Computational study of the effects of Sr-dopant on the lattice thermal conductivity of Mg2Si thermoelectric material

Abstract

Due to its high abundance, low density, non-toxic nature, and low cost of production, Magnesium Silicide is very important for thermoelectric applications. In recent years enormous investigations have been done to improve the thermoelectric figure of merit (ZT) of Mg2Si-based thermoelectric (TE) material by both experimental and computational methods. In this study, the first-principles pseudopotentials based on density functional theory (DFT) had been applied to study the effect of Sr dopant on the lattice thermal conductivity of Mg2Si. The effects of Sr dopant on other properties like electronic structure, the density of state (DOS), and phonon properties of doped Mg2Si had also investigated. The lattice constant, Converged kinetic energy cutoff, and K-point grid had been optimized from Self-calculation field (SCF) calculations by quantum espresso software and CASTEP(Cambridge Serial Total Energy Package) code in Material studio software. After optimizations had been done, all other calculations related to the thermoelectric like Seebeck coefficient, electrical conductivity, and thermal conductivity had calculated within various temperature ranges from 20K to 800K for both native and doped Mg2Si. Finally, we acquired a very good result from Sr-doped (Mg16-xSi8Srx, where ‘x’ is the amount of dopant atom). The lattice thermal conductivity had highly minimized to (0.02) W/Km at the temperature of (800) K for x =2 (Mg14Si8Sr2). It has shown a huge change when we compared to un-doped Mg16Si8 in temperature ranges of (200-1000) K