In
chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
, a nitride is an
inorganic
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 chemist ...
compound of
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
. The "nitride" anion, N
3- ion, is very elusive but compounds of nitride are numerous, although rarely naturally occuring. Some nitrides have a find applications, such as wear-resistant coatings (e.g.,
titanium nitride
Titanium nitride (TiN; sometimes known as Tinite) is an extremely hard ceramic material, often used as a physical vapor deposition (PVD) coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface prop ...
, TiN), hard ceramic materials (e.g.,
silicon nitride
Silicon nitride is a chemical compound of the elements silicon and nitrogen. is the most thermodynamically stable and commercially important of the silicon nitrides, and the term "silicon nitride" commonly refers to this specific composition. It ...
, Si
3N
4), and semiconductors (e.g.,
gallium nitride
Gallium nitride () is a binary III/ V direct bandgap semiconductor commonly used in blue light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords ...
, GaN). The development of GaN-based
light emitting diodes was recognized by the 2014
Nobel Prize in Physics
)
, image = Nobel Prize.png
, alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...
.
Metal nitrido complex
Metal nitrido complexes are coordination compounds and metal clusters that contain an atom of nitrogen bound only to transition metals. These compounds are ''molecular'', i.e. discrete in contrast to the polymeric, dense nitride materials that ar ...
es are also common.
Synthesis of inorganic metal nitrides is challenging because nitrogen gas (N
2) is not very reactive at low temperatures, but it becomes more reactive at higher temperatures. Therefore, a balance must be achieved between the low reactivity of nitrogen gas at low temperatures and the
entropy
Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynam ...
driven formation of N
2 at high temperatures. However, synthetic methods for nitrides are growing more sophisticated and the materials are of increasing technological relevance.
Uses of nitrides
Like
carbide
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece.
Interstitial / Metallic carbides
The carbides of the ...
s, nitrides are often
refractory material
In materials science, a refractory material or refractory is a material that is resistant to decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperatures. Refractories are polycrystalline, polyphase, ...
s owing to their high
lattice energy
In chemistry, the lattice energy is the energy change upon formation of one mole of a crystalline ionic compound from its constituent ions, which are assumed to initially be in the gaseous state. It is a measure of the cohesive forces that bind ...
, which reflects the strong bonding of "N
3−" to with metal cation(s). Thus,
cubic boron nitride
Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal ...
,
titanium nitride
Titanium nitride (TiN; sometimes known as Tinite) is an extremely hard ceramic material, often used as a physical vapor deposition (PVD) coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface prop ...
, and
silicon nitride
Silicon nitride is a chemical compound of the elements silicon and nitrogen. is the most thermodynamically stable and commercially important of the silicon nitrides, and the term "silicon nitride" commonly refers to this specific composition. It ...
are used as cutting materials and hard coatings. Hexagonal
boron nitride
Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal ...
, which adopts a layered structure, is a useful high-temperature lubricant akin to
molybdenum disulfide. Nitride compounds often have large
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 (in ...
s, thus nitrides are usually
insulators or
wide-bandgap semiconductor
Wide-bandgap semiconductors (also known as WBG semiconductors or WBGSs) are semiconductor materials which have a larger band gap than conventional semiconductors. Conventional semiconductors like silicon have a bandgap in the range of 0.6 †...
s; examples include
boron nitride
Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal ...
and silicon nitride. The wide-band gap material
gallium nitride
Gallium nitride () is a binary III/ V direct bandgap semiconductor commonly used in blue light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords ...
is prized for emitting blue light in
LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
s. Like some oxides, nitrides can absorb hydrogen and have been discussed in the context of
hydrogen storage
Hydrogen storage can be accomplished by several existing methods of holding hydrogen for later use. These include mechanical approaches such as using high pressures and low temperatures, or employing chemical compounds that release H2 upon demand ...
, e.g.
lithium nitride
Lithium nitride is a compound with the formula Li3N. It is the only stable alkali metal nitride. The solid has a reddish-pink color and high melting point.
Preparation and handling
Lithium nitride is prepared by direct combination of elemental ...
.
Examples
Classification of such a varied group of compounds is somewhat arbitrary. Compounds where nitrogen is not assigned −3 oxidation state are not included, such as
nitrogen trichloride where the oxidation state is +3; nor are
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 was ...
and its many organic derivatives.
Nitrides of the s-block elements
Only one
alkali metal
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
nitride is stable, the purple-reddish
lithium nitride
Lithium nitride is a compound with the formula Li3N. It is the only stable alkali metal nitride. The solid has a reddish-pink color and high melting point.
Preparation and handling
Lithium nitride is prepared by direct combination of elemental ...
(), which forms when lithium burns in an atmosphere of .
Sodium nitride
Sodium nitride is the inorganic compound with the chemical formula Na3N. In contrast to lithium nitride and some other nitrides, sodium nitride is an extremely unstable alkali metal nitride. It can be generated by combining atomic beams of sodium ...
and
potassium nitride
Potassium nitride is an unstable chemical compound. Several syntheses were erroneously claimed in the 19th century, and by 1894 it was assumed that it did not exist.
However, a synthesis of this compound was claimed in 2004. It is observed to have ...
has been generated, but remains a laboratory curiosity. The nitrides of the
alkaline earth metal
The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar properties: they are al ...
s that have the formula are however numerous. Examples include
beryllium nitride
Beryllium nitride, Be3N2, is a nitride of beryllium. It can be prepared from the elements at high temperature (1100–1500 °C);Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier unlike beryllium azide or BeN6, ...
(),
magnesium nitride
Magnesium nitride, which possesses the chemical formula Mg3N2, is an inorganic compound of magnesium and nitrogen. At room temperature and pressure it is a greenish yellow powder.
Preparation
* By passing dry nitrogen over heated magnesium:
: ...
(),
calcium nitride
Calcium nitride is the inorganic compound with the chemical formula Ca3 N2. It exists in various forms (isomorphs), α-calcium nitride being more commonly encountered.
Structure
α-Calcium nitride adopts an anti-bixbyite structure, similar to ...
(), and
strontium nitride
Strontium nitride, Sr3N2, is produced by burning strontium metal in air (resulting in a mixture with strontium oxide) or in nitrogen. Like other metal nitrides, it reacts with water to give strontium hydroxide and ammonia:
:Sr3N2 + 6 H2O → 3 Sr ...
(). The nitrides of electropositive metals (including Li, Zn, and the alkaline earth metals) readily hydrolyze upon contact with water, including the moisture in the air:
:
Nitrides of the p-block elements
Boron nitride
Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal ...
exists as several forms (
polymorphs). Nitrides of
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
and phosphorus are also known, but only the former is commercially important. The nitrides of
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
,
gallium
Gallium is a chemical element with the symbol Ga and atomic number 31. Discovered by French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminiu ...
, and
indium
Indium is a chemical element with the symbol In and atomic number 49. Indium is the softest metal that is not an alkali metal. It is a silvery-white metal that resembles tin in appearance. It is a post-transition metal that makes up 0.21 parts p ...
adopt diamond-like
wurtzite structure
In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the trigonal crysta ...
in which each atom occupies tetrahedral sites. For example, in aluminium nitride, each aluminium atom has four neighboring nitrogen atoms at the corners of a tetrahedron and similarly each nitrogen atom has four neighboring aluminium atoms at the corners of a tetrahedron. This structure is like hexagonal diamond (
lonsdaleite
Lonsdaleite (named in honour of Kathleen Lonsdale), also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice, as opposed to the cubical lattice of conventional diamond. It is found ...
) where every carbon atom occupies a tetrahedral site (however wurtzite differs from
sphalerite
Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimen ...
and
diamond
Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the Chemical stability, chemically stable form of car ...
in the relative orientation of tetrahedra).
Thallium(I) nitride () is known, but thallium(III) nitride (TlN) is not.
Transition metal nitrides
For the
group 3 Group 3 may refer to:
*Group 3 element, chemical element classification
*Group 3 (racing), FIA classification for auto racing
* Group 3, the third tier of races in worldwide Thoroughbred horse racing
* Group 3 image format, Group 3 & Group 4 are ...
metals, ScN and
YN are both known.
Group 4 Group 4 may refer to:
*Group 4 element, chemical element classification
*Group 4 (racing), classification for cars in auto racing and rallying
* G4S, formerly Group 4 Securicor, a prominent British security company
*IB Group 4 subjects
The Group 4 ...
,
5, and
6 transition metals (the titanium, vanadium and chromium groups) all form nitrides. They are
refractory
In materials science, a refractory material or refractory is a material that is resistant to decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperatures. Refractories are polycrystalline, polyphase, ...
, with high melting point and are chemically stable. Representative is
titanium nitride
Titanium nitride (TiN; sometimes known as Tinite) is an extremely hard ceramic material, often used as a physical vapor deposition (PVD) coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface prop ...
. These materials often adopt the rocksalt crystal structure.
Nitrides of the
group 7 Group 7 may refer to:
* G7, an international group of finance minister
*Group 7 element, chemical element classification
*Halogens (alternative name)
*Group 7 Rugby League, rugby league competition in New South Wales, Australia
*Group 7 (racing)
G ...
and
8 transition metals tend to be nitrogen-poor, and decompose readily at elevated temperatures. For example,
iron nitride
Iron nitrides are inorganic chemical compounds of iron and nitrogen.
Chemical properties
Iron has five nitrides observed at ambient conditions, Fe2N, Fe3N4, Fe4N, Fe7N3 and Fe16N2. They are crystalline, metallic solids. Group 7 and group 8 tra ...
, decomposes at 200 °C. Sometimes these materials are called "
interstitial
An interstitial space or interstice is a space between structures or objects.
In particular, interstitial may refer to:
Biology
* Interstitial cell tumor
* Interstitial cell, any cell that lies between other cells
* Interstitial collagenase ...
nitrides". Platinum nitride and osmium nitride may contain units, and as such should not be called nitrides.
Nitrides of heavier members from group
11 and
12 are less stable than copper nitride, and
zinc nitride
Zinc nitride ( Zn3 N2) is an inorganic compound of zinc and nitrogen, usually obtained as (blue)grey crystals. It is a semiconductor. In pure form, it has the anti-bixbyite structure.
Chemical properties
Zinc nitride can be obtained by thermally ...
(): dry silver nitride () is a
contact explosive
A contact explosive is a chemical substance that explodes violently when it is exposed to a relatively small amount of energy (e.g. friction, pressure, sound, light). Though different contact explosives have varying amounts of energy sensitivit ...
which may detonate from the slightest touch, even a falling water droplet.
Nitrides of the lanthanides and actinides
Nitride containing species of the lanthanides and actinides are of scientific interest as they can provide a useful handle for determining covalency of bonding. Nuclear magnetic resonance (NMR) spectroscopy along with quantum chemical analysis has often been used to determine the degree to which metal nitride bonds are ionic or covalent in character. One example, a uranium nitride, has the highest known nitrogen-15 chemical shift.
Molecular nitrides
Many metals form molecular nitrido complexes, as discussed in the specialized article. The
main group elements also form some molecular nitrides.
Cyanogen
Cyanogen is the chemical compound with the formula ( C N)2. It is a colorless and highly toxic gas with a pungent odor. The molecule is a pseudohalogen. Cyanogen molecules consist of two CN groups – analogous to diatomic halogen molecule ...
() and
tetrasulfur tetranitride
Tetrasulfur tetranitride is an inorganic compound with the formula . This gold-poppy coloured solid is the most important binary sulfur nitride, which are compounds that contain only the elements sulfur and nitrogen. It is a precursor to many S-N ...
() are rare examples of a molecular binary (containing one element aside from nitrogen) nitrides. They dissolve in nonpolar solvents. Both undergo polymerization. is also unstable with respect to the elements, but less so that the isostructural . Heating gives a polymer, and a variety of molecular sulfur nitride anions and cations are also known.
Related to but distinct from nitride is
pernitride diatomic anion () and the
azide
In chemistry, azide is a linear, polyatomic anion with the formula and structure . It is the conjugate base of hydrazoic acid . Organic azides are organic compounds with the formula , containing the azide functional group. The dominant applic ...
triatomic anion (N
3-).
References
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