lutetiumIII

Lutetium(III) refers to the trivalent oxidation state of the element lutetium, symbol Lu, and is the most common oxidation state in its compounds. In aqueous solution, Lu3+ exists as a highly hydrated ion, typically described as [Lu(H2O)6]3+. It is a small, highly charged lanthanide cation with a strong preference for higher coordination numbers, and it forms a variety of inorganic salts and oxides.

Occurrence and preparation

Lutetium is a rare earth element found in trace amounts in minerals such as monazite and xenotime, often recovered together with other rare earths. Commercially, lutetium is recovered from mixed rare earth concentrates and separated into individual elements by ion-exchange or solvent extraction techniques. The most common oxide is lutetium oxide (Lu2O3), a stable ceramic material, and the trivalent ion forms a wide range of salts including chlorides, fluorides, and nitrates.

Chemistry and coordination

Lu3+ forms stable coordination complexes with oxygen- and nitrogen-donor ligands. In water, it forms the hexaaquo complex [Lu(H2O)6]3+, which can undergo hydrolysis and polymerization at higher pH. Lu3+ exhibits typical lanthanide chemistry, including strong affinity for hard ligands and a tendency to form oxides at elevated temperatures.

Applications

Lutetium compounds are used in ceramics and phosphors, notably as hosts for scintillating materials. Lutetium aluminum garnet (LuAG) and lutetium oxyorthosilicate (LSO) are among prominent scintillators used in radiation detectors and medical imaging. Lutetium oxide, doped ceramics, and related materials are important in lighting, lasers, and high-density ceramics. In geology, the Lu–Hf dating system uses the decay of 176Lu to 176Hf to constrain the ages of rocks and minerals.

Isotopes

Natural lutetium consists of Lu-175 (stable) and Lu-176 (long-lived radioactive, about 2.6% of natural lutetium). The decay of 176Lu to 176Hf underpins Lu–Hf geochronology; other lutetium isotopes, such as 177Lu, are used in radiopharmaceutical applications, but these isotopes are not representative of the Lu3+ ion’s chemistry.