TY - JOUR
T1 - Atomic-scale phonon scatterers in thermoelectric colusites with a tetrahedral framework structure
AU - Suekuni, Koichiro
AU - Shimizu, Yuta
AU - Nishibori, Eiji
AU - Kasai, Hidetaka
AU - Saito, Hikaru
AU - Yoshimoto, Daichi
AU - Hashikuni, Katsuaki
AU - Bouyrie, Yohan
AU - Chetty, Raju
AU - Ohta, Michihiro
AU - Guilmeau, Emmanuel
AU - Takabatake, Toshiro
AU - Watanabe, Kosuke
AU - Ohtaki, Michitaka
N1 - Funding Information:
K. S. is grateful to S. Hata for his guidance with the TEM analysis. The synchrotron radiation experiments were performed at BL02B2 of SPring-8 (Proposal No. 2017B0074, 2018A0074). This work was supported nancially by grant from the International Joint Research Program for Innovative Energy Technology funded by METI, JSPS KAKENHI Grant No. JP17H04951 (K. S.), JP17H05328 (E. N.), and CREST JST Grant No. JPMJCR16Q6, Japan.
PY - 2019
Y1 - 2019
N2 - 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.
AB - 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.
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U2 - 10.1039/c8ta08248k
DO - 10.1039/c8ta08248k
M3 - Article
AN - SCOPUS:85058854000
SN - 2050-7488
VL - 7
SP - 228
EP - 235
JO - Journal of Materials Chemistry A
JF - Journal of Materials Chemistry A
IS - 1
ER -