Zirconium

Jai Ganesh · 2025-08-02 16:46:33

Zirconium

Gist

Zirconium (Zr) is a chemical element, a lustrous, greyish-white transition metal. It's known for its high melting point, resistance to corrosion, and ability to withstand high temperatures. It's also a key component in the production of nuclear fuel rods and various high-temperature and high-corrosion applications.

Zirconium is used in high-temperature applications due to its melting point, but its reactivity at high temperatures requires careful handling and shielding.

Summary

Zirconium is a chemical element; it has symbol Zr and atomic number 40. First identified in 1789, isolated in impure form in 1824, and manufactured at scale by 1925, pure zirconium is a lustrous transition metal with a greyish-white color that closely resembles hafnium and, to a lesser extent, titanium. It is solid at room temperature, ductile, malleable and corrosion-resistant. The name zirconium is derived from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian zargun (zircon; zar-gun, "gold-like" or "as gold").[ Besides zircon, zirconium occurs in over 140 other minerals, including baddeleyite and eudialyte; most zirconium is produced as a byproduct of minerals mined for titanium and tin.

Zirconium forms a variety of inorganic compounds, such as zirconium dioxide, and organometallic compounds, such as zirconocene dichloride. Five isotopes occur naturally, four of which are stable. The metal and its alloys are mainly used as a refractory and opacifier; zirconium alloys are used to clad nuclear fuel rods due to their low neutron absorption and strong resistance to corrosion, and in space vehicles and turbine blades where high heat resistance is necessary. Zirconium also finds uses in flashbulbs, biomedical applications such as dental implants and prosthetics, deodorant, and water purification systems.

Zirconium compounds have no known biological role, though the element is widely distributed in nature and appears in small quantities in biological systems without adverse effects. There is no indication of zirconium as a carcinogen. The main hazards posed by zirconium are flammability in powder form and irritation of the eyes.

Key Properties:

Atomic Number: 40
Symbol: Zr
Melting Point: 1855 °C
Corrosion Resistance: Highly resistant to acids, alkalis, and seawater.
High Temperature Applications: Zirconium is used in high-temperature applications due to its melting point, but its reactivity at high temperatures requires careful handling and shielding.
Discovery and Production: Zirconium was discovered by Martin Heinrich Klaproth in 1789.
* Pure zirconium was first isolated in 1925.
* Zirconium is primarily extracted from the mineral zircon (zirconium silicate).
* Major producers of zirconium include Australia, China, Indonesia, South Africa, and Ukraine.

Applications:

Nuclear Power: Zirconium alloys are crucial components in nuclear reactor fuel rods due to their low neutron absorption cross-section and resistance to corrosion in high-temperature water.
High-Temperature Applications: Used in jet engines, space and aeronautic industries, and various high-temperature parts.
Corrosion-Resistant Materials: Used in chemical processing equipment and other applications where corrosion resistance is essential.
Alloying Agent: Zirconium is used to improve the strength, ductility, and corrosion resistance of various alloys.
Ceramics: Zirconium dioxide (zirconia) is used in ceramics for its hardness, high melting point, and other unique properties.
Dental Applications: Zirconia is used in dental crowns and other restorations due to its strength and durability.
Other Applications: Surgical instruments, photographic flashbulbs, and television glass.

Important Considerations:

Reactivity: Zirconium is a reactive metal, particularly at high temperatures, requiring special handling and shielding during welding and other processes.
Toxicity: While not considered highly toxic, zirconium dust can cause skin and respiratory irritation, and some isotopes are radioactive.

Details

Zirconium (Zr) is a chemical element, metal of Group 4 (IVb) of the periodic table, used as a structural material for nuclear reactors.

Element Properties

atomic number : 40
atomic weight : 91.22
melting point : 1,852 °C (3,366 °F)
boiling point : 3,578 °C (6,472 °F)
specific gravity : 6.49 at 20 °C (68 °F)
oxidation state : +4

Properties, occurrence, and uses

Zirconium, obscure before the late 1940s, became a significant engineering material for nuclear energy applications because it is highly transparent to neutrons. The element was identified (1789) in zircon, ZrSiO4 (zirconium orthosilicate), from its oxide by the German chemist Martin Heinrich Klaproth, and the metal was isolated (1824) in impure form by the Swedish chemist Jöns Jacob Berzelius. The impure metal, even when 99 percent pure, is hard and brittle. The white, soft, malleable, and ductile metal of higher purity was first produced in quantity (1925) by the Dutch chemists Anton E. van Arkel and J.H. de Boer by the thermal decomposition of zirconium tetraiodide, ZrI4. In the early 1940s, William Justin Kroll of Luxembourg developed his cheaper process of making the metal based on the reduction of zirconium tetrachloride, ZrCl4, by magnesium. In the early 21st century, leading producers of zirconium included Australia, South Africa, China, and Indonesia; Mozambique, India, and Sri Lanka were additional producers.

Zirconium is relatively abundant in Earth’s crust, but not in concentrated deposits, and is characteristically observed in S-type stars. The mineral zircon, which is generally found in alluvial deposits in stream beds, ocean beaches, or old lake beds, is the only commercial source of zirconium. Baddeleyite, which is essentially pure zirconium dioxide, ZrO2, is the only other important zirconium mineral, but the commercial product is more cheaply recovered from zircon. Zirconium is produced by the same process as that used for titanium. These zirconium minerals generally have a hafnium content that varies from a few tenths of 1 percent to several percent. For some purposes separation of the two elements is not important: zirconium containing about 1 percent of hafnium is as acceptable as pure zirconium.

The most important use of zirconium is in nuclear reactors for cladding fuel rods, for alloying with uranium, and for reactor-core structures because of its unique combination of properties. Zirconium has good strength at elevated temperatures, resists corrosion from the rapidly circulating coolants, does not form highly radioactive isotopes, and withstands mechanical damage from neutron bombardment. Hafnium, present in all zirconium ores, must be scrupulously removed from the metal intended for reactor uses because hafnium strongly absorbs thermal neutrons.

Separation of hafnium and zirconium is generally accomplished by a liquid-liquid countercurrent-extraction procedure. In the procedure, crude zirconium tetrachloride is dissolved in an aqueous solution of ammonium thiocyanate, and methyl isobutyl ketone is passed countercurrent to the aqueous mixture, with the result that the hafnium tetrachloride is preferentially extracted.

The atomic radii of zirconium and hafnium are 1.45 and 1.44 Å, respectively, while the radii of the ions are Zr4+, 0.74 Å, and Hf4+, 0.75 Å. The virtual identity of atomic and ionic sizes, resulting from the lanthanoid contraction, has the effect of making the chemical behaviour of these two elements more similar than for any other pair of elements known. Although the chemistry of hafnium has been studied less than that of zirconium, the two are so similar that only very small quantitative differences—for example, in solubilities and volatilities of compounds—would be expected in cases that have not actually been investigated.

Zirconium absorbs oxygen, nitrogen, and hydrogen in astonishing amounts. At about 800 °C (1,500 °F) it combines chemically with oxygen to yield the oxide, ZrO2. Zirconium reduces such refractory crucible materials as the oxides of magnesium, beryllium, and thorium. This strong affinity for oxygen and other gases accounts for its use as a getter for removing residual gases in electron tubes. At normal temperatures in air, zirconium is passive because of the formation of a protective film of oxide or nitride. Even without this film, the metal is resistant to the action of weak acids and acidic salts. It is best dissolved in hydrofluoric acid, in which procedure the formation of anionic fluoro complexes is important in stabilizing the solution. At normal temperatures it is not particularly reactive but becomes quite reactive with a variety of nonmetals at elevated temperatures. Because of its high corrosion resistance, zirconium has found widespread use in the fabrication of pumps, valves, and heat exchangers. Zirconium is also used as an alloying agent in the production of some magnesium alloys and as an additive in the manufacture of certain steels.

Natural zirconium is a mixture of five stable isotopes: zirconium-90 (51.46 percent), zirconium-91 (11.23 percent), zirconium-92 (17.11 percent), zirconium-94 (17.40 percent), zirconium-96 (2.80 percent). Two allotropes exist: below 862 °C (1,584 °F) a hexagonal close-packed structure, above that temperature a body-centered cubic.

Compounds

Zirconium is predominantly in the +4 oxidation state in its compounds. Some less stable compounds, however, are known in which the oxidation state is +3. (The most important respect in which zirconium differs from titanium is that lower oxidation states are of minor importance.) The increased size of the atoms makes the oxides more basic and the aqueous chemistry somewhat more extensive and permits the attainment of coordination numbers 7 and, quite frequently, 8 in a number of zirconium compounds.

Various zirconium compounds have important applications in industry. Among these are zirconium dioxide (also called zirconia), ZrO2, a hard, white or yellow-brown solid with a high melting point—about 2,700° C (4,892° F). It is commonly used as a gem-diamond simulant, an abrasive, a refractory material, and a component of acid- and alkali-resistant glasses and of ceramics employed in fuel cells.

Other important industrial compounds of zirconium include the tetrachloride ZrCl4 and the sulfate Zr(SO4)2∙4H2O. Prepared by the chlorination of zirconium carbide or oxide, zirconium tetrachloride is used to produce organic zirconium compounds and as a catalyst in such reactions as the cracking of petroleum and polymerization of ethylene. Zirconium sulfate, produced by the action of sulfuric acid on zirconium hydoxide, Zr(OH)4, is useful as a lubricant, a chemical reagent, and in the tanning of white leather.

Additional Information:

Appearance

A hard, silvery metal that is very resistant to corrosion.

Uses

Zirconium does not absorb neutrons, making it an ideal material for use in nuclear power stations. More than 90% of zirconium is used in this way. Nuclear reactors can have more than 100,000 metres of zirconium alloy tubing. With niobium, zirconium is superconductive at low temperatures and is used to make superconducting magnets.

Zirconium metal is protected by a thin oxide layer making it exceptionally resistant to corrosion by acids, alkalis and seawater. For this reason it is extensively used by the chemical industry.

Zirconium(IV) oxide is used in ultra-strong ceramics. It is used to make crucibles that will withstand heat-shock, furnace linings, foundry bricks, abrasives and by the glass and ceramics industries. It is so strong that even scissors and knives can be made from it. It is also used in cosmetics, antiperspirants, food packaging and to make microwave filters.

Zircon is a natural semi-precious gemstone found in a variety of colours. The most desirable have a golden hue. The element was first discovered in this form, resulting in its name. Cubic zirconia (zirconium oxide) is a synthetic gemstone. The colourless stones, when cut, resemble diamonds.

Zircon mixed with vanadium or praseodymium makes blue and yellow pigments for glazing pottery.

Biological role

Zirconium has no known biological role. It has low toxicity.

Natural abundance

Zirconium occurs in about 30 mineral species, the major ones being zircon and baddeleyite. More than 1.5 million tonnes of zircon are mined each year, mainly in Australia and South Africa. Most baddeleyite is mined in Brazil.

Zirconium metal is produced commercially by first converting zircon to zirconium chloride, and then reducing the chloride with magnesium.

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#1 2025-08-02 16:46:33

Zirconium

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