Ferluccio, D. A., Halpin, J. E., MacIntosh, K. L., Quinn, R. J., Don, E., Smith, R. I., MacLaren, D. A. and Bos, J.-W. G. (2019) Low thermal conductivity and promising thermoelectric performance in AxCoSb (A = V, Nb or Ta) half-Heuslers with inherent vacancies. Journal of Materials Chemistry C, 7, pp. 6539-6547. (doi: 10.1039/C9TC00743A)
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Abstract
Half-Heuslers with vacancies that are stabilised by a semiconducting electron count offer new opportunities for discovering good thermoelectric performance. Here, we present a comparative study of AxCoSb half-Heuslers (A = V, Nb or Ta) with intrinsic vacancies. Structural analysis demonstrates that each system has a clear preference for a specific vacancy concentration, increasing from 13(1)% (V) to 15(1)% (Nb) and 17(1)% (Ta) with evidence for ~3% V/Co inversion. Hall measurements confirm the decreasing carrier concentration but also signal profound changes to the electronic bandstructure with decreasing density of states effective masses for heavier A elements. V0.87CoSb has an ultralow lattice thermal conductivity, κlat ~ 2.2 W m-1 K-1, which cannot be explained within the Callaway framework. Coupled to a promising power factor, S2/ρ = 2.25 mW m-1 K-2, this results in ZT = 0.6 at 950 K. Nb0.85CoSb has a power factor of S2/ρ = 2.75 mW m-1 K-2 with κ ~ 4.75 W m-1 K-1, yielding a similar ZT = 0.5 at 950 K. Ta0.81CoSb has a microstructure consisting of smaller grains than the other samples, impacting both the carrier and thermal transport, yielding a power factor S2/ρ = 0.75 mW m-1 K-2 and ZT = 0.3 at 950 K. The ultralow κlat for V0.87CoSb may be linked to porosity effects that do not impact on the charge transport, thus affording a new route towards improved performance.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | MacLaren, Dr Donald and Halpin, Dr John |
| Authors: | Ferluccio, D. A., Halpin, J. E., MacIntosh, K. L., Quinn, R. J., Don, E., 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: | Journal of Materials Chemistry C |
| Publisher: | Royal Society of Chemistry |
| ISSN: | 2050-7526 |
| ISSN (Online): | 2050-7534 |
| Published Online: | 13 March 2019 |
| Copyright Holders: | Copyright © 2019 Royal Society of Chemistry |
| First Published: | First published in Journal of Materials Chemistry C 7:6539-6547 |
| Publisher Policy: | Reproduced in accordance with the publisher copyright policy |
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