|Boiling Point: 4650°K, 4377°C, 7911°F
Melting Point: 2125°K, 1852°C, 3366°F
Electrons Energy Level: 2, 8, 18, 10, 2
Isotopes: 28 + 4 Stable
Heat of Vaporization: 58.2 kJ/mol
Heat of Fusion: 16.9 kJ/mol
Density: 6.51 g/cm3 @ 300°K
Specific Heat: 0.27 J/g°K
Atomic Radius: 2.16Å
Ionic Radius: 0.72Å
Electronegativity: 1.33 (Pauling); 1.22 (Allrod Rochow)
Vapor Pressure: 0.00168 Pa @ 1852°C
1s2 2s2p6 3s2p6d10 4s2p6d2 5s2
Zirconium (Arabic zarkûn from Persian zargûn meaning "gold like") was discovered in 1789 by Martin Heinrich Klaproth and isolated in 1824 by Jons Jakob Berzelius.
Martin Heinrich Klaproth
The zirconium-containing mineral zircon, or its variations (jargon, hyacinth, jacinth, or ligure), were mentioned in biblical writings. The mineral was not known to contain a new element until Klaproth analyzed a jargon from Ceylon in the Indian Ocean. He named the new element Zirkonertz (zirconia). The impure metal was isolated first by Berzelius by heating a mixture of potassium and potassium zirconium fluoride in a small decomposition process conducted in an iron tube. Pure zirconium wasn't prepared until 1914.
The crystal bar process (or Iodide process), discovered by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925, was the first industrial process for the commercial production of pure ductile metallic zirconium. It was superseded by the Kroll process.
Zirconium is a grayish-white metal, lustrous and exceptionally corrosion resistant that resembles titanium, zirconium is obtained chiefly from zircon and is very corrosion resistant. Zirconium is lighter than steel and its hardness is similar to copper. When it is finely divided, the metal can spontaneously ignite in air, especially at high temperatures (it is much more difficult to ignite the solid metal). Zirconium zinc alloy becomes magnetic at temperatures below 35oK. Oxidation state of zirconium is usually +4, although +3 and +2 can also be obtained.
Zirconium is primarily used in nuclear reactors due to its resistance to corrosion and low neutron cross-section.
Zirconium is never found in nature as a free metal. The principal economic source of zirconium is the zirconium silicate mineral, zircon (ZrSiO4), which is found in deposits located in Australia, Brazil, India, Russia, and the United States. (It is extracted as a dark sooty powder, or as a gray metallic crystalline substance). Zirconium and hafnium are contained in zircon at a ratio of about 50 to 1 and are difficult to separate. Zircon is a coproduct or byproduct of the mining and processing of heavy-mineral sands for the titanium minerals, ilmenite and rutile, or tin minerals. Zirconium is also in 30 other recognized mineral species including baddeleyite. This metal is commercially produced by reduction of the Zirconium (IV) chloride with magnesium in the Kroll process, and through other methods. Commercial-quality zirconium still has a content of 1 to 3% hafnium.
This element is also abundant in S-type stars and has been detected in the sun and meterorites. Lunar rock samples brought back from several Apollo progrm missions to the moon have a very high zirconium oxide content relative to terrestrial rocks.
The major end uses of zircon (ZrSiO4) are refractories, foundry sands (including investment casting), and ceramic opacification. Zircon is also marketed as a natural gemstone used in jewelry, oxide is processed to produce Cubic Zirconia, ZrO2, which forms a brilliant clear crystal used as a low-cost substitute for diamond.
Reactor-grade zirconium alloys must be made of purified zirconium free of hafnium contamination, as hafnium has very high neutron absorption cross-section, 600 times higher than zirconium. Commercial zirconium naturally contains 1-5% of hafnium which has to be removed. This removal process is difficult (zirconium and hafnium are two of the most difficult elements to separate). Two main process are in use: liquid-liquid extraction, exploiting the difference of solubility of metal thiocyanates in methyl isobutyl ketone, used mainly in United States, and extractive distillation, used primarily in Europe. The resulting reactor-grade zirconium is about 10 times as expensive as the hafnium-contaminated commercial grade. The separated hafnium is used for control rods. The zirconium is used mostly almost pure, in the form of low alloys, most often from the zircaloy group.
|Zircon, Zirconium Silicate, ZrSiO4|
|Zirconium (IV) Chloride, ZrCl4|
|Baddeleyite, Cubic Zirconia, Zirconium Dioxide, ZrO2|
|Zirconium Carbonate, 3ZrO2·CO2·H2O|
Naturally occurring zirconium is composed of four stable isotopes and one extremely long-lived radioisotope (96Zr). The second most stable radioisotope is 93Zr which has a half-life of 1.53 million years. Twenty-eight other radioisotopes have been characterized. Most of these have half lives that are less than a day except 95Zr (64.02 days), 88Zr (63.4 days), and 89Zr (78.41 hours). The primary decay mode is electron capture before 92Zr and the primary mode after is beta decay.
|Zr96||95.9083||>3.8E 19 years|
|Zr109||> 150 ns|
|Zr110||> 150 ns|
|Compounds containing zirconium are not noted for toxicity. The metal dust can ignite in air and should be regarded as a major fire and explosion hazard. Zirconium has no biological role.|
|Ionization Energy (eV): 6.634 eV
Estimated Crustal Abundance: 1.65×102 milligrams per kilogram
Estimated Oceanic Abundance: 3×10-5 milligrams per liter