The term "Rare Earth" refers to the group of elements with atomic numbers 57-71. Rare Earths were first discovered by Johann Gadolin in 1794 but, due to the difficulty in separation of the elements, the full range of rare earth metals was not complete until more advanced separation techniques were developed in the twentieth century. Contrary the name's implication, rare earths are widely distributed and fairly abundant in the earth's crust. The largest reserves are found in China, Australia, North America and Russia.
The rare earth metals are characterized by high density, high melting points, and high electrical and thermal conductivity. The elements do not fit well in the periodic table, and are often shown below it, separated from the main groupings. The rare earth elements include:
Mixtures of rare earths are refined into metals, oxides, and salts. Oxides, Carbonates and Fluorides are among the most popular Mixed Rare Earth compounds. Another common form of mixed rare earth, Mischmetal, is an alloy of rare earth metals containing cerium, lanthanum, neodymium and praseodymium as main components.
Rare earth metals have become key ingredients for enhancing the performance of many advanced technology products. These materials provide unique physical properties for advanced technology applications that cannot be achieved with other materials. Applications currently utilizing rare earth materials include alloys, catalysts, ceramics, glass, magnetics, nuclear, and phosphors.