Influence of shear strain on HPT-processed n-type skutterudites yielding ZT=2.1

Rogl, G and Ghosh, S and Renk, O and Yubuta, K and Grytsiv, A and Schafler, E and Zehetbauer, M and Mallik, RC and Bauer, E and Rogl, P (2021) Influence of shear strain on HPT-processed n-type skutterudites yielding ZT=2.1. In: Journal of Alloys and Compounds, 855 .

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Abstract

After our successful new and energy-saving production route to prepare bulk skutterudites with high ZTs from commercial powders via cold pressing (CP) and high-pressure torsion (HPT), we present in this paper a detailed study of the influence of shear strain and the preparation parameters, especially the temperature, on the micro-structural, thermoelectric and mechanical properties by analyzing specimens cut from various positions of the HPT disks of (Sm,Mm)0.15Co4Sb12. Across these large discs (30 mm in diameter and about 1 mm thickness) the shear strain γ rises linearly from the center of the sample to the rim reaching γ ∼ 450 (for 5 revolutions), a value first time realized for skutterudites. HPT-straining is essential for the introduction of high densities of crystal lattice defects, particularly dislocations, which result in a significant refining of the grains. Whereas the processing temperature mainly influences the density of the HPT consolidated samples and as a consequence, physical and mechanical properties, the applied shear strain rules the thermoelectric parameters. As an important feature, the Seebeck coefficient remained roughly unchanged under strain. Although the increasing shear strain caused the thermal conductivity to significantly decrease, this beneficial effect is accompanied by a concomitant significant increase of the electrical resistivity. Consequently, the interplay of the two controversial influences results in a maximum and record high thermoelectric figure of merit ZT ∼2.1. © 2020 Elsevier B.V.

Item Type:	Journal Article
Publication:	Journal of Alloys and Compounds
Publisher:	Elsevier Ltd
Additional Information:	The copyright for this article belongs to Elsevier Ltd.
Keywords:	Density (specific gravity); Energy conservation; High pressure effects; Processing; Shear flow; Skutterudites; Thermal conductivity; Torsional stress, Commercial powders; High pressure torsions; Important features; Physical and mechanical properties; Preparation parameters; Processing temperature; Thermoelectric figure of merit; Thermoelectric parameters, Shear strain
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	21 Feb 2023 03:07
Last Modified:	21 Feb 2023 03:07
URI:	https://eprints.iisc.ac.in/id/eprint/80405

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