Worldwide, about 35% of rare-earth elements are used as catalysts, mainly in the refining of crude oil. For example, addition of 1 to 5% rare-earth-element chloride to a zeolite catalyst increases the catalyst's cracking efficiency. Rare-earth elements are also included in catalytic converters of automobiles, where rare-earth elements stabilise the gamma-alumina support and enhance the oxidation of pollutants.
Approximately 30% of the rare-earth elements are used in the glass and ceramics industry as glass-polishing compounds, decolourising agents, UV absorbers and antibrowning agents, glass and ceramic colouring agents, additives to structural ceramics (such as stabilized zirconia and silicon nitride Si3N4) and in optical lenses and glasses.
About 30% are used in metallurgy as an alloying agent to desulphurise steels, as a nodularising agent in ductile iron, as lighter flints and as alloying agents to improve the properties of superalloys and alloys of magnesium, aluminium and titanium. A rapidly expanding application is in batteries. Mischmetal (a mixture of rare-earth elements) is a component of nickel metal hydride batteries, which are replacing nickel cadmium batteries in powering portable electronic equipment such as lap top computers and mobile phones.
The individual elements account for the remaining 5% of volume but over 50% of the monetary value.
A currently expanding application for rare-earth elements is in the production of permanent magnets. Samarium-cobalt (SmCo5-Sm2Co17) permanent magnets are used in industrial, military and aerospace applications. Less costly neodymium-iron-boron (Nd2Fe14B) magnets are used in automobile starting and accessory motors, medical magnetic-resonance-imaging devices, industrial motors, compact disc players, computer disk drives, personal stereos, and camera motors.
Other industrial uses include: phosphors in colour TV and fluorescent lighting, garnet bubble storage devices, oxygen sensors, microwave ferrites and garnets, fibre optics, synthetic crystals used in lasers (especially Nd), lanthanum-nickel alloy for hydrogen storage, and gallium-gadolinium-garnet (GGG) as a memory film in computers. Rare-earth elements are used in the nuclear industry in control rods, as dilutants, and in shielding, detectors and counters. Thorium is a potential atomic fuel source.
Information courtesy of University of Tartu (http://www.ut.ee/).
Cerium - Glass polishing, petroleum-cracking catalysts, radiation shielding, alloys with iron for lighter sparking flints, alloys with aluminium, magnesium and steel for improving heat and strength properties.
Dysprosium - Control rods for nuclear reactors, alloyed with neodymium for permanent magnets, catalysts.
Erbium - In ceramics to produce a pink glaze, infra-red absorbing glasses.
Europium - Control rods for nuclear reactors, coloured lamps, cathode-ray tubes, red phosphor in colour-television tubes, used in lasers and to absorb neutrons.
Gadolinium - Solid-state lasers, computer memory chips, high-temperature refractories, cryogenic refrigerants, used in improving high-temperature characteristics of iron, chromium, and related alloys.
Holmium - Control rods for nuclear reactors, catalysts, refractories.
Lanthanum - Ceramic glazes, high-quality optical glass, camera lenses, microwave crystals, ceramic capacitors, glass polishing, petroleum cracking and movie- and television-studio lighting
Lutetium - De-oxidiser in stainless-steel production, rechargeable batteries, medical uses, red phosphors for colour television, superconductors, used in nuclear technology.
Neodymium - Ceramic capacitors, glazes and coloured glass, lasers, high-strength permanent magnets, petroleum-cracking catalysts.
Praseodymium - Yellow ceramic pigments, tiles, ceramic capacitors, with neodymium for goggles to shield glass makers against sodium glare, permanent magnets, cryogenic refrigerant.
Samarium - In highly magnetic alloys for permanent magnets, nuclear-reactor controls and neutron shielding, laser, infrared-absorbing glass, and as a neutron absorber in certain nuclear reactors.
Scandium - X-ray tubes, catalysts for polymerisation, in hardened nickel-chromium superalloys, dental porcelain, used as a tracer in studies of oil wells and pipelines.
Terbium - Cathode-ray tubes for x-ray and color-television tubes, magnets, optical computer memories, computer hard-drive components; magnetostrictive alloys.
Thorium - Gas mantles, magnesium alloys, and can be used as nuclear fuel in place of uranium.
Thulium - X-ray equipment for small portable medical x-ray units.
Ytterbium - X-ray equipment for portable irradiation devices, lasers and in some special alloys.
Yttrium - De-oxidiser in stainless-steel production, strengthener in magnesium and aluminum alloys, rechargeable batteries, medical uses, red phosphors for colour television, superconductors, and various other metallurgical applications.