yttrium

Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery, soft, and ductile transition metal that is commonly grouped with the rare earth elements because it is frequently found together with them in minerals. In ordinary conditions it forms a protective oxide layer and is relatively stable in air. Its common oxidation state in compounds is +3.

Yttrium occurs in several minerals, most notably in ore minerals of the rare earth group such as xenotime and gadolinite, and it was first identified in a mineral from Ytterby, Sweden. The element was isolated in 1828 by Friedrich Wöhler, and its name honors Ytterby.

One stable isotope, 89Y, is the only naturally occurring isotope of yttrium; many other isotopes are radioactive. Yttrium has notable uses in materials science and technology. Yttrium oxide (Y2O3) is used as a phosphor host in red-emitting phosphors (for example when doped with europium) and as a component in phosphor materials for televisions and displays. Yttrium aluminum garnet (Y3Al5O12), especially when doped with neodymium (Nd:YAG), serves as a laser gain medium. Yttrium, in the form of oxides and alloys, improves the high-temperature strength and oxidation resistance of aluminum and magnesium alloys, and yttria-stabilized zirconia (YSZ) is widely used in thermal barrier coatings and solid oxide fuel cells.

Yttrium-90, a radioactive isotope, is used in medical applications such as targeted radiotherapy.