Effect of Spark Plasma Sintering on the Structure and Properties of Ti1-xZrxNiSn Half-Heusler Alloys

Ruth A Downie; Srinivas R Popuri; Huanpo Ning; Mike J Reece; Jan-Willem G Bos

doi:10.3390/ma7107093

Effect of Spark Plasma Sintering on the Structure and Properties of Ti_1-xZr_xNiSn Half-Heusler Alloys

Materials (Basel). 2014 Oct 20;7(10):7093-7104. doi: 10.3390/ma7107093.

Authors

Ruth A Downie¹, Srinivas R Popuri², Huanpo Ning³, Mike J Reece⁴, Jan-Willem G Bos⁵

Affiliations

¹ Institute of Chemical Sciences and Centre for Advanced Energy Storage and Recovery, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK. rad11@hw.ac.uk.
² Institute of Chemical Sciences and Centre for Advanced Energy Storage and Recovery, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK. s.r.popuri@hw.ac.uk.
³ School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK. h.ning@qmul.ac.uk.
⁴ School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK. m.j.reece@qmul.ac.uk.
⁵ Institute of Chemical Sciences and Centre for Advanced Energy Storage and Recovery, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK. j.w.g.bos@hw.ac.uk.

Abstract

XNiSn (X = Ti, Zr and Hf) half-Heusler alloys have promising thermoelectric properties and are attracting enormous interest for use in waste heat recovery. In particular, multiphase behaviour has been linked to reduced lattice thermal conductivities, which enables improved energy conversion efficiencies. This manuscript describes the impact of spark plasma sintering (SPS) on the phase distributions and thermoelectric properties of Ti_0.5Zr_0.5NiSn based half-Heuslers. Rietveld analysis reveals small changes in composition, while measurement of the Seebeck coefficient and electrical resistivities reveals that all SPS treated samples are electron doped compared to the as-prepared samples. The lattice thermal conductivities fall between 4 W·m^-1·K^-1 at 350 K and 3 W·m^-1·K^-1 at 740 K. A maximum ZT = 0.7 at 740 K is observed in a sample with nominal Ti_0.5Zr_0.5NiSn composition.

Keywords: TiNiSn; half-Heusler; in-gap states; spark plasma sintering; thermoelectric.