Investigation of substitution effects and the phase transition in type-I clathrates RbxCs8-xSn442 (1.3≤x≤2.1) using single-crystal X-ray diffraction, Raman spectroscopy, heat capacity and electrical resistivity measurements

Andreas Kaltzoglou, Thomas F. Fässler, Christian Gold, Ernst Wilhelm Scheidt, Wolfgang Scherer, Tetsuji Kume, Hiroyasu Shimizu

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Abstract

The substitution of cations in RbxCs8-xSn442(1.3≤x≤2.1) is reported. The compounds crystallize at room temperature in the space group la over(3, -) d adopting the type-I clathrate 2×2×2 superstructure with partly ordered framework vacancies (□), whereas at higher temperatures they transform to the primitive, more disordered modification (space group Pm over(3, -) n). The guest atom distributions in the Sn cages on the Rb: Cs ratios is studied by means of single-crystal X-ray diffraction for Rb2.1(1)Cs5.8(1)Sn44 at T=293 K (1), Rb1.42(8)Cs6.58(8)Sn44 at T=293 K (2a), Rb1.46(5)Cs6.54(5)Sn44 at T=373 K (2b) and Rb1.32(8)Cs6.68(8)Sn44 at T=293 K (3). The structural order-disorder phase transition influences the electrical resistivity. The hysteresis observed for the electrical resistivity in combination with the symmetric shape of the specific heat anomaly suggests that the transformation is of first-order type and is characterized by an entropy change of about 2.5 J mol-1 K-1. The Raman spectrum for the low-temperature modification of 2 is also reported.

Original languageEnglish
Pages (from-to)2924-2929
Number of pages6
JournalJournal of Solid State Chemistry
Volume182
Issue number10
DOIs
StatePublished - Oct 2009

Keywords

  • Alkali metals
  • Cation substitution
  • Electrical conductivity
  • Heat capacity
  • Raman spectroscopy
  • Type-I clathrates

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