Zirconium dioxide, also called zirconia, is a chemical compound of zirconium and oxygen. It has the chemical formula ZrO2.
Zirconium dioxide is normally made by separating zirconium silicate into zirconium dioxide and silicon dioxide. This can happen by heating the silicate to temperatures around 1,700 °C (3,090 °F; 1,970 K), or by dissolving it with sodium hydroxide or sodium carbonate, making sodium zirconate and sodium orthosilicate, which can be separated by their different solubility.
Zirconium dioxide is also found in nature as the rare mineral baddeleyite.
Zirconium dioxide is a refractory ceramic, meaning it does not melt until it reaches a very high temperature. Even though it does not melt, pure zirconia has two other phase transitions that change the solid's crystal structure and volume, which can make it crack or break apart. Because of this, small amounts of other refractory ceramics like yttrium(III) oxide are added to make stabilised zirconia that does not change shape.
Cubic zirconia is a type of stabilised zirconia used as a synthetic gemstone and diamond substitute.