Rare earths – Characteristics, Challenges and Opportunities

Rare earths – frequently used

The name rare earths dates back to the time when they were first mined, in which it was assumed that the metals in this group were very rare. In fact, as we know today, some of them, such as cerium, occur very frequently. The name earths also goes back to this time, when rare earths could only be extracted as oxides from certain materials. Earths is an old name for oxides.

Fortunately, the occurrence of rare earths is not at all rare, contrary to what their name suggests. After all, they are extremely important raw materials for our modern, high-tech lives. The demand for rare earth elements (REEs) has never been so high, as they are an important resource in the manufacturing of consumer electronics, smartphones, optical displays, illuminants, high-performance magnets and batteries, as well as in catalysis, electric motors, aerospace and medical applications. 

Superpowers for industry

Cerium – Cerium has a wide range of applications: it increases strength and ductility in aluminum alloys, colors glass and enamel; provides the spark in pyrophoric cerium alloys for lighters or gas lighters and is also used in UV filters for special glasses and windshields.

Lanthanum – Lanthanum is used by the glass industry primarily for the production of high-quality camera lenses. It is also found in flints.

Neodymium – initially called didymium (Greek for twin) because of its strong similarity to lanthanum, it is used primarily in the form of the alloy neodymium-iron-boron for strong permanent magnets.

Praseodymium – received its name because of its green coloration (Greek: prásinos, meaning "green") and its similarity to didymium. This made it another twin of the already existing twin pair didymium and lanthanum, which is why didymium was renamed neodymium (new twin). Praseodymium is used in alloys with magnesium to produce high-strength metal for aircraft engines, and in alloys with cobalt and iron as a strong permanent magnet. Like cerium, praseodymium compounds are used in the coloring of glass and enamel (for example, for green-colored headlight lenses). Because praseodymium compounds also improve UV absorption, they are used in the manufacture of eye protection lenses during welding. Praseodymium ion Pr3+ is also used as a dopant for laser media in solid-state lasers.  

Scandium – Named after the home of its discoverer, Lars Frederik Nilson, scandium is one of the rare elements. It does not occur elementally, but only in some rare minerals in enriched form. The use of the actually rare oxide is all the more wide-ranging for it: in high-pressure mercury vapor lamps, which are used for stadium lighting, for example. Together with holmium and dysprosium, scandium produces a light very similar to daylight. Scandium is also used in the production of laser crystals. In magnetic data storage devices, scandium increases speed. 

Terbium – Terbium is used to dope calcium fluoride, calcium tungstate and strontium molybdate for use in solid-state devices. It is also used together with zirconium(IV) oxide for microstructure stabilization in high-temperature fuel cells. Sodium terbium borate is used as a laser material for generating coherent light with a wavelength of 546 nm. Terbium is also added to the green phosphor in picture tubes and fluorescent lamps.

Yttrium – is named after its first place of discovery, the Ytterby mine near Stockholm, as are ytterbium, erbium and terbium. Its applications are vast: yttrium ceramics and alloys are used in lambda probes, superconductors, DS alloys and spark plugs. The oxidic yttrium compounds are used as coating material for incandescent lamps, as laser crystal, as microwave filter as solid electrolyte in fuel cells (SOFC). Yttrium oxides and yttrium oxide sulfides also play an important role in luminophores (phosphors) doped with trivalent europium (red) and thulium (blue) in television picture tubes and fluorescent lamps. By alloying with cobalt YCo5, yttrium can also be used as a rare earth magnet. Last but not least, yttrium is used as a material for heating wires in ion sources of mass spectrometers.

This selection shows how important the rare earths are for us.

Which analysis technology for which application?

Analytik Jena's ICP-OES (optical emission spectrometry with inductively coupled plasma) and ICP-MS (mass spectrometry using inductively coupled plasma) technology covers the comprehensive rare earth analysis process in a highly effective and efficient manner. 

Although ICP-MS and ICP-OES provide successful methods for analyzing REEs, they face some challenges: an unfavorable REO formation in the plasma tail and strong spectral interferences due to the large number of emission lines affect the detectability of REEs by ICP-MS or ICP-OES.

Solutions: A high-resolution array ICP-OES, the PlasmaQuant 9100 Elite, to resolve potential spectral interferences and a high-sensitivity ICP-MS solution, the PlasmaQuant MS Elite, with efficient removal of polyatomic interferences.

Summary

With the high-resolution spectrometer of the PlasmaQuant 9100 Elite and the highly effective interference management of the PlasmaQuant MS Elite, rare earths can be quantified particularly interference-free and thus reliably. Due to their high sensitivity and low detection limits, they cover the complete concentration range and convince with their precision.