Crystal structure and thermoelectric properties of clathrate, Ba 8Ni 3.5Si 42.0: Small cage volume and large disorder of the guest atom

John H. Roudebush, Mike Orellana, Sabah Bux, Tanghong Yi, Susan M. Kauzlarich

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Samples with the type-I clathrate composition Ba 8Ni xSi 46-x have been synthesized and their structure and thermoelectric properties characterized. Microprobe analysis indicates the Ni incorporation to be 2.62≤x≤3.53. The x=3.5 phase crystallizes in the type-I clathrate structure (space group: Pm-3n) with a lattice parameter of 10.2813(3) Å. The refined composition was Ba 8Ni 3.5Si 42.0, with small vacancies, 0.4 and 0.5 atoms per formula unit, at the 2a and 6c sites, respectively. The position of the Ba2 atom in the large cage was modeled using a 4-fold split position (24j site), displaced 0.18 Å from the cage center (6d site). The volume of the large cage is calculated to be 146 Å 3, smaller than other clathrates with similar cation displacement. The sample shows n-type behavior with a maximum of -50 μV/K at 823 K above which the Seebeck coefficient decreases, suggesting mixed carriers. Lattice thermal conductivity, κ l, is 55 mW/K above 600 K.

Original languageEnglish (US)
Pages (from-to)102-108
Number of pages7
JournalJournal of Solid State Chemistry
Volume192
DOIs
StatePublished - Aug 2012

Keywords

  • Cation disorder
  • Crystal structure
  • Thermoelectrics
  • Type-I clathrate
  • Vacancies

ASJC Scopus subject areas

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

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