Europium

Europium, chemical element, symbol Eu; for physical constants see Periodic Table. Europium was discovered in 1901 by Eugène Demarcay. The element occurs in the minerals monazite and bastnasite, the two principal sources of the rare-earth elements. It is prepared by heating the oxide with excess lanthanum metal under high vacuum in a tantalum crucible. Europium is a silvery-white, soft metal, and the most reactive member of the elements known as the rare-earth metals. Ion-exchange and solvent extraction techniques have led to much easier isolation of the rare-earth elements. Europium and its compounds are used in laser materials, as neutron absorbers in nuclear reactors, and in color phosphors for TV tubes.