New thermoelectric semiconductors Pb5Sb12+xBi6−xSe32 with ultralow thermal conductivity

Ruizhi Yang, Xia Li, Weiping Guo, Zixuan Chen, Hongwei Ming, Zhong-Zhen Luo*, Zhigang Zou

Chin. J. Struct. Chem., 2024, 43: 100268. DOI: 10.1016/j.cjsc.2024.100268

March 15, 2024

Thermoelectric; Semiconductors; Pavonite-type structure; Pb5Sb12+xBi6-xSe32; Mixed occupancies; Ultralow thermal conductivity

ABSTRACT

The five new semiconductors Pb5Sb12+xBi6−xSe32 (x = 0, 1, 2, 3, and 4) were synthesized for the first time, which adopted the pavonite-type structure and crystallized in the monoclinic space group C2/m. The crystal structure was composed of two different types of polyhedral slabs. Slab-I is a galena-like structure motif that forms with [MSe6] (M = Pb, Sb, and Bi) octahedra. Slab-II contains one octahedron [MSe6] block and paired squared pyramids [MSe5]. Pb5Sb12+xBi6−xSe32 exhibits n-type semiconductor behaviors and the remarkable Seebeck coefficient from −64.1 μV K−1 for x = 0 sample to −242 μV K−1 for x = 4 sample at 300 K. Moreover, the Pb5Sb12Bi6Se32 has the highest carrier concentration of 1.35 × 1020 cm−3 in pavonite-type materials. The complex compositions, mixed occupancies of the cations, and quasi-two-dimensional structure lead to the low lattice thermal conductivity (κlat) of less than 0.48 W m−1 K−1 from 300 K to 723 K. In especial, Pb5Sb16Bi2Se32 shows the ultralow κlat of 0.25 W m−1 K−1 at 723 K. As a result, the thermoelectric figure of merit, ZT ∼0.34 at 723 K, was obtained for the intrinsic Pb5Sb12Bi6Se32.
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