Element · Tb

Terbium

The green in a colour screen, and a metal that changes shape in a magnetic field enough to be useful.

Terbium is a lanthanide whose compounds fluoresce a very pure green, and that narrow, bright emission made it one of the three phosphors behind colour cathode-ray and fluorescent displays. A trichromatic lamp gets its green from terbium.

Its second property is stranger and more specialised. Terbium alloys change length appreciably in a magnetic field — enough that a coil driving a terbium-bearing rod becomes a usable actuator or sonar transducer, converting a magnetic signal directly into movement.

Uses

Green phosphors are the volume use, in fluorescent lighting and in display screens, where terbium's emission is narrow enough to give a saturated colour rather than a washed-out one.

Terfenol-D, an alloy of terbium, dysprosium and iron, is the standard magnetostrictive material: it is used in sonar projectors, precision positioners and vibration control, where a large force over a very small distance is what is wanted.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is used as

Lighting — application

is produced by

Rare earth separation — process · a heavy rare earth; the separation is the same cascade, run longer because the differences are smaller

is an alternative to

Dysprosium — element · as the heavy rare earth added to a neodymium magnet to stop it demagnetising when hot. Terbium does the job at lower addition rates and costs more, and reducing the need for either is an active research goal precisely because both are supply-concentrated

is a component of

Neodymium magnet — alloy · 0–3% · the same job as dysprosium at lower addition rates and higher cost

is found in

Phosphor — material · green, and the third of the trichromatic set

Sources

Material World
Our own writing
Wikidata
Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
PubChem
US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors

Where it comes from, and what it becomes

Follow Terbium back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

Terbium → is produced by (a heavy rare earth; the separation is the same cascade, run longer because the differences are smaller) → Rare earth separation → takes as input (the principal ore of the light rare earths, carrying all of them together) → Bastnäsite
Terbium → is produced by (a heavy rare earth; the separation is the same cascade, run longer because the differences are smaller) → Rare earth separation → takes as input (the other feed alongside bastnäsite, bringing thorium into the residues with it) → Monazite
Terbium → is produced by (a heavy rare earth; the separation is the same cascade, run longer because the differences are smaller) → Rare earth separation → takes as input (the heavy rare earth feed, where monazite and bastnäsite bring the light ones) → Xenotime

Downstream — what it becomes

Terbium → is a component of (the same job as dysprosium at lower addition rates and higher cost) → Neodymium magnet → is used as (the strongest in commercial use, and the reason a motor, a hard drive and an earbud can be small) → Permanent magnets
Terbium → is used as → Lighting
Terbium → is a component of (the same job as dysprosium at lower addition rates and higher cost) → Neodymium magnet → is used in (direct-drive wind turbine generators, which is what put rare-earth supply into energy policy) → Energy generation