Zirconium
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Zirconium is a
chemical element A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
with the
symbol A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...
Zr and
atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
40. The name ''zirconium'' is taken from the name of the mineral
zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the r ...
, the most important source of zirconium. The word is related to
Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, the majority ethnic group in Iran, not to be conflated with the Iranic peoples ** Persian language, an Iranian language of the ...
'' zargun'' (zircon; ''zar-gun'', "gold-like" or "as gold"). It is a
lustrous Lustre (British English) or luster (American English; see spelling differences) is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin ''lux'', meaning "light", and generally ...
, grey-white, strong
transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...
that closely resembles
hafnium Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri M ...
and, to a lesser extent,
titanium Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
. Zirconium is mainly used as a
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, ...
and
opacifier An opacifier is a substance added to a material in order to make the ensuing system opaque. An example of a chemical opacifier is titanium dioxide (TiO2), which is used as an opacifier in paints, in paper, and in plastics. It has very high refracti ...
, although small amounts are used as an alloying agent for its strong resistance to corrosion. Zirconium forms a variety of
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 ...
and
organometallic compounds Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
such as
zirconium dioxide Zirconium dioxide (), sometimes known as zirconia (not to be confused with zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabi ...
and
zirconocene dichloride Zirconocene dichloride is an organozirconium compound composed of a zirconium central atom, with two cyclopentadienyl and two chloro ligands. It is a colourless diamagnetic solid that is somewhat stable in air. Preparation and structure Zirconoce ...
, respectively. Five
isotopes Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
occur naturally, four of which are stable. Zirconium compounds have no known biological role.


Characteristics

Zirconium is a
lustrous Lustre (British English) or luster (American English; see spelling differences) is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin ''lux'', meaning "light", and generally ...
, greyish-white, soft,
ductile Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
,
malleable Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
metal that is solid at room temperature, though it is hard and
brittle A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Bre ...
at lesser purities. In powder form, zirconium is highly flammable, but the solid form is much less prone to ignition. Zirconium is highly resistant to corrosion by alkalis, acids, salt water and other agents. However, it will dissolve in
hydrochloric Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestiv ...
and
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
, especially when
fluorine Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reacti ...
is present.
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, ...
s with
zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
are
magnetic Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...
at less than 35 K.
The
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...
of zirconium is 1855 °C (3371 °F), and the
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envir ...
is 4409 °C (7968 °F). Zirconium has an
electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...
of 1.33 on the Pauling scale. Of the elements within the
d-block A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. The term appears to have been first used by Charles Janet. Each block is named after its characteristic orbital: s-blo ...
with known electronegativities, zirconium has the fifth lowest electronegativity after
hafnium Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri M ...
,
yttrium Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a " rare-earth element". Yttrium is almost always found in co ...
,
lanthanum Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lant ...
, and
actinium Actinium is a chemical element with the symbol Ac and atomic number 89. It was first isolated by Friedrich Oskar Giesel in 1902, who gave it the name ''emanium''; the element got its name by being wrongly identified with a substance An ...
. At room temperature zirconium exhibits a hexagonally close-packed crystal structure, α-Zr, which changes to β-Zr, a body-centered cubic crystal structure, at 863 °C. Zirconium exists in the β-phase until the melting point.


Isotopes

Naturally occurring zirconium is composed of five isotopes. 90Zr, 91Zr, 92Zr and 94Zr are stable, although 94Zr is predicted to undergo
double beta decay In nuclear physics, double beta decay is a type of radioactive decay in which two neutrons are simultaneously transformed into two protons, or vice versa, inside an atomic nucleus. As in single beta decay, this process allows the atom to move clos ...
(not observed experimentally) with a
half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...
of more than 1.10×1017 years. 96Zr has a half-life of 2.4×1019 years, and is the longest-lived radioisotope of zirconium. Of these natural isotopes, 90Zr is the most common, making up 51.45% of all zirconium. 96Zr is the least common, comprising only 2.80% of zirconium. Twenty-eight artificial isotopes of zirconium have been synthesized, ranging in atomic mass from 78 to 110. 93Zr is the longest-lived artificial isotope, with a half-life of 1.53×106 years. 110Zr, the heaviest isotope of zirconium, is the most radioactive, with an estimated half-life of 30 milliseconds. Radioactive isotopes at or above mass number 93 decay by
electron emission In physics, electron emission is the ejection of an electron from the surface of matter, or, in beta decay (β− decay), where a beta particle (a fast energetic electron or positron) is emitted from an atomic nucleus transforming the original nu ...
, whereas those at or below 89 decay by
positron emission Positron emission, beta plus decay, or β+ decay is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (). Positron ...
. The only exception is 88Zr, which decays by
electron capture Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Thi ...
. Five isotopes of zirconium also exist as metastable isomers: 83mZr, 85mZr, 89mZr, 90m1Zr, 90m2Zr and 91mZr. Of these, 90m2Zr has the shortest half-life at 131 nanoseconds. 89mZr is the longest lived with a half-life of 4.161 minutes.


Occurrence

Zirconium has a concentration of about 130 mg/kg within the
Earth's crust Earth's crust is Earth's thin outer shell of rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The ...
and about 0.026 μg/L in sea water. It is not found in nature as a
native metal A native metal is any metal that is found pure in its metallic form in nature. Metals that can be found as native deposits singly or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, manganese, m ...
, reflecting its intrinsic instability with respect to water. The principal commercial source of zirconium is
zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the r ...
(ZrSiO4), a
silicate mineral Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...
, which is found primarily in Australia, Brazil, India, Russia, South Africa and the United States, as well as in smaller deposits around the world. As of 2013, two-thirds of zircon mining occurs in Australia and South Africa. Zircon resources exceed 60 million
tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000  kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s worldwide and annual worldwide zirconium production is approximately 900,000 tonnes. Zirconium also occurs in more than 140 other minerals, including the commercially useful ores
baddeleyite Baddeleyite is a rare zirconium oxide mineral (ZrO2 or zirconia), occurring in a variety of monoclinic prismatic crystal forms. It is transparent to translucent, has high indices of refraction, and ranges from colorless to yellow, green, and dar ...
and
eudialyte Eudialyte, whose name derives from the Greek phrase , , meaning "well decomposable", is a somewhat rare, nine member ring cyclosilicate mineral, which forms in alkaline igneous rocks, such as nepheline syenites. Its name alludes to its ready ...
. Zirconium is relatively abundant in S-type stars, and it has been detected in the sun and in meteorites. Lunar rock samples brought back from several
Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...
missions to the moon have a high zirconium oxide content relative to terrestrial rocks. EPR spectroscopy has been used in investigations of the unusual 3+ valence state of zirconium. The EPR spectrum of Zr3+, which has been initially observed as a parasitic signal in Fe‐doped single crystals of ScPO4, was definitively identified by preparing single crystals of ScPO4 doped with isotopically enriched (94.6%)91Zr. Single crystals of LuPO4 and YPO4 doped with both naturally abundant and isotopically enriched Zr have also been grown and investigated.


Production


Occurrence

Zirconium is a by-product of the mining and processing of the
titanium Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
minerals
ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...
and
rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer Polymorphism (materials science), polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest ...
, as well as
tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
mining. From 2003 to 2007, while prices for the mineral zircon steadily increased from $360 to $840 per tonne, the price for unwrought zirconium metal decreased from $39,900 to $22,700 per ton. Zirconium metal is much more expensive than
zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the r ...
because the reduction processes are costly. Collected from coastal waters, zircon-bearing sand is purified by spiral concentrators to separate lighter materials, which are then returned to the water because they are natural components of beach sand. Using
magnetic separation Magnetic separation is the process of separating components of mixtures by using a magnet to attract magnetic substances. The process that is used for magnetic separation separates non-magnetic substances from those which are magnetic. This techniq ...
, the titanium ores
ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...
and
rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer Polymorphism (materials science), polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest ...
are removed. Most zircon is used directly in commercial applications, but a small percentage is converted to the metal. Most Zr metal is produced by the reduction of the zirconium(IV) chloride with
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
metal in the
Kroll process The Kroll process is a pyrometallurgical industrial process used to produce metallic titanium from titanium tetrachloride. The Kroll process replaced the Hunter process for almost all commercial production. Process In the Kroll process, the TiCl ...
. The resulting metal is sintered until sufficiently ductile for metalworking.


Separation of zirconium and hafnium

Commercial zirconium metal typically contains 1–3% of
hafnium Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri M ...
, which is usually not problematic because the chemical properties of hafnium and zirconium are very similar. Their neutron-absorbing properties differ strongly, however, necessitating the separation of hafnium from zirconium for nuclear reactors. Several separation schemes are in use.Nielsen, Ralph (2005) "Zirconium and Zirconium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim. The liquid-liquid extraction of the
thiocyanate Thiocyanate (also known as rhodanide) is the anion . It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Mercury(II) thiocyanate was formerly used in pyr ...
-oxide derivatives exploits the fact that the hafnium derivative is slightly more soluble in
methyl isobutyl ketone Methyl isobutyl ketone (MIBK) is the common name for the organic compound 4-methylpentan-2-one, condensed chemical formula (CH3)2CHCH2C(O)CH3. This colourless liquid, a ketone, is used as a solvent for gums, resins, paints, varnishes, lacquers, and ...
than in water. This method is used mainly in United States. In India, TBP-Nitrate solvent extraction process is used for the separation Zr and Hf can also be separated by fractional crystallization of potassium hexafluorozirconate (K2ZrF6), which is less soluble in water than the analogous hafnium derivative.
Fractional distillation Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation to ...
of the tetrachlorides, also called
extractive distillation Extractive distillation is defined as distillation in the presence of a miscible, high-boiling, relatively non-volatile component, the solvent, that forms no azeotrope with the other components in the mixture. The method is used for mixtures h ...
, is used primarily in Europe. The product of a quadruple VAM (vacuum arc melting) process, combined with hot extruding and different rolling applications is cured using high-pressure, high-temperature gas
autoclaving An autoclave is a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform steriliza ...
. This produces reactor-grade zirconium that is about 10 times more expensive than the hafnium-contaminated commercial grade. Hafnium must be removed from zirconium for nuclear applications because hafnium has a neutron absorption cross-section 600 times greater than zirconium. The separated hafnium can be used for reactor
control rods Control rods are used in nuclear reactors to control the rate of fission of the nuclear fuel – uranium or plutonium. Their compositions include chemical elements such as boron, cadmium, silver, hafnium, or indium, that are capable of absorbing ...
.


Compounds

Like other
transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...
s, zirconium forms a wide range of
inorganic compounds 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 chemi ...
and
coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...
es. In general, these compounds are colourless diamagnetic solids wherein zirconium has the
oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
+4. Far fewer Zr(III) compounds are known, and Zr(II) is very rare.


Oxides, nitrides, and carbides

The most common oxide is
zirconium dioxide Zirconium dioxide (), sometimes known as zirconia (not to be confused with zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabi ...
, ZrO2, also known as ''zirconia''. This clear to white-coloured solid has exceptional fracture toughness (for a ceramic) and chemical resistance, especially in its cubic form. These properties make zirconia useful as a thermal barrier coating, although it is also a common
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 ...
substitute. Zirconium monoxide, ZrO, is also known and
S-type star An S-type star (or just S star) is a cool giant with approximately equal quantities of carbon and oxygen in its atmosphere. The class was originally defined in 1922 by Paul Merrill for stars with unusual absorption lines and molecular bands no ...
s are recognised by detection of its emission lines. Zirconium tungstate has the unusual property of shrinking in all dimensions when heated, whereas most other substances expand when heated.
Zirconyl chloride Zirconyl chloride is the inorganic compound with the formula of r4(OH)8(H2O)16l8(H2O)12, more commonly written ZrOCl2·8H2O, and referred to as zirconyl chloride octahydrate. It is a white solid and is the most common water-soluble derivative of ...
is a rare water-soluble zirconium complex with the relatively complicated formula r4(OH)12(H2O)16l8.
Zirconium carbide Zirconium carbide ( Zr C) is an extremely hard refractory ceramic material, commercially used in tool bits for cutting tools. It is usually processed by sintering. Properties It has the appearance of a gray metallic powder with cubic crystal ...
and
zirconium nitride Zirconium nitride () is an inorganic compound used in a variety of ways due to its properties. Properties ZrN grown by physical vapor deposition (PVD) is a light gold color similar to elemental gold. ZrN has a room-temperature electrical resist ...
are refractory solids. The carbide is used for drilling tools and cutting edges. Zirconium hydride phases are also known.
Lead zirconate titanate Lead zirconate titanate is an inorganic compound with the chemical formula (0≤''x''≤1), commonly abbreviated as PZT. Also called lead zirconium titanate, it is a ceramic perovskite material that shows a marked piezoelectric effect, meaning ...
(PZT) is the most commonly used piezoelectric material, with applications such as ultrasonic transducers, hydrophones, common rail injectors, piezoelectric transformers and micro-actuators.


Halides and pseudohalides

All four common halides are known, ZrF4, ZrCl4, ZrBr4, and ZrI4. All have polymeric structures and are far less volatile than the corresponding monomeric titanium tetrahalides. All tend to
hydrolyse Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolys ...
to give the so-called oxyhalides and dioxides. The corresponding tetra alkoxides are also known. Unlike the halides, the alkoxides dissolve in nonpolar solvents. Dihydrogen hexafluorozirconate is used in the metal finishing industry as an etching agent to promote paint adhesion.


Organic derivatives

Organozirconium chemistry Organozirconium chemistry is the science of exploring the properties, structure, and reactivity of organozirconium compounds, which are organometallic compounds containing chemical bonds between carbon and zirconium. Organozirconium compounds have ...
is key to
Ziegler–Natta catalyst A Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, is a catalyst used in the synthesis of polymers of 1-alkenes ( alpha-olefins). Two broad classes of Ziegler–Natta catalysts are employed, distinguished by their solubility: * ...
s, used to produce
polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins a ...
. This application exploits the ability of zirconium to reversibly form bonds to carbon. Zirconocene dibromide ((C5H5)2ZrBr2), reported in 1952 by Birmingham and Wilkinson, was the first organozirconium compound.
Schwartz's reagent Schwartz's reagent is the common name for the organozirconium compound with the formula (C5H5)2ZrHCl, sometimes called zirconocene hydrochloride or zirconocene chloride hydride, and is named after Jeffrey Schwartz, a chemistry professor at Prince ...
, prepared in 1970 by P. C. Wailes and H. Weigold, is a
metallocene A metallocene is a compound typically consisting of two cyclopentadienyl anions (, abbreviated Cp) bound to a metal center (M) in the oxidation state II, with the resulting general formula Closely related to the metallocenes are the metallocene d ...
used in organic synthesis for transformations of
alkenes In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...
and alkynes. Most complexes of Zr(II) are derivatives of zirconocene, one example being (C5Me5)2Zr(CO)2.


History

The zirconium-containing mineral zircon and related minerals (
jargoon Jargoon or jargon (occasionally in old writings jargounce and jacounce) is a name applied by gemologists to those zircons which are fine enough to be cut as gemstones, but are not of the red color which characterizes the ''hyacinth'' or jacinth. T ...
, hyacinth, jacinth, ligure) were mentioned in biblical writings. The mineral was not known to contain a new element until 1789, when Klaproth analyzed a jargoon from the island of Ceylon (now Sri Lanka). He named the new element Zirkonerde (zirconia).
Humphry Davy Sir Humphry Davy, 1st Baronet, (17 December 177829 May 1829) was a British chemist and inventor who invented the Davy lamp and a very early form of arc lamp. He is also remembered for isolating, by using electricity, several elements for t ...
attempted to isolate this new element in 1808 through electrolysis, but failed. Zirconium metal was first obtained in an impure form in 1824 by Berzelius by heating a mixture of potassium and potassium zirconium fluoride in an iron tube. The '' crystal bar process'' (also known as the ''Iodide Process''), discovered by Anton Eduard van Arkel and
Jan Hendrik de Boer Jan Hendrik de Boer (19 March 1899 – 25 April 1971) was a Dutch physicist and chemist. De Boer was born in Ruinen, De Wolden, and died in The Hague. He studied at the University of Groningen and was later employed in industry. Together with ...
in 1925, was the first industrial process for the commercial production of metallic zirconium. It involves the formation and subsequent thermal decomposition of zirconium tetraiodide, and was superseded in 1945 by the much cheaper
Kroll process The Kroll process is a pyrometallurgical industrial process used to produce metallic titanium from titanium tetrachloride. The Kroll process replaced the Hunter process for almost all commercial production. Process In the Kroll process, the TiCl ...
developed by
William Justin Kroll :''See also German classic philologist, Wilhelm Kroll (philologist) (1869–1939).'' William Justin Kroll (born Guillaume Justin Kroll; November 24, 1889 – March 30, 1973) was a Luxembourgish metallurgist. He is best known for inventing the ...
, in which zirconium tetrachloride is reduced by magnesium: :ZrCl4 + 2Mg -> Zr + 2MgCl2


Applications

Approximately 900,000 tonnes of zirconium ores were mined in 1995, mostly as zircon.


Compounds

Most zircon is used directly in high-temperature applications. Because it is refractory, hard, and resistant to chemical attack, zircon finds many applications. Its main use is as an opacifier, conferring a white, opaque appearance to ceramic materials. Because of its chemical resistance, zircon is also used in aggressive environments, such as moulds for molten metals.
Zirconium dioxide Zirconium dioxide (), sometimes known as zirconia (not to be confused with zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabi ...
(ZrO2) is used in laboratory crucibles, in metallurgical furnaces, and as a refractory material. Because it is mechanically strong and flexible, it can be sintered into ceramic knives and other blades. Zircon (ZrSiO4) and
cubic zirconia Cubic zirconia (CZ) is the cubic crystalline form of zirconium dioxide (ZrO2). The synthesized material is hard and usually colorless, but may be made in a variety of different colors. It should not be confused with zircon, which is a zirco ...
(ZrO2) are cut into gemstones for use in jewelry. Zirconium dioxide is a component in some
abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...
s, such as grinding wheels and
sandpaper upright=1.35, Sheets of sandpaper with different grit sizes (40 (coarse), 80, 150, 240, 600 (fine)). Sandpaper and glasspaper are names used for a type of coated abrasive that consists of sheets of paper or cloth with abrasive material glued to ...
.


Metal

A small fraction of the zircon is converted to the metal, which finds various niche applications. Because of zirconium's excellent resistance to corrosion, it is often used as an alloying agent in materials that are exposed to aggressive environments, such as surgical appliances, light filaments, and watch cases. The high reactivity of zirconium with oxygen at high temperatures is exploited in some specialised applications such as explosive primers and as
getter A getter is a deposit of reactive material that is placed inside a vacuum system to complete and maintain the vacuum. When gas molecules strike the getter material, they combine with it chemically or by . Thus the getter removes small amounts of ...
s in
vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type kn ...
s. The same property is (probably) the purpose of including Zr nanoparticles as
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 organolit ...
material in explosive weapons such as the
BLU-97/B Combined Effects Bomb The BLU-97/B Combined Effects Bomb is the submunition used in several cluster bomb type weapon systems, mainly the CBU-87 and its precision-guided version CBU-103. When the bomblets fall, they separate from the main bomb and independently free f ...
. Burning zirconium was used as a light source in some photographic flashbulbs. Zirconium powder with a
mesh size Mesh is a measurement of particle size often used in determining the particle-size distribution of a granular material. For example, a sample from a truckload of peanuts may be placed atop a mesh with 5 mm openings. When the mesh is shaken ...
from 10 to 80 is occasionally used in pyrotechnic compositions to generate sparks. The high reactivity of zirconium leads to bright white sparks.


Nuclear applications

Cladding for nuclear reactor fuels consumes about 1% of the zirconium supply, mainly in the form of
zircaloy Zirconium alloys are solid solutions of zirconium or other metals, a common subgroup having the trade mark Zircaloy. Zirconium has very low absorption cross-section of thermal neutrons, high hardness, ductility and corrosion resistance. One of the ...
s. The desired properties of these alloys are a low neutron-capture cross-section and resistance to corrosion under normal service conditions. Efficient methods for removing the hafnium impurities were developed to serve this purpose. One disadvantage of zirconium alloys is the reactivity with water, producing
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
, leading to degradation of the fuel rod cladding: : Zr + 2H2O -> ZrO2 + 2H2 Hydrolysis is very slow below 100 °C, but rapid at temperature above 900 °C. Most metals undergo similar reactions. The redox reaction is relevant to the instability of fuel assemblies at high temperatures. This reaction occurred in the reactors 1, 2 and 3 of the
Fukushima I Nuclear Power Plant may refer to: Japan * Fukushima Prefecture, Japanese prefecture **Fukushima, Fukushima, capital city of Fukushima Prefecture, Japan *** Fukushima University, national university in Japan *** Fukushima Station (Fukushima) in Fukushima, Fukushim ...
(Japan) after the reactor cooling was interrupted by the earthquake and tsunami disaster of March 11, 2011, leading to the
Fukushima I nuclear accidents The was a nuclear accident in 2011 at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan. The proximate cause of the disaster was the 2011 Tōhoku earthquake and tsunami, which occurred on the afternoon of 11 March 2011 ...
. After venting the hydrogen in the maintenance hall of those three reactors, the mixture of hydrogen with atmospheric
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
exploded, severely damaging the installations and at least one of the containment buildings. Zirconium is a constituent of the
uranium zirconium hydride Uranium zirconium hydride (UZrH), a combination of uranium hydride and zirconium(II) hydride, is used as the fuel in TRIGA reactors. UZrH fuel is used in most research reactors at universities and has a large, prompt negative fuel temperature coeffi ...
(UZrH) nuclear fuel used in
TRIGA TRIGA (Training, Research, Isotopes, General Atomics) is a class of nuclear research reactor designed and manufactured by General Atomics. The design team for TRIGA, which included Edward Teller, was led by the physicist Freeman Dyson. Design ...
reactors.


Space and aeronautic industries

Materials fabricated from zirconium metal and ZrO2 are used in space vehicles where resistance to heat is needed. High temperature parts such as combustors, blades, and vanes in
jet engine A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
s and stationary
gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...
s are increasingly being protected by thin
ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
layers, usually composed of a mixture of zirconia and
yttria Yttrium oxide, also known as yttria, is Y2 O3. It is an air-stable, white solid substance. The thermal conductivity of yttrium oxide is 27 W/(m·K). Uses Phosphors Yttria is widely used to make Eu:YVO4 and Eu:Y2O3 phosphors that give the red ...
.


Medical uses

Zirconium-bearing compounds are used in many biomedical applications, including dental implants and
crowns A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
, knee and hip replacements, middle-ear ossicular chain reconstruction, and other restorative and
prosthetic In medicine, a prosthesis (plural: prostheses; from grc, πρόσθεσις, prósthesis, addition, application, attachment), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trau ...
devices. Zirconium binds
urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important r ...
, a property that has been utilized extensively to the benefit of patients with chronic kidney disease. For example, zirconium is a primary component of the
sorbent A sorbent is a material used to absorb or adsorb liquids or gases. Examples include: *A material similar to molecular sieve material, which acts by adsorption (attracting molecules to its surface). It has a large internal surface area and good th ...
column dependent dialysate regeneration and recirculation system known as the REDY system, which was first introduced in 1973. More than 2,000,000 dialysis treatments have been performed using the sorbent column in the REDY system. Although the REDY system was superseded in the 1990s by less expensive alternatives, new sorbent-based dialysis systems are being evaluated and approved by the U.S.
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
(FDA). Renal Solutions developed the DIALISORB technology, a portable, low water dialysis system. Also, developmental versions of a Wearable Artificial Kidney have incorporated sorbent-based technologies. Sodium zirconium cyclosilicate is used by mouth in the treatment of
hyperkalemia Hyperkalemia is an elevated level of potassium (K+) in the blood. Normal potassium levels are between 3.5 and 5.0mmol/L (3.5 and 5.0mEq/L) with levels above 5.5mmol/L defined as hyperkalemia. Typically hyperkalemia does not cause symptoms. Occasi ...
. It is a selective sorbent designed to trap
potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...
ions in preference to other
ions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
throughout the gastrointestinal tract. A mixture of monomeric and polymeric Zr4+ and Al3+ complexes with
hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...
,
chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
and
glycine Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid (carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinogeni ...
, called Aluminium zirconium tetrachlorohydrex gly or AZG, is used in a preparation as an antiperspirant in many deodorant products. It is selected for its ability to obstruct pores in the skin and prevent sweat from leaving the body.


Defunct applications

Zirconium carbonate (3ZrO2·CO2·H2O) was used in lotions to treat poison ivy but was discontinued because it occasionally caused skin reactions.


Safety

Although zirconium has no known biological role, the human body contains, on average, 250 milligrams of zirconium, and daily intake is approximately 4.15 milligrams (3.5 milligrams from food and 0.65 milligrams from water), depending on dietary habits. Zirconium is widely distributed in nature and is found in all biological systems, for example: 2.86 μg/g in whole wheat, 3.09 μg/g in brown rice, 0.55 μg/g in
spinach Spinach (''Spinacia oleracea'') is a leafy green flowering plant native to central and western Asia. It is of the order Caryophyllales, family Amaranthaceae, subfamily Chenopodioideae. Its leaves are a common edible vegetable consumed either f ...
, 1.23 μg/g in eggs, and 0.86 μg/g in ground beef. Further, zirconium is commonly used in commercial products (e.g.
deodorant A deodorant is a substance applied to the body to prevent or mask body odor due to bacterial breakdown of perspiration or vaginal secretions, for example in the armpits, groin, or feet. A subclass of deodorants, called antiperspirants, prevents ...
sticks, aerosol antiperspirants) and also in water purification (e.g. control of
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
pollution, bacteria- and pyrogen-contaminated water).Lee DBN, Roberts M, Bluchel CG, Odell RA. (2010) Zirconium: Biomedical and nephrological applications. ASAIO J 56(6):550-556. Short-term exposure to zirconium powder can cause irritation, but only contact with the eyes requires medical attention. Persistent exposure to
zirconium tetrachloride Zirconium(IV) chloride, also known as zirconium tetrachloride, () is an inorganic compound frequently used as a precursor to other compounds of zirconium. This white high-melting solid hydrolyzes rapidly in humid air. Structure Unlike molecular T ...
results in increased mortality in rats and guinea pigs and a decrease of blood
hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...
and
red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
s in dogs. However, in a study of 20 rats given a standard diet containing ~4% zirconium oxide, there were no adverse effects on growth rate, blood and urine parameters, or mortality. The U.S.
Occupational Safety and Health Administration The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
(OSHA) legal limit (
permissible exposure limit The permissible exposure limit (PEL or OSHA PEL) is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. Permissible exposure limits are established by the Occupational ...
) for zirconium exposure is 5 mg/m3 over an 8-hour workday. The
National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
(NIOSH)
recommended exposure limit A recommended exposure limit (REL) is an occupational exposure limit that has been recommended by the United States National Institute for Occupational Safety and Health. The REL is a level that NIOSH believes would be protective of worker safet ...
(REL) is 5 mg/m3 over an 8-hour workday and a short term limit of 10 mg/m3. At levels of 25 mg/m3, zirconium is
immediately dangerous to life and health The term immediately dangerous to life or health (IDLH) is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that is "likely to cause death or immediate or delayed permanent advers ...
. However, zirconium is not considered an industrial health hazard. Furthermore, reports of zirconium-related adverse reactions are rare and, in general, rigorous cause-and-effect relationships have not been established. No evidence has been validated that zirconium is carcinogenic or genotoxic. Among the numerous radioactive isotopes of zirconium, 93Zr is among the most common. It is released as a product of nuclear fission of 235U and 239Pu, mainly in nuclear power plants and during nuclear weapons tests in the 1950s and 1960s. It has a very long half-life (1.53 million years), its decay emits only low energy radiations, and it is not considered as highly hazardous.


See also

*
Zirconium alloy Zirconium alloys are solid solutions of zirconium or other metals, a common subgroup having the trade mark Zircaloy. Zirconium has very low absorption cross-section of thermal neutrons, high hardness, ductility and corrosion resistance. One of the ...
s *
Zirconia light A zirconia light is an intensely brilliant chemical light produced by incandescent zirconia. It is similar in design to the Drummond light (limelight), but uses a block of zirconia instead of quicklime. Both have been replaced by the electric lig ...


References


External links


Chemistry in its element podcast
(MP3) from the
Royal Society of Chemistry The Royal Society of Chemistry (RSC) is a learned society (professional association) in the United Kingdom with the goal of "advancing the chemistry, chemical sciences". It was formed in 1980 from the amalgamation of the Chemical Society, the Ro ...
's Chemistry World
Zirconium
at ''
The Periodic Table of Videos ''Periodic Videos'' (also known as ''The Periodic Table of Videos'') is a video project and YouTube channel on chemistry. It consists of a series of videos about chemical elements and the periodic table, with additional videos on other topics i ...
'' (University of Nottingham) {{Good article Chemical elements Transition metals Pyrotechnic fuels Chemical elements with hexagonal close-packed structure