Transport properties of tin clathrates

Transport data on tin compounds with the type-I clathrate crystal structure are reported. The data illustrates why these materials are of interest for thermoelectric applications. In general, the incoherent "rattling" of the "guest" atoms in the "cages" of these open structured materials results in thermal conductivities that are atypical of simple crystalline materials, in magnitude and temperature dependence, while possessing semiconducting electronic transport properties. The results on a number of tin clathrates are presented for the first time.