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Atomic-scale phonon scatterers in thermoelectric colusites with a tetrahedral framework structure

Abstract : Copper-based chalcogenides with tetrahedral framework structures have been attracting increasing attention as environmentally friendly thermoelectric materials. A representative group of such thermoelectric chalcogenides is the Cu26A2M6S32 (A = V, Nb, Ta; M = Ge, Sn) family of colusites, which exhibit low electrical resistivity, a large Seebeck coefficient, and low thermal conductivity; these properties are necessary for efficient thermal-to-electronic energy conversion. Here, we show the impact of crystal structure on the lattice thermal conductivity of colusite with A = Nb, M = Sn. The crystal structure can be modified by controlling the cationic compositions and the deficiency in the sulfur content as Cu26−xNb2Sn6+xS32−δ. The Cu/Sn ratio is found to be the key parameter for exsolution into distinct phases with ordered and disordered arrangements of cations. For the ordered-structure phase, sulfur sublimation induces atomic-scale defects/disordered states including interstitial defects, anti-site defects, and site splitting, which function as strong phonon scatterers, and the lowest lattice thermal conductivity of ∼0.5 W K−1 m−1 is achieved for the modified ordered structure. This finding provides a simple approach to modifying the crystal structure of thermoelectric chalcogenides via the loss of anions to reduce their lattice thermal conductivity.
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https://hal-normandie-univ.archives-ouvertes.fr/hal-02274207
Contributor : Emmanuel Guilmeau <>
Submitted on : Thursday, August 29, 2019 - 3:43:09 PM
Last modification on : Friday, January 24, 2020 - 11:22:07 AM

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Koichiro Suekuni, Yuta Shimizu, Eiji Nishibori, Hidetaka Kasai, Hikaru Saito, et al.. Atomic-scale phonon scatterers in thermoelectric colusites with a tetrahedral framework structure. Journal of Materials Chemistry A, Royal Society of Chemistry, 2019, 7 (1), pp.228-235. ⟨10.1039/c8ta08248k⟩. ⟨hal-02274207⟩

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