Synthesis and Physical Properties Investigations of Intermetallic Clathrates

Intermetallic clathrates have long been of interest for materials science research. The promise these materials hold for useful applications ranges from thermoelectrics to photovoltaics and optoelectronics to potentially ultra-hard materials and magnetic cooling applications. Their unique physical properties are intimately related to their intriguing structural properties. Thus a fundamental understanding of the chemistry and physics of inorganic clathrates offers the possibility to assess their potential for use in the various applications mentioned above. The purpose of the current work is to expand the current knowledge of the synthetic routes for obtaining clathrate materials, their structural, chemical, and physical properties, particularly those that from in the type I, II and VIII crystal structures. New synthesis routes are presented and used for preparation of single crystals of Na8Si46 and Na24Si136. Single-crystal X-ray analysis, and resistivity, Seebeck coefficient and thermal conductivity measurements are presented. In addition, two inverse clathrates with compositions Sn24P19.3Br8 and Sn17Zn7P22Br8 have been characterized in terms of their transport properties. Since the magnetic refrigeration based on the magnetocaloric effect is a topic of great interest, type VIII Eu8Ga16Ge30 clathrates are also explored in terms of their application for magnetic cooling