Aluminium phosphide

Aluminium phosphide is the chemical compound with the formula AlP. This colourless solid is generally sold as a grey-green-yellow powder due to the presence of impurities arising hydrolysis and oxidation. This material is a wide band gap semiconductor and is used as a fumigant.

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Structure, synthesis, and properties

AlP crystallizes in the cubic zinc blende motif, wherein all atoms have tetrahedral coordination. Related materials crystallize similarly, including GaAs.

Crude aluminium phosphide can be prepared in the laboratory by igniting a mixture of red phosphorus and powdered aluminium.^[1]

Aluminium phosphide reacts with water or acids to release phosphine.^[2]

2AlP + 3 H₂O → Al(OH)₃ + PH₃

Pesticide

AlP is used as a rodenticide, insecticide and fumigant for stored cereal grains. It is used to kill small verminous mammals such as moles, rabbits, and rodents. The tablets or pellets typically also contain other chemicals which evolve ammonia which helps to reduce the potential for spontaneous ignition or explosion of the phosphine gas. Pure phosphine is odorless, but technical grade phosphine has a highly unpleasant odor like garlic or rotting fish, due to the presence of substituted phosphine and diphosphine (P₂H₄).

As a killing rodents, aluminium phosphide pellets are provided as a mixture of food for the consumption by the rodents. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic phosphine gas. Other pesticides similar to aluminium phosphide are zinc phosphide and calcium phosphide.

As a rodenticide, aluminium phosphide can be encountered under names eg. Celphos, Fumitoxin, Phostoxin, and Quick Phos.

Semiconductor applications

Industrially, AlP is a semiconductor material that is usually alloyed with other binary materials for applications in devices such as light-emitting diodes (e.g. aluminium gallium indium phosphide).^[3]

References

1. ^ Wayne E. White, A. H. Bushey (1953). "Aluminum Phosphide". Inorganic Syntheses 4: 23-25. doi:10.1002/9780470132357.ch7.
2. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
3. ^ D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam 1995. ISBN 0-444-89307-5.