Thermoelectric properties of chlorine doped compounds of In₄Se_2.7Cl_x

Thermoelectric properties were investigated on the chlorine doped In₄Se_2.7Cl_x (0.0 ≤ x ≤ 0.05) polycrystalline materials. The chlorine doping has an effect of increasing chemical potential by electron doping, resulting in the increase of electrical conductivity. While the thermal conductivity κ(T) of chlorine doped compounds are increased at mid-temperature range, the κ(T)s of Cl-doped compounds are comparably small or decreased at high temperature range (T ≥ 275 °C). By virtue of decrease of the electrical resistivity and high Seebeck coefficient, power factors S²σ of chlorine doped compounds are increased at high temperature range (T ≥ 275 °C). The maximum ZT of In₄Se_2.7Cl_0.03 reaches about 0.67 at 400 °C, which is 59% improved result comparing with the undoped compound. The control of the Se-deficiency and chlorine doping concentration with optimized materials process routes can increase the ZT on the order of unity or more on those compounds.