Structural, chemical, and transport properties of a new clathrate compound:: Cs8Zn4Sn42

The synthesis and structural, chemical, and transport properties of a new clathrate compound with elemental composition Cs8Zn4Sn42 is reported. This compound is cubic with space group Pm(3) over bar n and a lattice parameter of 12.1226(19) Angstrom. Single-crystal X-ray diffraction and structural refinement indicate that Cs atoms reside in the polyhedral cavities formed by the tetrahedrally bonded network of Zn and Sn atoms. The Cs atom in the larger polyhedra (tetrakaidecahedra) exhibit greater and more anisotropic thermal motion than those of the smaller polyhedra (dodecahedra). This "rattling" of the Cs contributes to the low thermal conductivity of this compound, obtained on a polycrystalline pellet. In addition, Zn is ordered in this compound. Electronic properties and the potential of this type of Sn-clathrate for thermoelectric applications are also discussed.