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Journal of Electronic Materials

, Volume 39, Issue 9, pp 1687–1691 | Cite as

Giant Thermopower at Low Temperatures in Novel Clathrates Ba8{Cu,Zn} x Ge46−x

  • I. BednarEmail author
  • E. Royanian
  • S. Bühler-Paschen
  • E. Bauer
  • N. Nasir
  • A. Grytsiv
  • N. Melnychenko-Koblyuk
  • P. Rogl
Article

Abstract

In the present work we focus on cubic type I Ba-Ge-based clathrates, where Ge in \(\rm Ba_8Ge_{43} \square_3\) (where □ is a vacancy) is substituted by Cu, Zn, Pd, and Si. Structural investigations in all cases confirm cubic primitive symmetry consistent with the space group type \(Pm\bar{3}n\) of a typical type I clathrate structure with lattice parameter a ≈ 1.06 nm. Electronic transport has been studied in a broad temperature range from 4.2 K to about 800 K, demonstrating that substitution allows fine-tuning of the charge carrier density, shifting the materials into the proximity of a metal-to-insulator transition. This is evidenced from giant thermopower reaching values of 400 μV/K in the case of Ba8Cu5.2Zn0.8Ge40.0 at temperatures well below room temperature (T max S  ≈ 150 K).

Keywords

Type I clathrates Ba8Ge46−x transport properties figure of merit metal-to-insulator transition 

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Notes

Acknowledgements

We are grateful for financial support to the Austrian FFG, project “THECLA.”

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Copyright information

© TMS 2010

Authors and Affiliations

  • I. Bednar
    • 1
    Email author
  • E. Royanian
    • 1
  • S. Bühler-Paschen
    • 1
  • E. Bauer
    • 1
  • N. Nasir
    • 2
  • A. Grytsiv
    • 2
  • N. Melnychenko-Koblyuk
    • 2
  • P. Rogl
    • 2
  1. 1.Institute of Solid State PhysicsVienna University of TechnologyWienAustria
  2. 2.Institute of Physical ChemistryUniversity of ViennaWienAustria

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