(also zirconium dioxide or zirconia), ZrO2, a white crystalline compound, with a melting point of 2900°C. Zirconium oxide is insoluble in water, organic solvents, and the solutions of most acids, alkalies, and salts. It is soluble in hydrofluoric acid, concentrated sulfuric acid, and molten glass. It has amphoteric properties. In nature, it exists as the mineral baddeleyite.
Zirconium oxide is produced in industry by roasting zirconium sulfates or zirconium chlorides. Synthetic crystals of zirconium oxide have been produced (called fianites), which are stabilized by calcium oxide, yttrium oxide, and the oxides of other rareearth elements. More than 50 percent of the zirconium oxide obtained is used in the production of zirconium refractories, ceramics, enamels, and glass; zirconium oxide also serves as a starting material for the production of zirconium.