Electrical, Thermal, and Thermoelectric Transport Properties of Se-doped Polycrystalline Re2Te5

Re2Te5 is considered a potential thermoelectric material because of its intrinsically low thermal conductivity, due to its complex crystal structure. Herein, a series of Se-doped Re2Te5 (Re2Te5-xSex,x = 0, 0.2, 1, and 2) samples were synthesized, and their electrical and thermal transport properties were investigated. Pure orthorhombic Re2Te5 phases were successfully synthesized without any impurities for all compositions, and the continuous decrease in the calculated lattice parameters confirmed the substitution of Se atoms at the Te sites. A maximum power factor of 0.135 mW/mK2 was achieved for the sample withx = 0.2 at 880 K, mainly due to the increase in carrier concentration and electrical conductivity. The lattice thermal conductivity significantly decreased for all doped samples, which was attributed to the point defect phonon scattering caused by Se doping. The thermoelectric figure of merit,zT reached a maximum value of 0.20 at 880 K for Re2Te4.8Se0.2 (x = 0.2) sample, which was approximately 22% higher than that of the pristine Re2Te5 sample. The weighted mobility, quality factor, and expectedzT were calculated to evaluate the optimization of the power factor andzT.