Two Mixed-Anion Semiconductors in the Ba–Sn–Te–S System with Low Thermal Conductivity

• Published in: ACS applied energy materials Vol. 6; no. 4; pp. 2508 - 2514
• Main Authors: Guo, Weiping, Huang, Qing, Zhang, Wei-Long, Chen, Da-Gui, Chen, Anita, Ang, Edison Huixiang, Cui, Hong-Hua, Luo, Zhong-Zhen, Zou, Zhigang
• Format: Journal Article
• Language: English
• Published: American Chemical Society 27.02.2023
• Subjects: Ba7Sn3Te0.839S12.161; thermoelectric; Ba5Sn2Te1.327S7.673; thermal conductivity; 0D architecture
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.2c03941

We synthesized two mixed-anion tin chalcogenides, Ba5Sn2Te1.327S7.673 (1) and Ba7Sn3Te0.839S12.161 (2), by a typical high-temperature solid-state reaction using an evacuated silica tube for the first time in the system of Ba–Sn–Q (Q = S1–x Te x ; 0 ≤ x ≤ 1). Compound 1 crystallizes in the monoclinic space group P21/c with unit cell parameters of a = 17.501(5) Å, b = 8.908(2) Å, c = 12.508(3) Å, and Z = 4. Compound 2 has an orthorhombic space group Pnma with a = 12.386(5) Å, b = 24.17(2) Å, c = 8.872(4) Å, and Z = 4. The structures of compounds 1 and 2 are both zero-dimensional (0D), and the formulas can be written as Ba5(SnIVQ4)2Q and Ba7(SnIVQ4)3Q with Sn/Q ratios of 2/9 and 3/13, respectively. Compounds 1 and 2 exhibit Q2– anion units, which is unique among Ba–Sn−Q compounds due to the [SnQ4] tetrahedra and low Sn/Q ratios. The phonon transport can be significantly scattered because the weakly bond Ba atom and highly distorted [SnQ4] tetrahedra can enhance the lattice anharmonicity. As a result, compounds 1 and 2 have low lattice thermal conductivity (κlat) values of ∼0.3–0.4 W m–1 K–1 in the range of 300 to 773 K, which results in a design strategy as thermoelectric materials.