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Aluminium sulfide

Names
Other names Aluminium sulfide
Identifiers
CAS Number	1302-81-4
3D model (JSmol)	Interactive image
ChemSpider	140154
ECHA InfoCard	100.013.736
EC Number	215-109-0
PubChem CID	16684788
UNII	04PI6P2Z18
CompTox Dashboard (EPA)	DTXSID80893235
InChI InChI=1S/2Al.3S/q2*+3;3*-2Key: COOGPNLGKIHLSK-UHFFFAOYSA-N InChI=1/2Al.3S/q2*+3;3*-2Key: COOGPNLGKIHLSK-UHFFFAOYAY
SMILES ....
Properties
Chemical formula	Al2S3
Molar mass	150.158 g/mol
Appearance	gray solid
Density	2.02 g/cm
Melting point	1,100 °C (2,010 °F; 1,370 K)
Boiling point	1,500 °C (2,730 °F; 1,770 K) sublimes
Solubility in water	decomposes
Solubility	insoluble in acetone
Structure
Crystal structure	trigonal
Thermochemistry
Heat capacity (C)	105.1 J/mol K
Std molar entropy (S298)	116.9 J/mol K
Std enthalpy of formation (ΔfH298)	-724 kJ/mol
Hazards
GHS labelling:
Pictograms
Signal word	Danger
NFPA 704 (fire diamond)	4 0 2W
Safety data sheet (SDS)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is  ?) Infobox references

Aluminium sulfide is a chemical compound with the formula Al₂S₃. This colorless species has an interesting structural chemistry, existing in several forms. The material is sensitive to moisture, hydrolyzing to hydrated aluminium oxides/hydroxides. This can begin when the sulfide is exposed to the atmosphere. The hydrolysis reaction generates gaseous hydrogen sulfide (H₂S).

Crystal structure

More than six crystalline forms of aluminium sulfide are known and only some are listed below. Most of them have rather similar, wurtzite-like structures, and differ by the arrangement of lattice vacancies, which form ordered or disordered sublattices.

The β and γ phases are obtained by annealing the most stable α-Al₂S₃ phase at several hundred degrees Celsius. Compressing aluminium sulfide to 2–65 bar results in the δ phase where vacancies are arranged in a superlattice of tetragonal symmetry.

Unlike Al₂O₃, in which the Al(III) centers occupy octahedral holes, the more expanded framework of Al₂S₃ stabilizes the Al(III) centers into one third of the tetrahedral holes of a hexagonally close-packed arrangement of the sulfide anions. At higher temperature, the Al(III) centers become randomized to give a "defect wurtzite" structure. And at still higher temperatures stabilize the γ-Al₂S₃ forms, with a structure akin to γ-Al₂O₃.

Molecular derivatives of Al₂S₃ are not known. Mixed Al-S-Cl compounds are however known. Al₂Se₃ and Al₂Te₃ are also known.

Preparation

Aluminium sulfide is readily prepared by ignition of the elements

2 Al + 3 S → Al₂S₃

This reaction is extremely exothermic and it is not necessary or desirable to heat the whole mass of the sulfur-aluminium mixture; (except possibly for very small amounts of reactants). The product will be created in a fused form; it reaches a temperature greater than 1,100 °C and may melt its way through steel. The cooled product is very hard.

References

1. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
2. Hans Landolt; D. Bimberg, Richard Börnstein; Richard Börnstein (1982). Halbleiter. Springer. pp. 12–. ISBN 978-3-540-13507-4. Retrieved 23 September 2011.
3. Flahaut, J. (1952). "Contribution à l'étude du sulfure d'aluminium et des thioaluminates" [Contribution to the study of aluminum sulfide and thioaluminates]. Annales de Chimie (Paris) (in French). 7: 632–696.
4. Krebs, Bernt; Schiemann, Anke; läGe, Mechtild (1993). "Synthese und Kristallstruktur einer Neuen hexagonalen Modifikation von Al2S3 mit fünffach koordiniertem Aluminum". Zeitschrift für anorganische und allgemeine Chemie. 619 (6): 983. doi:10.1002/zaac.19936190604.
5. Donohue, P (1970). "High-pressure spinel type Al2S3 and MnAl2S4". Journal of Solid State Chemistry. 2 (1): 6–8. Bibcode:1970JSSCh...2....6D. doi:10.1016/0022-4596(70)90024-1.
6. McPherson, William; Henderson, William E. (1913). A course in general chemistry. Boston: Ginn and Company. p. 445.

• Sesquisulfides
• Aluminium compounds