Aluminium phosphide is a highly toxic

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistr ...

with the chemical formula AlP, used as a wide

band gap In solid-state physics, a band gap, also called an energy gap, is an energy range in a solid where no electronic states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference (i ...

semiconductor and a

fumigant Fumigation is a method of pest control or the removal of harmful micro-organisms by completely filling an area with gaseous pesticides—or fumigants—to suffocate or poison the pests within. It is used to control pests in buildings (s ...

. This colorless solid is generally sold as a grey-green-yellow powder due to the presence of impurities arising from hydrolysis and oxidation.

Properties

AlP crystals are dark grey to dark yellow in color and have a zincblende crystal structure with a lattice constant of 5.4510 Å at 300 K. They are thermodynamically stable up to . Aluminium phosphide reacts with water or acids to release phosphine: :AlP + 3 H₂O → Al(OH)₃ + PH₃ :AlP + 3 H⁺ → Al³⁺ + PH₃

Preparation

AlP is synthesized by

combination In mathematics, a combination is a selection of items from a set that has distinct members, such that the order of selection does not matter (unlike permutations). For example, given three fruits, say an apple, an orange and a pear, there are t ...

of the elements: : 4Al + P₄ → 4AlP : Caution must be taken to avoid exposing the AlP to any sources of moisture, as this generates toxic phosphine gas. Phosphine also poses fire hazards, as it is a dangerous

pyrophoric A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolith ...

compound, igniting easily in

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...

Uses

Pesticide

AlP is used as a

rodenticide Rodenticides are chemicals made and sold for the purpose of killing rodents. While commonly referred to as "rat poison", rodenticides are also used to kill mice, squirrels, woodchucks, chipmunks, porcupines, nutria, beavers, and voles. Despite ...

insecticide Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to ...

, and

for stored cereal grains. It is used to kill small verminous mammals such as moles and rodents. The tablets or pellets, known as "wheat pills", typically also contain other chemicals that evolve

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

which helps to reduce the potential for spontaneous

ignition Ignition may refer to: Science and technology * Firelighting, the human act of creating a fire for warmth, cooking and other uses * Combustion, an exothermic chemical reaction between a fuel and an oxidant * Fusion ignition, the point at which a ...

or explosion of the phosphine gas. AlP is used as both a fumigant and an oral pesticide. As a rodenticide, aluminium phosphide pellets are provided as a mixture with food for 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 Zinc phosphide ( Zn3 P2) is an inorganic chemical compound. It is a grey solid, although commercial samples are often dark or even black. It is used as a rodenticide. Zn3P2 is a II-V semiconductor with a direct band gap of 1.5 eV and may have ap ...

and

calcium phosphide Calcium phosphide (CP) is the inorganic compound with the formula Ca3P2. It is one of several phosphides of calcium, being described as the salt-like material composed of Ca2+ and P3−. Other, more exotic calcium phosphides have the formula CaP, ...

. In this application, aluminium phosphide can be encountered under various brand names, e.g. Quickphos, Celphos, Fostox, Fumitoxin, Phostek, Phostoxin, Talunex, Fieldphos, and Weevil-Cide. It generates phosphine gas according to the following hydrolysis equation. :2 AlP + 6 H₂O → Al₂O₃∙3 H₂O + 2 PH₃ It is used as a fumigant when other pesticide applications are impractical and when structures and installations are being treated, such as in ships, aircraft, and grain silos. All of these structures can be effectively sealed or enclosed in a gastight membrane, thereby containing and concentrating the phosphine fumes. Fumigants are also applied directly to rodent burrows.

Semiconductor applications

Industrially, AlP is a

semiconductor material A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

that is usually

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

ed with other binary materials for applications in devices such as light-emitting diodes (e.g.

aluminium gallium indium phosphide Aluminium gallium indium phosphide (, also AlInGaP, InGaAlP, GaInP, etc.) is a semiconductor material that provides a platform for the development of novel multi-junction photovoltaics and optoelectronic devices, as it spans a direct bandgap fro ...

Toxicology

Highly poisonous, aluminium phosphide has been used for suicide. Fumigation has also caused unintentional deaths. Known as "rice tablet" in Iran, for its use to preserve rice, there have been frequent incidents of accidental or intentional death. There is a campaign by the Iranian Forensic Medicine Organization to stop its use as a pesticide. Recycling of used aluminium phosphide containers caused the death of three family members in

Alcalá de Guadaira Alcalá, Alcalà or Alcala may refer to: People * Alcalá (surname), includes a list of people with that name Places Bolivia * Alcalá (Tomina), a town in Bolivia Colombia * Alcalá, Valle del Cauca, Colombia Philippines *Alcala, Cagayan, a mu ...

, Spain. They had been keeping them in plastic sacks in their bathroom. The deaths occurred accidentally due to aluminium phosphide reacting with water or moisture, and becoming phosphine, leading to their death within hours. Aluminium phosphide poisoning is considered a wide-scale problem in the Indian subcontinent.

References

{{Authority control Aluminium compounds Phosphides III-V semiconductors Inorganic insecticides Rodenticides III-V compounds Zincblende crystal structure