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Impact of Interstitial Ni on the Thermoelectric Properties of the Half-Heusler TiNiSn

DOI: 10.3390/ma11040536 DOI Help

Authors: Sonia A. Barczak (Heriot-Watt University) , Jim Buckman (Heriot-Watt University) , Ronald I. Smith (ISIS Facility) , Annabelle R. Baker (Diamond Light Source) , Eric Don (SemiMetrics Ltd; Northumbria University) , Ian Forbes (Northumbria University) , Jan-Willem Bos (Heriot-Watt University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Materials , VOL 11

State: Published (Approved)
Published: March 2018
Diamond Proposal Number(s): 14032

Open Access Open Access

Abstract: TiNiSn is an intensively studied half-Heusler alloy that shows great potential for waste heat recovery. Here, we report on the structures and thermoelectric properties of a series of metal-rich TiNi1+ySn compositions prepared via solid-state reactions and hot pressing. A general relation between the amount of interstitial Ni and lattice parameter is determined from neutron powder diffraction. High-resolution synchrotron X-ray powder diffraction reveals the occurrence of strain broadening upon hot pressing, which is attributed to the metastable arrangement of interstitial Ni. Hall measurements confirm that interstitial Ni causes weak n-type doping and a reduction in carrier mobility, which limits the power factor to 2.5–3 mW m−1 K−2 for these samples. The thermal conductivity was modelled within the Callaway approximation and is quantitively linked to the amount of interstitial Ni, resulting in a predicted value of 12.7 W m−1 K−1 at 323 K for stoichiometric TiNiSn. Interstitial Ni leads to a reduction of the thermal band gap and moves the peak ZT = 0.4 to lower temperatures, thus offering the possibility to engineer a broad ZT plateau. This work adds further insight into the impact of small amounts of interstitial Ni on the thermal and electrical transport of TiNiSn.

Journal Keywords: half-Heusler; TiNiSn; thermal conductivity; thermoelectric materials

Diamond Keywords: Alloys

Subject Areas: Materials, Environment

Instruments: I11-High Resolution Powder Diffraction

Other Facilities: ISIS Facility

Added On: 04/04/2018 11:31

Discipline Tags:

Quantum Materials Earth Sciences & Environment Climate Change Materials Science Thermoelectrics Metallurgy

Technical Tags:

Diffraction X-ray Powder Diffraction