TWELFTH IN THE LANTHANOID SERIES

Erbium belongs to a select quartet of elements (the other three are yttrium, terbium, and ytterbium) that were discovered in a coal-like mineral obtained from an old quarry near the small Swedish village of Ytterby, not far from Stockholm.

Erbium deserves to be a better-known element because of its central role in the high-speed global transmission of internet and telecommunications data. The further data travels via light signals through fiber optic cables, the more the signal intensity deteriorates, because the light unavoidably scatters within the fibers. To prevent signal deterioration, short sections (say, 10 m) of erbium-doped optical fiber are incorporated at regular intervals (about every 20 to 50 km) along the cable route. Pulses from laser diodes elevate the erbium in these short sections to an excited energetic state. The incoming weak light signals stimulate the excited erbium, causing it to emit additional photons of light that amplify the original incoming signal, and presto! Weak light in, strong light out—all thanks to erbium-doped fiber amplifiers!

Erbium forms compounds in which its oxidation state is +3. This means that many erbium salts contain the trivalent cation Er³⁺, which causes them to be pink in color. Erbium salts, in particular erbium oxide (Er₂O₃), produce an appealing pink tint when added to glass or ceramic glazes.

Erbium oxide is occasionally added to the glass in welders’ safety goggles. It helps protect their eyes by absorbing the harmful rays of IR light.

Erbium can be found in nuclear reactors. Here, perhaps a little counterintuitively, it helps to cool (and thus control) the nuclear processes by burning up as it absorbs the neutrons produced during the fission reactions. (See “Holmium, Ho” on page 194 for more on burnable poisons.)

Erbium-doped YAG solid-state lasers have a relatively shallow penetrating ability. This enables their safe dermatological use for the removal of surface skin blemishes, such as moles and acne scars. Dentists also use these lasers to buff up discolored teeth. (See “Yttrium, Y” on page 114 for more information on YAG.)