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 language | English |
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Pages (from-to) | 2146-2157 |
Number of pages | 12 |
Journal | Acta Materialia |
Volume | 60 |
Issue number | 5 |
DOIs | |
Publication status | Published - 2012 |
Austrian Fields of Science 2012
- 104017 Physical chemistry
- 1030 Physics, Astronomy
- 104006 Solid state chemistry
- 103018 Materials physics