Threefold enhancement of the thermoelectric figure of merit for pressure tuned Sr8Ga16Ge30

Semiconducting germanium clathrates are thermoelectric materials with cage- like structures that exhibit "phonon glass, electron crystal" behavior. We report an improvement by at least a factor of 3 in the dimensionless thermo electric figure of merit for the clathrate semiconductor Sr8Ga16Ge30 upon c ompression to 7 GPa. These results suggest that there is potential for furt her improving the thermoelectric properties of this material at ambient pre ssure by chemical or other methods. (C) 2001 American Institute of Physics.