TENTH IN THE LANTHANOID SERIES

Dysprosium contradicts its classification as a rare-earth metallic element because it is more than twice as abundant in nature as tin. (See “Scandium, Sc” on page 60 for information on the rare earths.) This classification was initially based on the fact that dysprosium is not found in nature as a free element. Rather, it’s dispersed among various minerals, often in very small amounts. Its original separation from a sample of holmium oxide in 1886 by French chemist Paul-Émile Lecoq de Boisbaudran (1838–1912) proved so difficult that he derived the new element’s name from dysprositos, which is Greek for hard to get!

The addition of small amounts of dysprosium to neodymium-iron-boron (NIB) magnets ensures that they maintain their renowned magnetic strength, even at elevated temperatures. This enables NIB magnets to be used in high-temperature environments, such as the engines of hybrid cars.

When dysprosium is combined with a blend of terbium and iron, the resulting alloy (known as Terfenol-D) exhibits an unusual property: it increases or decreases in length when placed within a magnetic field. (For more on this magnetostrictive phenomenon, see “Terbium, Tb” on page 190.)

Dysprosium iodide (DyI₃) is used in halide discharge lamps where the atoms of dysprosium absorb and then reemit energy as an intense white light.

A cermet is a temperature- and corrosion-resistant composite material made from ceramic and metallic materials. Dysprosium cermets tame the wild neutrons whizzing around inside nuclear reactor cores by absorbing them, thus controlling (cooling) the chain reaction.