High-pressure torsion, a new processing route for thermoelectrics of high ZTs by means of severe plastic deformation

Gerda Rogl (Corresponding author), Daria Setman, Erhard Schafler, Jelena Horky, Michael Kerber, Michael Zehetbauer, Matthias Falmbigl, Peter Franz Rogl, Esmaeil Royanian, Ernst Bauer

Publications: Contribution to journalArticlePeer Reviewed

Abstract

High-pressure torsion (HPT) is a type of severe plastic deformation (SPD) that is highly suited to produce bulk ultrafine-grained and nanocrystalline materials, as it introduces many grain boundaries as well as dislocations and point defects. In this paper, HPT-mediated nanocrystallization was used to reduce the thermal conductivity and enhance the Seebeck coefficient of skutterudites. Both p- and n-type skutterudites have been processed by HPT with 4 and 5 GPa at temperatures up to 773 K, resulting in a strongly strengthened nanocrystalline structure, revealing oriented, lamellar-shaped crystallites with a size of similar to 50 nm and an enhanced dislocation density. In comparison with ball-milled plus hot-pressed skutterudites, the HPT-processed samples show a reduction of the thermal conductivity up to 40%. This and the slightly higher Seebeck coefficient are the reasons why HPT proved to enhance the figure of merit (ZT) values up to a factor of 2, in spite of a markedly enhanced electrical resistivity.
Original languageEnglish
Pages (from-to)2146-2157
Number of pages12
JournalActa Materialia
Volume60
Issue number5
DOIs
Publication statusPublished - 2012

Austrian Fields of Science 2012

  • 104017 Physical chemistry
  • 1030 Physics, Astronomy
  • 104006 Solid state chemistry
  • 103018 Materials physics

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