The role of excess Sn in Cu4Sn7S16 for modification of the band structure and a reduction in lattice thermal conductivity

He, Tongtong, Lin, Naiming, Du, Zhengliang, Chao, Yimin and Cui, Jiaolin (2017) The role of excess Sn in Cu4Sn7S16 for modification of the band structure and a reduction in lattice thermal conductivity. Journal of Materials Chemistry C, 5 (17). pp. 4206-4213. ISSN 2050-7526

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Abstract

In this work, we have investigated the band structures of ternary Cu4Sn7+xS16 (x = 0–1.0) compounds with an excess of Sn, and examined their thermoelectric (TE) properties. First principles calculations reveal that the excess Sn, which exists as Sn2+ and is preferentially located at the intrinsic Cu vacancies, unpins the Fermi level (Fr) and allows Fr to enter the conduction band (CB) at x = 0.5. Accordingly, the Hall carrier concentration (nH) is enhanced by about two orders of magnitude when the x value increases from x = 0 to x = 0.5. Meanwhile, the lattice thermal conductivity (κL) is reduced significantly to 0.39 W K−1 m−1 at 893 K, which is in reasonably good agreement with the estimation using the Callaway model. As a consequence, the dimensionless TE figure of merit (ZT) of the compound Cu4Sn7+xS16 with x = 0.5 reaches 0.41 at 863 K. This value is double that of the stoichiometric Cu4Sn7S16, proving that excess Sn in Cu4Sn7S16 is beneficial for improving the TE performance.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Related URLs:
Depositing User: Pure Connector
Date Deposited: 09 Jun 2017 05:05
Last Modified: 25 Jun 2020 00:11
URI: https://ueaeprints.uea.ac.uk/id/eprint/63717
DOI: 10.1039/C7TC00420F

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