Excellent thermoelectric performance of BaMgSi driven by low lattice thermal conductivity: A promising thermoelectric material

Abstract

Searching for low lattice thermal conductivity has been one of main research direction for obtaining high performance thermoelectric materials, because of the weak coupling between the electrical transport properties and lattice thermal conductivity. We are keenly interested in the thermoelectric properties of BaMgSi due to the double-filled honeycomb crystal structure with the heavy Ba atoms. Using first-principles density functional theory (DFT) calculations combined with the Boltzmann transport theory, we systematically investigate the dynamic stability, electronic structures, and transport properties of BaMgSi. The results show that the lattice thermal conductivity of this material is only 1.27 W/mK at 300 K and 0.46 W/mK at 800 K, which is comparable to these of known thermoelectric materials i.e. 1.4 W/mK at 300 K for Bi2Te3 and 0.3 W/mK at 800 K for SeSn. Such ultralow lattice thermal conductivity and high band degeneracy lead to a high thermoelectric figure of merit ZT = 2.96 for p-type at 800 K and 1.68 for n-type BaMgSi at 1000 K in an optimum doping concentration, exhibiting good potential in thermoelectric applications.