Syntheses and Characterization of Ternary Alkali-Metal Silicon or Tin Clathrates and Li-Rich Silicides

A8Al8Si38 (A = K, Rb and Cs), K8Zn3.5Si42.5, Rb7.9Zn3.6Si42.4 and Cs8-xGa8-ySi38+y clathrates were obtained by a combined flux method. Their crystal structure and thermoelectric properties are presented. Rb8Tl1.71Sn42.54 * 1.5 and Cs8Tl0.75Sn43.54 * 1.71 represent a new type of superstructure for type-I clathrates. Thermoelectric properties for K8Zn4Sn42 are presented.

Li15-xAlxSi4, Li15-xMgxSi4, Li14.1Zn0.9Si4 and Li17-e-sZneSi4 were obtained by Li flux and/or conventional high temperature synthesis. Crystal structures and their thermodynamic stability are discussed.