EuIII

EuIII, or Eu3+, denotes the trivalent oxidation state of europium and is the most common form of europium in inorganic compounds. In most environments Eu3+ is the stable oxidation state; Eu2+ is only rarely stabilized under strongly reducing conditions or in specific phosphor hosts, and is far less prevalent in aqueous solution or standard salts.

In solution and many solids, europium(III) forms nine-coordinated aqua ions and various complexes with ligands such as fluoride, chloride, sulfate, phosphate, and oxalate. The chemistry is governed by the 4f6 configuration, yielding relatively sharp electronic transitions and limited ligand-field splitting; Eu3+ compounds are typically pale or colorless, with luminescent properties often dominating optical behavior.

Luminescence and applications: Eu3+ exhibits characteristic narrow f–f transitions; the most intense red emission corresponds to the 5D0 → 7F2 transition near 612 nm, with other lines around 590–700 nm. In phosphors, Eu3+ is often sensitized by a host lattice or by an organic antenna to boost absorption. Common hosts include Y2O3:Eu3+ and other rare-earth oxides and fluorides. Eu3+-doped materials are widely used in display phosphors, lighting, and fluorescence-based probes due to their sharp lines and relatively long excited-state lifetimes.

Occurrence and production: Europium is a rare-earth element found in minerals such as bastnäsite and monazite. It is recovered during processing of rare-earth ores and separated by solvent extraction and ion-exchange techniques. Global production is concentrated in a few countries, with China accounting for a large share; refining occurs in Australia and other regions. In most commercial europium compounds Eu3+ is the prevailing oxidation state.