Some properties of Re/sub 2/Te/sub 5/-based materials

Re/sub 2/Te/sub 5/ is a semiconducting compound with an energy band gap of about 0.8 eV. It has a relatively complex crystal structure with 84 atoms per unit cell. Initial results obtained at the Jet Propulsion Laboratory on p-type polycrystalline samples showed that they possess large Seebeck coefficient values but also large electrical resistivity values. They also exhibit very low thermal conductivity with a room temperature value of 13 mW/cmK. Another attractive feature of Re/sub 2/Te/sub 5/ is the possibility of inserting a variety of atoms in the large voids (2.8 /spl Aring/ in diameter) of the crystal structure to form Re/sub 6/M/sub 2/Te/sub 15/ filled compositions. The void fillers could act as phonon scattering centers, further reducing the thermal conductivity in these materials. As part of an effort to evaluate the potential of Re/sub 2/Te/sub 5/-based materials for thermoelectric applications, we are currently exploring the synthesis and properties of filled compositions as well as n-type Re/sub 2/Te/sub 5/ samples. We present and discuss in this paper initial results obtained on Fe and Ag doped Re/sub 2/Te/sub 5/ samples.