Terbium, Tb, Atomic number 65

General

Terbium is a chemical element with the element symbol Tb and atomic number 65. In the periodic table it is in the group of lanthanides and is thus also one of the rare earth metals. Terbium is after the first locality, the pit Ytterby near Stockholm, named, as well as yttrium, Ytterbium and erbium.
The discovery of the element terbium is very confused and still not resolved. Generally seen as the discoverer of Carl Gustav Mosander, the early 1840s, discovered by Johan Gadolin yttria examined. The supposedly pure terbium compound was a mixture of several lanthanides (Bunsen).
Pure terbium was only with the advent of ion exchange technology to 1945 produced. From the name of the Swedish pit Ytterby headed Mosander the element name from. Terbium is found in nature only in compounds ago. Minerals are known terbiumhaltige :
Cerit
Monazite (This,LaTh,Nd,And)PO4 with a Tb content of max. 0,03 %, the major ore for Tb
Gadolinit (Deposits are depleted in Ytterby)
Euxenit (And,As,He,The,This,You,Th)(Nb,Take,You)2O6 with a Tb content of max. 1 %

Extraction

After an extensive separation of the other Terbiumbegleiter, the oxide with hydrogen fluoride to the terbium fluoride reacted. Is then reduced with calcium to form calcium fluoride to terbium. The removal of residual calcium residues and contaminants carried in an additional remelting in vacuum.

Special features

The silver-gray metal of the rare earths is ductile and malleable. At temperatures above 1315 ° C converts to α-terbium (hcp lattice) Terbium in β-um. Terbium is relatively stable in air, it becomes covered 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 hydroxide.

Use

Terbium is for doping calcium fluoride, Calcium tungstate and strontium molybdate for use in semiconductors (solid-state devices) used. Together with zirconium(IV)-oxide is used to stabilize the structure in high-temperature fuel cells. The oxide is added to the green phosphor in cathode ray tubes and fluorescent lamps. Natriumterbiumborat serves as a laser material to produce coherent light having a wavelength of 546 nm.
Terbium-Eisen-Cobalt- or terbium-gadolinium-iron-cobalt alloys are used as a coating on rewritable magneto-optical (MO) Disks. Terbium-dysprosium-containing alloys show a strong magnetostriction (Change in length by a magnetic field or magnetic impulses at length change). Such alloys are used in materials testing technology.
In neodymium-iron-boron magnet, they increase the coercivity, that is, the demagnetization resistance is increased.
Terbium and Terbiumverbindungen should be considered as low toxicity. The element has no biological significance for the human body. Terbiummetallstäube are like almost all the metal dust fire- and potentially dangerous.

General
Name, Symbol, Number Terbium, Tb, 65
Series Lanthanides
group, Period, Block The, 6, f
Appearance silvery white
CAS-Nummer 7440-27-9
Mass fraction of element 0,85 ppm
Atomic
Atomic mass 158,92534 you
Atomradius 175 pm
Kovalenter Radius 194 pm
Elektronenkonf. [Car] 4f(9) 6s2
1. Ionization 565,8 KJ / mol
2. Ionization 1110 KJ / mol
3. Ionization 2114 KJ / mol
Physically
Physical State fixed
Crystal structure hexagonal
Density 8,253 g/cm3 (25 ° C)
Magnetism paramagnetisch (χm = 0,11)
Melting point 1629 K (1356 C)
Boiling point 3503 K (3230 C)
Molar Volume 19,30 * 10(-6)m(3)/mol
Heat of vaporization 295 KJ / mol
Schmelzwärme 10,8 KJ / mol
Electrical conductivity 0,870*10(6) A/(V * m)
Thermal conductivity 11 W /(m*K)
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