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Material World
Element · Ce

Cerium

The most abundant rare earth, and the reason a lighter sparks.

Abrasive

Cerium is more abundant in the crust than copper, which makes the "rare earth" label especially misleading here. It is also the most chemically useful of them: cerium oxide is the standard glass-polishing compound, and cerium in a catalytic converter's washcoat buffers the oxygen supply so the catalyst keeps working through changes in the fuel mixture.

Mischmetal, a cerium-iron alloy, sparks when scraped. Every disposable lighter contains a small rod of it.

Uses

Cerium is the most abundant rare earth, and its uses reflect the fact that it is cheap enough to consume rather than conserve.

Ceria is the standard polishing compound for glass — optical lenses, mirrors and screens are finished with it. In catalytic converters cerium oxide buffers oxygen, storing and releasing it to keep the catalyst working as the engine's mixture shifts. Cerium is also the main component of ferrocerium, the alloy that sparks in a lighter flint, and it decolourises glass and screens ultraviolet in it.

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

  • Abrasive — application
  • Catalysis — application · as an oxygen buffer in the catalyst washcoat

is produced by

  • Rare earth separation — process · a light rare earth, separated from its neighbours by countercurrent solvent extraction

is extracted from

  • Bastnäsite — mineral · the most abundant rare earth in the ore, and usually the largest product by mass

is a component of

  • Mischmetal — alloy · 45–55% · about half, because that is the proportion the ore delivers — mischmetal is the light rare earths left unseparated

is found in

  • Yttrium aluminium garnet — compound · the dopant that turns blue light yellow, which is how almost every white LED in the world is made
  • Phosphor — material · in the scintillators and in the yellow LED phosphor
  • Bastnäsite — mineral · substitutes within a solid solution — an individual specimen may hold little of it
  • Monazite — mineral · substitutes within a solid solution — an individual specimen may hold little of it

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
  • NIST — National Institute of Standards and Technology
    United States Department of Commerce · US Government work — public information, credit requested

Questions this page answers

Where it comes from, and what it becomes

Follow Cerium 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

  • Cerium → is produced by (a light rare earth, separated from its neighbours by countercurrent solvent extraction) → Rare earth separation → takes as input (the principal ore of the light rare earths, carrying all of them together) → Bastnäsite
  • Cerium → is extracted from (the most abundant rare earth in the ore, and usually the largest product by mass) → Bastnäsite
  • Cerium → is produced by (a light rare earth, separated from its neighbours by countercurrent solvent extraction) → Rare earth separation → takes as input (the other feed alongside bastnäsite, bringing thorium into the residues with it) → Monazite
  • Cerium → is produced by (a light rare earth, separated from its neighbours by countercurrent solvent extraction) → Rare earth separation → takes as input (the heavy rare earth feed, where monazite and bastnäsite bring the light ones) → Xenotime

Downstream — what it becomes

  • Cerium → is a component of (about half, because that is the proportion the ore delivers — mischmetal is the light rare earths left unseparated) → Mischmetal → is used as (added to molten steel to scavenge sulfur and oxygen and reshape the inclusions that remain, which improves toughness — an unglamorous use that consumes a great deal of it) → Alloying
  • Cerium → is used as → Abrasive
  • Cerium → is used as (as an oxygen buffer in the catalyst washcoat) → Catalysis
  • Cerium → is a component of (about half, because that is the proportion the ore delivers — mischmetal is the light rare earths left unseparated) → Mischmetal → is used as (the negative electrode of the nickel-metal hydride battery, which powered hybrid vehicles and portable electronics before lithium-ion displaced it) → Battery electrodes