Materials Transactions Online

Materials Transactions, Vol.53 No.04 (2012) pp.588-591
© 2012 The Japan Institute of Metals

Effects of Low Rotational Speed on Crystal Orientation of Bi2Te3-Based Thermoelectric Semiconductors Deformed by High-Pressure Torsion

Maki Ashida1, Natsuki Sumida2, Kazuhiro Hasezaki2, Hirotaka Matsunoshita1 and Zenji Horita1

1Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan
2Department of Materials Science, Faculty of Science and Engineering, Shimane University, Matsue 690-8504, Japan

Bi2Te3-based thermoelectric semiconductors were deformed by high-pressure torsion (HPT) using a low rotational speed of 0.1 rpm, which is less than the speed of 1 rpm used in our previous studies. The effects of different rotational speeds were investigated by metallographic and thermoelectric studies. Sample disks of p-type Bi0.5Sb1.5Te3.0 were cut from sintered compacts made by mechanical alloying (MA) followed by hot-pressing. The disks were deformed by HPT with 1, 3, and 5 turns at 473 K under 6.0 GPa of pressure at a rotational speed of 0.1 rpm. The preferred orientation was investigated using X-ray diffraction. The orientation factors of the disks changed from 0.054 for pre-rotation up to 0.653 for post-rotation samples. The maximum power factor of the disk using 5 turns and a speed of 0.1 rpm was 6.6 × 10−3 W m−1 K−2 at 363 K, which was larger than the reported power factors of 4.3 × 10−3 W m−1 K−2 for a disk using 5 turns and a speed of 1 rpm, and 4.6 × 10−3 W m−1 K−2 for melt-grown materials. Slow deformation by HPT was found to enhance the electrical conductivities and Seebeck coefficients of Bi2Te3-based thermoelectric semiconductors by producing a preferred orientation and grain refinement.

(Received 2011/06/09; Accepted 2011/11/14; Published 2012/03/25)

Keywords: high-pressure torsion, Bi2Te3, rotational speed, preferred orientation, electrical conductivity

PDF(Free)PDF (Free) Table of ContentsTable of Contents

REFERENCES

  1. D. M. Rowe (ed.): Thermoelectrics handbook: macro to nano, (CRC Press, London, New York, Tokyo, 2006) Chap. 1.
  2. Y. Shinohara and Y. Isoda: J. Japan Inst. Metals 71 (2007) 869-875.
  3. T. Ueda, C. Okamura and K. Hasezaki: Mater. Trans. 50 (2009) 2473-2475.
  4. D. M. Rowe (ed.): Thermoelectrics handbook: macro to nano, (CRC Press, London, New York, Tokyo, 2006) Chap. 27-3.
  5. S. Nakajima: J. Phys. Chem. Solids 24 (1963) 479-485.
  6. J. Nagano, M. Ferhat, E. Hatta and K. Musaka: Phys. Status Solidi B 219 (2000) 347-349.
  7. H. T. Kaibe, M. Sakata and I. A. Nishida: J. Phys. Chem. Solids 51 (1990) 1083-1087.
  8. M. Ashida, T. Hamachiyo, K. Hasezaki, H. Matsunoshita, M. Kai and Z. Horita: Mater. Sci. Forum 584-586 (2008) 1006-1011.
  9. K. Hasezaki, T. Hamachiyo, M. Ashida, T. Ueda and Y. Noda: Mater. Trans. 51 (2010) 863-867.
  10. P. W. Bridgman: Phys. Rev. 48 (1935) 825-847.
  11. G. Sakai, Z. Horita and T. G. Langdon: Mater. Sci. Eng. A 393 (2005) 344-351.
  12. C. Xu, S. V. Dobatkin, Z. Horita and T. G. Langdon: Mater. Sci. Eng. A 500 (2009) 170-175.
  13. M. Kai, Z. Horita and T. G. Langdon: Mater. Sci. Eng. A 488 (2008) 117-124.
  14. Y. Harai, M. Kai, K. Kaneko, Z. Horita and T. G. Langdon: Mater. Trans. 49 (2008) 76-83.
  15. M. Ashida, T. Hamachiyo, K. Hasezaki, H. Matsunoshita and Z. Horita: Adv. Mater. Res. 89-91 (2010) 41-46.
  16. T. Sakai, H. Miura, A. Goloborodko and S. Sitdikov: Acta Mater. 57 (2009) 153-162.
  17. Y. Todaka, M. Umemoto, A. Yamazaki, J. Sasaki and K. Tsuchiya: Mater. Trans. 49 (2008) 7-14.
  18. F. K. Lotgering: J. Inorg. Nucl. Chem. 9 (1959) 113-123.
  19. F. Izumi: The Rietveld Method, ed. by R. A. Young (Oxford University Press, Oxford, 1995) Chap. 13.
  20. H. Kaibe, Y. Tanaka, M. Sakata and I. Nishida: J. Phys. Chem. Solids 50 (1989) 945-950.
  21. K. Uemura and I. A. Nishida: Thermoelectric semiconductor and its applications, (Nikkankougyou Shinbunsya, Tokyo, 1988) p. 150.
  22. K. Uemura and I. A. Nishida: Thermoelectric semiconductor and its applications, (Nikkankougyou Shinbunsya, Tokyo, 1988) p. 179.


[JIM HOME] [JOURNAL ARCHIVES]

© 2012 The Japan Institute of Metals
Comments to us : editjt@jim.or.jp