Thermoelectric Transport Properties of Sb-doped SnSe₂ Polycrystalline Alloys

SnSe₂ alloys have been investigated in recent times as potential n-type thermoelectric materials. In this study, the thermoelectric transport properties of a series of Sb-doped SnSe₂, Sn(Se_1-xSb_x)₂ (x = 0, 0.015, 0.03, 0.045, 0.06) alloys are investigated. The electrical conductivity was generally enhanced with Sb doping owing to a large increase in electron concentration. However, the Seebeck coefficient largely decreased with doping. Consequently, the power factor was significantly lower at a low doping of x = 0.015, and then began rising as the doping was increased beyond x = 0.015. It was found that the density-of-states effective mass and weighted mobility decreased with Sb doping, implying that the electrical transport properties of SnSe₂ were degraded by Sb doping. The total and lattice thermal conductivities gradually decreased due to additional point defect scattering. Thus, the thermoelectric figure of merit declined significantly, from 0.30 of the pristine sample with a low doping of Sb (x = 0.015) at 750 K, to 0.18, and then for x = 0.06 it gradually recovered to the value of the undoped sample. The thermoelectric quality factor decreased as the Sb doping was increased, implying that Sb doping did not enhance the thermoelectric transport properties, despite the large increase in electron concentration.