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Impact of Interstitial Ni on the Thermoelectric Properties of the Half-Heusler TiNiSn
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
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
Energy Materials
Materials Science
Thermoelectrics
Metallurgy
Technical Tags:
Diffraction
X-ray Powder Diffraction