Thermoelectric performance of multiphase XNiSn (X = Ti, Zr, Hf) half-Heusler alloys

Downie, R.A., MacLaren, D.A. and Bos, J.-W.G. (2014) Thermoelectric performance of multiphase XNiSn (X = Ti, Zr, Hf) half-Heusler alloys. Journal of Materials Chemistry A, 2(17), pp. 6107-6114. (doi: 10.1039/C3TA13955G)

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Quantitative X-ray powder diffraction analysis demonstrates that mixing Ti, Zr and Hf on the ionic site in the half-Heusler structure, which is a common strategy to lower the lattice thermal conductivity in this important class of thermoelectric materials, leads to multiphase behaviour. For example, nominal Ti0.5Zr0.5NiSn has a distribution of Ti1−xZrxNiSn compositions between 0.24 ≤ x ≤ 0.70. Similar variations are observed for Zr0.50Hf0.5NiSn and Ti0.5Hf0.5NiSn. Electron microscopy and elemental mapping demonstrate that the main compositional variations occur over micrometre length scales. The thermoelectric power factors of the mixed phase samples are improved compared to the single phase end-members (e.g. S2/ρ = 1.8 mW m−1 K−2 for Ti0.5Zr0.5NiSn, compared to S2/ρ = 1.5 mW m−1 K−2 for TiNiSn), demonstrating that the multiphase behaviour is not detrimental to electronic transport. Thermal conductivity measurements for Ti0.5Zr0.5NiSn0.95 suggest that the dominant reduction comes from Ti/Zr mass and size difference phonon scattering with the multiphase behaviour a secondary effect.

Item Type:Articles
Glasgow Author(s) Enlighten ID:MacLaren, Dr Donald
Authors: Downie, R.A., 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 A
Publisher:Royal Society of Chemistry
ISSN (Online):2050-7496
Copyright Holders:Copyright © 2014 The Royal Society of Chemistry
First Published:Journal of Materials Chemistry A 2(17):6107-6114
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
589771Ultra-high temperature synthesis of high-performance Zintl thermoelectricsDonald MaclarenEngineering & Physical Sciences Research Council (EPSRC)EP/J000884/1P&A - PHYSICS & ASTRONOMY