Thermoelectric properties of binary Mg2Sn and ternary Mg2Sn1−xYx (Y = Si, Ge) with the addition of Cu2S

Abstract

Doped and undoped ternary and binary Mg2Sn solid solutions were fabricated using high-energy ball milling followed by hot pressing according to the nominal Mg2Sn1−xYx (X = 0, 0.25 and Y= Si, Ge) composition with the addition of 20 at% of Cu2S. The effects of Cu2S addition on the thermal conductivity, Seebeck coefficient and electrical conductivity were investigated in the temperature range of 300–800 K. It was found that the Cu2S addition increased both the electrical conductivity and Seebeck coefficient simultaneously, which is unusual in thermoelectricity, leading to enhancement of the power factors. Additionally, the addition of Cu2S significantly decreases the thermal conductivity. It was also observed that the ternary compositions (i.e. compositions containing Si, Ge) results in a high power factor as a result of the combined optimized Seebeck coefficient and electrical conductivity. This is as a result of phase separations into SnS and Mg3Sb2 phases, which are enhanced by the addition of Si and Ge. Overall, the ZT values significantly improved to 1.35 at 700 K and 1.3 at 750 K for Si and Ge ternary samples, respectively.