Tb’s magnetostrictive feats exploit the Joule effect,
Thus Terfenol-D helps flick the switch, helps sonar to detect.
In TV tube, fluorescent light . . .
. . . its phosphors glow so green ’n’ bright;
What’s more, they’re used for X-ray scans, where patients they protect.
tee-bees
ter-fenn’l-dee
NINTH IN THE LANTHANOID SERIES
Terbium has an unusual property for a lanthanoid: it will increase or decrease in length by a small amount when placed within a magnetic field. This phenomenon, known as magnetostriction, is a physical manifestation of the Joule effect, where certain materials extend or contract in the same direction as the magnetic field or in some other direction. Although the elemental metal exhibits moderate magnetostriction, some of its alloys exhibit a more pronounced effect. The best example is Terfenol-D, an alloy of terbium, iron, and dysprosium. Terfenol-D is used to make actuators (switches that flick from one position to another) and sonar transceivers (which use sound waves to detect the locations of objects underwater).
tee-vee
Terbium phosphors provided the green component on the cathode ray tubes (CRTs) in pre–flat-screen-era color TVs. They also combine with europium’s red and blue phosphors to provide the illumination source in white fluorescent lights. (See “Europium, Eu” on page 184 for more on phosphors.)
Terbium-doped phosphors are used in X-ray imaging screens. Their enhanced response to X-rays enables significantly shorter scan times. This allows a corresponding reduction in patient exposure to harmful X-rays, improving patient safety.
