Univ. Prof.

Dr. Silke BÜHLER-PASCHEN

QUANTUM MATERIALS GROUP

Schematic representation of rattling guest atoms in a type-I clathrate.
Melt-spinning apparatus for clathrate synthesis by ultrafast cooling.

THERMOELECTRICS

 

Intermetallic clathrates are solids made up of a three-dimensional network of covalently bonded „host“ atoms forming large cavities. These are filled by mostly non-covalently bonded „guest“ atoms. The current interest in these cage compounds derives from their potential as thermoelectric materials: The vibrations („rattling“ or Einstein modes) of the guest atoms within the cages are believed to strongly scatter heat-carrying phonons, and to flatten the dispersion of the acoustic phonons. Both effects reduce the phonon thermal conductivity of the material. The charge carriers are much less affected by the rattling modes, thus leading to an enhanced ratio of electrical to thermal conductivity ?/?. This enhances the thermoelectric figure of merit

 

Z = (?/?)S2 where S is the thermopower.

Our current research focusses on

 

  • the search for and investigation of clathrates with new compositions

  • the use and optimization of the melt-spinning technique for clathrates patented by us in 2008