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1996 Fiscal Year Final Research Report Summary

Improvement of Thermoelectric Properties of Iron Disilicide by Plasma Processing and Its Relation with Microstructure

Research Project

Project/Area Number 07680534
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field エネルギー学一般・原子力学
Research InstitutionYamaguchi University

Principal Investigator

MIKI Toshikatsu  Yamaguchi University, Faculty of Engineering, Professor, 工学部, 教授 (70091212)

Co-Investigator(Kenkyū-buntansha) MURATA Takuya  Yamaguchi University, Faculty of Engineering, Research Associate, 工学部, 助手 (70263796)
KISHIMOTO Kengoh  Yamaguchi University, Faculty of Engineering, Research Associate, 工学部, 助手 (50234216)
Project Period (FY) 1995 – 1996
KeywordsThermoelectric material / Iron disilicide / Plasma processing / Grain boundary / Silicon germanium
Research Abstract

To improve the thermoelectric figure-of-merit of FeSi_2 and SiGe ceramics, we have employed rf-plasma processing of micrograins prior to sintering. Either SiH_4 or GeH_4 were used as plasma gas for processing. The plasma processed grains were sintered by the ordinary method and the thermoelectric properties of the resultant ceramic specimens were measured. The experimental results are shown in the followings :
(1) Plasma-processed ceramics shows electrical conductivity higher than non-processed ceramics. This conductivity increase occurs by either SiH_4 or GeH_4 plasma processing. The Hall measurements revealed that the conductivity increase is mainly due to the increase of carrier mobility.
(2) Electron paramagnetic resonance study indicates that some paramagnetic centers are annihilated by plasma processing. The conductivity increase is probably due to the decrease of potential barrier height at grain boundaries.
(3) In case of SiH_4 plasma processing, no significant change was oberved in thermal conductivity. However, GeH_4 plasma processing reduces the thermal conductivity.
(4) The effect of plasma procesisng on Seebeck coefficient is somewhat complicated, but in most cases plasma processing increases the Seebeck.
(5) The effects of plasma processing described above are observed not only for FeSi_2 but also SiGe ceramics.
On the basis of these experimental results, we can summarize the effect of plasma processing on FeSi_2 and SiGe ceramics as follows.
(1) Plasma processing and resulting microstructure modification improve the thermoelectric properties of FeSi_2 and SiGe ceramics by factor 2 or 3.
(2) SiH_4 plasma processing is effective to the electrical conductivity improvement, but GeH_4 plasma processing primarily contributes to the decrease of thermal conductivity. Therefore, it is expected that plasma processing with suitably mixed SiH_4 and GeH_4 gases further improves the themoelectric properties.

  • Research Products

    (13 results)

All Other

All Publications (13 results)

  • [Publications] T.Miki,他5名: "Point defects and thermoelectric properties of iron disilicide ceramics sintered with SiH_4-plasma-processed micrograins" Jouranal of Applied Physics. 76. 2097-2103 (1994)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Kishimoto,他5名: "Microstructure control of FeSi_2 ceramics by rf-plasma processing in SiH_4 and GeH_4" AlP Conference Procedings. 316. 123-126 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Miki,他3名: "Effect of intergrain defects on thermoelectric properties of FeSi_2" Proceedings of 14th lnternational Conferece on Thermoelectircs. 227-230 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Kishimoto,他4名: "Thermoelectric properties of SiGe ceramics sintered with GeH_4 plasma processed micrograins" Proceedings of 14th lnternational Conferece on Thermoelectrics. 274-276 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 岸本堅剛,他3名: "微細構造を制御した熱電セラミックスの性能指数のシミュレーション" FGMニュース. 29. 14-17 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 岸本堅剛,他2名: "プラズマプロセス技術による熱電変換材料の微細構造制御" 材料科学. 33. 54-60 (1996)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Miki, Y.Matsui, Y.Teraoka, Y.Ebina, K.Matsubara and K.Kishimoto: "Point defects and thermoelectric properties of iron disilicide ceramics sintered with SiH_4-plasma-processed micrograins" J.Appl.Phys.Vol76. 2097-2103 (1994)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Kishimoto, Y.Nagamoto, K.Nagao, T.Miki, T.Koyanagi and K.Matsubara: "Microstructure control of FeSi_2 ceramics by rf-plasma processing in SiH_4 and GeH_4" AIP Conference Proc.316. 123-126 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] T.Miki, Y.Teraoka, K.Kishimoto and K.Matsubara: "Effect of intergrain defects on thermoelectric properties of FeSi_2" Proc.14th Int.Conf.Thermoelectrics. 227-230 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Kishimoto, Y.Nagamoto, T.Miki, T.Koyanagi and K.Matsubara: "Thermoelectric properties of SiGe ceramics sintered with GeH_4 plasma processed micrograins" Proc.14th Int.Conf.Thermoelectrics. 274-276 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Kishimoto, K.Nagao, T.Koyanagi and K.Matsubara: "A numeric simulation of thermoelectric figure of merit of microstructure-controlled ceramics (In Japanese)" FGM News. 29. 14-17 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Kishimoto, T.Koyanagi and K.Matsubara: "Microstructure control of thermoelectric materials by plasma processing (in Japanese)" ZAIRYO. Vol.33. 54-60 (1996)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] S.Jida and T.Miki: "Electron paramagnetic resonance of Nb-doped BaTiO_3 ceramics with positive temperature conefficient of resistivity" J.Appl.Phys.Vol.80. 5234-5239 (1996)

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

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Published: 1999-03-09  

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