Electronic structure and thermoelectric properties of pnictogen-substituted A Sn1.5Te1.5 (A Co, Rh, Ir) skutterudites

Alex Zevalkink*, Kurt Star, Umut Aydemir, G. Jeffrey Snyder, Jean Pierre Fleurial, Sabah Bux, Trinh Vo, Paul Von Allmen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Substituting group 14 and 16 elements on the pnictogen site in the skutterudite structure yields a class of valence-precise ternary AX1.5Y1.5 compounds (ACo, Rh, Ir, XSn, Ge, and YS, Se, Te), in which X and Y form an ordered sub-structure. Compared with unfilled binary skutterudites, pnictogen-substituted phases exhibit extremely low lattice thermal conductivity due to increased structural complexity. Here, we investigate the role of the transition metal species in determining the electronic structure and transport properties of ASn1.5Te1.5 compounds with ACo, Rh, Ir. Density functional calculations using fully ordered structures reveal semiconducting behavior in all three compounds, with the band gap varying from 0.2 to 0.45eV. In CoSn1.5Te1.5, the electronic density of states near the gap is significantly higher than for AIr or Rh, leading to higher effective masses and higher Seebeck coefficients. Experimentally, Ir and Rh samples exhibit relatively large p-type carrier concentrations and degenerate semiconducting behavior. In contrast, CoSn1.5Te1.5 shows mixed conduction, with n-type carriers dominating the Seebeck coefficient and light, high mobility holes dominating the Hall coefficient. zT values of up to 0.35 were obtained, and further improvement is expected upon optimization of the carrier concentration or with n-type doping.

Original languageEnglish (US)
Article number035107
JournalJournal of Applied Physics
Volume118
Issue number3
DOIs
StatePublished - Jul 21 2015

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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