Zirconium (Zr)
Zirconium (Zr) is a lustrous, grayish-white metal classified as a transition metal in Group IVB of the periodic table, with an atomic number of 40. It is found in the Earth's crust at a concentration of 0.028 percent, surpassing the collective abundance of several other metals, and is primarily extracted from minerals such as zircon and baddeleyite. Major reserves of zirconium are located in countries like Australia, South Africa, Brazil, and China, with smaller deposits also found in the United States.
Zirconium is highly valued for its resistance to corrosion and its low neutron absorption, making it particularly useful in the nuclear energy sector for applications such as fuel element jackets and coatings for pipes. Beyond nuclear applications, it is widely used in ceramics, foundry work, opacifiers, and as a material in surgical instruments and various alloys. The element was first isolated in the 18th century after being identified in semiprecious stones from Sri Lanka. The commercial production of zirconium typically involves a process that purifies zirconium tetrachloride using molten magnesium. Zirconium's versatility also extends to its applications in catalysts, superconducting magnets, and high-temperature laboratory equipment.
Zirconium (Zr)
Where Found
The known deposits of zirconium constitute 0.028 percent of the Earth’s crust, which is greater than the combined total of all known copper, nickel, lead, tin, zinc, and mercury deposits. reserves of zirconium minerals are found in Australia, Brazil, China, India, South Africa, Ukraine, Sri Lanka, Russia, and Canada. Deposits in the United States are located in Florida, North Carolina, California, Oregon, Colorado, and Idaho. The largest deposits are in Australia and South Africa.
Primary Uses
Zirconium is used mainly in ceramics, foundry applications, opacifiers, and refractories, as well as in abrasives, chemicals alloys, welding rod coatings, and sandblasting.
Technical Definition
Zirconium (symbol Zr) is a grayish-white, lustrous metal. It is a member of the second series of transition metals in Group IVB in the periodic table of elements.
Zirconium’s atomic number is 40, and its atomic weight is 91.22; it has five stable isotopes and three unstable isotopes. Zirconium has a melting point of 1,852° Celsius, a boiling point of 4,377° Celsius, and a density of 6.506 grams per cubic centimeter.
Description, Distribution, and Forms
Zirconium occurs in abundance in S-type stars and has been identified in the Sun and meteorites. Zirconium is found in many minerals, such as zircon (zirconium silicate) and baddeleyite (almost pure zirconium dioxide), and it is typically found in igneous rocks (mainly granite and diorite).
History
Zirconium was discovered by German chemist M. H. Klaproth in 1789, while he was studying some semiprecious stones from Sri Lanka. The name comes from the Arabic word zargun, which means gold color, describing the gemstone now known as zircon. Impure zirconium was first isolated by Jöns Jacob Berzelius by heating a mixture of potassium zirconium fluoride with potassium in an iron tube.
Obtaining Zirconium
Metallic zirconium is produced commercially by the purification of zirconium tetrachloride by sublimation and reduction of the tetrachloride vapor with molten magnesium (the Kroll process). Unless special separation methods, such as column chromatography, are used in this process, the zirconium produced contains between 0.5 and 3 percent hafnium, chemical element number 72.
Uses of Zirconium
Because zirconium has a low tendency to absorb slow neutrons and a remarkable resistance to the corrosive environments in nuclear reactors, it finds many uses in the field of nuclear energy. Zirconium and its tin-iron-nickel-chromium alloy (zircaloy) are used as coatings for pipes and fuel element jackets in fission reactor cores. Zirconium is also used in deodorants, surgical instruments, pins, screws for bone repairs, spinnerets for the spinning of rayon fibers, alloys, and powder metallurgy. In powdered form, zirconium is used as an ammunition primer, in smokeless flash powders, in blasting caps, and in the manufacture of vacuum tubes. Various zirconium compounds are used as catalysts for ammonia synthesis, for organic oxidations, for polymerizations, and in the conversion of sulfur dioxide to sulfur trioxide. Along with niobium (columbium), zirconium is a superconductor (it can conduct electricity without any resistance) at low temperatures and is used in the construction of superconducting magnets with potential applications to the generation of electrical power. Baddeleyite, a compound of zirconium and oxygen, can withstand extremely high temperatures. It is used for laboratory crucibles (melting pots for metals) and the linings for certain furnaces.
Bibliography
U.S. Geological Survey.