Electronic structure and thermoelectric properties of pnictogen-substituted ASn{sub 1.5}Te{sub 1.5} (A = Co, Rh, Ir) skutterudites
- Thermal Energy Conversion Technologies Group, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)
- Department of Materials Science, California Institute of Technology, 1200 E California Blvd, Pasadena, California 91125 (United States)
- Instrument Software and Science data systems Group, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)
Substituting group 14 and 16 elements on the pnictogen site in the skutterudite structure yields a class of valence-precise ternary AX{sub 1.5}Y{sub 1.5} compounds (A = Co, Rh, Ir, X = Sn, Ge, and Y = S, 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 ASn{sub 1.5}Te{sub 1.5} compounds with A = Co, 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 0.45 eV. In CoSn{sub 1.5}Te{sub 1.5}, the electronic density of states near the gap is significantly higher than for A = Ir 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, CoSn{sub 1.5}Te{sub 1.5} 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.
- OSTI ID:
- 22489531
- Journal Information:
- Journal of Applied Physics, Vol. 118, Issue 3; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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