Electronic structure and thermoelectric properties of clathrate compounds Ba8AlxGe46-x

Thermoelectric properties of Al-substituted Ge clathrate compounds Ba8AlxGe46-x were investigated experimentally and theoretically. Polycrystalline Ba8AlxGe46-x (x=12-18) was synthesized by using an arc melting and a spark plasma sintering technique. The obtained samples show the n-type behavior and the carrier concentration decreases with increasing amount of Al composition from x=12 to 16. The reasonably large power factors was obtained: 900-1000 mu W/cm K-2 around 900 K. Theoretically electronic structure of Ba8Al16Ge30 was calculated by means of a first-principles method and then thermoelectric properties were analyzed on the basis of the result of the calculated electronic structure. The calculated thermoelectric properties agree with the experimental results very well in the wide range of temperature between room temperature and 900 K. (c) 2008 American Institute of Physics.