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

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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.

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

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Publication details

The article was received on 24 Aug 2018, accepted on 27 Nov 2018 and first published on 28 Nov 2018


Article type: Paper
DOI: 10.1039/C8TA08248K
Citation: J. Mater. Chem. A, 2019, Advance Article
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    Atomic-scale phonon scatterers in thermoelectric colusites with a tetrahedral framework structure

    K. Suekuni, Y. Shimizu, E. Nishibori, H. Kasai, H. Saito, D. Yoshimoto, K. Hashikuni, Y. Bouyrie, R. Chetty, M. Ohta, E. Guilmeau, T. Takabatake, K. Watanabe and M. Ohtaki, J. Mater. Chem. A, 2019, Advance Article , DOI: 10.1039/C8TA08248K

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