Endotaxial Intergrowth of Copper Telluride in GeTe-Rich Germanium Antimony Tellurides Leads to High Thermoelectric Performance

Stefan Schwarzmüller*, Daniel Souchay, Gerald Wagner, Paul Kemmesies, Daniel Günther, Michael Bittner, Guanhua Zhang, Zefeng Ren, Armin Feldhoff, G. Jeffrey Snyder, Oliver Oeckler

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

In composite materials with nominal compositions Cu2GexSb2Tex+4(11 ≤ x ≤ 18, i.e., between Cu6.7Ge36.7Sb6.7Te50and Cu4.5Ge40.9Sb4.5Te50), precipitates consisting of copper tellurides are endotaxially intergrown in a matrix of Cu-doped germanium antimony tellurides. The precipitates as well as the matrix material undergo various phase transitions as shown by temperature-dependent X-ray diffraction and X-ray absorption contrast imaging. Eventually, the precipitates dissolve in the matrix at temperatures exceeding 580 °C. The temperature-dependent behavior was also traced by photoemission electron microscopy up to 460 °C. At high temperatures, the thermoelectric properties are superior to those of pure germanium antimony tellurides obtained by comparable syntheses; a maximal zT value of 1.83 for Cu2Ge16Sb2Te20is reached at 500 °C. The application of an effective mass model reveals optimal charge carrier concentrations for all three compositions investigated. The p-type Cu2Ge16Sb2Te20material was used in combination with PbTe:In (n-type) to construct a thermoelectric module. Concludingly, the measurement of the Hall effect that suggests no significant changes in Cu-doping levels of the matrix with temperature application of grain boundary optimization and a temperature-induced reset of the microstructure are proposed as strategies for overcoming material degradation upon applying electrical currents.

Original languageEnglish (US)
Pages (from-to)10025-10039
Number of pages15
JournalChemistry of Materials
Volume34
Issue number22
DOIs
StatePublished - Nov 22 2022

ASJC Scopus subject areas

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

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