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For fluorescent lamps.
(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.
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 earths, 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.
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.
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
The element is priced at about $30/g (99.9%).
Little is known of the toxicity of terbium. It should be handled with care as with
other lanthanide elements.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.