Half-Heusler alloys: Enhancement of ZT after severe plastic deformation (ultra-low thermal conductivity)

Rogl, G and Ghosh, S and Wang, L and Bursik, J and Grytsiv, A and Kerber, M and Bauer, E and Mallik, RC and Chen, X-Q and Zehetbauer, M and Rogl, P (2020) Half-Heusler alloys: Enhancement of ZT after severe plastic deformation (ultra-low thermal conductivity). In: Acta Materialia, 183 . pp. 285-300.

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Abstract

Several n- and p-type Half-Heusler (HH) thermoelectric materials (Ti0.5Zr0.5NiSn-based and NbFeSb-based) have been processed by high-pressure torsion (HPT) to improve their thermoelectric performance via a drastic reduction towards ultra-low thermal conductivity. This reduction occurs due to grain refinement and a high concentration of deformation-induced defects, i.e. vacancies and dislocations as inferred by this severe plastic deformation and documented via SEM and TEM investigations. In most cases the figure of merit, ZT, and the thermo-electric conversion efficiency were enhanced up to η ∼ 10% for the thermally stable HPT-processed sample. Raman spectroscopy, backed by DFT calculations, proves that HPT induces a stiffening of the lattice and as a consequence, a blue-shift of the lattice vibrations occurs. Furthermore for all investigated specimens Vickers hardness values after HPT were significantly higher, whereas the change in the elastic moduli was less than 5% in comparison to the HP reference sample.

Item Type:	Journal Article
Publication:	Acta Materialia
Publisher:	Acta Materialia Inc
Additional Information:	The copyright for this article belongs to Acta Materialia Inc.
Keywords:	Antimony compounds; Blue shift; Grain refinement; High pressure engineering; Iron compounds; Lattice vibrations; Nickel compounds; Niobium compounds; Plastic deformation; Thermoelectric equipment; Thermoelectricity; Tin compounds; Titanium compounds; Torsional stress; Transmission electron microscopy; Vickers hardness; Zirconium compounds, Electric conversion efficiency; Half-heusler; High pressure torsions; Low thermal conductivity; Severe plastic deformations; Thermo-Electric materials; Thermoelectric performance; Thermoelectric properties, Thermal conductivity of solids
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	06 Feb 2023 09:55
Last Modified:	06 Feb 2023 09:55
URI:	https://eprints.iisc.ac.in/id/eprint/79930

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