Terbium

Terbium is a silvery rare earth metal that produces green phosphorescence and is an essential component in the phosphors used in LED lighting, colour TV screens and fluorescent lamps. Without terbium, truly high-quality green light in displays would be much harder to achieve.

• Atomic Number6565 protons, 65 electrons
• Atomic Mass158.92535 u65× heavier than hydrogen
• State at Room TempSolidSolid
• Density8.23 g/cm³
• Melting / Boiling1355.8°C / 3229.8°C
• Discovered1843

What is Terbium?

Terbium is a lanthanide rare earth metal with 65 protons. Terbium-doped green phosphors are used in LED lighting, flat-panel displays and fluorescent lamps. Terbium is also used in magneto-optical devices and in the alloy Terfenol-D, which changes shape in magnetic fields (magnetostriction), used in sonar transducers and acoustic devices.

Fact Terbium is element 65 in the periodic table, symbol Tb. As a lanthanide, it is part of the group of 15 elements sharing very similar chemistry, formed by the filling of the 4f electron subshell. All lanthanides form stable +3 ions and are found together in rare earth mineral deposits.

Where you find Terbium

On Earth

Terbium is found alongside other rare earth elements in minerals such as monazite, bastnäsite and xenotime. China produces the vast majority of world supply, with smaller contributions from Australia, the United States, Russia and India. It is never found as a free metal in nature.

• Monazite and bastnäsite. The primary rare earth minerals that contain Terbium.
• Ion-adsorption clays. Certain clay deposits in southern China are particularly rich in heavier lanthanides including Terbium.

How we use Terbium

Terbium-doped green phosphors are used in LED lighting, flat-panel displays and fluorescent lamps. Terbium is also used in magneto-optical devices and in the alloy Terfenol-D, which changes shape in magnetic fields (magnetostriction), used in sonar transducers and acoustic devices.

Did you know? Terbium was one of the last lanthanides to be isolated in pure form. The extraordinary chemical similarity between adjacent lanthanides made separation extraordinarily difficult until ion exchange chromatography was developed in the 1940s.

How it was discovered

Terbium was identified and separated from the mixture of rare earth elements found in minerals from Ytterby, Sweden and other locations, through painstaking fractional crystallisation and spectroscopic analysis over many decades in the 19th century.

Deeper dive: terbium and rare earth supply chains

The lanthanides, often called rare earth elements, are critically important for clean energy technologies. Neodymium and praseodymium go into the powerful magnets in EV motors and wind turbines. Dysprosium improves those magnets at high temperatures. Lanthanum and cerium go into NiMH batteries, catalysts and glass. Europium and terbium provide red and green in LED phosphors. This means that the global transition to clean energy depends heavily on rare earth elements, and their supply is dominated by China, which produces over 60% of the world's rare earth output. Concerns about supply security have spurred investment in rare earth mining projects in Australia, Canada, the USA and elsewhere.

Moving to 66 protons brings us to the next element on the periodic table.