Grain-by-grain compositional variations and interstitial metals—a new route toward achieving high performance in half-Heusler thermoelectrics

Barczak, S. A., Halpin, J. E., Buckman, J., Decourt, R., Pollet, M., Smith, R. I., MacLaren, D. A. and Bos, J.-W. G. (2018) Grain-by-grain compositional variations and interstitial metals—a new route toward achieving high performance in half-Heusler thermoelectrics. ACS Applied Materials and Interfaces, 10(5), pp. 4786-4793. (doi:10.1021/acsami.7b14525) (PMID:29313341)

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Abstract

Half-Heusler alloys based on TiNiSn are promising thermoelectric materials characterised by large power factors, good mechanical and thermal stabilities; but they are limited by large thermal conductivities. A variety of strategies have been used to disrupt their thermal transport, including alloying with heavy, generally expensive, elements and nanostructuring, enabling figures of merit, ZT ≥ 1 at elevated temperatures (>773 K). Here, we demonstrate an alternative strategy that is based around the partial segregation of excess Cu leading to grain-by-grain compositional variations, the formation of extruded Cu ‘wetting’ layers between grains and – most importantly – the presence of statistically distributed interstitials that reduce the thermal conductivity effectively through point-defect scattering. Our best TiNiCuySn (y ≤ 0.1) compositions have a temperature-averaged ZTdevice = 0.3-0.4 and estimated leg power outputs of 6-7 W cm-2 in the 323-773 K temperature range. This is a significant development as these materials were prepared using a straightforward processing method, do not contain any toxic, expensive or scarce elements and are therefore promising candidates for large scale production.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Halpin, Dr John and MacLaren, Dr Donald
Authors: Barczak, S. A., Halpin, J. E., Buckman, J., Decourt, R., Pollet, M., Smith, R. I., MacLaren, D. A., and Bos, J.-W. G.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:ACS Applied Materials and Interfaces
Publisher:American Chemical Society
ISSN:1944-8244
ISSN (Online):1944-8252
Published Online:09 January 2018
Copyright Holders:Copyright © 2018 American Chemical Society
First Published:First published in ACS Applied Materials and Interfaces 10(5):4786–4793
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
707401Nanostructured half-Heuslers for thermoelectric waste heat recoveryDonald MaclarenEngineering and Physical Sciences Research Council (EPSRC)EP/N017218/1S&E P&A - PHYSICS & ASTRONOMY