Synthesis and Investigations of type I and II clathrates of Group 14

Clathrates are a class of new materials that have an open-framework structure that allows guest atoms or molecules to be enclosed inside of their polyhedral framework. Varying the number, weight, and size of the guest species in a particular framework allows one to alter the physical properties of the clathrate. This relationship enables one to further the fundamental understanding of the physics and chemistry of the clathrate structure and use this knowledge to tune certain properties. This tunability of inorganic clathrates is of great interest as it allows one to optimize their physical properties; making them promising candidates for a range of applications such as thermoelectric, optoelectronic, and superconductivity. In this study, new synthesis methods of type I and II clathrates of group 14 are introduced, along with two new compositions of type I clathrates. A new synthesis method used to produce single crystal and microcrystalline Na8Si46 and Na24Si136 clathrates by the spark plasma sintering technique is introduced. Microcrystalline type I Na8Si46 and type II Na24Si136 are also selectively synthesized with no phase impurity of the other type using the low temperature ionic liquid method. In addition, the synthesis of microcrystalline Na8Ge3Si38 and single crystal Ba2Cs6Ga8Sn38 type I clathrates are presented for the first time