Thermoelectric Properties of Sb-Doped Mg2Si0.3Sn0.7

Abstract

Mg2(Si0.3Sn0.7)1−ySby (0 ≤ y ≤ 0.04) solid solutions were prepared by a two-step solid-state reaction method combined with the spark plasma sintering technique. Investigations indicate that the Sb doping amount has a significant impact on the thermoelectric properties of Mg2(Si0.3Sn0.7)1−ySby compounds. As the Sb fraction y increases, the electron concentration and electrical conductivity of Mg2(Si0.3Sn0.7)1−ySby first increase and then decrease, and both reach their highest value at y = 0.025. The sample with y = 0.025, possessing the highest electrical conductivity and one of the higher Seebeck coefficient values among all the samples, has the highest power factor, being 3.45 mW m−1 K−2 to 3.69 mW m−1 K−2 in the temperature range of 300 K to 660 K. Meanwhile, Sb doping can significantly reduce the lattice thermal conductivity (κph) of Mg2(Si0.3Sn0.7)1−ySby due to increased point defect scattering, and κph for Sb-doped samples is 10% to 20% lower than that of the nondoped sample for 300 K < T < 400 K. Mg2(Si0.3Sn0.7)0.975Sb0.025 possesses the highest power factor and one of the lower κph values among all the samples, and reaches the highest ZT value: 1.0 at 640 K.