ICT2014 Abstracts

Intermetallic clathrates based on the group 14 elements Si, Ge, and Sn are known to have a high potential as thermoelectric materials. This study focuses on a subset of such compounds in the systems A-Cu-Sn and A-Zn-Sn (A = K, Rb, Cs).  The two new series of tin-based clathrates have formuale A₈Cu_2.67Sn_43.33 and A₈Zn₄Sn₄₂ (A = K, Rb, Cs), respectively, and crystallize in the cubic type-I structure (space group Pm-3n).  The framework of these cage compounds is made up by 46 atoms on the three sites 24k, 16i and 6c.  Both 24k and 16i sites are exclusively occupied by tin, while the 6c site is where the statistical substitution of Sn with Cu or Zn metal atoms occurs. The cages in the structure are filled completely with alkali metals.  Structure refinements based on single x-ray diffraction data indicate that in the larger tetrakaidecahedral cages, the larger Cs atoms remain at the center, whereas the smaller K and Rb atoms are displaced off-center. Thermoelectric property measurements were carried out on single crystals of A₈Cu_2.67Sn_43.33 with A = K and Cs and A₈Zn₄Sn₄₂ with A = K and Rb. The results of temperature depending measurements of the Seebeck coefficients (300 – 500 K) and electrical resistivity (100 – 400 K) will be presented and compared.