The 17 Rare Earth Elements, Their Properties, and Their Uses
Periodic Table from MNDMF, Ontario Geological Survey, Kenora District, Recommndations for Exploration, untitled document, graphic attributed as unpublished report, Sinton, 2005.
Atomic number 21. Scandium is variously included or not included among the rare earth elements. Annual global scandium production is very low, but only small amounts are used by current technologies. Increases in application in metal alloys and for fuel cell production would probably accompany an increase in supply.
Scandium is used in the production of certain high performance aluminum and titanium alloys for sports equipment and for the aerospace industry. It is also used in some specialized high intensity and 'true-color' light sources.
Atomic number 39. Yttrium is only present in significant quantities in a few known ore locations. Others contain very little of the element. Expected future demands far exceed current global production.
The largest demand for Yttrium is in the production of phosphors such as those necessary to create the red colors on CRT displays (television screens). Other applications are rapidly emerging. The element is also currently used for high powered lasers, energy saving white LED light sources, to increase the strength and durability of aluminum and magnesium alloys, in specialized glass types and optical lenses, in various electronics and gas sensors, in high performance ceramics, in ornamental cubic zirconia (cz), and in cancer fighting drugs.
Atomic number 57. Lanthanum is one of the 4 most 'abundant' rare earth elements, making up 20 to 40% or more of the REE content of some ore bodies. This is fortunate, considering its varied and unique usefulness.
Lanthanum is used in the production of speciallized steel and other metal alloys, fiber optic and optical glass, rechargeable batteries, including those used in consumer electronics and electric and hybrid cars, mischmetal 'sparking' alloys such as are used in lighters, high intensity lighting, such as for movie projection, ion thrusters for some space craft, high sensitivity sensors, emission sources for instruments such as electron microscopes, and in petroleum refining for fuel production.
Other Important Facts:
Atomic number 58. Cerium is one of the most commonly available of the rare earth elements. It is the most abundant of the REEs in the earths crust and makes up a substantial percentage of the REE present in many ore bodies. Cerium is also more easily separated from the ores and from its accompanying elements than are many of the other rare earths, making extraction and refining of this element far more efficient and affordable than comparable processes for several of the other rare earths.
Cerium is very heavily used as a polishing agent for optical and other glass products, as well as for metal (including jewelry), and other materials that require precision surfaces. It is also widely employed in the production of catalytic converters to reduce toxic and reactive emissions from vehicle exhaust. Cerium is also used to produce UV blocking glass, to produce optically clear glass, in a variety of aluminum, iron, steel, and magnesium alloys, in mischmetal sparking alloys, in high intensity lighting, and in rechargeable batteries. Cerium demand for the production of energy efficient fluorescent and compact fluorescent light bulbs is expanding rapidly. It has also shown promising future potential in the development of hydrogen fuel cells, a sustainable green energy alternative.
Atomic number 59. Praseodymium is not one of the more common rare earth elements, but unlike some of the most scarce types, it is found in recoverable quantities (1 to 6% oxide by weight)in nearly all REE ores. The supply vs demand tension for praseodymium is reduced, despite its scarcity, by a currently (comparatively) narrow range of applications. This may change unexpectedly with the broad based and well financed applications research currently underway in China and elsewhere around the globe.
Praseodymium is currently primarily used in the production of permanent magnets, in high performance magnesium alloys, as a glass and ceramic colorant, in some batteries and catalytic converters, and in high intensity lighting and mischmetal 'sparking' alloys.
Demand for this metal in magnet production has been steadily increasing. It should also be noted that, because alloys of praseodymium exhibit some of the strongest known magnetocaloric effects, emergent magnetocaloric refrigeration and cooling technology has the potential to impact demand for this element profoundly in coming decades.
Atomic number 60. Neodymium is one of the most critically important rare earth elements in terms of both existing technologies and emergent sustainable and energy efficient future technologies. Neodymium is the most important REE in the manufacturing of high strength types of permanent magnets. The most commonly manufactured neodymium magnets, and the most commonly used rare earth permanent magnets overall, are neodymium-iron-boron magnets. The importance of these magnets to modern technology cannot be overstated. They are used in everything from cell phones and disc drives to MRI imaging, satellites, hybrid cars, and wind power generators. When averaged among ore bodies, Neodymium is the third most highly concentrated RE element in REE ores. This means that production is relatively stable, and that the element makes up a significant portion of overall global annual REE production. Scarcity is a function of both supply and demand, however, not just supply. The growth in demand levels, compared to growth in production of the resource, point out a serious need for expanded short and mid-term production.
In addition to 1000s of ever-increasing uses in the form of magnet alloys, Neodymium is also used in the production of advanced batteries, as a glass colorant, in certain lasers, and in a few other metal alloys.
Atomic number 61. Only a little over 1/2 kilogram of promethium is estimated to exist naturally in the entire earth's crust. It is a highly radioactive element with a short half life (its longest lived isotope half-life is only 17.7 years) and few commercial uses. Promethium exists, on earth, only as a temporary intermediate product in the ongoing radioactive decay of other elements. It is not mined in any meaningful sense, and is absent in meaningful quantities in REE ores. Small quantities of this element, manufactured in nuclear reactors, are used in the production of nuclear batteries and for a few other specialized applications. Since it is not mineable from the earth, virtually all of this material is created in a laboratory, mostly from nuclear waste, rather than from nature. Promethium is technically one of the rare earth elements, but it is not a part of the supply-demand chain that informs the current globally significant environmental, technological, and mining issues surrounding these elements.
Atomic number 62. Samarium is a significantly mined, but relatively scarce, REE. It is present in concentrations of about 1 to 5%, by mass, in most rare earth ore bodies. Samarium is primarily used, currently, in high strength permanent magnets. Samarium-cobalt magnets are only slightly weaker than neodymium magnets, but have a much higher resistance to degradation with exposure to high temperatures than neodymium-iron-boron magnets. Samarium magnets can withstand temperatures over 700 degrees C (the highest of any currently known magnet variety), while neodymium magnets lose their magnetism at less than 400 degrees C. Applications of, and potential applications for, samarium magnets are extremely diverse. Additional (non-magnet) applications of samarium include anti-cancer drugs, lasers, including some speciallized lasers used in analytic equipment. Samarium is also used, because of its exceptional ability to absorb neutrons, in the control rods for nuclear power plants. Samarium shows significant potential in the future production of super-conductors that operate at practically achievable temperature ranges. For the moment, supply and demand of samarium are relatively balanced but, as with many of the other rare earth elements, increasing numbers of potential applications await increases in supply of the material.
Atomic number 63. Europium is both rare and expensive. Potential applications far exceed supply. Both new applications and the realisation of the full potentials of currently known applications await cost reductions. Europium is present in most rare earth ores at low levels (below 1% of REE oxide by mass). It is currently used, with yttrium, to produce red phosphors that are key to the manufacture of energy efficient (white) compact fluorescent light bulbs, as well as to the function of most computer and television screens. Many other applications are already known, but available resources are absorbed by current demand.
Atomic number 64. Gadolinium content in REE ores varies substantially, from less than 1% to up to almost 7% (in chinese laterites and others). Gadolinium is used for radiation shielding and to slow rates of reaction in nuclear reactors. It is also used as a contrasting medium in medical MRI imaging, as a phosphor in medical X-Ray imaging, to create temperature tolerant and oxidation resistant alloys of iron and other metals, in compact disks (CDs), in a variety of sensors and analytic instruments, and in green phosphors for television and computer screens. Gadolinium has also shown promise in the development of superconducting materials.
Gadolinium, in certain alloys, exhibits a strong magnetocaloric effect. This property of the element may become very important in the future development of energy efficient magnetic refrigeration technologies that benefit the environment by eliminating the use of chemical (HFC) refrigerants. The effect is already employed in specialized refrigeration systems used to reach extremely cold temperatures (<4K) neccesary for certain types of research.
Atomic number 65. Terbium is found in small quantities (0 to 1% by mass) in most rare earth element ores. Global demand and expected future demands for terbium far exceed supply.
Terbium is used in solid state electronics, in potentially environmentally important fuel cell technologies, in a variety of precision sensors and actuators, and in sonar systems. Its most significant current consumption, however, is in the production of energy efficient fluorescent and compact fluorescent light bulbs, where it serves as a phosphor (light source). It is also used as a yellow or green phosphor in computer monitors and televisions. Some of the uses of terbium derive from its 'magnetostrictive' alloy, Terfenol-D (Terbium, Dysprosium, and Iron), which exhibits a pronounced change in size when exposed to changes in magnetic field. Terbium may also become important in emergent nano-technology applications.
Atomic number 66. A December, 2010, U.S. Department of Energy report titled 'Critical Materials Strategy,' listed Dysprosium as the most critical element resource, in terms of both importance to clean energy technology and in terms of vulnerability of supply, in both the short-term and mid-term future. Demand for dysprosium for hybrid car production, only one of dozens of critical current applications, is expected to exceed current global production in the short term. The inadequacy of supply is due, in large part, to an inadequate number of active source mines. In short, too much of the worlds production is from a small number of mines in China, and other countries need to bring REE mines into immediate production.
Dysprosium is used, with Neodymium, in the production of very strong permanent magnets that are critical to a wide range of emerging high tech instruments (cell phones, computers, etc) and environmentally sustainable technologies such as hybrid cars and wind power generators. Small percentages of this metal increase both the strength and corrosion resistance of these magnets. Dysprosium is also used in several of the most common types of computer memory and data storage devices and, with Terbium, to produce Terfenol-D, a magnetostrictive (megnetically size-changing) alloy important in many sensors, actuators, and analytic instruments. Additionally, Dysprosium is used in high intensity light sources, in infrared phosphors, and is employed in nuclear power generation, to control and limit nuclear reactions.
Atomic number 67. Holmium is one of the least abundant of the rare earth elements, which is unfortunate, since it has the strongest magnetic moment (attraction) of any element. It is found in mineable quantities in relatively few rare earth element ore bodies. In those cases where it is most abundant, it still makes up, typically, less than 2 percent of the ore by mass. While expanded mining and recapture from waste may increase available quantities of this material, it is likely to remain scarce. Small quantites of Holmium, however, can be used with other elements, to significantly increase the strength of magnets. Many of its other applications, similarly, require little of the material in order to be effective.
Holmium finds modest employment in the production of very powerful magnets and in nuclear control rods (due to its ability to absorb large quantities of stray neutrons). Other, more common, elements are probably more appropriate to nuclear applications, due to the scarcity of this element and its other potential applications. Holmium lasers are used as surgical lasers in the medical and dental fields, as well as in fiber optic communications. Holmium is also used in several analytic instruments, as a colorant in glass, and as a dichroic colerant in cubic zirconia for jewelry. The commercial potential of this element has not yet been fully explored, and may expand radically with increased supply.
Atomic number 68. Erbium is a relatively scarce REE, completely lacking in some rare earth ore bodies, and representing up to 5% of the recoverable metal in others. Erbium is used in the production of amplifying lasers for fiber optic cable communications. Erbium in glass cables reduces signal loss substantially. Lasers made with this element are used widely in medical, dental, and and dermatological applications. Stronger lasers, combining erbium and ytterbium, are used in metal cutting and welding. This element is also used as a pink colorant in glass, ceramics, and cubic zirconia. It is a uniquely stable colorant in certain applications. As with many other REEs, erbium absorbs free neutrons effectively, and thus is used in control and limitation of nuclear reactions in nuclear power generation facilities.
Atomic number 69. Thulium is an exceedingly scarce metal. It is the most rare of the rare earth elements. Thulium is found only in very small quantities (up to 1/2 of 1% of oxides) in some rare earth ores. Like promethium, thulium is currently so rare that it has little influence on supply/demand dynamics in the world of rare earth element mining, distribution, or in the manufacturing of end-use products.
The price of Thulium limits its utility, but, unlike promethium, which will never be mined on this planet in commercially important quantities, thulium availability will change with expanded production. The element can be used in medical (and other) lasers, as well as to make safer medical X-ray equipment. The element also shows potential in the development of superconductive materials. Applications (and thus demand) for Thulium may well expand with greater research and material availability.
Atomic number 70. Very few rare earth ores contain appreciable concentrations of ytterbium. Notable among these, are locations in Malaysia and Canada, as well as the Chinese REE bearing laterites. Chinese laterites produce, essentially, all Ytterbium used in the world today (about 50 metric tons), though other deposits are richer in this scarce REE, and could potentially produce largr quantities. Supply limitations strongly inhibit many known applications of this element. Rapidly expanding potential applications far exceed even the most robust estimates of future increase in supply.
Ytterbium is an astoundingly useful element employed in technologies such as solar electric cells, high performance steel alloys, high-powered lasers, anti-forgery inks, night vision technology, and stress measuring instruments. Its potential market demand for applications as an alloy component, as a fiber optic amplifier, and in solar electric generation, as well as others, may expand substantially with greater availability of the resource.
Atomic number 71. Lutetium is astoundingly scarce, even in the richest REE ores. It ranges from 0% to 1% of recoverable metal in most ores, but most commonly represents 0.1% or less. World production is only around 10 metric tons per year, and the prices of the metal and its oxides are correspondingly high.
Lutetium has been used, on a small scale, as a chemical catalyst and in the petroleum refining process. It also has important current medical applications, including use in cancer treatment and as a sensor material in PET scans. If price and availability change, lutetium shows substantial promise in a variety of applications in analytic tools, advanced computer memory, manufacturing, the nuclear industry, in phosphors, and in both medical diagnosis and treatment. Supply limitations and high prices currently constitute substantial limitations on use of this element.
Bibliography for this page:
Haxel et al 2006
Long et al 2010
Bauerlein, P; Antonius, C; Loffler, J; Kumpers, J (2008). "Progress in high-power nickel metal hydride batteries". Journal of Power Sources 176: 547
Information about REE uses was compiled and derived from a broad base of sources including, but not limited to Long et al. 2010 (USGS); Bauer et al., 2010 (DOE); Humphries, 2010 (CRS); Hedrick, various (1997, 2002, 2006, 2008, etc) including USGS mineral yearbooks; the Molycorp and Tianjiao websites; the Los Alamos National Laboratory website, wikipedia, and a variety of articles in current literature and publication. This page represents a 'best effort' summary, and should not be treated as quantified data. The listed uses do not include any specifically military applications, though these exist as well, and are related to consumer applications. Also unlisted are an enormous range of very specific applications in scientific and analytic tools that make basic modern scientific inquiry and industrial research and development possible. These uses in scientific and analytic instrumentation do not represent significant quantities of materials, but the significance of these REE dependent applications to society are inestimable. They make possible progress in technologies ranging from advanced medicine to communications, computing, agricultural development, and space exploration.
Links to additional websites and resources.