Effects of Te doping on the transport and thermoelectric properties of Zn4Sb3

The transport and thermoelectric properties of Te-doped Zn4Sb3 compounds, Zn4(Sb1−xTex)3 (x = 0, 0.005 and 0.02), were investigated. The results showed that thermal conductivity of the Te-doped compounds were reduced remarkably as compared to that of Zn4Sb3 presumably due to enhanced impurity (dopant) scattering of phonons. Thermopower S was found to decrease with increase in Te content, which could be ascribed to the excess Zn in the doped compounds acting as p-type dopant that leads to an increase in the carrier concentration. Moreover, it was found that the β to α phase transition of Zn4Sb3 could be completely prohibited by Te doping. The figure of merit, ZT, for doped compounds was greater than the un-doped Zn4Sb3 for the temperature range investigated. In particular, the ZT of Zn4(Sb0.995Te0.005)3 reached a value of 1.08 at 680 K, which is 69% greater than that of the un-doped Zn4Sb3 obtained in this study.