Microstructure investigations and thermoelectrical properties of an N-type magnesium-silicon-tin alloy sintered from a gas-phase atomized powder

An antimony doped magnesium-silicon-tin alloyed powder, prepared by gas-phase atomization from a melt made of the raw elements, has been sintered by spark plasma sintering to manufacture 60 mm diameter pellets of the Mg2Si0.5875Sn0.4Sb0.0125 material. TEM observations enabled to detect nanometer-sized inclusions (averaged diameter of 7 and 10 nm, depending on the sort, 5.1 × 10−3 inclusions/nm2) dispersed in the bulk of individual grains constituting the as-sintered polycrystal (grain size around 7 μm). These inclusions (most are enriched in Sn and impoverished in Mg/Si in comparison to the surrounding matrix) are thought to scatter lattice vibrations, leading to a dimensionless-thermoelectrical figure of merit (ZT) around 1.4 at 510 °C. It has also been scrupulously verified that the thermoelectrical properties are robust from one area of a given pellet to another one and from one as-sintered pellet to another one.