Element 65 in our International Year of the Periodic Table series is terbium. Terbium and its compounds are used in sonar and phone and TV screens, and some of its compounds have the interesting property of being triboluminescent.

An alloy of terbium, dysprosium and iron, terfenol-D, has the unusual property of changing shape in magnetic fields. This property gives it uses in naval sonar systems and sensors.

Terbium-based phosphors are used to give the green light in many screens. Combined with red- and blue-emitting europium compounds they can make white light fluorescent lamps.

Some terbium compounds also have the unusual property of being triboluminescent. This means that when materials made from these compounds are stressed or fractured, light is emitted. The effect is still not fully understood but is thought to be a consequence of the separation and recombination of electrical charges.

Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.