Enhanced thermoelectric properties of Zn-doped GaSb nanocomposites

In this work, Zn-doped GaSb nanocomposites (Ga_1- Zn Sb, x = 0.002, 0.005, 0.01, and 0.015) have been synthesized via ball milling followed by hot pressing. It is shown that thermoelectric properties of the synthesized Ga_1- Zn Sb nanocomposites vary with both the grain size and the Zn content. The grain boundaries formed in the nanocomposites not only scatter phonons and reduce thermal conductivity, but also trap charge carriers and reduce electrical conductivity. Zn doping is adopted to compensate for the trapping effect of grain boundaries on carrier transport in order to enhance the thermoelectric figure of merit, ZT, of Ga_1- Zn Sb alloys. By optimizing the amount of Zn doping, the maximum ZT value was found to be 0.087 at 500 K for Ga_0.99Zn_0.01Sb nanocomposites, which is 51% higher than the reported value in the literature for bulk Ga_1- Zn Sb alloys.