Aluminum sulfide or aluminium sulphide is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
with the formula
Al2 S3. This colorless species has an interesting structural chemistry, existing in several forms. The material is sensitive to moisture, hydrolyzing to hydrated aluminum oxides/hydroxides. This can begin when the sulfide is exposed to the atmosphere. The hydrolysis reaction generates gaseous
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
(H
2S).
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
Wurtzite is a zinc and iron sulfide mineral with the chemical formula , a less frequently encountered Polymorphism (materials science), structural polymorph form of sphalerite. The iron content is variable up to eight percent.Palache, Charles, Har ...
-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-Al
2S
3 phase at several hundred degrees Celsius. Compressing aluminum sulfide to 2–65
bar
Bar or BAR may refer to:
Food and drink
* Bar (establishment), selling alcoholic beverages
* Candy bar
* Chocolate bar
Science and technology
* Bar (river morphology), a deposit of sediment
* Bar (tropical cyclone), a layer of cloud
* Bar (u ...
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 Al
2S
3 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
Wurtzite is a zinc and iron sulfide mineral with the chemical formula , a less frequently encountered Polymorphism (materials science), structural polymorph form of sphalerite. The iron content is variable up to eight percent.Palache, Charles, Har ...
" structure. And at still higher temperatures stabilize the γ-Al
2S
3 forms, with a structure akin to γ-Al
2O
3.
Molecular derivatives of Al
2S
3 are not known. Mixed Al-S-Cl compounds are however known. Al
2Se
3 and Al
2Te
3 are also known.
Preparation
Aluminum sulfide is readily prepared by ignition of the elements
:2 Al + 3 S → Al
2S
3
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
{{Authority control
Sulfides
Aluminium compounds