Thermoelectric properties of Bi_0.5Sb_1.4−xNa_xIn_0.1Te₃ alloys

The Bi_0.5Sb_1.4−xNa_xIn_0.1Te₃ (x = 0.02–0.20) alloys were fabricated by high vacuum melting and hot-pressing technique. The phase structures and morphology of the bulk samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Effects of In and Na co-doping on the electrical and thermal transport properties were studied from room temperature to 500 K. Seebeck coefficient of the Bi_0.5Sb_1.5Te₃ can be enhanced by substituting Sb with In and Na at near room temperature. The electrical conductivity of the In and Na co-doped samples is lower than that of the Bi_0.5Sb_1.5Te₃ alloy from room temperature to 500 K. In and Na co-doping of appropriate percentage optimizes the thermal conductivity of the Bi_0.5Sb_1.5Te₃ alloy. The minimum value of thermal conductivity of Bi_0.5Sb_1.36Na_0.04In_0.1Te₃ alloy is 0.45 W·m⁻¹·K⁻¹ at 323 K, which leads to a great improvement in the thermoelectric figure of merit (zT). The maximum zT value reaches 1.42 at 323 K.