Journal
ACTA MATERIALIA
Volume 60, Issue 5, Pages 2146-2157Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2011.12.023
Keywords
High-pressure torsion; Severe plastic deformation; Nanocrystalline material; Skutterudites
Funding
- Austrian Science Fund (FWF) [T 512] Funding Source: researchfish
- Austrian Science Fund (FWF) [T512] Funding Source: Austrian Science Fund (FWF)
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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. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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