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

Materials

Ian Forbes¹  Annabelle R. Baker²  Ronald I. Smith³  Jan-Willem G. Bos⁴  Sonia A. Barczak⁴  Jim Buckman⁵  Eric Don⁶ 

[1] Department of Physics and Engineering, Northumbria University, Newcastle NE1 8ST, UK;Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK;ISIS Facility, Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, UK;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;Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh EH14 4AS, UK;SemiMetrics Ltd., Kings Langley WD4 9WB, UK;

关键词: half-Heusler;    TiNiSn;    thermal conductivity;    thermoelectric materials;   

DOI  :  10.3390/ma11040536

来源: DOAJ

【 摘 要 】

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.

【 授权许可】

Unknown