Rapid microwave preparation of thermoelectric TiNiSn and TiCoSb half-Heusler compounds

Christina S. Birkel, Wolfgang G. Zeier, Jason E. Douglas, Bethany R. Lettiere, Carolyn E. Mills, Gareth Seward, Alexander Birkel, Matthew L. Snedaker, Yichi Zhang, G. Jeffrey Snyder, Tresa M. Pollock, Ram Seshadri, Galen D. Stucky

Research output: Contribution to journalArticlepeer-review

108 Scopus citations

Abstract

The 18-electron ternary intermetallic systems TiNiSn and TiCoSb are promising for applications as high-temperature thermoelectrics and comprise earth-abundant, and relatively nontoxic elements. Heusler and half-Heusler compounds are usually prepared by conventional solid state methods involving arc-melting and annealing at high temperatures for an extended period of time. Here, we report an energy-saving preparation route using a domestic microwave oven, reducing the reaction time significantly from more than a week to one minute. A microwave susceptor material rapidly heats the elemental starting materials inside an evacuated quartz tube resulting in near single phase compounds. The initial preparation is followed by a densification step involving hot-pressing, which reduces the amount of secondary phases, as verified by synchrotron X-ray diffraction, leading to the desired half-Heusler compounds, demonstrating that hot-pressing should be treated as part of the preparative process. For TiNiSn, high thermoelectric power factors of 2 mW/mK 2 at temperatures in the 700 to 800 K range, and zT values of around 0.4 are found, with the microwave-prepared sample displaying somewhat superior properties to conventionally prepared half-Heuslers due to lower thermal conductivity. The TiCoSb sample shows a lower thermoelectric figure of merit when prepared using microwave methods because of a metallic second phase.

Original languageEnglish (US)
Pages (from-to)2558-2565
Number of pages8
JournalChemistry of Materials
Volume24
Issue number13
DOIs
StatePublished - Jul 10 2012
Externally publishedYes

Keywords

  • Heusler
  • TiCoSb
  • TiNiSn
  • intermetallics
  • microwave synthesis
  • thermoelectrics

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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