Structure and thermoelectric properties of Ba6Ge(25-x), Ba6Ge23Sn2, and Ba6Ge22In3: Zintl phases with a chiral clathrate structure

Sung Jin Kim, Siqing Hu, Ctirad Uher, Tim Hogan, Baoquan Huang, John D. Corbett, Mercouri G. Kanatzidis

Research output: Contribution to journalArticle

92 Citations (Scopus)

Abstract

A single phase of Ba6Ge(25-x) (x ~ 1) was obtained from a direct element combination reaction in a sealed graphite tube at 830°C. Its structure was determined by single-crystal X-ray diffraction methods. Ba6Ge(25-x) adopts the chiral cubic space group P4132 (No. 213) with dimensions of a = 14.5483(2) Å and Z = 4. The structure consists of helical chains of Ba atom-centered pentagonal dodecahedra, Ba@Ge20, and zeolite-like cages formed by those chains. There are vacancies distributed over the Ge sites giving a composition of Ba6Ge24, in which charge balance according to the Zintl formalism is retained. The compound therefore satisfies the classical Zintl concept. Polycrystalline ingots of Ba6Ge(25-x) showed an electrical conductivity of 2000 S/cm and a Seebeck coefficient of - 18 μV/K at room temperature. An anomalous broad transition in the electrical conductivity and Seebeck coefficient was observed at Å 100 K. Ba6Ge23.32Sn1.68 and Ba6Ge21.93In3.07 as ternary derivatives of Ba6Ge(25-x) were also synthesized and their structural and physical properties compared with those of Ba6Ge(25-x). (C) 2000 Academic Press.

Original languageEnglish
Pages (from-to)321-329
Number of pages9
JournalJournal of Solid State Chemistry
Volume153
Issue number2
DOIs
Publication statusPublished - Jan 1 2000

Keywords

  • Chiral clathrate
  • Electron crystal
  • Phonon gas
  • Thermoelectric
  • Zintl phase

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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