Microstructure evolution of Ag-alloyed PbTe-based compounds and implications for thermoelectric performance

Tom Grossfeld, Ariel Sheskin, Yaniv Gelbstein, Yaron Amouyal

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

We investigate the microstructure evolution of Ag-alloyed PbTe compounds for thermoelectric (TE) applications with or without additions of 0.04 at. % Bi. We control the nucleation and temporal evolution of Ag2Te-precipitates in the PbTe-matrix applying designated aging heat treatments, aiming to achieve homogeneous dispersion of precipitates with high number density values, hypothesizing that they act as phonon scattering centers, thereby reducing lattice thermal conductivity. We measure the temperature dependence of the Seebeck coefficient and electrical and thermal conductivities, and correlate them with the microstructure. It is found that lattice thermal conductivity of PbTe-based compounds is reduced by controlled nucleation of Ag2Te-precipitates, exhibiting a number density value as high as 2.7 × 1020 m-3 upon 6 h aging at 380 °C. This yields a TE figure of merit value of ca. 1.4 at 450 °C, which is one on the largest values reported for n-type PbTe compounds. Subsequent aging leads to precipitate coarsening and deterioration of TE performance. Interestingly, we find that Bi-alloying improves the alloys’ thermal stability by suppressing microstructure evolution, besides the role of Bi-atoms as electron donors, thereby maintaining high TE performance that is stable at elevated service temperatures. The latter has prime technological significance for TE energy conversion.

Original languageEnglish
Article number281
JournalCrystals
Volume7
Issue number9
DOIs
StatePublished - 18 Sep 2017

Keywords

  • Microstructure evolution
  • PbTe
  • Phase transformations
  • Phonon scattering
  • Thermal conductivity
  • Thermoelectric materials

ASJC Scopus subject areas

  • Chemical Engineering (all)
  • Materials Science (all)
  • Condensed Matter Physics
  • Inorganic Chemistry

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