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

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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 (former - to 2024)
UEA Research Groups: Faculty of Science > Research Groups > Physical and Analytical Chemistry (former - to 2017)
Faculty of Science > Research Groups > Chemistry of Materials and Catalysis
Faculty of Science > Research Groups > Energy Materials Laboratory
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Depositing User: Pure Connector
Date Deposited: 09 Jun 2017 05:05
Last Modified: 06 Feb 2025 07:14
URI: https://ueaeprints.uea.ac.uk/id/eprint/63717
DOI: 10.1039/C7TC00420F

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