Scrutinize the effect of Ge and Sn doping on electronic and thermoelectric properties of Mg 2 Si as thermoelectric material

Abstract

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 Mg₂Si_1−xA_x (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. Mg₂Si_1−xGe_x and Mg₂Si_1−xSn_x has maximum figure of merit 0.077 and 0.15 at x = 0.125 respectively.

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