Rare earth elements have drawn worldwide attention in recent months, with uncertainty from the world’s largest producer, China, making investors uneasy about products and industries that require these substances.
Rare earth elements are a collection of seventeen members of the periodic table, as defined by the International Union of Pure and Applied Chemistry, but the name is somewhat misleading.
Composed mostly of members of the Periodic table’s lanthanide series, rare earths are similar in abundance as more familiar elements such as copper, nickel or zinc, while even the least abundant naturally occurring rare earths are 200 times more common than gold.
However, rare earth elements are only found in commercially viable amounts in several areas of the world. This situation has been compounded by Chinese production that has undercut costs of production in the US, by way of lower labor costs and less stringent environmental regulation. Once self-sufficient in rare earth production, sites in the US such as the Mountain Pass Mine in California’s Mojave Desert operates far below capacity, according to the USGS, for these environmental and economic concerns.
With uncertainty in the global rare earth markets, it pays to know what the rare earth elements are, and what they do. Click ahead for an element-by-element breakdown of the rare earth elements and how they are used in today’s economy.
By Paul ToscanoPosted Nov 5 2010
Although chemists technically differentiate Scandium from the other rare earth metals, this element is present in most rare earth or uranium deposits and is only found in a handful of mines worldwide.
Scandium is a metal with a hard and silvery appearance and has a somewhat abundant on the planet, estimated to be the 50th most common element in the earth’s crust. However, it is sparsely dispersed and is found mostly in trace amounts, except in regions of Scandinavia (from which it gets its name) and Madagascar where large concentrations can be found.
Scandium can be added to aluminum, creating an alloy that increases the strength of the metal in heat-affected zones, such as around welds. Applications of this alloy are found in some aerospace components Scandium alloys were used in Russian MiG 21 and MiG 29 aircraft), as well as consumer products like baseball bats, lacrosse sticks and bicycle frames. Scandium is also used in some hand guns (revolvers), while some molecules containing the element are used in high-intensity discharge lamps and light bulbs.
Another transition metal, Yttrium is chemically similar to the lanthanides and is only found combined with other rare earth metals and uranium ores and is never found as a free element in nature. Despite this, Yttrium is estimated to be the 28th most abundant element in the earth’s crust, about 400 times more abundant than silver.
Yttrium’s primary application is in LED televisions, where yttrium oxide is combined with europium to help produce red pixels. It can also be used for increasing strength of aluminum and magnesium alloys and has been used in superconductors that must be kept at ultra-low temperatures. Yttrium also has applications in the treatment of various cancers such as lymphoma, leukemia, ovarian, pancreatic and bone cancers.
The first member in the Lanthanide series, it is a silvery-white metallic element that is usually found in combination with cerium and other rare earth elements. Lanthanum is relatively abundant, appearing about twice as frequently in the earth’s crust as nitrogen, lead or lithium.
Lanthanum is used in nickel-metal hydride batteries in Hybrid cars, which carry between 20-25 pounds of the element. As engineers devise ways to increase fuel mileage, it is expected that up to twice the amount of lanthanum could be used in each vehicle. Lanthanum is also used in the production of electronic vacuum tubes, camera and telescope lenses, as a steel additive and even in certain medications.
The most abundant of the rare earth metals, Cerium is estimated to make up approximately 0.0046% of the earth’s crust by weight, with about 24,000 tons of the metal produced per year.
Cerium is used in a number of technical applications, but is most notable for being a component in the catalytic converter of automobiles, reducing carbon emissions from the exhaust gas and it is often added to diesel fuels. Cerium is also used in the manufacture of glass as well as aluminum and iron alloys. Other applications include TV phosphors, magnets and carbon-arc lighting used by the motion picture industry.
According to the USGS, Bastnasite ore found in Mountain Pass, California is composed of over 50% Cerium.
Praseodymium is found in relatively small amounts and must be separated from other rare earth elements by chemical processes. It is generally considered difficult to purify.
The element is used as an alloying agent for metals used in aircraft engines, for coloring of cubic zirconias and other glass, and small amounts are also found in cigarette lighters and other handheld fire-starters.
Neodymium can be found in metallic form, unaccompanied by other rare earth metals, and is relatively abundant in the earth’s crust, although the bulk of it exists in China.
Magnets made with neodymium are known to be among the strongest permanent magnets that are currently known, with the ability to lift around 1000x its own weight. Stronger than their counterparts, this type of magnet is used in microphones, professional loudspeakers, headphones and computer hard disks where a magnetic field is required.
Neodymium is also used in lasers for both commercial and military use, as well as glass coloration and florescent lighting.
A radioactive element, promethium is formed in nature as a result of fission or decay of heavier elements, with only trace amounts found in naturally occurring ores. It is extremely rare , with less than 500 grams thought to be on the planet at any given time.
It has few applications, including use in nuclear batteries and a beta radiation source for thickness gauges, but some believe it could eventually be used as a power source for space probes and satellites.
Samarium is a shiny silver metal, that has an estimated annual production of 700 tons although it is not found free in nature. It is relatively abundant in rare earth ores but requires specialized processors to extract the element.
Samarium has applications alongside other rare earth metals in magnets, lasers and carbon-arc lighting, but also can be used as a neutron absorber in nuclear reactors and one of Samarium’s radioactive isotopes is used to treat severe pain associated with bone cancers in a drug with the trade name Quadramet.
One of the most sought-after rare earth metals, Europium is also one of the most reactive in the group and is not found in nature as a free element.
Europium is widely used as a phosphor in LED televisions, computer screens and florescent lamps. The element is also used in screening for genetic diseases, such as Down Syndrome and if you happen to have a Euro note in your wallet, Europium is used in the anti-counterfeiting phosphors of the bills.
Gadolinium is a silvery-white metal that is found in rare earth deposits around the world, with an estimated 1 million tons in mining areas in China, US, Brazil, India and Australia. However, only about 400 tons of pure gadolinium are produced per year.
Due to its extremely high neutron capture rate, Gadolinium is used in nuclear reactors as both a shield and a secondary emergency shutdown mechanism in certain types of reactors. The element is also used in MRI imaging, making certain metal alloys resistant to high temperature, marine propulsion systems and X-ray systems.
Although never found in nature as a free element, it is contained in minerals alongside other rare earth metals. The most abundant commercially viable source of Terbium is in the ion-absorption clays of Southern China, found alongside Yttrium.
Terbium is used in solid-state devices such as the crystal stabilizer of fuel cells, naval sonar systems and certain alloys. The largest commercial application of Terbium is in color television tubes. When the green terbium phosphor is used with blue and red Europium phosphors, it creates the color technology in trichromatic lighting.
A metal that is soft enough to cut with a knife, Dysprosium is another rare earth metal that comes primarily from Southern China.
The element is used in making laser materials and neutron-absorbing control rods in nuclear reactors. Dysprosium is also used in hard disks, absorption rods in nuclear reactors and high intensity lighting.
Holmium is credited as having the highest magnetic strength of any element on the periodic table. Its major mining areas are in China, the US, Brazil, India, Sri Lanka and Australia, with an estimated 400,000 tons of the material currently in the earth’s crust.
For its magnetic strength, Holmium is used as a component in powerful magnets, as well as nuclear control rods, since it has the ability to absorb neutrons expelled by nuclear fission. Holmium is also used in microwave equipment and medical devices, such as lasers made with Holmium, which are safe to use on human eyes.
When artificially isolated, Erbium is a silvery-white solid metal, but in nature it is always found combined with other elements, most usually other rare earths.
Erbium’s main uses include combination with Europium isotopes to give them certain florescent properties. It is also used in optical amplifiers, fiber optic cables, as well as for medical and dental lasers.
The least abundant element in the lanthanide series, it is never found in pure form in nature and is generally purified through an ion-exchange process. The world’s principle sources for Thulium comes from Southern China, although the element is considered to be economically unimportant from its high cost and few applications.
Thulium has been used in surgical lasers, portable x-ray devices and high temperature superconductors.
A soft metal, ytterbium is found in China, the US, Brazil, India, Sri Lanka and Australia, with about 1 million tons of reserves in the Earth’s crust. The element is found in the earth’s crust at approximately 3 parts per million, but are found in the highest concentrations in the adsorption clays of Southern China.
Ytterbium can be used in portable x-ray devices, the strengthening of steel, solid state lasers and stress gauges that monitor ground deformation from earthquakes or explosions.
Found in the earth’s crust in the small abundance of 0.5 parts per million, Lutetium is also difficult to separate from the other rare earth metals it is found alongside in nature. The global production of Lutetium is approximately 10 tons annually, and is mined primarily in China, the US, Brazil, India, Sri Lanka and Australia.
Lutetium is worth approximately $10,000 per kilogram and for its high price it has found few commercial uses, although it has applications in the petroleum industry for petroleum cracking and has experimental uses in certain cancer treatments.