With worldwide demand for rare-earth metals amounting to 134,000 tons last year, and only 124,000 tons being produced, the difference has had to be made up from dwindling stockpiles. By 2012, demand is expected to reach 180,000 tons, which could exhaust the world’s remaining inventory. The result has been panic throughout industrial countries.
What makes the rare earths so special is the way they can react with other elements to get results that neither could achieve alone. They are used, a pinch here and a pinch there, to make powerful permanent magnets for lightweight electric motors, phosphors for colour television and flat-panel displays, catalysts for cars and chemical refineries, rechargeable batteries for hybrid and electric cars, generators for wind turbines, as well as numerous optical, medical and military devices. To give just one example, every Toyota Prius has over 25 pounds of lanthanum in its nickel-metal hydride battery.
A misnomer if ever there was one, the rare earths may be strategic and in short supply but they are certainly not rare. Some are as abundant in the earth’s crust as nickel, copper, zinc or lead. Even the two rarest (thulium and lutetium) are around 200 times more common than gold. Minerals containing rare-earth elements are to be found all over the world, especially where iron deposits paint the landscape as red as northern Arizona. The largest source today is a by-product of China’s huge iron-ore mining operations in Inner Mongolia.
The problem is that, though widely dispersed, the rare-earth elements occur in extremely low concentrations. Only a handful or so places exist—in Australia, Brazil, Canada, China, India, South Africa and the United States—where deposits have been found rich enough to justify mining them. Even then, abundance in their host minerals is usually measured in concentrations of a percent or two.
Because of their similar chemical properties, the rare earths tend to clump together in rocks, often along with radioactive thorium or uranium. That makes extracting, separating and refining them difficult. A lot of water, acid and electricity has to be used in the ion-exchange, fractional crystallisation and liquid-liquid extraction processes used to manufacture them. Handling the radioactive and chemical waste produced in the process adds significantly to the cost. Lax environmental standards, along with low wages, has allowed Chinese producers to undercut competitors abroad and corner the market.
According to the United States Geological Survey, as of 2000, China produced well over 90% of world demand for rare earth metals. Their ores are rich in yttrium, lanthanum, and neodymium.
In order of increasing atomic mass, the rare earth metals and some of their common applications are given below.
- Scandium: Atomic weight 21. Used to strengthen aluminum alloys.
- Yttrium: Atomic weight 39. Used in superconductors and exotic light sources.
- Lanthanum: Atomic weight 57. Used in specialty glasses and optics, electrodes and for hydrogen storage.
- Cerium: Atomic weight 58. Makes an excellent oxidizer, used in oil cracking during petroleum refining and is used for yellow color in ceramics and glass.
- Praseodymium: Atomic weight 59. Used in magnets, lasers and as green color in ceramics and glass.
- Neodymium: Atomic weight 60. Used in magnets, lasers and as purple color in ceramics and glass.
- Promethium: Atomic weight 61. Used in nuclear batteries.
- Samarium: Atomic weight 62. Used in magnets, lasers and for neutron capture.
- Europium: Atomic weight 63. Makes colored phosphors, lasers, and mercury-vapor lamps.
- Gadolinium: Atomic weight 64. Used in magnets, specialty optics, and computer memory.
- Terbium: Atomic weight 65. Used as green in ceramics and paints, and in lasers and fluorescent lamps.
- Dysprosium: Atomic weight 66. Used in magnets and lasers.
- Holmium: Atomic weight 67. Used in lasers.
- Erbium: Atomic weight 68. Used in steel alloyed with vanadium, as well as in lasers.
Thulium: Atomic weight 69. Used in portable x-ray equipment.
- Ytterbium: Atomic weight 70. Used in infrared lasers. Also, works as a great chemical reducer.
- Lutetium: Atomic weight 71. Used in specialty glass and radiology equipment.
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