Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10620462 | Acta Materialia | 2012 | 12 Pages |
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 5Â GPa at temperatures up to 773Â K, resulting in a strongly strengthened nanocrystalline structure, revealing oriented, lamellar-shaped crystallites with a size of â¼50Â 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.
Related Topics
Physical Sciences and Engineering
Materials Science
Ceramics and Composites
Authors
Gerda Rogl, Daria Setman, Erhard Schafler, Jelena Horky, Michael Kerber, Michael Zehetbauer, Matthias Falmbigl, Peter Rogl, Esmaeil Royanian, Ernst Bauer,