 | |
 | |
| Names | |
|---|---|
| Preferred IUPAC name Magnesium silicide | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
|
| ECHA InfoCard | 100.041.125 |
| EC Number |
|
| UNII | |
| UN number | 2624 |
| |
| |
| Properties | |
| Mg2Si | |
| Molar mass | 76.695 g·mol−1 |
| Appearance | Gray cubic crystals[1] |
| Density | 1.99 g cm−3[1] |
| Melting point | 1,102 °C (2,016 °F; 1,375 K)[1] |
| reacts[1] | |
| Structure[2] | |
| Antifluorite (cubic),cF12 | |
| Fm3m, #225 | |
a = 0.6351 nm | |
Formula units (Z) | 4 |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | reacts with water to produce pyrophoricsilane |
| GHS labelling: | |
 | |
| Warning | |
| H261 | |
| P231+P232,P280,P370+P378,P402+P404,P501 | |
| Related compounds | |
Othercations | Calcium silicide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Magnesium silicide, Mg2Si, is aninorganic compound ofmagnesium andsilicon. As-grown Mg2Si usually forms black crystals; they aresemiconductors with n-type conductivity and have potential applications inthermoelectric generators.[3]
Mg2Si crystallizes in theantifluorite structure. In theface-centered cubic lattice, Si centers occupy the corners and face-centered positions of the unit cell, and Mg centers occupy eight tetrahedral sites in the interior of the unit cell. The coordination numbers of Si and Mg are eight and four, respectively.[2]
It can be produced by heatingsilicon dioxide, SiO2, found insand, with excessmagnesium. The process first forms elemental silicon andmagnesium oxide:
If an excess of Mg is present, Mg2Si is formed from the reaction of the remaining magnesium with the elemental silicon:
These reactions proceed exothermically,[4] even explosively.[5]
Magnesium silicide can be viewed as consisting of Si4− ions. As such, it is reactive toward acids. Thus, when magnesium silicide is treated withhydrochloric acid,silane (SiH4) andmagnesium chloride are produced:
Sulfuric acid can be used as well. Theseprotonolysis reactions are typical of agroup 2 (alkaline earth metal) andgroup 1 (alkali metal)silicides. The early development of silicon hydrides relied on this reaction.[5]
Magnesium silicide is used to create aluminium alloys of the6000 series, containing up to approximately 1.5% Mg2Si. An alloy of this group can be age-hardened to formGuinier-Preston zones and a very fine precipitate, resulting in increased alloy strength.[6]
Magnesium silicide is anarrow-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 Mg2Si is inthermoelectric generators.[3][7]
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