Effects of in-doping on the thermoelectric properties of β-Zn4Sb3

Thermoelectric properties of β-Zn4Sb3 can be improved by doping with In. Solubility limit of In substituting Zn in the β-Zn4Sb3 matrix is determined to be ∼3.5 at% according to EDS and WDS analyses. The carrier concentration is decreased by In-doping, leading to increased electrical resistivity and Seebeck coefficient of the compound. At a low doping level (x<0.02), the power factors of the doped samples are close to that of the undoped binary one. However, the power factor decreases at a high doping level. Thermal conductivity is decreased by the doping mainly due to a solid solution effect from dissolved In. Consequently, a noticeable enhancement in ZT is attained by (Zn0.995In0.005)4Sb3 whose thermal conductivity is ∼20% lower than the undoped one.