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

Daniella A. Ferluccio, Blair Fitzgerald Kennedy, Sonia A. Barczak, Srinivas R. Popuri, Claire Murray, Michael Pollet, Jan-Willem G. Bos

Research output: Contribution to journalArticlepeer-review

Abstract

Half-Heusler (HH) 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 HH alloys. 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 and 848 K. The α(T) of VFeSb and TiNiSn are well-matched, but NbFeSb has a 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.
Original languageEnglish
Article number035001
JournalJournal of Physics: Energy
Volume3
Issue number3
Early online date27 Apr 2021
DOIs
Publication statusE-pub ahead of print - 27 Apr 2021

Keywords

  • TiNiSn
  • VFeSb
  • half-Heusler
  • thermal conductivity
  • thermal expansion
  • thermoelectric

ASJC Scopus subject areas

  • Energy(all)
  • Materials Chemistry
  • Materials Science (miscellaneous)

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