Europium

History

(Europe) In 1890 Boisbaudran obtained basic fractions from samarium-gadolinium concentrates which had spark spectral lines not accounted for by samarium or gadolinium. These lines subsequently have been shown to belong to europium. The discovery of europium is generally credited to Demarcay, who separated the rare earth in reasonably pure form in 1901. The pure metal was not isolated until recent years.[1]

Sources

Europium has been identified spectroscopically in the sun and certain stars. Seventeen isotopes are now recognized. Europium isotopes are good neutron absorbers and are being studied for use in nuclear control applications.[1]

Properties

General
Name : europium
Symbol : Eu
Atomic Number : 63
Chemical Series : Lanthanide
Block, Period : -, 6
Appearance : silvery white
Atomic Properties
Atomic Weight (amu) : 151.964
Covalent Radius (pm) : n/a
Physical Properties
Matter : solid (paramagnetic)
Density (kg/) : 5244
Hardness : n/a
Melting Point (K) : 1099
Boiling Point (K) : 1800
Evaporation Heat (kJ/mol) : 143.5
Fusion Heat (kJ/mol) : 9.21
Specific Heat (J/(kg*K) ) : 180
Miscellaneous
Electrical Conductivity (MS/m) : 1.12
Thermal Conductivity (W/(m*K) ) : 13.9

As with other rare-earth metals, except for lanthanum, europium ignites in air at about 150 to 180oC. Europium is about as hard as lead and is quite ductile. It is the most reactive of the rare-earth metals, quickly oxidizing in air. It resembles calcium in its reaction with water. Bastnasite and monazite are the principal ores containing europium.[1]

Production

Europium is now prepared by mixing Eu2O3 with a 10%-excess of lanthanum metal and heating the mixture in a tantalum crucible under high vacuum. The element is collected as a silvery-white metallic deposit on the walls of the crucible.[1]

Uses

Europium oxide is now widely used as a phospor activator and europium-activated yttrium vanadate is in commercial use as the red phosphor in color TV tubes. Europium-doped plastic has been used as a laser material. With the development of ion-exchange techniques and special processes, the cost of the metal has been greatly reduced in recent years.[1]

Notes

[1] From Los Alamos National Laboratory's Chemistry Division Website