Aluminium selenide (Al2Se3)

Composition and structure

The nominal stoichiometry Al2Se3 balances two Al3+ ions with three Se2− ions. In crystalline form the arrangement of atoms can vary with preparation conditions; the local coordination of aluminium by selenium is usually consistent with small, highly charged metal centers surrounded by chalcogen anions. For context on the aluminium center consult aluminium chemistry.

Preparation and history

Aluminium selenide is most commonly prepared by high-temperature combination of the elements, i.e., heating aluminium metal with elemental selenium under an inert atmosphere. Other laboratory methods include solid-state metathesis routes or reactions that produce selenide precursors, followed by thermal treatment. Historical and technical notes on its synthesis are summarized in specialist references (synthesis overview).

Chemical behavior and uses

A defining chemical property is its reactivity with moisture: aluminium selenide hydrolyzes on contact with water or humid air to form aluminium hydroxide or oxide and hydrogen selenide gas (H2Se). Hydrogen selenide is a colorless, foul-smelling gas that is highly toxic, so Al2Se3 must be handled under dry, controlled conditions. Because of this reactivity, Al2Se3 is used mainly as a reagent in research for preparing other selenide materials or as an in situ source of selenide under inert conditions. Further technical applications and material data can be found at materials resources.

Safety and handling

Due to release of H2Se on hydrolysis, aluminium selenide must be stored dry and manipulated in an inert atmosphere or with appropriate gas scrubbing. Personal protective measures and emergency procedures are important; consult chemical safety guides and supplier information before use (safety guidance). Comparatively, its behavior parallels that of other metal chalcogenides such as aluminium sulfide, which produces H2S on hydrolysis.