Gallium Antimonide-Doped Germanium Clathrate––A p-Type Thermoelectric Cage Structure

A germanium clathrate compound doped with gallium antimonide has been synthesized and characterized. The structure of Ba8Ga16(GaSb)xGe30-2x with x=2 was determined using single-crystal X-ray analysis, and the Sb atoms were found to be selectively sited. A slight excess of antimony was confirmed by microprobe elemental analysis, resulting in uncompensated doping of the framework. A positive and relatively high Seebeck coefficient of 100 MU V/K indicates this compound is a potential p-type thermoelectric material. Single-crystal temperature-dependent conductivity indicates that the sample behaves as a poor metal. This is the first example of p-doping reported for clathrates.