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Issue 17, 2014
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Thermoelectric performance of multiphase XNiSn (X = Ti, Zr, Hf) half-Heusler alloys

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Abstract

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.

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

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Publication details

The article was received on 01 Oct 2013, accepted on 05 Nov 2013 and first published on 05 Nov 2013


Article type: Paper
DOI: 10.1039/C3TA13955G
Citation: J. Mater. Chem. A, 2014,2, 6107-6114
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    Thermoelectric performance of multiphase XNiSn (X = Ti, Zr, Hf) half-Heusler alloys

    R. A. Downie, D. A. MacLaren and J.-W. G. Bos, J. Mater. Chem. A, 2014, 2, 6107
    DOI: 10.1039/C3TA13955G

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