Phosphide

phosphide

Any of a class of chemical compounds in which phosphorous is combined with a metal. Phosphides exhibit a wide variety of chemical and physical properties. Phosphides that are rich in metal have high melting points and are hard, brittle, and chemically inert; these compounds have high thermal and electrical conductivities.

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phosphide [′fä‚sfīd]

(inorganic chemistry)

Binary compound of trivalent phosphorus, as in Na₃P.

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Phosphide 

any of the compounds of phosphorus with metals or with nonmetals, such as B, Si, and As, that are more electropositive than phosphorus. Phosphides of nontransition metals and of metals of the copper subgroup, which have the compositions Me₃P and Me₂P₅ in the case of alkali metals, Me₃P₂ with alkaline-earth metals, and Me₃P and MeP₂ with metals of the copper subgroup (Me denoting the metal), are ionic, saltlike compounds. Phosphides of alkali and alkaline-earth metals are readily decomposed by water and dilute acids, phosphine being liberated in the process. Phosphides of alkaline-earth metals and metals of the copper subgroup are not stable at elevated temperatures; at relatively high phosphorus concentrations, these phosphides are semiconducting.

Phosphides of transition metals (CrP, MoP, TiP), including lanthanides and actinides (LaP, PuP, U₃P₄), are chemically stable and do not decompose in water or dilute acids; their physical properties are close to those of either semiconductors (UP, NbP, MnP) or metals (TiP, ZrP). The phosphides of boron, aluminum, and indium are covalent compounds that are high-melting and semiconducting. Phosphides also include volatile molecular compounds, such as those with sulfur, selenium, and tellurium.

Phosphides are formed by a synthesis of the elements at temperatures of 600°–1200°C in a vacuum or atmosphere of inert gases; by the reaction of phosphine with metals and nonmetals or with the corresponding oxides; by the double exchange of phosphine with halides or sulfides, for example, B₂S₃ + 2PH₃ = 2BP + 3H₂S; and by the reduction of metal phosphates by hydrogen at high temperatures.

A number of phosphides (InP, GaP) have great importance as semiconductor materials. Zinc phosphide is used as a rodenticide. Phosphides are used in certain nonferrous alloys, such as phosphor bronze, for deoxidation and improvement of antifriction properties. The tendency of certain phosphides to decompose with the liberation of phosphines, which ignite spontaneously in air, is used in the production of signal devices.

L. V. KUBASOVA