The not so Rare Earths

When we think of the influence of chemistry in everyday life, we might think of medicines, polymers or even fertilisers.

But chemistry is at the heart of all areas of modern technology from mobile phones and computers to lasers and camera lenses, none of which would be available without recent developments in Chemistry.

These items all involve the Rare Earth elements, which have been in the news recently as China, the main supplier, has announced a restriction on exports. There are concerns that manufacturing might be hit and the European Union is to consider recovery of these elements by recycling.

The Rare Earths are 17 elements with unfamiliar names. The lightest is called Scandium, as it was first found in Scandinavia.

The elements have similar chemical properties and are found together in ore deposits. They are so similar that chemists had great difficulty in separating them until spurred on by the need to separate another group of similar elements, radioactive ones needed for the development of the atomic bomb during World War Two, a method based on their slightly different sizes was developed.

Despite their name, they are not rare, but in total abundance, with one, cerium, being more plentiful that copper. There are, however, only a limited number of deposits where they are sufficiently concentrated to make it worthwhile mining at current prices.

Such is the recent growth in demand for the Rare Earths and incidentally some other metals, that demand has begun to outstrip production.

Around 97 per cent of the Rare Earths currently come from China, although this is because China was able to undercut the prices of other producers about 20 years ago. China has claimed that it is now limiting exports in order to ensure long term sustainability, but many believe that the change is more likely to be China wishing to support its own electronics industry. It is probable that deposits in alternative sources in Australia, Brazil, North America and South Africa will now be extracted, although it may take some years to develop this capacity again.

A major use for cerium is in catalytic converters in car exhausts. The catalytic converter is used to remove carbon monoxide, oxides of nitrogen and hydrocarbons from the exhaust gases to reduce pollution. The catalyst is platinum or a related metal which speeds up reactions which remove the unwanted gases.

There is an additional process in the catalytic converter, which uses cerium oxides to remove un-burnt fuel in the exhaust by releasing oxygen during the lean part of the engine’s cycle while absorbing the oxygen during the rich stage.

Another use of Rare Earth elements is in permanent magnets found in for example in speakers, headphones and disc drives.

Permanent magnets used to be made from iron, because it is the only element which is strongly magnetic at normal temperatures. Then some compounds of the Rare Earths were discovered to show magnetism like iron.

Rare Earth magnets made from neodymium with iron and boron are up to three times more powerful than iron magnets enabling much lighter magnets to be used in headphones, speakers and disc drives.

Sony changed the listening habits of the world with the introduction of the portable Walkman about 30 years ago. The credit went to the chairman of the company who had asked for the Walkman to be made, but the lightweight headphones would not have been possible without the scientific research which led to Rare Earth magnets.

These magnets are also found in hybrid cars and in some wind turbines.

Hybrid cars also use significant quantities of lanthanum in the nickel hydride batteries which use an alloy of lanthanum and nickel. The elements, cerium, lanthanum and yttrium are also used in fluorescent lighting which is replacing the traditional incandescent light bulbs and yttrium and several other Rare Earth elements are used in lasers. While these are just a few of the many uses of these elements it is worth mentioning one more. Yttrium is used in the so called “high temperature” superconductors, which hold the promise of much cheaper electricity distribution.

The Rare Earths are not rare or even precious metals, but with the predicted shortages the prices have been rising rapidly at a time when many modern developments and technologies are using them.