What are rare earths?

Rare earth elements are relatively plentiful in the earth’s crust, with cerium being the 25th most abundant element at 68 parts per million. This makes it as abundant as copper. Because of their geochemical properties, rare earth elements are typically dispersed. This means they are often found in concentrated enough clusters to make them viable to mine. It was the scarcity of these minerals that led to them being called rare earths. Rare earths are categorised into light elements (lanthanum to samarium) and heavy elements (europium to lutetium). The latter are less common and consequently more expensive.

Chemically, rare earths are strong reducing agents. Their compounds are generally ionic and they display high melting and boiling points. Rare earths are relatively soft when in their metallic state while those with a higher atomic number tend to be harder. Rare earths react with other metallic and non-metallic elements to form compounds each of which has specific chemical behaviours. This makes them indispensable and non-replaceable in many electronic, optical, magnetic, and catalytic applications. Rare earth compounds are commonly fluorescent under ultraviolet light, which can assist in their identification. Rare earths also react with water or diluted acid to produce hydrogen gas. ​​

 Rare Earth ElementCurrent Applications
ScandiumMetals alloys used by the aerospace industry
YttriumPhosphors , ceramics, metal alloys
LanthanumBatteries, catalysts for petroleum refining
CeriumAutocatalysts, Chemical Catalyst, glass polishing, metal alloys
PraseodymiumHigh power magnets, yellow ceramic pigment, Autocat
NeodymiumHigh power magnets
PromethiumBeta radiation source
SamariumHigh temperature magnets,
Europiumfluorescent lighting
GadoliniumMagnetic resonance imaging contrast agent, nuclear reactor rods
TerbiumPhosphors for lighting, high power high temperature magnets
DysprosiumHigh power high temperature magnets, lasers
HolmiumHighest power magnets in existence
ErbiumLasers, glass colourant
ThuliumCeramic magnetic materials which are still under development
YtterbiumFibre optic technology, solar panels
LutetiumPET scanners
Rare Earths Compound Applications
CatalystsPetroleum refining
Chemical processing
Catalytic converters
Diesel additives
Industrial pollution scrubbers
GlassPolishing compounds
Optical glass
UV resistant glass
X-ray imaging
Thermal control mirrors
Colourisers / deodarisers
Metal AlloysHydrogen storage – NiMH batteries; fuel cells
Steel
Lighter flints
Aluminum / magnesium
Cast iron
Superalloys
ElectronicsDisplay phosphors – LCD, PDP, CRT
Medical imaging phosphors
Lasers
Fibre optics
Optical temperature sensors
CeramicsCapacitors
Sensors
Colourants
Scintillators
MagnetsMotors
Disk drives and disk drive motors
Power generation
Actuators
Microphones and speakers
MRI
Anti-lock brake systems
Automotive parts
Communication systems
Electric drive and propulsion
Frictionless bearings
Magnetic storage disks
Microwave power tubes
Magnetic refrigeration
Magnetostrictive alloys

Click here for a summary of Rare Earths and their key attributes