dysprosium

dysprosium

[dis-proh-see-uhm, -shee-]
dysprosium [Gr.,=hard to get at], metallic chemical element; symbol Dy; at. no. 66; at. wt. 162.50; m.p. 1,412°C;; b.p. 2,562°C;; sp. gr. 8.54 at 25°C;; valence+3. Dysprosium is a lustrous silvery metal; it is very soft and can be cut with a knife. It is in Group 3 of the periodic table and is a member of the lanthanide series; all members of this series are rare-earth metals and resemble one another in their chemical properties. Dysprosium is stable in air at room temperature. It dissolves in both dilute and concentrated mineral acids; forms a white oxide known as dysprosia; and, with other elements, forms several brightly colored salts. It is commonly found with other rare-earth metals in several minerals, including gadolinite and euxenite. Dysprosium and its compounds are among the most highly susceptible to magnetization of all substances and are used in special magnetic alloys. A cermet of dysprosium oxide and nickel is used in nuclear reactor control rods. Dysprosium is used with argon in mercury-vapor lamps to give a higher light output and balance the color spectrum. Although dysprosium was discovered (but not isolated) in 1886 by P. E. Lecoq de Boisbaudran, a French chemist, it did not become available in relatively pure form until the 1950s.
Dysprosium is a chemical element with the symbol Dy and atomic number 66.

Characteristics

Dysprosium is a rare earth element that has a metallic, bright silver luster, relatively stable in air at room temperature, but dissolving readily in dilute or concentrated mineral acids with the emission of hydrogen. It is soft enough to be cut with bolt-cutters (but not with a knife), and can be machined without sparking if overheating is avoided. Dysprosium's characteristics can be greatly affected even by small amounts of impurities.

Applications

Dysprosium is used, in conjunction with vanadium and other elements, in making laser materials. Its high thermal neutron absorption cross-section and melting point also suggests that it is useful for nuclear control rods. Dysprosium oxide (also known as dysprosia), with nickel cement compounds, which absorb neutrons readily without swelling or contracting under prolonged neutron bombardment, is used in neutron-absorbing control rods in nuclear reactors. Dysprosium-cadmium chalcogenides are sources of infrared radiation for studying chemical reactions. Furthermore, dysprosium is used for manufacturing computer hard drives and compact discs. Because it is highly paramagnetic, dysprosium has been used as a contrast agent in magnetic resonance imaging.

Neodymium-iron-boron magnets can have up to 6% of the neodymium substituted with dysprosium to raise the coercivity for demanding applications such as drive motors for hybrid electric vehicles ; this leads to a demand for up to 100 grams of dysprosium per hybrid car sold, which under most predictions of hybrid vehicle demand would require new sources of dysprosium to be found.

As a component of Terfenol-D (an alloy that expands or contracts to a high degree in the presence of a magnetic field), dysprosium is of use in actuators, sensors and other magnetomechanical devices.

Below 85K dysprosium is ferromagnetic, with a high susceptibility. It is often used for the fabrication of nanomagnets, particularly in research. Its usefulness, however, is limited by its high readiness to oxidise.

History

Dysprosium was first identified in Paris in 1886 by French chemist Paul Émile Lecoq de Boisbaudran. He was only able to isolate dysprosium from its oxide after more than 30 attempts to dissolve it in acid. Upon succeeding, he named the element dysprosium from the Greek dysprositos, meaning "hard to get". However, the element itself was not isolated in relatively pure form until after the development of ion exchange by Frank Spedding in the early 1950s.

Occurrence

Dysprosium is never encountered as a free element, but is found in many minerals, including xenotime, fergusonite, gadolinite, euxenite, polycrase, blomstrandine, monazite and bastnäsite; often with erbium and holmium or other rare earth elements. Currently, most dysprosium is being obtained from the ion-adsorption clay ores of southern China. In the high-yttrium version of these, dysprosium happens to be the most abundant of the heavy lanthanides, comprising up to 7-8% of the concentrate (as compared to about 65% for yttrium).

Compounds

Nearly all dysprosium compounds are in the +3 oxidation state, and are highly paramagnetic. Holmium(III) oxide (Ho2O3) and Dysprosium(III) oxide (Dy2O3) are the most powerfully paramagnetic substances known.

Dysprosium compounds include:

See also Dysprosium compounds.

Isotopes

Naturally occurring dysprosium is composed of 7 stable isotopes, 156Dy, 158Dy, 160Dy, 161Dy, 162Dy, 163Dy and 164Dy, with 164-Dy being the most abundant (28.18% natural abundance). 28 radioisotopes have been characterized, with the most stable being 154Dy with a half-life of 3.0x106 years, 159Dy with a half-life of 144.4 days, and 166Dy with a half-life of 81.6 hours. All of the remaining radioactive isotopes have half-lifes that are less than 10 hours, and the majority of these have half lifes that are less than 30 seconds. This element also has 5 meta states, with the most stable being 165mDy (t½ 1.257 minutes), 147mDy (t½ 55.7 seconds) and 145mDy (t½ 13.6 seconds).

The primary decay mode before the most abundant stable isotope, 164Dy, is electron capture, and the primary mode after is beta minus decay. The primary decay products before 164Dy are terbium isotopes, and the primary products after are holmium isotopes.

Precautions

As with the other lanthanides, dysprosium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. Dysprosium does not have any known biological properties.

See also

Notes

External links

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