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)

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: MacLaren, Professor Donald and Halpin, Dr John
• 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

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
70740	1	Nanostructured half-Heuslers for thermoelectric waste heat recovery	Donald Maclaren	Engineering and Physical Sciences Research Council (EPSRC)	EP/N017218/1	S&E P&A - PHYSICS & ASTRONOMY