Lifting the Optical and Thermoelectric Properties of Mg₂Si as a Function of Sn Incorporation—Potential Thermoelectric Materials

Abstract

By means of Density Functional Theory (DFT) study, we have performed the structural, electronic, optical and thermoelectric properties calculations of tin doped Mg2Si (Mg2Si1−xSnx, x = 0, 0.125, 0.25, 0.5, 0.75, 0.875, 1) using Full Potential Linearized Augmented Plane Wave (FP-LAPW) Method. The DFT study yields satisfactory results for electronic and thermoelectric properties of Sn doped Mg2Si compared with experimental values. With semiclassical Boltzmann transport theory, the transport properties of Mg2Si and Sn doped Mg2Si alloys has been investigated systematically. According to the calculated band structure, density of states and electron density, the parent Mg2Si/Sn materials having indirect energy gap (Γ−x) with ionic bonding; Sn doped ternary combinations Mg2Si1−xSnx, x = 0.125, 0.25, 0.5, 0.75, 0.875 having direct band gap (Γ−Γ) with a mixed covalent and ionic bonding nature. Band gap decreases linearly with the increase of Sn-concentration in each alloy system except for Mg2Si0.75Sn0.25 combination. The optical properties calculations have been performed for the energy range between 0–13.5 eV. The thermoelectric properties have been calculated for the temperature range 100 K to 800 K. Out of the five studied materials, Mg2Si0.75Sn0.25 found to be a better thermoelectric material with increased Power factor, Seebeck coefficient, electrical conductivity and corresponding thermal conductivity at high temperature range.