Mg₂Si_1−xSn_x compounds are a type of low-price, environment-friendly medium temperature thermoelectric materials with very important prospects for practical application, and the exploration of high performance Mg₂Si_1−xSn_x compounds is currently attracting worldwide interest. In this study, Sb-doped Mg₂Si_0.6Sn_0.4 compounds were prepared through a two-step, low-temperature solid state reaction method combined with the spark plasma sintering technique for rapid densification. The influence of Sb doping amount on the thermoelectric properties of Mg₂Si_0.6−ySn_0.4Sb_y (0 ⩽ y ⩽ 0.015) compounds was investigated. The solid solubility limit of Sb in Mg₂Si_0.6Sn_0.4 compounds was estimated around y = 0.0125. As y increased, the electrical conductivity of Mg₂Si_0.6−ySn_0.4Sb_y (0 ⩽ y ⩽ 0.0125) compounds increased considerably, while the absolute value of the Seebeck coefficient and the lattice thermal conductivity decreased. The sample with y = 0.0125 had the highest ZT, reaching 1.11 at 860 K, and the samples with 0.005 ⩽ y ⩽ 0.015 all attained ZT _max > 0.95. The adopted synthesis process also showed very good repeatability and regularity in obtaining thermoelectric properties, together with the capability of precise composition control of Mg₂Si_0.6−ySn_0.4Sb_y, making it promising for the practical application of Mg₂Si based thermoelectric materials.

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