zirconium

Zirconium is a chemical element with the symbol Zr and atomic number 40. It is a hard, silvery-gray transition metal known for its strength, low density for a heavy metal, and exceptional resistance to corrosion. Zirconium metal has a high melting point of about 1,855 °C (3,371 °F) and forms a stable, protective oxide layer that reduces further reaction in air and water. The most common oxidation state is +4, and it produces zirconium dioxide, ZrO2, a durable ceramic.

Zirconium occurs naturally in the minerals zircon (ZrSiO4) and baddeleyite (ZrO2). The principal commercial source is zircon sand. The metal is produced commercially by converting zirconium to zirconium tetrachloride and then reducing it, typically via the Kroll process, with magnesium or sodium to yield metal. Additional high-purity metal can be obtained by methods such as the Van Arkel–de Boer process.

Historically, zirconium was identified in 1789 by Martin Klaproth in zircon and was first isolated as a metal by Friedrich Wöhler in 1824. The name derives from the mineral zircon.

Applications include its use in nuclear reactors as cladding for uranium fuel due to its low neutron-capture cross-section and corrosion resistance. Zirconium alloys, such as Zircaloy and ZIRLO, are common in reactor equipment. Zirconia ceramic is used in dental crowns, oxygen sensors, and thermal barrier coatings. Zirconium compounds are also used in ceramics and glass and in some dental and medical devices.

Producer regions include Australia, South Africa, Russia, and China.