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Uses of europium - by Angelina Souren
Of all the rare earth elements, europium is reported to be the most expensive. One of the reasons why rare earth elements are so expensive is the cost of extracting them and concentrate them from their ores.
As someone who has determined very small concentrations of rare earth elements - in seawater from around Antarctica - I have some idea of what it involves.
Europium (symbol Eu) is a metal as soft as lead. It can have the divalent oxidation state, mainly in rocks from deep in the earth. In the p, T and redox conditions of the earth's surface, europium strongly prefers to be trivalent.
Its strong preference for an advanced oxidized state makes the metal highly reactive and, as a result, toxic, corrosive, irritant and particularly flammable. It readily reacts with oxygen and water if not protected and handled carefully (stored under oil, for instance, and kept away from heat).
This is what wrapped europium metal powder looks like in various stages of oxidation:
The metal's oxide is therefore much more stable.
Europium has many technological uses. Europium complexes are used to distinguish genuine bank notes from falsified ones and have applications in analytical chemistry as well. Examples of other uses of Eu involve CRT and flat screens for color TVs and computers, and laser equipment.
Europium absorbs neutrons quite well, hence its use in control rods in, for example, uranium plants in Russia and Ukraine.
One newer development focuses on the commercial application of this particular (spent) europium (Eu-152, 154 and 155) as a much-needed gamma source for sterilization purposes (against microorganisms). That would take care of this nuclear-waste storage problem as well.
Rare earth elements are also increasingly used in green technologies>. The motor of a Toyota Prius, for example, contains 1 to 2 kilograms of another rare earth element, neodymium.
Note that europium's naturally occurring isotopes - Eu-151 and 153 - are not radioactive. In nature, europium and the other rare earth elements often occur together with actinides, however, because of their chemical similarities. Actinides are radioactive.
This is one of the reasons why some scientists study the properties and behavior of rare earth elements, for instance in seawater. The research results can lead to a proxy for actinide behavior, which would have environmental implications.
To those who are interested in the biochemistry of rare earth elements, I can recommend the book "Biochemistry of the lanthanides" by C.H. Evans. It was published by Plenum Press (Springer) in 1990, and counts around 450 pages.