Enhanced thermoelectric properties of p-type argyrodites Cu8GeS6 through Cu vacancy

Cu8GeS6 compound with room temperatures orthorhombic phase, high temperatures cubic phase and the low intrinsic lattice thermal conductivity is a potential thermoelectric material. However, its performance is limited by low electrical conductivity. In this study, p-type polycrystalline Cu8(1-x)GeS6...

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Bibliographic Details
Published in:Journal of alloys and compounds 2020-05, Vol.822, p.153665, Article 153665
Main Authors: Fan, Yijing, Wang, Guoyu, Wang, Rui, Zhang, Bin, Shen, Xingchen, Jiang, Pengfei, Zhang, Xiao, Gu, Hao-shuang, Lu, Xu, Zhou, Xiao-yuan
Format: Article
Language:English
Subjects:
Argyrodites
Carrier density
Chemical synthesis
Copper
Cu8GeS6
Cubic lattice
Density functional theory
Electrical resistivity
Fabrication method
Hot pressing
Lattice vacancies
Mathematical analysis
Orthorhombic phase
Room temperature
Solid phases
Thermal conductivity
Thermoelectric materials
Thermoelectric properties
Thermoelectricity
Valence band
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Summary:Cu8GeS6 compound with room temperatures orthorhombic phase, high temperatures cubic phase and the low intrinsic lattice thermal conductivity is a potential thermoelectric material. However, its performance is limited by low electrical conductivity. In this study, p-type polycrystalline Cu8(1-x)GeS6 (x = 0.03, 0.05, 0.08, 0.10) are successfully synthesized through solid-phase reaction and hot pressing. The electrical conductivity of the wide band gap semiconductor Cu8GeS6 as verified by the density functional theory (DFT) calculation can be greatly enhanced by intentionally introduced Cu vacancy. Also, the calculation indicates that the top of valence band is mainly comprised of the Cu 3d orbitals. As a consequence, the Hall carrier concentrations are significantly enhanced to ∼1018 cm−3 with Cu vacancy. Owing to the improved electrical conductivity, the compound with nominal composition of Cu7.36GeS6 reaches a maximum zT ∼0.29 at 819 K. •The first systematic experimental investigation on thermoelectric properties of Cu8GeS6 compounds.•Cu vacancy can effectively create holes, leading to a markedly increased n and a considerably enhanced σ.•The intrinsically κL associated with enlarged σ leads to a peak zT ∼ 0.29 at 819 K for Cu7.36GeS6.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2020.153665