More About Rare Earths
ESPI is a manufacturer of rare earth powders, rods, sheet, and foils for research applications.
The term rare earths refers to the lanthanide series of elements comprised of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and the transition metals scandium and yttrium. Some texts refer to the actinide series as rare earths also. All of these metals are in group III of the periodic table.
The rare earth elements are not really rare. At one time these materials were considered to be rare because they occur in nature in very low concentrations and are difficult to separate one from the others. It turns out that the rare earth elements are actually widely scattered throughout the earths crust and so are not rare at all. Even the least common rare earths are more abundant than the platinum-group metals and gold. However few concentrated, exploitable ore deposits have been found so far.
The first rare earth to be reported was yttria, by Johann Gadolin in 1794. During the eighteenth century, a number of rare earth oxides were isolated and were believed to be elements. These materials had alkaline properties, and the scientists at that time were unable to melt them or observe any changes occurring in them when heated. Since yttria resembled the >common= earths such as lime and alumina, yttria was referred to as a >rare= earth (earth being an obsolete term for oxide).
With the advent of the nuclear age the demand for high purity uranium and thorium led to improved separation methods for the rare earths. Rare earths occur with uranium and thorium in deposits and must be removed in the refining process. The rare earths and other fission products must also be separated from unconsumed fuel in order to recover the fuel for re-use. With these improved separation methods came new availability of material which led to increased research. New uses for these materials were, and continue to be, discovered.
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