Abstract:
We investigated the electronic structure, dynamic stability, optical, and thermoelectric properties
of strontium doped Mg2−x SiSrx, x = 0, 1, using First Principle approach with ultra-soft
pseudopotential method to treat the interaction between the valence electron and the ion core and
the Generalized Gradient Approximation (GGA) in Perdex Burke Emzerhof (PBE) form is used
to process the exchange-related energy function. Sr modified Mg2Si show good agreement with
the experimental result for the electronic and thermoelectric properties. With semiclassical
Boltzmann transport theory, the transport properties of Mg2Si and Sr doped Mg2Si alloys have
been investigated systematically. The result of DFT conformed that, the undoped Mg2Si system
has indirect energy gap to a value of 0.222 eV; Sr doped 2x1x1 Mg2Si supercell, showing direct
bandgap with a value of 0.195 eV. The carrier concentration of Sr doped Mg2Si thermoelectric material
increased. After the doping, the fermi level shifts towards the conduction band and comprises of via a
strong hybridization between the Sr-s, Si-p, Mg-s, and Mg-p orbitals, indicating that the covalent
bonds formed by Sr, Si, and Mg atoms is very strong. The electrical conductivity of Sr doped
Mg2Si material is due to electrons, which is justified from the negative value of the Seebeck
coefficient and its value increases with temperature. The lattice thermal conductivity dominates
the electronic thermal conductivity as a function of temperature for Sr doped Mg2Si system.
In this work, the Sr-doped Mg2Si materials were found to be a better thermoelectric material with
increased Seebeck coefficient, electrical conductivity, and corresponding electronic thermal
conductivity at a high-temperature range.
