Tb - Terbium
|Chemical Element||Terbium||Melting Point °C||1356|
|Chemical Symbol||Tb||Boiling Point °C||3120|
|Atomic Number||65||Density g/cm3||8.2|
Terbium is a silvery metal, and similar to gold, it is soft enough to cut with a knife, making it a malleable and ductile substance. It has similarities to lead, too, but is much heavier. Terbium is one of the rarest of the rare earth elements, and is the 57th most abundant element within the Earth’s crust. Terbium is slowly oxidised and reacts with cold water; it is reasonably stable in air, and is aso fairly resistant to corrosion.
Terbium was discovered in 1843 by Carl Gustaf Mosander. Whilst analysing the mineral yttria, which is ytterbium oxide, Mosander concluded that this oxide may contain other elements which had not yet been found. He had suspected this, as a few years previously he had extracted the element lanthanum from a sample of cerium oxide. Mosander turned out to be correct, and from yttria he was able to extract two new oxides, terbium oxide and erbium oxide. He then named these elements after the Swedish town, Ytterby after which the mineral yttria was named, and where it is often found.
Terbium can be extracted from the ores, monazite, bastnäsite and euxenite, occurring in the proportion of 0.05% in monazite, 0.02% in bastnäsite and 1% in euxenite. Despite its presence being so small, it is still economically viable to extract. The main areas of mining and production of terbium are in China, in the ion-absorption clays found in the southern region, as well as in the USA, Brazil, India, Sri Lanka and Australia. There are reserves of terbium in the region of 10mt per year. The production of terbium metal requires terbium fluoride to be heated with calcium (Ca) metal in a tantalum (Ta) crucible under a vacuum.
Terbium has few, yet rather important, applications. When alloyed with zirconium oxide (ZrO2), it is used a crystal stabiliser of fuel cells. It also is used to make solid-state devices, energy efficient light-bulbs and, again, when alloyed with other metals can help provide metallic films for magneto-optic recording data.
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- Gray, Theodore. The Elements, A Visual Exploration of Every Known Atom in the Universe, Black Dog & Leventhal Publishers, Inc, NY, 2009
- Stwertka, Albert. A Guide to the Elements, 3rd Edition, Oxford University Press, 2012