Zirconium: the essentials
Zirconium is a greyish-white lustrous metal. The finely divided metal can ignite spontaneously in air, especially at elevated temperatures. The solid metal is much more difficult to ignite. The inherent toxicity of zirconium compounds is low. Hafnium is invariably found in zirconium ores, and the separation is difficult. Commercial grade zirconium contains from 1 to 3% hafnium. The hafnium is removed from the zirconium used in the nuclear power industry.
Zirconium is found in S-type stars, and has been identified in the sun and meteorites. Analyses of lunar rock samples show a surprisingly high zirconium oxide content as compared with terrestrial rocks. Some forms of zircon (ZrSiO4) have excellent gemstone qualities.
The image above is a virtual representation of zirconium metal calculated by Patrick Callet using the complex diectric function of the element only.
Zirconium: historical information
The name zircon probably originated from the arabic "zargun", which describes the colour of the gemstone now known as zircon (ZrSiO4). The minerals jargon, hyacinth, and jacinth also contain zircon and these have been known since biblical times and are mentioned in the bible in several places. The existence of a new element within these minerals was not suspected until studies by Martin Heinrich Klaproth in the late 18th century.
The impure metal was first isolated by Jöns Jacob Berzelius in 1824 who heated a mixture of potassium and potassium zirconium fluoride together in an iron tube. Pure zirconium was first prepared in 1914.
Zirconium around us Read more »
Zirconium has no biological role. The tolerance of human tissues to it makes the metal suitable for some artificial joints and limbs.
Zirconium is never found as the free metal. The main ore is Zircon (ZrSiO4) and this is found in deposits in Australia, Brazil, India, Malysis, Russia, and the USA. All these minerals contain a little hafnium as well and the separation of the two is difficult.
Zirconium has been found in the spectra of S-type stars and has been identified in the sun and meteorites. Lunar rock samples show a surprisingly high zirconium oxide content as compared to rocks from earth.
|Location||ppb by weight||ppb by atoms||Links|
|Human||50 ppb by weight||3 atoms relative to C = 1000000|
Physical properties Read more »
Heat properties Read more »
- Melting point: 2128 [1855 °C (3371 °F)] K
- Boiling point: 4682 [4409 °C (7968 °F)] K
- Enthalpy of fusion: |203| kJ mol-1
Crystal structure Read more »
The solid state structure of zirconium is: hcp (hexagonal close-packed).
Zirconium: orbital properties Read more »
Zirconium atoms have 40 electrons and the shell structure is 126.96.36.199.2. The ground state electronic configuration of neutral Zirconium is [Kr].4d2.5s2 and the term symbol of Zirconium is 3F2.
- Pauling electronegativity: 1.33 (Pauling units)
- First ionisation energy: 640.1 kJ mol‑1
- Second ionisation energy: 1270 kJ mol‑1
Isolation: zirconium is available from commercial sources so preparation in the laboratory is not normally required. In industry, reduction of ores with carbon is not a useful option as intractable carbides are produced. As for titanium, the Kroll method is used for zirconium and involves the action of chlorine and carbon upon baddeleyite (ZrO2). The resultant zirconium tetrachloride, ZrCl4, is separated from the iron trichloride, FeCl3, by fractional distillation. Finally ZrCl4 is reduced to metallic zirconium by reduction with magnesium, Mg. Air is excluded so as to prevent contamination of the product with oxygen or nitrogen.
ZrO2 + 2Cl2 + 2C (900°C) → ZrCl4 + 2CO
ZrCl4 + 2Mg (1100°C) → 2MgCl2 + Zr
Excess magensium and magnesium dichloride is removed from the product by treatment with water and hydrochloric acid to leave a zirconium "sponge". This can be melted under helium by electrical heating.
Zirconium isotopes Read more »
Zirconium has five stable isotopes, of which a few are used for the production of radioisotopes. Although radioactive Zr-95 is a fission product, it can also produced by neutron irradiation of Zr-94. Zr-96 has been used for the production of the radioisotope Zr-97. Zr-90 can be used for the production of the PET isotope Nb-90. Finally, Zr-90 has been proposed for cladding in nuclear fuel. The use of Zr-90 would lower even further the already low neutron absorption cross section of natural Zr that is currently used as fuel cladding.
|90Zr||89.9047026 (26)||51.45 (40)||0|
|91Zr||90.9056439 (26)||11.22 (5)||5/2||-1.30362|
|92Zr||91.9050386 (26)||17.15 (8)||0|
|94Zr||93.9063148 (28)||17.38 (28)||0|
|96Zr||95.908275 (4)||2.80 (9)||0|