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Thermal properties of TiNiSn and VFeSb half-Heusler thermoelectrics from synchrotron X-ray powder diffraction

DOI: 10.1088/2515-7655/abf41a DOI Help

Authors: Daniella Ferluccio (Heriot-Watt University) , Blair Fitzgerald Kennedy (Heriot-Watt University) , Sonia Barczak (Heriot-Watt University) , Srinivas Popuri (Heriot-Watt University) , Claire Murray (Diamond Light Source) , Michael Pollet (ICMCB) , Jan-Willem Bos (Heriot-Watt University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Physics: Energy

State: Published (Approved)
Published: March 2021
Diamond Proposal Number(s): 17825

Open Access Open Access

Abstract: Half-Heusler alloys are an important class of thermoelectric materials that combine promising performance with good engineering properties. This manuscript reports a variable temperature synchrotron X-ray diffraction study of several TiNiSn- and VFeSb-based half-Heuslers. A Debye model was found to capture the main trends in thermal expansion and atomic displacement parameters. The linear thermal expansion coefficient α(T) of the TiNiSn based samples was found to be independent of alloying or presence of Cu interstitials with αav = 10.1 × 10-6 K-1 between 400-850 K. The α(T) of VFeSb and TiNiSn are well-matched, but NbFeSb has a much reduced αav = 8.9 × 10-6 K-1, caused by a stiffer lattice structure. This is confirmed by analysis of the Debye temperatures, which indicate significantly larger bond force constants for all atomic sites in NbFeSb. This work also reveals substantial amounts of Fe interstitials in VFeSb, whilst these are absent for NbFeSb. The Fe interstitials are linked to low thermal conductivities, but also reduce the bandgap and lower the onset of thermal bipolar transport.

Diamond Keywords: Alloys

Subject Areas: Materials, Physics

Instruments: I11-High Resolution Powder Diffraction

Added On: 06/04/2021 13:56


Discipline Tags:

Quantum Materials Physics Materials Science Thermoelectrics Metallurgy

Technical Tags:

Diffraction X-ray Powder Diffraction