For high strength magnets for disk drives.
(Gr. neos, new, and didymos, twin) In 1841, Mosander, extracted from cerite a new
rose-colored oxide, which he believed contained a new element. He named the element
didymium, as it was an inseparable twin brother of lanthanum. In 1885 von Welsbach
separated didymium into two new elemental components, neodymia and praseodymia, by
repeated fractionation of ammonium didymium nitrate. While the free metal is in misch
metal, long known and used as a pyrophoric alloy for light flints, the element was not
isolated in relatively pure form until 1925. Neodymium is present in misch metal to the
extent of about 18%. It is present in the minerals monazite and bastnasite, which are
principal sources of rare-earth metals.
The element may be obtained by separating neodymium salts from other rare earths by
ion-exchange or solvent extraction techniques, and by reducing anhydrous halides such as
NdF3 with calcium metal.
Other separation techniques are possible.
The metal has a bright silvery metallic luster, Neodymium is one of the more reactive
rare-earth metals and quickly tarnishes in air, forming an oxide that spalls off and
exposes metal to oxidation. The metal, therefore, should be kept under light mineral oil
or sealed in a plastic material. Neodymium exists in two allotropic forms, with a
transformation from a double hexagonal to a body-centered cubic structure taking place at
Natural neodymium is a mixture of seven stable isotopes. Fourteen other radioactive
isotopes are recognized.
Didymium, of which neodymium is a component, is used for coloring glass to make welders
goggles. By itself, neodymium colors glass delicate shades ranging from pure violet
through wine-red and warm gray. Light transmitted through such glass shows unusually sharp
absorption bands. The glass has been used in astronomical work to produce sharp bands by
which spectral lines may be calibrated. Glass containing neodymium can be used as a laser
material to produce coherent light. Neodymium salts are also used as a colorant for
The price of the metal is about $1/g.
Neodymium has a low-to-moderate acute toxic rating. As with other rare earths,
neodymium should be handled with care.