Zirconium

October 11, 2011, 9:23 am

Zirconium (Zr) is a grayish-white, metallic element with an atomic number of 40. It naturally combines with silica and oxygen to form the mineral zircon (ZrSiO4), the primary ore of this element. Zircon has been known since biblical times, and it has been called by a variety of names, including jargon, hyacinth and jacinth.

Single euhedral zircon crystal with coarse massive zircon crystals: ZrSiO4. (Source: Massachusetts Institute of Technology)

 

In the late 1700’s, the German chemist Martin Heinrich Klaproth suspected that there was a new element to be found in this mineral. He reduced the mineral zircon to zirconium oxide in 1789, but never isolated the metal. In 1824, Swedish chemist Jöns Jacob Berzelius isolated an impure zirconium metal, but it wasn’t until 1914 when pure zirconium was finally produced.

Zirconium reacts with oxygen, forming a thin coating of zirconium oxide on its surface. This coating protects the metal from further oxidation. Zirconium is quite resistant to corrosion by acids and other chemicals, and is valued in industry for this resistant quality.

Zirconium has no beneficial or adverse effect on living organisms, and is resistant to corrosion. Based on these properties, it has proven to be a good material for artificial limbs and joints.

Analysis of the rocks collected on the moon has shown that zirconium is a common element on the surface of the moon.

Name

Previous Element: Yttrium

Next Element: Niobium
40

Zr

91.22
Physical Properties
Color grayish-white
Phase at Room Temp. solid
Density (g/cm3) 6.51
Hardness (Mohs) ---
Melting Point (K) 2125.2
Boiling Point (K) 4473
Heat of Fusion (kJ/mol) 23
Heat of Vaporization (kJ/mol) 582
Heat of Atomization (kJ/mol) 609
Thermal Conductivity (J/m sec K) 22.7
Electrical Conductivity (1/mohm cm) 25
Source Zircon (silicate)
Atomic Properties
Electron Configuration [Kr]5s24d2
Number of Isotopes 37 (5 natural)
Electron Affinity (kJ/mol) 41.1
First Ionization Energy (kJ/mol) 660
Second Ionization Energy (kJ/mol) 1266.8
Third Ionization Energy (kJ/mol) 2218.2
Electronegativity 1.33
Polarizability (Å3) 17.9
Atomic Weight 91.22
Atomic Volume (cm3/mol) 14
Ionic Radius2- (pm) ---
Ionic Radius1- (pm) ---
Atomic Radius (pm) 160
Ionic Radius1+ (pm) ---
Ionic Radius2+ (pm) ---
Ionic Radius3+ (pm) ---
Common Oxidation Numbers +4
Other Oxid. Numbers +1, +2, +3
Abundance
In Earth's Crust (mg/kg) 1.65x102
In Earth's Ocean (mg/L) 3.0x10-5
In Human Body (%) 0.000001%
Regulatory / Health
CAS Number 7440-67-7
OSHA Permissible Exposure Limit (PEL) TWA: 5 mg/m3
OSHA PEL Vacated 1989 TWA: 5 mg/m3
STEL: 10 mg/m3
NIOSH Recommended Exposure Limit (REL) TWA: 5 mg/m3
STEL: 10 mg/m3
IDHL: 50 mg/m3
Sources:
Mineral Information Institute
Jefferson Accelerator Laboratory
EnvironmentalChemistry.com
 

Zirconium was named after the silicate mineral in which it was first discovered, zircon. The mineral name zirconzargun which means gold color, a reference to the color of some zircon crystals. Zirconium was created from the Arabic word.

Sources

Zirconium is found in two minerals, zircon (zirconium silicate, ZrSiO4) and baddeleyite (zirconium oxide, ZrO2). The most important of these ores, zircon, occurs as grains concentrated in sand deposits in the southeastern United States, and in Australia and Brazil. Russia and Brazil also have large deposits of baddeleyite. World resources are estimated to be more than 60 million tons worldwide.

Fourteen million tons of zirconium are in heavy-mineral sand deposits in the United States. The sands are called zircon sands because they contain sand-sized mineral zircon grains. Most heavy-mineral sands also have a high content of titanium-bearing minerals, such as ilmenite and rutile.

Several American metal companies in Oregon and Utah recover zirconium metal when recycling scrap metals created during metal production. Zirconium chemicals (like zirconium dioxide) are made in Alabama, New Hampshire, New York and Ohio.

In addition, zirconium ore and zirconium metal is imported. The ore is imported primarily from South Africa and Australia. Zirconium metal is imported primarily from France, Germany, Canada, and Japan.

Uses

Zirconium is used in a number of industrial applications because it is so resistant to corrosion. It is used in pumps and valves and the cores of nuclear reactors. Zirconium oxide is used to make laboratory crucibles and to line furnaces.

When zirconium is alloyed (mixed) with the element niobium, it becomes superconductive. This means that it is able to conduct electricity with very little loss of energy to electric resistance. Superconductivity is possible only at very low temperatures.

Another feature of zirconium is that it does not absorb neutrons (unlike hafnium, which absorbs neutrons, and is also found in zirconium deposits). This makes it useful in nuclear applications, where it is used as fuel cladding in nuclear reactors, and as a coating on nuclear fuel parts.

Zirconium is also used in everyday home products. Zirconium compounds are used in deodorants, flashbulbs, lamp filaments, and in artificial gemstones. Cubic zirconia is a hard, clear, gem-like material that is marketed as an inexpensive diamond-like gemstone. Colored cubic zirconia is sold as simulants of many different gemstones.

Substitutes and Alternative Sources

Different materials can be used in place of zirconium depending on the application. For example, titanium and other compounds can be used in a few of zirconium’s chemical applications. Niobium, stainless steel, and tantalum can be used in some limited nuclear applications.

Further Reading

 

 

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Mineral Information Institute. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Mineral Information Institute should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

Glossary

Citation

Institute, M. (2011). Zirconium. Retrieved from http://www.eoearth.org/view/article/157226

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