Phase separation and antisite defects iN the thermoelectric TiNiSn half-Heusler alloys

K. Kirievsky, Y. Gelbstein, D. Fuks

Research output: Contribution to journalArticlepeer-review

106 Scopus citations

Abstract

The half-Heusler TiNiSn alloys have recently gained an attention as promising candidates for thermoelectric applications. Improvement of these alloys for such applications can be obtained by both electronic and compositional optimizations. The latter can result in a miscibility gap, allowing a phase separation in the nano-scale and consequently a thermal conductivity reduction. Combination of ab initio calculations and statistical thermodynamics was applied for studying the relative stability of a number of superstructures in TiNiSn based alloys. The quasi-binary phase diagram beyond T=0K for TiNiSn-TiNi2Sn solid solutions was calculated using energy parameters extracted from the total energy calculations for ordered structures in the Ni sublattice. We demonstrated that a decomposition of the off-stoichiometric Ni-rich half-Heusler alloy into the stoichiometric TiNiSn phase and into Ni deficient Heusler TiNi2Sn phase occurs at elevated temperatures-an effect which recently had been observed experimentally. Furthermore, favorable energetic conditions for antisite defects formation were deduced, based on calculations of the energy of formation, an effect which was explained as a cooperative process of partial disordering on the Ni sublattice. The influence of these two effects on improvement of the thermoelectric performance of TiNiSn based half Heusler compounds is discussed.

Original languageEnglish
Pages (from-to)247-254
Number of pages8
JournalJournal of Solid State Chemistry
Volume203
DOIs
StatePublished - 1 Jan 2013

Keywords

  • Half-Heusler
  • Phase seperation
  • Thermoelectrics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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