Electronic structure and thermoelectric properties of Sn1.2- xNb x Ti0.8S3 with a quasi-one-dimensional structure

Koichiro Suekuni, Hidetomo Usui, Siying Qiao, Katsuaki Hashikuni, Tatsuya Hirano, Hirotaka Nishiate, Chul Ho Lee, Kazuhiko Kuroki, Kosuke Watanabe, Michitaka Ohtaki

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2 Citations (Scopus)

Abstract

We report the electronic structure and thermoelectric properties of a tin titanium trisulfide, Sn1.2Ti0.8S3. The crystal structure is composed of infinite "ribbons" of double edge-sharing (Sn4+/Ti4+)S6 octahedra capped by Sn2+. First-principles calculations predict a nearly unidirectional transport of electrons along the ribbon axis for a single crystal and the existence of lone-pair electrons on Sn2+. Experiments on polycrystalline pressed samples demonstrate that Sn1.2Ti0.8S3 exhibits semiconducting temperature dependence of electrical resistivity and a large negative Seebeck coefficient at room temperature. Substitution of Nb5+ for Sn4+ at the octahedral sites increases the electron carrier concentration, leading to an enhancement of the thermoelectric power factor. Anisotropy in the electronic properties is weak because of a weak orientation of the ribbon axis of crystallites in the pressed sample. The lattice thermal conductivity is less than 1 W K-1 m-1 for the pristine and substituted samples, which is attributed to weak bonding between the ribbons via the lone-pair electrons of Sn2+ and to random occupation of Sn4+, Ti4+, and Nb5+ at the octahedral sites.

Original languageEnglish
Article number175111
JournalJournal of Applied Physics
Volume125
Issue number17
DOIs
Publication statusPublished - May 7 2019

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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