Enhancement in the thermoelectric performance of colusites Cu26A2E6S32 (A = Nb, Ta; E = Sn, Ge) using E-site non-stoichiometry. Issue 17 (11th April 2017)

• Record Type: Journal Article
• Authors: Bouyrie, Yohan; Ohta, Michihiro; Suekuni, Koichiro; Kikuchi, Yuta; Jood, Priyanka; Yamamoto, Atsushi; Takabatake, Toshiro
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 17(2017)
• Page Start: 4174
• Page End: 4184
• Publication Date: 2017-04-11
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7tc00762k
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : The thermoelectric performance of colusite materials Cu26 A2 E6 S32 (A = Nb, Ta; E = Sn, Ge) has been successfully enhanced using E-site non stoichiometry. Value of ZT near unity is achieved at 670 K. Abstract : Colusite-based materials have attracted significant interest in the field of thermoelectrics because of their earth-abundant elements (Cu, S) and high thermoelectric performance. In this study, we demonstrate the enhancement of the thermoelectric figure of merit ZT in colusites Cu26 A2 E6− x S32 (A = Nb, Ta; E = Sn, Ge; x = 0, 0.5) by modifying their chemical composition. Colusite samples were prepared by melting a mixture of their constituent elements in evacuated quartz tubes followed by hot pressing. The electrical resistivity decreased with Sn and Ge contents, leading to an improvement in the power factor. Energy-dispersive X-ray spectroscopy analysis revealed cation-rich compositions in all the colusite samples. The extra cations were most likely formed during the sintering processes, and they effectively scattered heat-carrying phonons, yielding a low total thermal conductivity (<0.80 W K −1 m −1 ). For Cu26 Ta2 Sn6− x S32, scanning electron microscopy analysis revealed the insertion of CuS- and Cu2 S-based microscale precipitates, which further reduced the lattice thermal conductivity. At 670 K, a ZT of ∼1.0 was achieved in Cu26 Ta2 Sn5.5 S32, arising from a power factor of ∼800 μW K −2 m −1 . Moreover, the low total thermal conductivity (∼0.47 W K −1 m −1 at 670 K) in Cu26 Nb2 Ge6.0 S32 leaded to a high ZT of ∼1.0 at 670 K.