Zirkonium

Zirkonium, or zirconium (symbol Zr, atomic number 40), is a silvery-gray transition metal in group 4 of the periodic table. It occurs naturally in the mineral zircon (ZrSiO4) and is valued for a combination of high strength, high melting point, and exceptional corrosion resistance. In air, a stable oxide layer forms on the surface, protecting the metal at room temperature. Its melting point is about 1,855°C and its boiling point around 4,600°C. The metal has a density near 6.5 g/cm³.

Chemically, zirconium is reactive with oxygen and water at high temperatures, producing zirconium dioxide (ZrO2) among other compounds. It forms zirconium alloys, notably Zircaloy, which are important in nuclear reactors because of their low neutron-capture cross-section and good high-temperature performance.

Natural isotopes include five stable forms, with 90Zr being the most abundant. Zirconium’s isotopes and properties make it suitable for scientific studies and trace analyses in some contexts.

Production and refin­ing involve extracting zirconium from its minerals and converting it into metal via the Kroll process. This typically starts from zirconium tetrachloride (ZrCl4), which is reduced with magnesium to yield metal, followed by purification and alloying as needed.

Major uses include nuclear reactor components (cladding and structural parts), chemical processing equipment, high-temperature alloys for aerospace applications, and dental or ceramic materials where zirconia-based ceramics are employed. The element has a long-established history of identification in the late 18th century and was named after the mineral zircon; it was later isolated as a metal in the 19th century.