Semiconductor clathrates: a pgec system with potential for thermoelectric applications

摘要

An investigation into the s tructural, chemical, electronic, and themral properties of polycrystalline semiconductor clatherate compounds with different "guest" ions in the viods of these structures is presently underway by the author and his colleges. Despite the wellpdefined crystalline structure of these semiconductor materials, the thermal conductivity shows a magnitude and temperature dependence more typical of amorphous materials than crystalline materials. The localizaed low fequency vigrations of these "guest" ions is believed to interact with the acoustic phonons of the host lattice resulting in a very low thermal conductivity. Indeed in the case of Ge-clathrates a "glass-like" thermal conductivity was observed. The markedly low thermal conductivity displayed by these semiconductor materials. along with the high power factors, demonstrates the potential of this material system for thermoelectric applications.