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

Koichiro Suekuni, Yuta Shimizu, Eiji Nishibori, Hidetaka Kasai, Hikaru Saito, Daichi Yoshimoto, Katsuaki Hashikuni, Yohan Bouyrie, Raju Chetty, Michihiro Ohta, Emmanuel Guilmeau, Toshiro Takabatake, Kosuke Watanabe, Michitaka Ohtaki

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

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 Cu 26 A 2 M 6 S 32 (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 Cu 26-x Nb 2 Sn 6+x S 32-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.

Original languageEnglish
Pages (from-to)228-235
Number of pages8
JournalJournal of Materials Chemistry A
Volume7
Issue number1
DOIs
Publication statusPublished - 2019

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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