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

Autor: Barczak SA; 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. sb306@hw.ac.uk., Buckman J; Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh EH14 4AS, UK. J.Buckman@hw.ac.uk., Smith RI; ISIS Facility, Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, UK. ron.smith@stfc.ac.uk., Baker AR; Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK. annabelle.baker@diamond.ac.uk., Don E; SemiMetrics Ltd., Kings Langley WD4 9WB, UK. eric.don@semimetrics.com.; Department of Physics and Engineering, Northumbria University, Newcastle NE1 8ST, UK. eric.don@semimetrics.com., Forbes I; Department of Physics and Engineering, Northumbria University, Newcastle NE1 8ST, UK. ian.forbes@northumbria.ac.uk., Bos JG; 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.
Jazyk: angličtina
Zdroj: Materials (Basel, Switzerland) [Materials (Basel)] 2018 Mar 30; Vol. 11 (4). Date of Electronic Publication: 2018 Mar 30.
DOI: 10.3390/ma11040536
Abstrakt: 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 TiNi 1+y Sn 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.
Competing Interests: The authors declare no conflict of interest. The sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.
Databáze: MEDLINE
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