Role of Pb Doping on the Thermoelectric Properties of Mg₃Sb_1.8‐yBi_0.2Pb_y Alloys

Abstract

In this work, we focused on the matrix material with a composition of Mg 3 Sb 1.8 Bi 0.2 . The effect of Pb doping on the thermoelectric properties of Mg 3 Sb 1.8-y Bi 0.2 Pb y (y = 0, 0.005, 0.01, 0.02) compounds was investigated. Mechanical alloying followed by spark plasma sintering was employed to synthesize the corresponding bulk materials. The x-ray diffraction results indicate that the doping limit of Pb in Mg 3 Sb 1.8 Bi 0.2 is 0.01 ~0.02. Pb doping significantly increases the carrier concentration up to > 10 19 cm À 3 , while decreasing the Seebeck coefficient. Moreover, the thermal conductivity of the matrix material is reduced upon Pb doping at 400-700 K. As a result, the thermoelectric figure of merit is improved in the low-temperature range, and a ZT value of 0.039 is obtained for the y = 0.005 sample at 500 K, which is 77% higher than that of the undoped sample.