Terbium

Terbium is a silvery-white allotropes exist, with a transformation temperature of 1289 °C. Terbium(III) cation is brilliantly fluorite owes its creamy-yellow fluorescence in part to terbium.

Applications

Terbium is used to fuel cells which operate at elevated temperatures, together with ZrO₂.

Terbium is also used in Terfenol-D (an alloy that expands or contracts to a high degree in the presence of a magnetic field), terbium is of use in actuators, sensors and other magenetomechanical devices.

Terbium Europium blue phosphors and trivalent europium red phosphors to provide the "trichromatic" lighting technology, which is by far the largest consumer of the world's terbium supply. Trichromatic lighting provides much higher light output for a given amount of electrical energy than does incandescent lighting.

History

Terbium was discovered in 1843 by Swedish chemist Carl Gustaf Mosander, who detected it as an impurity in Yttrium-oxide, Y₂O₃, and named after the village Ytterby in Sweden. It was not isolated in pure form until the recent advent of ion exchange techniques. When Mosander first partitioned "yttria" into three fractions, "terbia" was the fraction that contained the pink color (due to what is now known as erbium), and "erbia" was the fraction that was essentially colorless in solution, but gave a brown-tinged oxide. Later workers had difficulty in observing the latter, but the pink fraction was impossible to miss. Arguments went back and forth as to whether "erbia" even existed. In the confusion, the original names got reversed, and the exchange of names stuck. It is now thought that those workers who used the double sodium or potassium sulfates to remove "ceria" from "yttria" inadvertently lost the terbium content of the system into the ceria-containing precipitate. In any case, what is now known as terbium was only about 1% of the original yttria, but that was sufficient to impart a yellowish color to the oxide. Thus, terbium was a minor component in the original terbium fraction, dominated by its immediate neighbors, gadolinium and dysprosium. Thereafter, whenever other rare earths were teased apart from this mixture, whichever fraction gave the brown oxide retained the terbium name, until at last it was pure. The 19th century investigators did not have the benefit of fluorescence technology, wherewith to observe the brilliant fluorescence that would have made this element much easier to track in mixtures.

Terbium is classified as a rare earth element. The term "rare" is misleading because terbium is more common than metals such as silver and mercury. The name "rare earth" meant something else to early chemists. It was used because the rare earth elements were very difficult to separate from each other. They were not "rare" in the Earth, but they were "rarely" used for anything. Also, it was initially believed that they were rare, but actually it was later discovered that it wasn't the case.^{[citation needed]}.

Occurrence

Terbium is never found in nature as a free element, but it is contained in many euxenite ((Y,Ca,Er,La,Ce,U,Th)(Nb,Ta,Ti)₂O₆, which contains 1% or more of terbium). The richest current commercial sources of terbium are the ion-adsorption clays of southern China. The high-yttrium concentrate versions of these are about two-thirds yttrium oxide by weight, and about 1% terbia. However, small amounts occur in gadolinium concentrate" (SEG concentrate), the terbium content of the ore ends up therein. Due to the large volumes of bastnaesite processed, relative to the richer ion-adsorption clays, a significant proportion of the world's terbium supply comes from bastnaesite.

Compounds

Terbium compounds include:

Fluorides: TbF₃, TbF₄
Chlorides: TbCl₃
Bromides: TbBr₃
Iodides: TbI₃
Tb₄O₇
Sulfides: Tb₂S₃
Nitrides: TbN

See also terbium compounds.

Isotopes

Main article: isotopes of terbium

Naturally occurring terbium is composed of 1 stable radioactive isotopes have half-lifes that are less than 6.907 days, and the majority of these have half lifes that are less than 24 seconds. This element also has 18 meta states, with the most stable being 156m1-Tb (t_½ 24.4 hours), 154m2-Tb (t_½ 22.7 hours) and 154m1-Tb (t_½ 9.4 hours).

The primary dysprosium) isotopes.

Precautions

As with the other lanthanides, terbium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. Terbium has no known biological role.

References

Los Alamos National Laboratory – Terbium