Increasing Seebeck Coefficients and Thermoelectric Performance of Sn/Sb/Te and Ge/Sb/Te Materials by Cd Doping

Simon Welzmiller, Felix Fahrnbauer, Felix Hennersdorf, Sascha Dittmann, Michael Liebau, Christina Fraunhofer, Wolfgang G. Zeier, Gerald Jeffrey Snyder, Oliver Oeckler*

*Corresponding author for this work

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

Ge and Sn in (GeTe)nSb2Te3 (GST) and (SnTe)nSb2Te3 compounds, respectively, are partially substituted by Cd. These layered compounds (n = 1) consist of NaCl-type slabs that are separated by van der Waals gaps. Resonant X-ray diffraction yields different Cd-atom distributions in Cd0.2Ge0.8Sb2Te4 and Cd0.2Sn0.8Sb2Te4, which indicate how van der Waals gaps in metastable cubic GeTe-rich or SnTe-rich compounds (n ≥ 7) are surrounded. The latter exhibit promising thermoelectric properties with figures of merit ZT ≈ 0.8 at 450 °C. Alloying with Sb2Te3 increases the ZT value of SnTe by a factor of up to two because of an increased Seebeck coefficient and a reduced thermal conductivity; the hole concentration is significantly reduced. A further improvement in ZT by ≈20% is possible by Cd-doping, most likely due to a more covalent bonding character, yielding a ZT of ≈1.1 at 450 °C for Cd1.2Sn10.8Sb2Te15. In order to understand the electronic transport properties of these p-type semiconductors, the single parabolic band model is applied. By contrast, Cd doping in GST materials reduces the Hall mobility and therefore decreases the power factor compared to undoped GST materials.

Original languageEnglish (US)
Article number1500266
JournalAdvanced Electronic Materials
Volume1
Issue number12
DOIs
StatePublished - Dec 1 2015

Keywords

  • doped semiconductors
  • metastable compounds
  • resonant X-ray scattering
  • single parabolic band model
  • thermoelectrics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials

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    Welzmiller, S., Fahrnbauer, F., Hennersdorf, F., Dittmann, S., Liebau, M., Fraunhofer, C., Zeier, W. G., Snyder, G. J., & Oeckler, O. (2015). Increasing Seebeck Coefficients and Thermoelectric Performance of Sn/Sb/Te and Ge/Sb/Te Materials by Cd Doping. Advanced Electronic Materials, 1(12), [1500266]. https://doi.org/10.1002/aelm.201500266