Spark plasma sintering of fine Mg2Si particles

Nanostructuration is an efficient way to improve thermoelectric properties. In this paper, the densification of micro and nanocrystalline Mg2Si is studied using Spark Plasma Sintering process. It seems very problematic to successfully sinter Mg2Si nanoparticles because the nano-size promotes oxidation at grain boundaries and prevent obtaining high green densities of the compacts. The in situ synthesis of Mg2Si under reductive atmosphere, during SPS process, has not led to dense samples, demonstrating that the grain size is the key factor in densifying magnesium silicide powders. Moreover, the sintering of micronic Mg2Si grains has been successfully carried out confirming this assumption. Our results show that mixing powders made of small and large particles give access to 95% dense composite materials with a large amount of fine grains homogeneously distributed in the large grain matrix.