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2006 Fiscal Year Final Research Report Summary

Improvements of thermoelectric properties of clathrate compounds by control of their crystal structures and chemical compositions

Research Project

Project/Area Number 17560618
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Structural/Functional materials
Research InstitutionYamaguchi University

Principal Investigator

KISHIMOTO Kengo  Yamaguchi University, Graduate School of Science and Engineering, Research Associate, 大学院理工学研究科, 助手 (50234216)

Co-Investigator(Kenkyū-buntansha) KOYANAGI Tsuyoshi  Yamaguchi University, Graduate School of Science and Engineering, Professor, 大学院理工学研究科, 教授 (90178385)
Project Period (FY) 2005 – 2006
Keywordsthermoelectric materials / clathrates / crystal structure / rattling / cationic
Research Abstract

We attempted to improve of thermoelectric properties of some clathrate compounds by control of their crystal structures and chemical compositions. The obtained results are mainly as follows:
1. We have examined the influences of the kind of filled atoms on thermoelectric properties of n-type germanium clathrates. Firstly, we prepared potassium-filled K_8Ga_8Ge_<38> samples to compare their properties with those of Ba_8Ga_<16>Ge_<30>. Although the K_8Ga_8Ge_<38> had only a half number of Ga atoms for carrier compensation, the K_8Ga_8Ge_38 possessed a lower mobility than that of the Ba_8Ga_<16>Ge_<30>. However, the K_8Ga_8Ge_<38> had a larger effective mass, resulting in a higher power factor at room temperature. This result is consistent with their calculated band structures. Secondly, we prepared mixed clathrate Sr_<8-x>Ba_xGa_<16>Ge_<30> samples with various Ba-to-Sr ratios. Their thermoelectric properties varied systematically with the Ba content x. The electrical conductivity decreas … More ed with the Ba content x, while the activation temperature range and the temperature where the Seebeck coefficient reached the maximum value increased. The results may be associated with the band structures.
2. We investigated some cationic clathrates to obtain a, high efficiency p-type thermoelectric material. Firstly, we successfully synthesized iodine-or tellurium-filled cationic clathrate compounds Sn_<38>Sb_8I_8, Ge_<38>Sb_8I_8, Ge_<30>P_<16>Te_8 and Si_<30>P_<16>Te_8 by sintering with mechanical alloying technique. The obtained samples were big in size enough to measure their properties, whereas cationic clathrates prepared by ampoule technique or high pressure technique are small. Secondly, we examined their thermoelectric properties. The obtained cationic clathrates Sn_<38>Sb_8I_8, Ge_<38>Sb_8I_8 and Ge_<30>P_<16>Te_8 possessed as low thermal conductivities as that of anionic clathrates such as Ba_8Ga_<16>Ge_<30> conductivities. Although the iodine-filled clathrates were n-type, the tellurium-filled clathrates Ge_<30>P_<16>Te_8 and Si_<30>P_<16>Te_8 showed p-type conductivity. In addition, the Si_<30>P_<16>Te_8 could be doped with carriers, resulting in a relatively high dimensionless figure of merit ZT of 0.45 for p-type materials. Less

  • Research Products

    (11 results)

All 2006 2005

All Journal Article (11 results)

  • [Journal Article] Thermoelectric properties of sintered clathrate compounds Sr_8Ga_xGe_<46-x> with various carrier concentrations2006

    • Author(s)
      Isao Fujita
    • Journal Title

      Journal of Applied Physics vol. 99

      Pages: 093707-1-093707-8

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Preparation and thermoelectric properties of sintered iodine-containing clathrate compounds Ge_<38>Sb_8I_8 and Sn_<38>Sb_8I_82006

    • Author(s)
      Kengo Kishimoto
    • Journal Title

      Applied Physics Letters vol. 88

      Pages: 222115-1-222115-3

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Synthesis and thermoelectric properties of type-I clathrate Ge <30>P_<16>Te_82006

    • Author(s)
      Kengo Kishimoto
    • Journal Title

      Applied Physics Letters vol. 89

      Pages: 172106-1-172106-3

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] タイプIIIクラスレート化合物Ba_6In_xGe_<25-x>の作製とその熱電気的特性2006

    • Author(s)
      石原剛志
    • Journal Title

      第3回日本熱電学会学術講演会論文集

      Pages: 34-35

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] クラスレート化合物Ba_8Ga_<16>Ge_<30>の作製と熱電気的特性2006

    • Author(s)
      三代俊介
    • Journal Title

      第3回日本熱電学会学術講演会論文集

      Pages: 98-99

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Thermoelectric properties of sintered clathrate compounds Sr_8Ga_xGe_<46-x> with various carrier concentrations2006

    • Author(s)
      Isao Fujita, Kengo Kishimoto, Masaya Sato, Hiroaki Anno, Tsuyoshi Koyanagi
    • Journal Title

      Journal of Applied Physics vol.99

      Pages: 093707-1-093707-8

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Preparation and thermoelectric properties of sintered iodine-containing clathrate compounds Ge_<38>Sb_8I_8 and Sn<38>Sb_8I_82006

    • Author(s)
      Kengo Kishimoto, Shuntaro Arimura, Tsuyoshi Koyanagi
    • Journal Title

      Applied Physics Letters vol.88

      Pages: 222115-1-222115-3

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Synthesis and thermoelectric properties of type-I clathrate Ge_<30>P_<16>Te_82006

    • Author(s)
      Kengo Kishimoto, Koji Akai, Noriaki Muraoka, Tsuyoshi Koyanagi, Mitsuru Matsuura
    • Journal Title

      Applied Physics Letters vol.89

      Pages: 172106-1-172106-3

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] クラスレート化合物I_8Sb_8 (Sn, Ge)_<38-x-y>A_xB_y (A=III,B=V)の作製と熱電気的特性2005

    • Author(s)
      村岡徳章
    • Journal Title

      第2回日本熱電学会学術講演会論文集

      Pages: 42-43

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] クラスレート化合物Sr_<8-x>Ba_xGa_<16>Ge_<30>の作製と熱電特性2005

    • Author(s)
      渡辺 光
    • Journal Title

      第2回日本熱電学会学術講演会論文集

      Pages: 44-45

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] クラスレート化合物K_<8-x>Ba_xGa_xGe_<46-y>の作製と熱電特性2005

    • Author(s)
      阿武正悟
    • Journal Title

      第2回日本熱電学会学術講演会論文集

      Pages: 46-47

    • Description
      「研究成果報告書概要(和文)」より

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Published: 2008-05-27  

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