Two-Dimensional CsAg5Te3- xSx Semiconductors: Multi-anion Chalcogenides with Dynamic Disorder and Ultralow Thermal Conductivity

James M. Hodges, Yi Xia, Christos D. Malliakas, Grant C.B. Alexander, Maria K.Y. Chan, Mercouri G. Kanatzidis*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Metal chalcogenides underpin a wide variety of energy-related applications and are ideal systems for probing lattice dynamics and fundamental transport phenomena. Here we describe the synthesis and transport properties of CsAg5TeS2 and its solid solution CsAg5Te3-xSx (x = 1-2), new semiconductors with tunable band gaps ranging from 0.17 to 0.30 eV. CsAg5TeS2 has a fully ordered two-dimensional structure that includes a group of Ag atoms in a heteroleptic tetrahedral coordination geometry (AgTe2S2). Single-crystal X-ray diffraction indicates that the compounds crystallize in the tetragonal space group P4/mmm, while pair distribution function (PDF) analysis reveals off-centering at the heteroleptic Ag sites, signifying the lower-symmetry I4/mcm space group. The underlying disorder acts as a phonon-blocking mechanism that helps facilitate an ultralow lattice thermal conductivity below 0.40 W·m-1·K-1 at ∼300 K, highlighting the importance of local disorder in thermal transport. Density functional theory provides additional insight into the electronic and thermal properties of the materials, which are good candidates for p-type thermoelectrics.

Original languageEnglish (US)
Pages (from-to)7245-7254
Number of pages10
JournalChemistry of Materials
Issue number20
StatePublished - Oct 23 2018

ASJC Scopus subject areas

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

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