In
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...
, a nitride is an
inorganic 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, Si
3N
4), and semiconductors (e.g.,
gallium nitride, GaN). The development of GaN-based
light emitting diode
A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (co ...
s 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 complexes are also common.
Synthesis
Synthesis or synthesize may refer to:
Science Chemistry and biochemistry
* Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors
**Organic synthesis, the chemical synthesis of organ ...
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 thermodyna ...
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 t ...
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 bin ...
, which reflects the strong bonding of "N
3−" to with metal cation(s). Thus,
cubic boron nitride,
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 are used as cutting materials and hard coatings. Hexagonal
boron nitride, which adopts a layered structure, is a useful high-temperature lubricant akin to
molybdenum disulfide. Nitride compounds often have large
band gaps, 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 and silicon nitride. The wide-band gap material
gallium nitride is prized for emitting blue light in
LEDs. Like some oxides, nitrides can absorb hydrogen and have been discussed in the context of
hydrogen storage, 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 li ...
.
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 ...
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 li ...
(), which forms when lithium burns in an atmosphere of .
Sodium nitride and
potassium nitride has been generated, but remains a laboratory curiosity. The nitrides of the
alkaline earth metals 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 (). 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 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 ...
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. It ha ...
,
gallium
Gallium is a chemical element with the Symbol (chemistry), symbol Ga and atomic number 31. Discovered by France, French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in boron group, group 13 of the periodic table and is similar to ...
, and
indium 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 crystal ...
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) where every carbon atom occupies a tetrahedral site (however wurtzite differs from
sphalerite and
diamond
Diamond is a 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 chemically stable form of carbon at room temperature and pressure, b ...
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 metals, ScN and
YN are both known.
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 and
8 transition metals tend to be nitrogen-poor, and decompose readily at elevated temperatures. For example,
iron nitride, decomposes at 200 °C. Sometimes these materials are called "
interstitial 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 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 element
In chemistry and atomic physics, the main group is the group of elements (sometimes called the representative elements) whose lightest members are represented by helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, and fluorine as arran ...
s 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 molec ...
() and
tetrasulfur tetranitride () 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 triatomic anion (N
3-).
References
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