Improvement of Thermoelectric Properties through Reduction of Thermal Conductivity by Nanoparticle Addition and Stoichiometric Change to Mg2Si

摘要

Thermoelectric materials have been of interest for several decades due to their ability to recapture waste heat of various systems and convert it to useful electricity. One method used to improve the thermoelectric figure of merit, given by ZT = (σS2T)/(ke+kp), is to reduce the lattice thermal conductivity (kp) while not affecting the other properties. In order to reduce kp of the material, this paper introduces nanoparticles of Si in Mg2Si to manipulate phonon scattering and mean free path. LAMMPS molecular dynamics software is employed using the nonequilibrium molecular dynamics (NEMD) method to perform a series of simulations with the metal silicide thermoelectric material MgxSix. The objective of this work is two-fold: 1) to determine the optimal nanoparticle concentration and 2) to determine the optimal MgxSix stoichiometry for minimizing the thermal conductivity of the system. It should be noted, however, that the assumed reduction in thermal conductivity is only a result of reduced phonon transport and minimal impact is made on the transport of electrons. Interestingly, the uniform off-stoichiometry (41.37 percent Si) sample of MgxSix resulted in a reduction of kp of 72.39 percent, while the Si nanoparticle sample, with matching percent Si, resulted in a reduction of kp of 65.59 percent.