Dependence of mechanical and thermoelectric properties of Mg₂Si-Sn nanocomposites on interface density

We prepared Sn nanoparticle-embedded Mg_1.96Al_0.04Si_0.97Bi_0.03 nanocomposites and measured their thermoelectric properties and fracture toughness to elucidate the trade-off relationship between thermoelectric and mechanical properties. When Sn nanoparticles (50–150 nm) were introduced at the grain boundaries of the thermoelectric Mg_1.96Al_0.04Si_0.97Bi_0.03 matrix, the fracture toughness improved because of the inhibition of crack propagation. However, the power factor deteriorated due to the decrease in carrier mobility. We found that interface (between thermoelectric matrix and nanoparticles) density is a critical factor to determine the mechanical properties as well as thermoelectric transport properties. Optimized values of figure of merit (∼0.66 @ 873 K) and fracture toughness (1.10 MPa m^1/2) were obtained for 0.9 vol % Sn nanoparticle-embedded Mg_1.96Al_0.04Si_0.97Bi_0.03 nanocomposite.