Aluminium sulfide
Aluminum sulfide or aluminium sulphide 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 aluminum oxides/hydroxides.[1] This can begin when the sulfide is exposed to the atmosphere. The hydrolysis reaction generates gaseous hydrogen sulfide (H2S).
Names | |
---|---|
Other names
Aluminium sulfide | |
Identifiers | |
| |
3D model (JSmol) |
|
ChemSpider | |
ECHA InfoCard | 100.013.736 |
EC Number |
|
PubChem CID |
|
UNII | |
CompTox Dashboard (EPA) |
|
| |
| |
Properties | |
Al2S3 | |
Molar mass | 150.158 g/mol |
Appearance | gray solid |
Density | 2.02 g/cm3 |
Melting point | 1,100 °C (2,010 °F; 1,370 K) |
Boiling point | 1,500 °C (2,730 °F; 1,770 K) sublimes |
decomposes | |
Solubility | insoluble in acetone |
Structure | |
trigonal | |
Thermochemistry | |
Heat capacity (C) |
105.1 J/mol K |
Std molar entropy (S |
116.9 J/mol K |
Std enthalpy of formation (ΔfH⦵298) |
-724 kJ/mol |
Hazards | |
Safety data sheet | |
GHS pictograms | ![]() ![]() |
GHS Signal word | Danger |
NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
![]() ![]() ![]() | |
Infobox references | |
Crystal structure
More than six crystalline forms of aluminum 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.[2][3]
Form | Symmetry | Space group | a (A) | c (A) | ρ (g/cm3) |
---|---|---|---|---|---|
α | Hexagonal | 6.423 | 17.83 | 2.32 | |
β | Hexagonal | P63mc | 3.579 | 5.829 | 2.495 |
γ | Trigonal | 6.47 | 17.26 | 2.36 | |
δ | Tetragonal | I41/amd | 7.026 | 29.819 | 2.71 |
The β and γ phases are obtained by annealing the most stable α-Al2S3 phase at several hundred degrees Celsius.[4] Compressing aluminum sulfide to 2–65 kbar results in the δ phase where vacancies are arranged in a superlattice of tetragonal symmetry.[5]
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
Aluminum sulfide is readily prepared by ignition of the elements[6]
- 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-aluminum mixture; (except possibly for very small amounts of reactants). The product will be created in a fused form; it reaches a temperature greater than 1100 °C and may melt its way through steel. The cooled product is very hard.
References
- Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- Hans Landolt; D. Bimberg, Richard Börnstein; Richard Börnstein (1982). Halbleiter. Springer. pp. 12–. ISBN 978-3-540-13507-4. Retrieved 23 September 2011.
- Flahaut J. Ann. Chim. (Paris) 7 (1952) 632–696
- 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.
- Donohue, P (1970). "High-pressure spinel type Al2S3 and MnAl2S4". Journal of Solid State Chemistry. 2: 6. Bibcode:1970JSSCh...2....6D. doi:10.1016/0022-4596(70)90024-1.
- McPherson, William (1913). Laboratory manual. Boston: Ginn and Company. p. 445.