Dysprosium (Dy)

• Element Symbol: Dy
• Atomic Number: 66
• Atomic Mass: 162.5
• Group # in Periodic Table: n/a
• Group Name: Lanthanides
• Period in Periodic Table: 6
• Block of Periodic Table: f-block
• Discovered by: Paul-Émile Lecoq de Boisbaudran (1886)

Dysprosium is a soft, silvery-white metal. It is part of the lanthanide series, which includes the elements with atomic numbers between 57 and 71 in the periodic table. Like the other elements in this series, dysprosium is a rare earth element. It is a component of a variety of minerals in Earth’s crust, including bastnaesite, blomstrandine, euxenite, fergusonite, gadolinite, monazite, polycrase, and xenotime. Dysprosium is not found in its pure form in nature.

Dysprosium was discovered in 1886 by French chemist Paul-Émile Lecoq de Boisbaudran. In the 1870s Boisbaudran had isolated the elements holmium and thulium from the element erbium. During his work with holmium oxide, he discovered the oxide of an unknown element. Boisbaudran used a series of complicated and laborious chemical steps to get a pure sample of this new oxide. He named the element that was part of this oxide "dysprosium," which derives from the Greek word dysprositos, meaning "hard to obtain."

A relatively pure sample of the element was isolated in 1906 by French chemist Georges Urbain. Then, in 1950, Canadian chemist Frank Spedding developed a purification technique called ion exchange chromatography, which allowed for the creation of larger quantities of pure dysprosium.

Physical Properties

Dysprosium is a silvery-white element with a metallic luster that is a solid in its standard state—that is, its state at 298 kelvins (K). The element is a relatively soft metal that can be cut using a knife. Dysprosium has a density of 8.551 grams per cubic centimeter (g/cm³) at standard state. Its melting point is 1412 degrees Celsius (ºC). Its boiling point is 2567 ºC. The specific heat of dysprosium is 167 joules per kilogram-kelvin (J/kg·K). Dysprosium is a good conductor of both heat and electricity. Its thermal conductivity is 11 watts per meter-kelvin (W/m·K). Its electrical conductivity is 1.1 × 10⁶ siemens per meter (S/m). Its resistivity is 9.1 × 10⁻⁷ meter-ohms (m·Ω). Dysprosium is paramagnetic, which means it has only a small response to a magnetic field. The mass magnetic susceptibility of dysprosium is 5.45 × 10⁻⁶.

Chemical Properties

Dysprosium has three structural forms, depending on the temperature of the element. At room temperature, dysprosium has a simple hexagonal crystal structure that is closely packed. At temperatures below −90 K, the closely packed hexagonal structure experiences an orthorhombic distortion. At a temperature of 1654 K, the structure of dysprosium becomes body-centered cubic, which, as its name suggests, is a cube with an atom located at each corner and another one in the center of the cube.

Dysprosium is reactive with air and water. This element tarnishes slowly in the presence of oxygen. Shavings of dysprosium catch fire easily and burn at a high temperature. Dysprosium produces hydrogen gas when reacting with water. Therefore, it is dangerous to throw water on burning dysprosium. This element reacts strongly with the halogens at temperatures above 200 ºC. Halogens that react with dysprosium include fluorine, chlorine, bromine, and iodine. Dysprosium dissolves in most acids to form solutions.

The electron affinity of dysprosium is 50 kilojoules per mole (kJ/mol). Dysprosium has three valence electrons. Its ionization energies are 573, 1130, 2200, and 3990 kJ/mol. Its electronegativity is 1.22. Dysprosium has seven naturally occurring stable isotopes. The most common are dysprosium-164, dysprosium-162, dysprosium-163, and dysprosium-161. There are no radioactive isotopes of dysprosium. This element has an electron configuration of [Xe]4f¹⁰6s².

Applications

Dysprosium can be found in small quantities in a variety of minerals in Earth’s crust. The overall crustal abundance of dysprosium is 0.3 parts per million. Around one hundred tons of dysprosium are isolated from minerals annually through commercial separation processes. These processes include liquid-liquid extraction, ion exchange, metallothermic reduction, and vacuum distillation. Dysprosium can also be extracted from dysprosium trifluoride during a reduction reaction with calcium metal.

The top producers of dysprosium are China, Russia, and Malaysia. The top reserve holders are China, the former Soviet Republics (also known as the Commonwealth of Independent States), and the United States. These countries have varying political stability.

Dysprosium used to have very limited uses. However, changes in technology have vastly increased demand for dysprosium. The element is used in the coating of computer hard drives. It is also added to neodymium-iron-boron (Nd₂Fe₁₄B) alloys that are used to make the magnets in electric motors and generators. The addition of dysprosium allows the magnets to maintain power as motor temperatures rise to 150–160 ºC.

Electric motors and generators containing Nd₂Fe₁₄B magnets are used in wind turbines and hybrid and electric vehicles. Each magnet requires a relatively small amount of dysprosium. For example, around one hundred grams of dysprosium are needed for each set of magnets in one electric or hybrid car. However, as production of these technologies increases to hundreds of thousands of units per year, a significant amount of dysprosium is required.

As demand for dysprosium has significantly increased, so has the price of the element. In 2003 dysprosium cost around $15 per kilogram. By the end of 2014, the price of dysprosium had risen to nearly $500 per kilogram. High demand has also increased concerns about a global dysprosium shortage.

Computer disks and magnets for motors and generators are not the only technologies that use dysprosium. Dysprosium iodide and dysprosium bromide are sometimes added to commercial discharge lamps to increase the intensity of the light produced. Discharge lamps are used in public places, such as parking lots, stores, and sports stadiums. Dysprosium is also added to rods in nuclear reactors. These rods are composed of dysprosium oxide and nickel cermet (a composite material that combines nickel and ceramic). The dysprosium allows the rods to absorb neutrons produced inside the reactor while preventing the rods from swelling or contracting. Radioactive dose detectors, or dosimeters, also use dysprosium. The dysprosium is introduced into calcium crystals in the detector. The detector then glows after being exposed to x-ray or to gamma-ray radiation.

Bibliography

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Gray, Theodore. The Elements: A Visual Exploration of Every Known Atom in the Universe. New York: Black Dog, 2009. Print.

Parsons, Paul, and Gail Dixon. The Periodic Table: A Visual Guide to the Elements. New York: Quercus, 2014. Print.

"Technical Data for Dysprosium." The Photographic Periodic Table of the Elements. Element Collection, n.d. Web. 8 Sept. 2015.