Six Quaternary Chalcogenides of the Pavonite Homologous Series with Ultralow Lattice Thermal Conductivity

Jing Zhao, Shiqiang Hao, Saiful M. Islam, Haijie Chen, Gangjian Tan, Shulan Ma, Christopher Wolverton, Mercouri G Kanatzidis

Research output: Contribution to journalArticle

Abstract

Six new quaternary chalcogenides belonging to the pavonite sulfosalt mineral family with the general formula M n+1 (Bi/Sb) 2 Q n+5 (n = 2-7) were synthesized by direct reactions of the elements at high temperatures. The compounds include InPbBi 3 S 7 (n = 2), In 0.5 Mn 2 Bi 3.5 Se 8 (n = 3), CdPb 2 Bi 4 S 9 (n = 4), Ag 1.5 CdBi 5.5 Se 10 (n = 5), Ag 2 CdBi 6 Se 11 (n = 6), and Ag 2.5 CdSb 6.5 Se 12 (n = 7) and crystallized in the monoclinic space group C2/m. The pavonite structure consists of two alternating slabs, a thinner slab composed of pairs of monocapped trigonal prisms separated by octahedra and a thicker slab with a galena-like structure motif. In the general formula, n corresponds to the number of octahedra along the diagonal direction of the galena-like slab. The complex compositions, mixed occupancies of the cations, and quasi-two-dimensional structures endow compounds of this family with extremely low thermal conductivity. The charge and thermal transport properties of CdPb 2 Bi 4 S 9 and CdAg 2 Bi 6 Se 11 were characterized from 300 to 810 K, and both materials exhibited n-type semiconductor behaviors and ultralow lattice thermal conductivities of less than 0.35 W·m -1 ·K -1 for CdAg 2 Bi 6 Se 11 and 0.73 W·m -1 ·K -1 for CdPb 2 Bi 4 S 9 in the measured temperature range. Density functional theory calculations revealed the origins of this low lattice thermal conductivity to be a combination of the low Debye temperature, small phonon velocities, and large Grüneisen parameters. Thermoelectric properties were measured, and the highest ZT values of 0.53 and 0.95 for undoped CdPb 2 Bi 4 S 9 and CdAg 2 Bi 6 Se 11 , respectively, were attained at 775 K.

Original languageEnglish
Pages (from-to)3430-3439
Number of pages10
JournalChemistry of Materials
Volume31
Issue number9
DOIs
Publication statusPublished - May 14 2019

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ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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