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Rare Earths

 

Rare Earths 101

 

Rare earth elements are a group of 17 elements with diverse and important applications in industry. They can be subdivided into “light” and “heavy” rare earths based on the fact that heavy rare earths hold the electrons closer to the nucleus than light rare earths and hence are denser. Their location in the periodic table is shown below.

 

Periodic Table of Elements
Periodic Table of Elements

 

At present almost all REE production comes from China, with Chinese output accounting for approximately 95% of global production in 2010. China has begun to significantly restrict the exports of REEs which are used in the manufacture of a wide variety of consumer electronics, green technology, and industry. This vulnerability to REE exports has been realised by the US, Japan and the EU who are all now seeking new sources of REEs. As China only accounts for 38% of global REE reserves, there is clearly scope for rare earth production outside of China.

 

Rare Earth Uses

 

The uses of rare earth elements in terms of economic value (2008) are shown below. The two principal applications of magnets and phosphors accounted for 70% of the value while accounting for just 30% of REE output. The major REE application categories are magnets, phosphors and luminescence, metal alloy/batteries, catalysts and glass and polishing and ceramics, as detailed in a comprehensive report by the German Oko-Institute, are discussed below.

 

Uses of Rare Earth Elements Graph magnets phosphers metal alloys catalysts ceramics polishing other glass

                Magnets       Phosphers   Metal Alloys   Catalysts       Ceramics       Polishing         Other             Glass

 

Source: Roskill 2010

 

Magnets

 

Rare earths are used in the production of neodymium-iron-boron and samarium-cobalt magnets. Samarium-cobalt magnets, which also contain some lanthanum, play only a minor role, as they have mainly been replaced by the more powerful neodymium magnets. Neodymium magnets are the strongest available magnets and exceed other permanent magnets such as samarium-cobalt magnets by a factor of 2.5 and other aluminium and iron based magnets by a factor of 7-12. Neodymium magnets, also called neo-magnets, are essential to a wide variety of products. These include:

 

  • head actuators for computer hard disks
  • magnetic resonance imaging (MRI)
  • magnetic guitar pickups
  • loudspeakers and headphones
  • magnetic bearings and couplings
  • electric motors
    • wind turbines
    • cordless tools
    • servo motors
    • lifting and compressor motors
    • synchronous motors
    • spindle and stepper motors
    • electrical power steering
    • drive motors for hybrid and electric vehicles, such as the Toyota Prius
    • actuators

 

The strong rare earth permanent magnets enabled the miniaturisation of electric devices such as small speakers (ear phones) and hard disks. Two further large fields of application are electric motors used in hybrid electric vehicles, plug-in hybrid electric vehicles, electric vehicles and wind turbine generators. Wind generators which use neo magnets can harness wind more efficiently than other turbines and the tower top mass of these wind turbines is significantly lower than other traditional wind turbines. In addition permanent magnets are very reliable which is important in offshore wind generation where maintenance is extremely expensive. Neodymium magnets are also used for industrial equipment such as lifters or magnetic separators. In the defense sector, the M1A2 Abrams tank uses heat resistant Samarium-cobalt magnets for navigation and the DDG-51 Hybrid Electric Drive Ship Program uses Neodymium magnets for propulsion. Rare earth permanent magnets represent approximately 20% of the global magnet market by volume. The basic chemical formula of Nd magnetic material is Nd2Fe14B, which comprises a mix of neodymium and praseodymium (approx. 30%) and mostly the additives dysprosium (approx. 3%) and terbium in even lower concentrations.

 

While the forecasts for Nd-magnets varies, strong growth in the use of rare earth elements is expected as vehicle electrification takes place and as wind manufacturers increase the use of permanent magnets in their designs.

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Phosphors and Luminescence

 

Europium

Almost all future energy saving lighting and display technologies, such as compact fluorescent lamps (CFLs), light emitting diodes (LEDs), organic light emitting diodes (OLEDs), plasma displays and LCDs require the use of rare earths as phosphors, providing a high energy efficiency and high colour quality.

 

Europium oxide (Eu2O3) is used as a red and blue phosphor in television sets and fluorescent lamps, and as an activator for Yttrium-based phosphors. Whereas trivalent europium (Eu3+) gives red phosphors, the luminescence of divalent europium (Eu2+) depends on the host lattice, but tends to be on the blue side.

 

Terbium "green" phosphors (which fluoresce a brilliant lemon-yellow) are combined with divalent europium blue phosphors and trivalent europium red phosphors to provide the "trichromatic" lighting technology used in compact fluorescent lightbulbs and liquid crystal displays which is by far the largest consumer of the world's terbium supply. Trichromatic lighting provides much higher light output for a given amount of electrical energy than incandescent lighting.

 

Yttria (Y2O3) can serve as host lattice for doping with Eu3+ cations as well as reactant to gain doped yttrium orthovanadate YVO4:Eu3+ or yttrium oxide sulfide Y2O2 S:Eu3+ phosphors that produce the red colour in colour television though the red itself is actually emitted from the europium while the yttrium collects energy from the electron gun and passes it to the phosphor.

 

The overall global growth of lighting is estimated at 7 % per year by Philips for the years 2004 to 2011. Incandescent bulbs are being phased out due to their high energy demand in for example, the European Union, Australia, Canada and the United States. They will be replaced by other lighting systems, mainly compact fluorescent lamps (CFL) and halogen lamps. As such the demand for yttrium, terbium and europium is expected to grow strongly.

 

Currently LEDs play a minor role in lighting with a market share of 2.4 % in 2008. The main current uses are decorative effect lighting and orientation light but LEDs are also starting to replace other lighting systems, e.g. automobile headlights. The development of LEDs is progressing rapidly, and wider uses at very high efficiencies are expected. Trendforce assumes a growth rate of 32 % from 2008 to 2013 with a market share of about 8 % in 2013.

 

Cathode-ray tubes which which were used in TVs have been replaced by plasma displays and LCDs. In 2008, around 130 million television sets with plasma and LCD displays were sold. DisplaySearch forecasts an increase to approx. 280 million units in 2014. This corresponds to an annual growth rate of 14%.

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Metal alloys/batteries

 

Lanthanum

One of the oldest applications of rare earth elements is the use of cerium and lanthanum in pyrophoric alloys which are used in flint ignition devices for lighters and torches. Mischmetal (a mix of lanthanum, cerium, neodymium and praseodymium) and cerium are used as minor alloys for the casting of steel and iron to improve the stability of the casted product. The addition of yttrium, lanthanum and cerium to heat-resistant superalloys can dramatically improve their performance. Lanthanum often combined with some mischmetal is used in Ni-MH batteries which in turn are used in hybrid electric vehicles (e.g.Toyota Prius) and portable appliances.

 

The market share of Ni-MH batteries in hybrid electric vehicles is currently very high because the market is dominated by the Toyota Prius, which is equipped with a Ni-MH battery. In 2008, the Prius had a market share of HEVs amounting to approx. 83%. In the long term, however, demand is expected to decline if Li-ion batteries replace Ni-MH batteries in hybrids, and Toyota has plans to move away from Ni-MH batteries.

 

The main application of scandium by weight is in aluminium-scandium alloys for minor aerospace industry components. These alloys contain between 0.1% and 0.5% ofsScandium.

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Catalysts

 

Cerium and lanthanum are widely used as catalysts. Cerium compounds are used in automotive catalysts and as diesel additives in order to provide clean combustion. Lanthanum and cerium are important in petroleum refining as fluid cracking catalysts (FCC). Further applications are used in chemical processing. The demand for rare earth as catalysts contributes approximately 20% of total rare earth volume. These applications are highly relevant in terms of emission reduction, energy efficiency and the reduction of embedded precious metals (platinum, palladium and rhodium) in the catalysts due to better catalyst performance. Demand for automotive catalysts may increase as the global stock of fuel driven vehicles increases steadily by approximately 3% per year.

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Glass, Polishing and Ceramics

 

There are several rare earth elements which have applications in the glass, polishing and ceramic industries. Some of these are shown below.

 

Uses of Rare Earth Elements in Glass, Polishing and Ceramics

 

The applications described consume approximately 30 % of REEs according to an estimate from consultancy IMCOA. IMCOA also provide more detailed estimates for the sectors in 2008:

  • Glass polishing 15 000 t REO (44 %)
  • Glass additives 12 000 t REO (35 %)
  • Ceramics 7 000 t REO (21 %)
IMCOA estimate an increase in the demand of the whole application group of less than 5 %. They expect almost no growth for glass additives and moderate growth rates for polishing and ceramics.

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Others

 

The applications which do not fit in the other categories are mainly those below.

 

Other Rare Earth Applications

 

Many military components contain rare earths. The rare earths neodymium, yttrium, lanthanum, lutetium and europium allow for the amplification and enhanced resolution of signals which is very important in military communications. The lasers used by the military rely on yttrium, europium and terbium. There is evidence that the addition of small amounts (0.04-0.16%) of REEs to fertilizer can improve crop yields and lessen plant disease. A new application of cerium is in water treatment for the removal of arsenic.

 

The uses of rare earths by element are further discussed on the next page.

Individual Rare Earth Elements >>




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