What is terbium used for?
By RareMetals.net Editorial Team · Updated
Terbium is used mainly to make NdFeB permanent magnets keep their strength at high temperature, in electric-vehicle motors and wind turbines. Other uses are green phosphors (lamps and X-ray screens), Terfenol-D magnetostrictive alloys for sonar and actuators, and terbium gallium garnet crystals that protect high-power lasers.
Main uses of terbium at a glance
| Application | What terbium does | Examples |
|---|---|---|
| High-temperature NdFeB magnets | Keeps the magnet from demagnetising when hot | EV traction motors, wind turbines, industrial servo motors |
| Phosphors | Tb³⁺ emits bright green light | Fluorescent lamps, X-ray screens, some displays |
| Magnetostrictive alloys | Terfenol-D (terbium-dysprosium-iron) changes shape in a magnetic field | Sonar, precision actuators, vibration control |
| Electronics and optics | Magneto-optical properties | Optical isolators in fibre-laser systems |
High-temperature magnets
A standard NdFeB magnet starts to lose magnetism above about 80 °C. Adding terbium or dysprosium raises its coercivity, its resistance to demagnetising, so it keeps working in a hot EV traction motor or generator. Terbium is roughly twice as effective as dysprosium per kilogram but much more expensive.
Magnet makers now apply terbium mainly by grain-boundary diffusion: a thin terbium coating is diffused into the finished magnet so that the terbium sits only at the edges of the grains, where it does the most good. This has cut the amount needed per magnet.
Phosphors
The Tb³⁺ ion gives a bright green light. Terbium phosphors were a large share of demand when tri-band fluorescent lamps were common, and they are still used in X-ray intensifying screens (gadolinium oxysulfide doped with terbium) and some displays.
Terfenol-D
An alloy of terbium, dysprosium and iron called Terfenol-D changes length noticeably in a magnetic field. It is used in sonar transducers, precision actuators, vibration control and some energy harvesters.
Optics and research
Terbium gallium garnet (TGG) crystals are Faraday rotators in optical isolators, which stop reflections from damaging high-power lasers. The isotope terbium-161 is being studied as a cancer radiopharmaceutical.
Products that contain terbium
- Electric-vehicle traction motors
- Wind-turbine generators
- Fluorescent tubes and X-ray screens
- Sonar and precision actuators
- Optical isolators in fibre and industrial lasers
Can terbium be replaced?
Dysprosium can replace terbium in magnets, at about twice the amount. Grain-boundary diffusion, finer-grained magnets and motors designed to run cooler reduce the terbium needed; the USGS notes that light rare earths can substitute for heavy rare earths in several uses.
Terbium uses FAQ
What is terbium used for in electric cars?
Small amounts in the NdFeB magnets of the traction motor keep them from losing strength when the motor gets hot.
What products contain terbium?
EV motors, wind turbines, fluorescent tubes, X-ray screens, sonar transducers and optical isolators in high-power lasers.
Why is terbium so valuable?
It is scarce (about 1.2 ppm of the crust), comes mainly from clay deposits in China and Burma, and is hard to replace in high-temperature magnets.