Scrutinize the effect of Ge and Sn doping on electronic and thermoelectric properties of Mg2Si as thermoelectric material

We have analyzed the effect of Ge and Sn doping on the electronic and thermoelectric properties of Mg2Si using density functional theory and Boltzmann equations. The calculated results show that Mg2Si1−xAx (A = Ge, Sn, 0.125 ≤ x ≤ 0.5) systems exhibit semiconductor nature and doping with Ge slightly widen the energy gap at x = 0.125. In all doped systems, the seebeck coefficient has a negative sign, which indicates that conduction is due to electrons. With an increase in doping concentrations, the seebeck coefficient decreases, while electrical conductivity, electronic thermal conductivity increases. A classical kinetic theory has been employed to calculate the contribution of lattice thermal conductivity. We have elucidated that both doped systems attained minimum lattice thermal conductivity. Mg2Si1−xGex and Mg2Si1−xSnx has maximum figure of merit 0.077 and 0.15 at x = 0.125 respectively.