Issue 40, 2015

Compositions and thermoelectric properties of XNiSn (X = Ti, Zr, Hf) half-Heusler alloys

Abstract

Rietveld analysis of neutron powder diffraction data has been used to investigate the compositions of XNiSn (X = Ti, Zr, Hf) half-Heusler alloys prepared by solid state reactions. All samples containing Ti have 2–3% excess Ni, whereas the samples with X = Zr, Hf are almost stoichiometric. Samples with mixed X-metals are characterised by the presence of 3–4 distinct X1−xX′xNi1+ySn half-Heusler phases. Variable temperature and time dependent neutron powder diffraction for X = Ti and X = Ti0.5Hf0.5 demonstrates that both the amount of excess Ni and the phase distribution are stable up to at least 600 °C. Debye temperatures of 367(2) K and 317(2) K were obtained from the thermal displacement parameters. The samples containing Ti are characterised by a ∼0.15 eV bandgap and a monotonously decreasing Seebeck coefficient. The compositions with Zr and Hf have similar bandgap values but show ambipolar transitions. Analysis of the thermoelectric transport data of degenerately doped Ti0.5Zr0.5NiSn1−zSbz samples using a single parabolic band model demonstrates that the transport is limited by alloy scattering and yielded an effective carrier mass of 2.5(1) me.

Graphical abstract: Compositions and thermoelectric properties of XNiSn (X = Ti, Zr, Hf) half-Heusler alloys

Article information

Article type
Paper
Submitted
06 Jūl. 2015
Accepted
05 Aug. 2015
First published
05 Aug. 2015
This article is Open Access
Creative Commons BY license

J. Mater. Chem. C, 2015,3, 10534-10542

Author version available

Compositions and thermoelectric properties of XNiSn (X = Ti, Zr, Hf) half-Heusler alloys

R. A. Downie, S. A. Barczak, R. I. Smith and J. W. G. Bos, J. Mater. Chem. C, 2015, 3, 10534 DOI: 10.1039/C5TC02025E

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements