Terbium

History

(Ytterby, a village in Sweden) Discovered by Mosander in 1843. Terbium is a member of the lanthanide or "rare earth" group of elements. It is found in cerite, gadolinite, and other minerals along with other rare earths. It is recovered commercially from monazite in which it is present to the extent of 0.03%, from xenotime, and from euxenite, a complex oxide containing 1% or more of terbia.[1]

Properties

General
Name : terbium
Symbol : Tb
Atomic Number : 65
Chemical Series : Lanthanide
Block, Period : -, 6
Appearance : silvery white
Atomic Properties
Atomic Weight (amu) : 158.92534
Covalent Radius (pm) : n/a
Physical Properties
Matter : solid (paramagnetic)
Density (kg/) : 8219
Hardness : n/a
Melting Point (K) : 1629
Boiling Point (K) : 3503
Evaporation Heat (kJ/mol) : 330.9
Fusion Heat (kJ/mol) : 10.8
Specific Heat (J/(kg*K) ) : 180
Miscellaneous
Electrical Conductivity (MS/m) : 0.889
Thermal Conductivity (W/(m*K) ) : 11.1

Terbium is reasonably stable in air. It is a silver-gray metal, and is malleable, ductile, and soft enough to be cut with a knife. Two crystal modifications exist, with a transformation temperature of 1289oC. Twenty one isotopes with atomic masses ranging from 145 to 165 are recognized. The oxide is a chocolate or dark maroon color.[1]

Production

Terbium has been isolated only in recent years with the development of ion-exchange techniques for separating the rare-earth elements. As with other rare earth metals, it can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible. Calcium and tantalum impurities can be removed by vacuum remelting. Other methods of isolation are possible.[1]

Uses

Sodium terbium borate is used in solid-state devices. The oxide has potential application as an activator for green phosphors used in color TV tubes. It can be used with ZrO2 as a crystal stabilizer of fuel cells which operate at elevated temperature. Few other uses have been found.[1]

Handling

Little is known of the toxicity of terbium. It should be handled with care as with other lanthanide elements.[1]

Notes

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