Magnesium silicide, Mg<sub>2</sub>Si, is an inorganic compound of magnesium and silicon. As-grown Mg<sub>2</sub>Si usually forms black crystals; they are semiconductors with n-type conductivity and have potential applications in thermoelectric generators. even explosively.
Reactions
thumb|left|280px|The reaction of magnesium silicide with 10% hydrochloric acid.
Magnesium silicide can be viewed as consisting of Si<sup>4−</sup> ions. As such, it is reactive toward acids. Thus, when magnesium silicide is treated with hydrochloric acid, silane (SiH<sub>4</sub>) and magnesium chloride are produced:
:Mg<sub>2</sub>Si + 4 HCl → SiH<sub>4</sub> + 2 MgCl<sub>2</sub>
Sulfuric acid can be used as well. These protonolysis reactions are typical of a group 2 (alkaline earth metal) and group 1 (alkali metal) silicides. The early development of silicon hydrides relied on this reaction.
Magnesium silicide is a narrow-gap semiconductor. Its as-grown crystal exhibits n-type conductivity, but it can be changed to p-type by doping with Ag, Ga, Sn and possibly Li (at high doping levels). The major potential electronic application of Mg<sub>2</sub>Si is in thermoelectric generators.
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