Lutetium

Lutetium (Lu) is a chemical element with atomic number 71, belonging to the lanthanide series of the periodic table. It is a silvery-white metal and is the densest and one of the least abundant of the rare-earth elements found in Earth's crust.

Lutetium was discovered in 1907 by Georges Urbain and independently by Carl Auer von Welsbach, who named it after Lutetia, the Latin name for Paris. The discovery helped resolve a debated position in the rare-earth series at the time, and lutetium has since been used in various high-precision applications.

Occurrence and production of lutetium are limited by its scarcity in nature. It occurs only in trace amounts in minerals such as monazite and bastnäsite, usually alongside other rare-earth elements. Commercially, lutetium is obtained as lutetium oxide (Lu2O3) through processing of these minerals and is refined to the metal in specialized facilities.

Isotopically, natural lutetium consists of two isotopes: Lu-175, which is stable, and Lu-176, a long-lived radioisotope with a half-life of about 3.8 × 10^10 years, comprising roughly 2.6% of natural lutetium. A radioisotope of medical importance is lutetium-177, produced by neutron irradiation of Lu-176; Lu-177 is a beta emitter used in targeted radionuclide therapy, notably in some cancer treatments.

Applications of lutetium include catalysts for petroleum refining and the development of specialized materials. Lutetium-based scintillators, such as lutetium oxyorthosilicate (LSO) and lutetium–yttrium oxyorthosilicate (LYSO), are widely used in PET detectors for medical imaging. Lutetium aluminum garnet (LuAG) and related hosts are studied as laser and scintillator materials, reflecting lutetium’s role in advanced optical and diagnostic technologies.