Tin clathrates

The Formation of Silicon, Germanium and Tin Clathrates from the Elements. 

Applying the same recipe to binary germanium and tin clathrates of alkali metals one obtains an unbalanced situation considering a complete host framework ... 

Binary clathrates AgSn44 (A = Rb, Cs) provide an interesting example of a superstructure formation due to the ordering of vacancies within the clathrate framework [49, 70]. As it was pointed out earlier tin clathrates often exhibit vacancies in the framework for the electron precise composition, e.g. (A+),(4/7-Sn°)3g(3h-Sn-) gD2. Two vacancies in the four-bonded framework... 

Table 5.4 Thermoelectric properties of selected tin clathrates at room temperature...

Clathrate hydrates have been known since the early 19th Century, but their formation and nature were only understood a few decades ago . The closely related clathrates of silicon, germanium and tin are more recent °. ... 

The Formation of Clathrates Having a Silicon, Germanium and Tin Host Lattice... 

Type I clathrate structures are synthesized from finely divided Si or Ge powder with potassium vapor at 700°C under low pressure . The homologous Sn compound is formed by melting together stoichiometric amounts of potassium and tin. ... 

In spite of their apparent fragility, the two silicon clathrates proved to be remarkably stable under high pressure and their behavior appeared quite comparable to that of diamond-type silicon in the same experimental conditions. Above 8 and up to 15 GPa, a smooth drop of seven degrees of magnitude was observed, giving a metallic tin-like structure. The sharp transition in the conductivity of Na3Sii36 at 10 GPa was proposed to be used as a pressure calibration standard. 

J.-T. Zhao, J.D. Corbett, Zintl-phase in alkali-metal-Tin systems KgSn25 with condensed pentagonal dodecahedra of tin two AgSn44 phases with a defect clathrate structure. Inorg. Chem. 33, 5721-5726 (1994)... 

Chemistry and Physics of Inverse (Cationic) Clathrates and Tin Anionic Clathrates... 

Keywords Clathrates Cage compounds Crystal structure Thermoelectric materials Tin Germanium Silicon Pnicogens... 

Distribution of atoms of different nature over the framework positions deserves more discussion. It is noticed that the 16 site of the space group Pm3n is always occupied by atoms of the most electronegative elements— phosphorus or arsenic, whereas the most electropositive elements prefer the 24 site. The latter position is always occupied by various metal atoms, including transition metals copper and zinc and p-metals, such as tin and indium. Another important feature is that vacancies form at the 6c or 24k sites but never at the 16 sites. This pattern is remarkably different from that observed for anionic clathrates. In them, electropositive substituents, including group 13 and some transition metals, either exclusively sit on the 6c site or also occupy the 24 site but always avoid the... 

Qualitatively, the semiconducting behavior of the germanium- and tin-based cationic clathrates can be rationalized within the frames of the Zintl counting scheme, assuming the reversed host-guest polarity. In traditional Zintl phases of a general... 

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