Maximization of transporting bands for high-performance SnTe alloy thermoelectrics. (June 2019)

• Record Type: Journal Article
• Authors: Tang, J.; Yao, Z.; Chen, Z.; Lin, S.; Zhang, X.; Xiong, F.; Li, W.; Chen, Y.; Pei, Y.
• Is Part Of: Materials today physics. Volume 9(2019)
• Publication Date: 2019-06
• Subjects: Materials science -- Periodicals; Physics -- Periodicals; Electronic journals; 530.41
• DOI: 10.1016/j.mtphys.2019.03.005
• Languages: English
• ISSNs: 2542-5293

Abstract

Abstract: Environment-friendly thermoelectric SnTe has recently attracted much attention as a top candidate for replacing conventional p-type PbTe. Effective strategies leading to great advancements in this material are typified by manipulation of valence bands and chemical defects, among of which MgTe- and Cu2 Te-alloying are particularly successful, respectively, for valence band convergence and lattice thermal conductivity minimization. However, pristine SnTe enables a MgTe solubility of only ∼12%, which might limit the full convergence of possibly transporting bands for an electronic performance maximization. In this work, we show an approach to increase the MgTe solubility up to ∼20%, leading to an involvement of one more highly degenerated valence band Λ for charge transport in addition to existing L and Σ bands. Such a collection of many transporting valence bands enables a great improvement in electronic performance, as well as a significant enhancement in thermoelectric figure of merit with a well-reduced lattice thermal conductivity by the point defects introduced in these SnTe alloys. Graphical abstract: Calculated band structures (a, b, c, d, e) and density of states (f) for SnTe-MgTe alloys. The Fermi level is located at 0 eV. Temperature dependent power factor for Sn0.75+d Ge0.05 Mg0.2 Te(a), and thermoelectric figure of merit for Sn0.75 + d Ge0.05Mg0.2Te(Cu2Te)0.05 (b). Image 1 Highlights: This work successfully increases the MgTe solubility up to ∼20% in SnTe, with the assistant of 5% GeTe-alloying. The increase of MgTe solubility up to ∼20% enables an involvement of one more valence band Λ to be transporting in SnTe. A further Cu2 Te-alloying leads to a reduction in lattice thermal conductivity, resulting in a zT ∼ 1.6 in SnTe alloys.