Magnesium silicide

Magnesium silicide
Names
	Preferred IUPAC name Magnesium silicide
Identifiers
CAS Number	22831-39-6 ;
3D model (JSmol)	Interactive image;
ChemSpider	81111 ;
EC Number	245-254-5;
PubChem CID	89858;
UNII	475E6FMG3K ;
UN number	2624
	InChI InChI=1S/2Mg.Si Key: YTHCQFKNFVSQBC-UHFFFAOYSA-N ; InChI=1/2Mg.Si/rMg2Si/c1-3-2 Key: YTHCQFKNFVSQBC-GEBTXNJDAA;
	SMILES [Mg]=[Si]=[Mg];
Properties
Chemical formula	Mg2Si
Molar mass	76.695 g·mol−1
Appearance	Gray cubic crystals
Density	1.99 g cm−3
Melting point	1,102 °C (2,016 °F; 1,375 K)
Solubility in water	reacts
Structure
Crystal structure	Antifluorite (cubic), cF12
Space group	Fm3m, #225
Lattice constant	a = 0.6351 nm
Formula units (Z)	4
Hazards
Main hazards	reacts with water to produce pyrophoric silane
GHS pictograms
GHS Signal word	Warning
GHS hazard statements	H261
GHS precautionary statements	P231+232, P280, P370+378, P402+404, P501
Related compounds
Other cations	Calcium silicide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

Magnesium silicide, Mg₂Si, is an inorganic compound consisting of magnesium and silicon. As-grown Mg₂Si usually forms black crystals; they are semiconductors with n-type conductivity and have potential applications in thermoelectric generators.^[3]

Crystal structure

Mg₂Si crystallizes in the antifluorite structure. In the face-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]

Synthesis

File:04. Добивање на аморфен силициум и магнезиум силицид.webm It can be produced by heating silicon dioxide, SiO₂, found in sand, with excess magnesium. The process first forms silicon metal and magnesium oxide, and, if an excess of SiO₂ is used, then elemental silicon is formed:

2 Mg + SiO₂ → 2 MgO + Si

If an excess of Mg is present, Mg₂Si is formed from the reaction of the remaining magnesium with the silicon:

2 Mg + Si → Mg₂Si

These reactions proceed exothermically,^[4] even explosively.^[5]

Reactions

File:05. Реакција на магнезиум силицид во солна киселина.webm Magnesium silicide can be viewed as consisting of Si⁴⁻ ions. As such it is reactive toward acids. Thus, when magnesium silicide is treated with hydrochloric acid, silane (SiH₄) and magnesium chloride are produced:

Mg₂Si + 4 HCl → SiH₄ + 2 MgCl₂

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.^[5]

Uses

Magnesium silicide is used to create aluminium alloys of the 6000 series, containing up to approximately 1.5% Mg₂Si. An alloy of this group can be age-hardened to form Guinier-Preston zones and a very fine precipitate, both resulting in increased strength of the alloy.^[6]

Magnesium silicide is a narrow-gap semiconductor. Its as-grown crystal exhibit n-type conductivity, but it can be changed to p-type by doping with Ag, Ga, Sn and possibly Li (at high doping level). The major potential electronic application of Mg₂Si is in thermoelectric generators.^[3]^[7]

References

↑ ^1.0 ^1.1 ^1.2 ^1.3 Haynes, William M., ed (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.74. ISBN 1439855110.
↑ ^2.0 ^2.1 Noda Y., Kon H., Furukawa Y., Otsuka N., Nishida I.A., Masumoto K. (1992). "Preparation and Thermoelectric Properties of Mg₂Si_1−xGe_x (x=0.0~0.4) Solid Solution Semiconductors". Mater. Trans., JIM 33 (9): 845–850. doi:10.2320/matertrans1989.33.845. https://www.jim.or.jp/journal/e/33/09/845.html.
↑ ^3.0 ^3.1 Hirayama, Naomi (2019). "Substitutional and interstitial impurity p-type doping of thermoelectric Mg₂Si: a theoretical study". Sci. Technol. Adv. Mater. 20 (1): 160–172. doi:10.1080/14686996.2019.1580537. PMID 30891103. Bibcode: 2019STAdM..20..160H.
↑ Ehrlich, P. (1963) "Alkaline Earth Metals", p. 920 in Handbook of Preparative Inorganic Chemistry, 2nd ed., Vol. 1. G. Brauer (ed.). Academic Press, New York.
↑ ^5.0 ^5.1 Stock, Alfred; Somieski, Carl (1916). "Siliciumwasserstoffe. I. Die aus Magnesiumsilicid und Säuren entstehenden Siliciumwasserstoffe". Berichte der Deutschen Chemischen Gesellschaft 49: 111–157. doi:10.1002/cber.19160490114. https://zenodo.org/record/1426597.
↑ "Properties and Selection: Non-ferrous Alloys and Special Purpose Materials" in ASM Handbook, 10th ed., Vol. 1, 1990, ASM International, Materials Park, Ohio. ISBN 0871703785.
↑ Borisenko, Victor E. (2013). Semiconducting Silicides: Basics, Formation, Properties. Springer Science & Business Media. pp. 187, 287. ISBN 978-3-642-59649-0. https://books.google.com/books?id=F0zoCAAAQBAJ&pg=PA187.

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Original source: https://en.wikipedia.org/wiki/Magnesium silicide. Read more

[b92-1] 1.0 ^1.1 ^1.2 ^1.3 Haynes, William M., ed (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.74. ISBN 1439855110.

[str-2] 2.0 ^2.1 Noda Y., Kon H., Furukawa Y., Otsuka N., Nishida I.A., Masumoto K. (1992). "Preparation and Thermoelectric Properties of Mg₂Si_1−xGe_x (x=0.0~0.4) Solid Solution Semiconductors". Mater. Trans., JIM 33 (9): 845–850. doi:10.2320/matertrans1989.33.845. https://www.jim.or.jp/journal/e/33/09/845.html.

[stam-3] 3.0 ^3.1 Hirayama, Naomi (2019). "Substitutional and interstitial impurity p-type doping of thermoelectric Mg₂Si: a theoretical study". Sci. Technol. Adv. Mater. 20 (1): 160–172. doi:10.1080/14686996.2019.1580537. PMID 30891103. Bibcode: 2019STAdM..20..160H.

[brauer-4] Ehrlich, P. (1963) "Alkaline Earth Metals", p. 920 in Handbook of Preparative Inorganic Chemistry, 2nd ed., Vol. 1. G. Brauer (ed.). Academic Press, New York.

[Stock-5] 5.0 ^5.1 Stock, Alfred; Somieski, Carl (1916). "Siliciumwasserstoffe. I. Die aus Magnesiumsilicid und Säuren entstehenden Siliciumwasserstoffe". Berichte der Deutschen Chemischen Gesellschaft 49: 111–157. doi:10.1002/cber.19160490114. https://zenodo.org/record/1426597.

[6] "Properties and Selection: Non-ferrous Alloys and Special Purpose Materials" in ASM Handbook, 10th ed., Vol. 1, 1990, ASM International, Materials Park, Ohio. ISBN 0871703785.

[Borisenko2013-7] Borisenko, Victor E. (2013). Semiconducting Silicides: Basics, Formation, Properties. Springer Science & Business Media. pp. 187, 287. ISBN 978-3-642-59649-0. https://books.google.com/books?id=F0zoCAAAQBAJ&pg=PA187.

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