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| Names | |
|---|---|
| Other names Aluminium sulfide | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.013.736 |
| EC Number |
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| UNII | |
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| 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 inacetone |
| Structure | |
| trigonal | |
| Thermochemistry | |
| 105.1 J/mol K | |
Std molar entropy(S⦵298) | 116.9 J/mol K |
Std enthalpy of formation(ΔfH⦵298) | −724 kJ/mol |
| Hazards | |
| GHS labelling: | |
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| Danger | |
| NFPA 704 (fire diamond) | |
| Safety data sheet (SDS) | [1] |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Aluminum sulfide is achemical compound with the formulaAl2S3. 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 gaseoushydrogen sulfide (H2S).
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 | P61 | 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 2–65bar results in the δ phase where vacancies are arranged in a superlattice of tetragonal symmetry.[5]
UnlikeAl2O3, 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 "defectwurtzite" 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.
Aluminum sulfide is readily prepared by ignition of the elements[6]
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 1,100 °C and may melt its way through steel. The cooled product is very hard.
