Valence Band Modification and High Thermoelectric Performance in SnTe Heavily Alloyed with MnTe

Gangjian Tan, Fengyuan Shi, Shiqiang Hao, Hang Chi, Trevor P. Bailey, Li Dong Zhao, Ctirad Uher, Chris Wolverton, Vinayak P. Dravid, Mercouri G. Kanatzidis*

*Corresponding author for this work

Research output: Contribution to journalArticle

197 Scopus citations

Abstract

We demonstrate a high solubility limit of >9 mol% for MnTe alloying in SnTe. The electrical conductivity of SnTe decreases gradually while the Seebeck coefficient increases remarkably with increasing MnTe content, leading to enhanced power factors. The room-temperature Seebeck coefficients of Mn-doped SnTe are significantly higher than those predicted by theoretical Pisarenko plots for pure SnTe, indicating a modified band structure. The high-temperature Hall data of Sn1-xMnxTe show strong temperature dependence, suggestive of a two-valence-band conduction behavior. Moreover, the peak temperature of the Hall plot of Sn1-xMnxTe shifts toward lower temperature as MnTe content is increased, which is clear evidence of decreased energy separation (band convergence) between the two valence bands. The first-principles electronic structure calculations based on density functional theory also support this point. The higher doping fraction (>9%) of Mn in comparison with ∼3% for Cd and Hg in SnTe gives rise to a much better valence band convergence that is responsible for the observed highest Seebeck coefficient of ∼230 μV/K at 900 K. The high doping fraction of Mn in SnTe also creates stronger point defect scattering, which when combined with ubiquitous endotaxial MnTe nanostructures when the solubility of Mn is exceeded scatters a wide spectrum of phonons for a low lattice thermal conductivity of 0.9 W m-1 K-1 at 800 K. The synergistic role that Mn plays in regulating the electron and phonon transport of SnTe yields a high thermoelectric figure of merit of 1.3 at 900 K.

Original languageEnglish (US)
Pages (from-to)11507-11516
Number of pages10
JournalJournal of the American Chemical Society
Volume137
Issue number35
DOIs
StatePublished - Sep 9 2015

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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