issue number2
DOIs
Publication statusPublished - Jan 22 2019

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structural design
thermoelectric materials
Structural design
spinel
Electronic structure
Carrier concentration
electronic structure
Derivatives
Paramagnetism
Seebeck coefficient
paramagnetism
Thermoelectric power
Seebeck effect
Chemical analysis
figure of merit
Chemical elements
Transition metals
Thermal conductivity
Magnetic properties
thermal conductivity

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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Thermoelectric Properties and Electronic Structures of CuTi 2 S 4 Thiospinel and Its Derivatives : Structural Design for Spinel-Related Thermoelectric Materials. / Hashikuni, Katsuaki; Suekuni, Koichiro; Usui, Hidetomo; Chetty, Raju; Ohta, Michihiro; Kuroki, Kazuhiko; Takabatake, Toshiro; Watanabe, Kosuke; Ohtaki, Michitaka.

In: Inorganic Chemistry, Vol. 58, No. 2, 22.01.2019, p. 1425-1432.

Research output: Contribution to journalArticle

Hashikuni, Katsuaki ; Suekuni, Koichiro ; Usui, Hidetomo ; Chetty, Raju ; Ohta, Michihiro ; Kuroki, Kazuhiko ; Takabatake, Toshiro ; Watanabe, Kosuke ; Ohtaki, Michitaka. / Thermoelectric Properties and Electronic Structures of CuTi 2 S 4 Thiospinel and Its Derivatives : Structural Design for Spinel-Related Thermoelectric Materials. In: Inorganic Chemistry. 2019 ; Vol. 58, No. 2. pp. 1425-1432.
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abstract = "We report the preparations, thermoelectric and magnetic properties, and electronic structures of Cu-Ti-S systems, namely, cubic thiospinel c-Cu 1-x Ti 2 S 4 (x ≤ 0.375), a derivative cubic and Ti-rich phase c-Cu 1-x Ti 2.25 S 4 (x = 0.5, 0.625), and a rhombohedral phase r-CuTi 2 S 4 . All samples have the target compositions except for r-CuTi 2 S 4 , whose actual composition is Cu 1.14 Ti 1.80 S 4 . All of the phases have n-type metallic character and exhibit Pauli paramagnetism, as proven by experiments and first-principles calculations. The Cu and Ti deficiencies in c-Cu 1-x Ti 2 S 4 and r-CuTi 2 S 4 , respectively, decrease the electron-carrier concentration, whereas the {"}excess{"} of Ti ions in c-Cu 1-x Ti 2.25 S 4 largely increases it. For r-CuTi 2 S 4 , the reduced carrier concentration increases the electrical resistivity and Seebeck coefficient, leading to the highest thermoelectric power factor of 0.5 mW K -2 m -1 at 670 K. For all of the Cu-Ti-S phases, the thermal conductivity at 670 K is 3.5-5 W K -1 m -1 , where the lattice part of the conductivity is as low as 1 W K -1 m -1 at 670 K. As a result, r-CuTi 2 S 4 shows the highest dimensionless thermoelectric figure of merit ZT of 0.2. The present systematic study on the Cu-Ti-S systems provides insights into the structural design of thermoelectric materials based on Cu-M-S (M = transition-metal elements).",
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T1 - Thermoelectric Properties and Electronic Structures of CuTi 2 S 4 Thiospinel and Its Derivatives

T2 - Structural Design for Spinel-Related Thermoelectric Materials

AU - Hashikuni, Katsuaki

AU - Suekuni, Koichiro

AU - Usui, Hidetomo

AU - Chetty, Raju

AU - Ohta, Michihiro

AU - Kuroki, Kazuhiko

AU - Takabatake, Toshiro

AU - Watanabe, Kosuke

AU - Ohtaki, Michitaka

PY - 2019/1/22

Y1 - 2019/1/22

N2 - We report the preparations, thermoelectric and magnetic properties, and electronic structures of Cu-Ti-S systems, namely, cubic thiospinel c-Cu 1-x Ti 2 S 4 (x ≤ 0.375), a derivative cubic and Ti-rich phase c-Cu 1-x Ti 2.25 S 4 (x = 0.5, 0.625), and a rhombohedral phase r-CuTi 2 S 4 . All samples have the target compositions except for r-CuTi 2 S 4 , whose actual composition is Cu 1.14 Ti 1.80 S 4 . All of the phases have n-type metallic character and exhibit Pauli paramagnetism, as proven by experiments and first-principles calculations. The Cu and Ti deficiencies in c-Cu 1-x Ti 2 S 4 and r-CuTi 2 S 4 , respectively, decrease the electron-carrier concentration, whereas the "excess" of Ti ions in c-Cu 1-x Ti 2.25 S 4 largely increases it. For r-CuTi 2 S 4 , the reduced carrier concentration increases the electrical resistivity and Seebeck coefficient, leading to the highest thermoelectric power factor of 0.5 mW K -2 m -1 at 670 K. For all of the Cu-Ti-S phases, the thermal conductivity at 670 K is 3.5-5 W K -1 m -1 , where the lattice part of the conductivity is as low as 1 W K -1 m -1 at 670 K. As a result, r-CuTi 2 S 4 shows the highest dimensionless thermoelectric figure of merit ZT of 0.2. The present systematic study on the Cu-Ti-S systems provides insights into the structural design of thermoelectric materials based on Cu-M-S (M = transition-metal elements).

AB - We report the preparations, thermoelectric and magnetic properties, and electronic structures of Cu-Ti-S systems, namely, cubic thiospinel c-Cu 1-x Ti 2 S 4 (x ≤ 0.375), a derivative cubic and Ti-rich phase c-Cu 1-x Ti 2.25 S 4 (x = 0.5, 0.625), and a rhombohedral phase r-CuTi 2 S 4 . All samples have the target compositions except for r-CuTi 2 S 4 , whose actual composition is Cu 1.14 Ti 1.80 S 4 . All of the phases have n-type metallic character and exhibit Pauli paramagnetism, as proven by experiments and first-principles calculations. The Cu and Ti deficiencies in c-Cu 1-x Ti 2 S 4 and r-CuTi 2 S 4 , respectively, decrease the electron-carrier concentration, whereas the "excess" of Ti ions in c-Cu 1-x Ti 2.25 S 4 largely increases it. For r-CuTi 2 S 4 , the reduced carrier concentration increases the electrical resistivity and Seebeck coefficient, leading to the highest thermoelectric power factor of 0.5 mW K -2 m -1 at 670 K. For all of the Cu-Ti-S phases, the thermal conductivity at 670 K is 3.5-5 W K -1 m -1 , where the lattice part of the conductivity is as low as 1 W K -1 m -1 at 670 K. As a result, r-CuTi 2 S 4 shows the highest dimensionless thermoelectric figure of merit ZT of 0.2. The present systematic study on the Cu-Ti-S systems provides insights into the structural design of thermoelectric materials based on Cu-M-S (M = transition-metal elements).

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JF - Inorganic Chemistry

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