|Melting Point:||1855 șC|
|Atomic Symbol:||Zr||Boiling Point:||4409 șC|
|Atomic Weight:||91.22 amu||Density:||6511
|Covalent Radius:||148 pm||Electron Configuration:||[Kr]5s24d2|
|van der Waals Radius:||
|State of Matter:||solid|
(Persian zargun: gold like) Zircon, the primary gemstone of zirconium, is also known as jargon, hyacinth, jacinth, or ligure. This mineral, or its variations, is mentioned in biblical writings. The mineral was not known to contain a new element until Klaproth, in 1789, analyzed a jargon from from Ceylon and found a new earth, which Werner named zircon (silex circonius), and Klaproth called Zirkonertz (zirconia). The impure metal was first isolated by Berzelius in 1824 by heating a mixture of potassium and potassium zirconium fluoride in a small decomposition process they developed.
It is a grayish-white lustrous metal. When finely divided, the metal may 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.
Zirconium is exceptionally resistant to corrosion by many common acids and alkalis, by sea water, and by other agents. Commercial-grade zirconium contains from 1 to 3% hafnium. Zirconium has a low absorption cross section for neutrons, and is therefore used for nuclear energy applications, such as for cladding fuel elements. Commercial nuclear power generation now takes more than 90% of zirconium metal production. Reactors of the commercial size, now being made, may use as much as a half-million linear feet of zirconium alloy tubing.
Zirconium is found in abundance in S-type stars, and has been identified in the sun and meteorites. Analysis of lunar rock samples obtained during the various Apollo missions to the moon show a surprisingly high zirconium oxide content, compared with terrestrial rocks. Zirconium also occurs in some 30 other recognized mineral species. Zirconium is produced commercially by reduction of chloride with magnesium (the Kroll Process), and by other methods.
It is used extensively by the chemical industry where corrosive agents are employed. Zirconium is used as a getter in vacuum tubes, as an alloying agent in steel, in surgical appliances, photoflash bulbs, explosive primers, rayon spinnerets, lamp filaments, etc. It is used in poison ivy lotions in the form of the carbonate as it combines with urushiol. With niobium, zirconium is superconductive at low temperatures and is used to make superconductive magnets, which offer hope of direct large-scale generation of electric power. Zirconium oxide (zircon) has a high index of refraction and is used as a gem material. The impure oxide, zirconia, is used for laboratory crucibles that will withstand heat shock, for linings of metallurgical furnaces, and by the glass and ceramic industries as a refractory material. Its use as a refractory material accounts for a large share of all zirconium consumed.
Reactor-grade zirconium is essentially free of hafnium. Zircaloy(R) is an important alloy developed specifically for nuclear applications. Alloyed with zinc, zirconium becomes magnetic at temperatures below 35oK.
Naturally occurring zirconium contains five isotopes. Fifteen other isotopes are known to exist. Zircon, ZrSiO4, the principal ore, is pure ZrO2 in crystalline form having a hafnium content of about 1%.
Compounds containing zirconium are encountered relatively rarely by most people and their inherent toxicity is low. The metal dust can ignite in air and should be regarded as a major fire and explosion hazard. Zirconium has no biological role.