Aluminium sulfide

Aluminium sulfide is the name for the chemical compound with the formula Al₂S₃. This colorless species has an interesting structural chemistry, existing in three different forms. The material is sensitive to moisture, hydrolyzing readily to hydrated aluminium oxides/hydroxides. The hydrolysis reaction also generates the odoriferous and toxic gas hydrogen sulfide (H2S).

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 wurzite" 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. Also Al₂Se₃ and Al₂Te₃ are also known.

Preparation: Aluminum sulfide is readily prepared by ignition of the elements; (2Al + 3S = 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 preps). The product will be created in a fused form; that is at greater than 1100 C and may melt its way through steel. The cooled product is very hard.

References

MSDS: http://www.espi-metals.com/msds's/Aluminum%20Sulfide.htm