Encyclopedia > Zirconium

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Name, Symbol, NumberZirconium, Zr, 40
Chemical series transition metals
Group, Period, Block4[?], 5 , d
Density, Hardness 6511 kg/m3, 5
Appearance Silvery white
Atomic Properties
Atomic weight 91.224 amu
Atomic radius (calc.) 155 (206) pm
Covalent radius 148 pm
van der Waals radius no data
Electron configuration [Kr]4d25s2
e- 's per energy level2, 8, 18, 10, 2
Oxidation states (Oxide) 4 (amphoteric)
Crystal structure Hexagonal
Physical Properties
State of matter Solid (__)
Melting point 2128 K (3371 °F)
Boiling point 4682 K (7968 °F)
Molar volume 14.02 ×10-3 m3/mol
Heat of vaporization 58.2 kJ/mol
Heat of fusion 16.9 kJ/mol
Vapor pressure 0.00168 Pa at 2125 K
Speed of sound 3800 m/s at 293.15 K
Electronegativity 1.33 (Pauling scale)
Specific heat capacity 0.27 J/(kg*K)
Electrical conductivity 2.36 106/m ohm
Thermal conductivity 22.7 W/(m*K)
1st ionization potential 640.1 kJ/mol
2nd ionization potential 1270 kJ/mol
3rd ionization potential 2218 kJ/mol
4th ionization potential 3313 kJ/mol
5th ionization potential 7752 kJ/mol
6th ionization potential 9500 kJ/mol
Most Stable Isotopes
isoNAhalf-life DMDE MeVDP
90Zr51.45%Zr is stable with 50 neutrons
91Zr11.22%Zr is stable with 51 neutrons
92Zr17.15%Zr is stable with 52 neutrons
93Zr{syn.}1.53 E6 y β-0.09193Nb
94Zr17.38%Zr is stable with 54 neutrons
96Zr2.8%>3.8 E19 yβ-3.35096Mo
SI units & STP are used except where noted.
Zirconium is a chemical element in the periodic table that has the symbol Zr and atomic number 40. A lustrous gray-white, strong transition metal that resembles titanium, zirconium is obtained chiefly from zircon and is very corrosion resistant. Zirconium is primarily used in nuclear reactors for a neutron absorber and to make corrosion-resistant alloys.

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Notable Characteristics It is a grayish-white metal, lustrous and exceptionally 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 35° K. Common oxidation states of zirconium include +2, +3 and +4. Applications 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, and its oxide is processed to produce the diamond stimulant, cubic zirconia. Other uses;

  • Zirconium has a low absorption cross section for neutrons, which makes it ideal for nuclear energy uses, such as cladding fuel elements. More than 90% of zirconium metal production is consumed by commercial nuclear power generation. Modern commercial scale reactors can use as much as a half-million linear feet of zirconium alloy tubing.
  • Extensively used by the chemical industry for piping in corrosive environments.
  • Zirconium is pyrophoric (flammable) and has been used in military incendiaries.
  • Its carbonate is used in poison ivy lotions.
  • Impure zirconium oxide, zirconia, is used to make laboratory crucibles that can withstand heat shock, for linings of metallurgical furnaces, and by the ceramic and glass industries as a refractory material.
  • Human tissues can easily tolerate this metal which makes it suitable for some artificial joints and limbs.
  • Also used in heat exchangers, as a "getter" in vacuum tubes, in lamp filaments and various specialty alloys.

When alloyed with niobium, zirconium becomes superconductive at low temperatures and is used to make superconductive magnets with possible large-scale electrical power[?] uses. History Zirconium (Arabic zarkūn from Persian zargūn meaning "gold like") was discovered in 1789 by Martin Klaproth[?] and isolated in 1824 by Jons Jakob Berzelius.

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 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. Occurrence 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 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 meteorites. Lunar rock samples brought back from several Apollo program missions to the moon have a very high zirconium oxide content relative to terrestrial rocks. Isotopes Naturally occurring zirconium is composed of four stable isotopes and one extremely long-lived radioisotope (Zr-96). The second most stable radioisotope is Zr-93 which has a half life of 1.53 million years. Eighteen other radioisotopes have been characterized. Most of these have half lives that are less than a day except Zr-95 (64.02 days), Zr-88 (63.4 days), and Zr-89 (78.41 hours). The primary decay mode is electron capture before Zr-92 and the primary mode after is beta decay. Precautions 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.

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