General information

Terbium is a chemical element with the element symbol Tb and the atomic number 65. In the periodic table it is in the group of lanthanides and thus also belongs to the metals of the rare earths. Terbium is named after the first site, the Ytterby mine near Stockholm, as well as Yttrium, Ytterbium and Erbium.
The discovery of the element Terbium is very confused and still unsolved. In general, Carl Gustav Mosander is seen as the discoverer who examined the early days of 1840er's Yttererde discovered by Johan Gadolin. The supposedly pure terbium compound was a mixture of several lanthanides (Bunsen).
Pure terbium was only produced with the advent of ion exchange technology after 1945. Mosander derived the element designation from the name of the Swedish mine Ytterby. Terbium occurs in nature only in compounds. Well-known minerals containing terbium are:
Cerit
Monazite (Ce, LaTh, Nd, Y) PO4 with a Tb content of max. 0,03%, the main word for Tb
Gadolinite (occurrence at Ytterby is exhausted)
Euxenite (Y, Ca, Er, La, Ce, U, Th) (Nb, Ta, Ti) 2O6 with a Tb content of max. 1%

Recovery

After a complex separation of the other Terbiumbegleiter the oxide is reacted with hydrogen fluoride to terbium fluoride. Subsequently, it is reduced to terbium with calcium to form calcium fluoride. The separation of remaining calcium residues and impurities takes place in an additional remelting in vacuo.

Features

The silver-gray metal of the rare earths is ductile and malleable. At temperatures above 1315 ° C, α-terbium (hcp crystal lattice) transforms into β-terbium. In air, terbium is relatively stable, it covers itself with an oxide layer. In the flame it burns to brown terbium (III, IV) oxide (Tb4O7). With water it reacts with evolution of hydrogen to the hydroxide.

Usage

Terbium is used for doping calcium fluoride, calcium tungstate and strontium molybdate for use in solid state devices. Together with zirconium (IV) oxide, it serves to stabilize the structure in high-temperature fuel cells. The oxide is added to the green phosphor in picture tubes and fluorescent lamps. Sodium erbbium borate serves as a laser material for generating coherent light having a wavelength of 546 nm.
Terbium iron cobalt or terbium gadolinium iron cobalt alloys serve as a coating on rewritable magneto-optic (MO) disks. Terbium-dysprosium-containing alloys show a strong magnetostriction (change in length by a magnetic field or magnetic impulses with change in length). Such alloys are used in materials testing.
In neodymium-iron-boron magnets they increase the coercivity, that is, the demagnetization resistance is increased.
Terbium and terbium compounds are considered to be of low toxicity. The element has no biological significance for the human organism. Terbiummetallstäube are fire and explosive as almost all metal dusts.

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