Thermoelectric Properties Prediction of n-Type Mg₂Si_1−xSn_x Compounds by First Principles Calculation

A comprehensive analysis has been made of the n-type Mg₂Si_1−xSn_x (0.25 ≤ x ≤ 0.75) compounds by the first principles calculation method. The calculated band structures in n-type Mg₂Si_1−xSn_x show the conduction band convergence directly. This convergence in energy at x = 0.625 can enhance the Seebeck coefficient of the solid solution in comparison with other Sn contents. The Seebeck coefficient of Mg₂Si_0.375Sn_0.625 could reach − 246 μV K⁻¹ at the optimal doping density of 3 × 10²⁰ cm⁻³. The enhancement of the Seebeck coefficient in the Mg₂Si_0.375Sn_0.625 alloy results in a higher power factor of 6.2 mW m⁻¹ K⁻² at T = 550 K, and the predicted figure of merit is 1.53 at T = 700 K. Additionally, the ZT values can be maintained larger than 1.4 in a wide temperature range from 550 K to 800 K.