Europium REE Collection rare earth metals elements

Europium

Europium gets a glowing review from its use as a luminescent material. It has had people worldwide seeing red, from the red color on television screens to the LEDs used in flat panel displays, score boards, and “Vegas-style” billboards. An array of colors can be created from europium’s trivalent and divalent compounds, creating reds, greens, and blues, and combined to create white.

Applications

  • Taggant phosphors with europium are used as anti-forgery marks on Euro and various currencies.
  • The primary use of europium is in phosphors used in pilot display screens, televisions (reddish-orange), and trichromatic fluorescent lights (reddish-orange and blue).
  • Europium EuB6 absorbs neutrons in fast breeder nuclear reactors to control the fission process.

Interesting Facts

  • In 1964, the development of a new phosphor Eu:Y2O3, allowed the first true red in color televisions. Earlier televisions displayed an orange hue.
  • The world’s first major producer of europium oxide for the television industry was Molycorp, also known as, Molybdenum Corporation of America.
  • Europium is used in anti-counterfeiting fluorescent phosphors in Euro banknotes. The red fluorescence in the Euros is a Eu3+-β-diketone complex.

Discovery

In 1890, French chemist Paul E. Lecoq de Boisbaudran, fractionated a samarium-gadolinium concentrate that showed spark spectrum lines that did not match either of these elements. One of his students, French chemist and geologist, Eugène-Anatole Demarçay, constructed an improved induction coil that produced extremely hot, luminous, globular sparks from electrodes of high-purity platinum. The high-purity eliminated the spectral lines from impurities in the electrodes and provided superior spark spectra from the sample to allow the identification of new elements (Weeks and Leicester, 1968, p. 689). Demarçay then made a series of extensive fractionations of an impure samarium-magnesium nitrate that resulted in the discovery of a new rare earth, europia, displaying the characteristic sharp spectral lines (Demarçay, 1901). Europium is named in honor of the continent of Europe where the element was discovered.

Definition

Europium is a silvery-white metal that will ignite in air at about 150 °C to 180 °C. The metal is soft, very ductile, and the most reactive of the rare-earth metals. The element has two valence states, +2 and +3, and is divalent in the metallic state. Europium metal has a body centered cubic structure, a density of 5.259 gm/cm3, a melting point of 826 °C, and a boiling point of 1439 °C. Europium oxide, or europia, occurs as a sesquioxide with the formula Eu2O3, however it will readily form divalent compounds. The trivalent oxide is a light-pink powder with a specific gravity of 7.30 gm/cm3, a melting point of 2350 °C and a formula weight of 351.92. The oxide is hygroscopic and will readily absorb moisture and carbon dioxide from the atmosphere.

Preparation of Metal

Europium metal is typically prepared by metallothermic reduction of the oxide, since it will not reduce from the trihalide because of its high vapor pressure. The oxide is is heated in air to 800 °C for 15 hours to drive off absorbed moisture, carbon dioxide, and other compounds. Europium oxide is reduced with lanthanum metal turnings (15% in excess of theoretical amount) by volatilization within a tantalum crucible with an attached tantalum condenser. The reactants are heated in a vacuum reduction furnace by slowing raising the temperature to 1400 °C and held at temperature for several hours (Beaudry and Gschneidner, Jr., 1978). Europium metal is formed starting at 700 °C when the oxide preferentially separates from the europium oxide and combines with the lanthanum metal forming lanthanum oxide and forms a sublimated europium metal within the tantalum condenser.

Source

Resources of europium are largely contained in LREE-enriched minerals. Europium occurs in the Earth’s crust at an average concentration of 1 parts per million. The primary source of europium is from carbonatites and the LREE-mineral bastnäsite. Bastnäsite deposits in China and the United States constitute the largest percentage of the world’s rare-earth economic resources. Europium is also a constituent in the LREE-mineral monazite which constitutes the second largest segment of rare-earth resources. Monazite deposits are located in Australia, Brazil, China, India, Malaysia, South Africa, Sri Lanka, Thailand, and the United States in paleoplacer and recent placer deposits, sedimentary deposits, veins, pegmatites, carbonatites, and alkaline complexes (Hedrick, 2010). Europium sourced from the LREE-mineral loparite is recovered from a large alkali igneous intrusion in Russia (Hedrick, Sinha, and Kosynkin, 1997).

Mining

Europium, a light-group rare-earth element (LREE) is mined from a variety of ore minerals and deposits using various methods. Bastnäsite is mined in the United States as a primary product from a hard-rock carbonatite. The deposit is mined via bench-cut open pit methods. Ore is drilled and blasted, loaded into trucks by loaders, and hauled to the mill. At the mill the blasted ore is crushed, screened, and processed by flotation to produce a bastnäsite concentrate. In China, bastnäsite and lesser amounts of associated monazite are also mined from a carbonatite. The ore is recovered as a byproduct of iron ore mining by hard-rock open pit methods. After crushing the ore is separated from the iron ore by flotation to produce a bastnäsite concentrate and a bastnäsite-monazite concentrate (Hedrick, 1990).

Monazite is recovered from heavy-mineral sands (specific gravity >2.9) deposits in various parts of the world as a byproduct of mining zircon and titanium-minerals or tin minerals. Heavy mineral sands are recovered by surface placer methods from unconsolidated sands. Many of these deposits are mined using floating dredges which separate the heavy-mineral sands from the lighter weight fraction with an on-board wet mill through a series of wet-gravity equipment that includes screens, hydrocyclones, spirals, and cone concentrators. Consolidated or partially consolidated sand deposits that are too difficult to mine by dredging are mined by dry methods. Ore is stripped by typical earth-moving equipment with bulldozers, scrapers, and loaders or by water jet methods. Ore recovered by these methods is crushed and screened and then processed by the wet mill described above. Wet mill heavy-mineral concentrate is sent to a dry mill for processing to separate the individual heavy-minerals using a combination of scrubbing, drying, screening, electrostatic, electromagnetic, magnetic, and gravity processes. Vein monazite has been mined by hard-rock methods in South Africa and the United States (Hedrick, 2010). Loparite is mined by underground methods using room and pillar methods. Ore is drilled and blasted and removed from the mine. The ore is then processed by the same hard-rock methods as applied to bastnäsite to make a loparite concentrate.

Selected europium minerals

Bastnäsite-(Ce) (Ce,La,Nd,Pr)(CO3)F
Monazite-(Ce) (Ce,La,Nd,Th)(PO4)
Loparite-(Ce) (Ce,Na,Ca,Sr,Th)(Ti,Nb,Ta,Fe+3)O3
Allanite-(Ce) (Ca,Ce)(Al2,Fe+2)(Si2O7)(SiO4)O(OH)
Parisite-(Ce) Ca(Ce,La)2(CO3)3F2
Ancylite-(Ce) Sr,Ce(CO3)2(OH)• H2O
Britholite-(Ce) Ca2(Ca,Ce)3(SiO4,PO4)3(OH,F)
Cerite-(Ce) (Ca,Ce)9(Fe,Mg)(SiO4)3(HSiO4)4(OH)3
Ion adsorption
lateritic clays
Y-enriched lateritic clays

References

Beaudry and Bernard J. and Karl A. Gschneidner, Jr., 1978, Preparation and Basic Properties of the Rare Earth Metals: chapter 2 in Handbook of the Physics and Chemistry of Rare Earths-Volume 1:Metals, (Gschneidner, Jr. and Eyring, editors), North-Holland, New York, p. 173-232.

Denarçay, Eugène-Anatole, 1901, Sur un nouvel élément l’europium [On a new element europium]: Comptes Rendu, June 17, v. 132,, p. 1484-1486.

Gschneidner, Karl A. Jr., 2011, The Rare Earth Crisis—The Supply/Demand Situation for 2010-2015: article in Material Matters, Aldrich Chemical Co., Milwaukee, Wisconsin, v. 6, no. 2, p. 34-35.

Hedrick, James B., 1990, Rare earths—The lanthanides, yttrium, and scandium: chapter in Minerals Yearbook 1990, U.S. Geological Survey, v. 1, p. 903-922.

Hedrick, James B., 1991, Rare earths—The lanthanides, yttrium, and scandium: chapter in Minerals Yearbook 1991, U.S. Geological Survey, v. 1, p. 1211-1237.

Hedrick, James B., 2010, Rare earths: chapter in Mineral commodity summaries 2010, U.S. Geological Survey, p. 128-129.

Hedrick, James B., Shyama P. Sinha, and Valery D. Kosynkin, 1997, Loparite—a rare-earth ore (Ce,Na,Sr,Ca)(Ti,Nb,Ta,Fe+3)O3: Journal of Alloys and Compounds, v. 250, p. 467-470.

Weeks, Mary E., and Henry M. Leicester, 1968, Discovery of the Elements (7th ed.): Easton, Pennsylvania, Journal of Chemical Education, 896 p.

Electrons per shell:
2, 8, 18, 25, 8, 2
Atomic number,
Protons, Electrons:
63
Number of Neutrons:
89
Atomic Mass:
151.964 amu
Melting Point:
822.0 °C
Boiling Point:
1597.0 °C
Density @ 293 K:
5.259 g/cm3
Crystal structure:
cubic
Color:
silvery