Effect of microstructure on the thermal conductivity of nanostructured Mg2(Si,Sn) thermoelectric alloys: An experimental and modeling approach

In this work, we produce bulk nanostructured Mg2Si0.4Sn0.6 thermoelectric materials made of nanograins with sizes below 200 nm and containing a fine distribution of Sn-rich nanoparticles. These materials are obtained by the mechanical alloying followed by spark plasma sintering. The microstructure and transport properties, and their evolutions upon aging, are investigated. A model is developed to capture the different contributions to the phonon scattering processes arising from the nano/microstructural parameters. The calculations show quantitative agreement with the temperature and the temporal dependence of the lattice thermal conductivity of the nanostructured Mg2Si0.4Sn0.6 alloy. This work provides a general analytic approach for identifying the individual contributions of the microstructural parameters on the thermal conductivity which is a very important property controlling the performance of thermoelectric materials.