Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.
Dysprosium is one of 15 rare earth elements. The name rare earth is misleading because the elements in this group are not especially uncommon. However, they often occur together in the earth and are difficult to separate from each other. A better name for the rare earth elements is lanthanides. This name comes from the element lanthanum , which is sometimes considered part of the lanthanides group in the periodic table. The periodic table is a chart that shows how chemical elements are related to one another.
Dysprosium was discovered in 1886, but was not commercially available until after 1950. The reason for the long delay was that methods for separating dysprosium from other lanthanides had not been developed. Dysprosium has relatively few applications today.
(rare earth metal)
Discovery and naming
In 1787, Carl Axel Arrhenius (1757-1824), a Swedish army officer and amateur mineralogist, found a rock in a mine at Ytterby, a region near Stockholm. He named the rock ytterite. A few years later, the rock was analyzed by Johan Gadolin (1760-1852), a professor of chemistry at the University of Abo in Finland, who found that the rock contained a new kind of "earth," which a colleague called yttria.
The term "earth" in mineralogy refers to a naturally-occurring form of an element, usually an oxide. For example, one kind of earth is magnesia, a term that refers to magnesium oxide. Magnesium oxide is one form in which the element magnesium occurs naturally in the earth.
The discovery by Arrhenius and Gadolin initiated a long series of experiments on yttria. These experiments produced puzzling results for two reasons. First, it turned out that yttria is actually a mixture of many similar elements. Second, the equipment that chemists had to work with was still very primitive. They had serious difficulties separating these elements from each other.
Over a period of more than a century, chemists argued about the composition of yttria. Eventually, chemists agreed that yttria is actually a combination of nine different elements that had not been seen before. One of those elements is dysprosium. Dysprosium was finally proved to be a new element in 1886 by French chemist Paul-Emile Lecoq de Boisbaudran (1838-1912). The name chosen for this new element comes from the Greek word meaning "difficult to obtain."
Dysprosium has a metallic appearance with a shiny silver luster. The metal is so soft it is easily cut with a knife. It has a melting point of 1,407°C (2,565°F) and a boiling point of about 2,300°C (about 4,200°F). The density is 8.54 grams per cubic centimeter.
Dysprosium is relatively unreactive at room temperatures. It does not oxidize very rapidly when exposed to the air. It does react with both dilute and concentrated acids, however. For example, it reacts with hydrochloric acid to form dysprosium trichloride.
Occurrence in nature
More than 100 minerals are known to contain one or more of the rare lanthanides. Only two of these minerals, monazite and bastnasite, are commercially important. These minerals occur in North and South Carolina, Idaho, Colorado, and Montana in the United States, and in Australia, Brazil, Canada, and India.
Experts estimate that no more than about 8.5 parts per million of dysprosium occur in the Earth's crust. That makes the element more common than better known elements such as bromine, tin, and arsenic. Studies of stony meteorites have found about 0.3 parts per million of dysprosium.
Seven naturally occurring isotopes of dysprosium are known. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. The four most abundant isotopes of dysprosium are dysprosium-161, dysprosium-162, dysprosium-163, and dysprosium-164.
At least eight radioactive isotopes of dysprosium have been made. A radioactive isotope is one that is unstable, gives off radiation, and breaks down to form a new isotope. Of these eight isotopes, only one, dysprosium-166, has much commercial importance.
The radioactive isotope dysprosium-165 is also being studied for some potential applications in medicine. Radiation with dysprosium-165 has proved to be more effective in treating damaged joints than traditional surgery.
The dysprosium in monazite and bastnasite is first converted to dysprosium trifluoride (DyF3). The compound then reacts with calcium metal to obtain pure dysprosium:
Dysprosium comes from the Greek word for "difficult to obtain."
Dysprosium has a tendency to soak up neutrons, which are tiny particles that occur in atoms and are produced in nuclear reactions. Metal rods (control rods) containing dysprosium are used in nuclear reactors to control the rate at which neutrons are available.
Dysprosium is also used to make alloys for various electrical and electronic devices. An alloy is made by melting and mixing two or more metals. The mixture has properties different than any of the elements. Some dysprosium alloys have very good magnetic properties that make them useful in CD players.
Like the element itself, some compounds of dysprosium are used in nuclear reactors and the manufacture of electrical and electronic equipment.
Radiation with dysprosium-165 has proved to be more effective in treating damaged joints than traditional surgery.
Very little is known about the health effects of dysprosium.
Dysprosium, taking its name from the Greek word dysprositos, meaning "hard to obtain," is a metallic element, discovered, but not isolated, in 1886 in Paris by the French scientist Paul-Émile Lecoq de Boisbaudran. Its isolation was made possible by the development of ion-exchange separation in the 1950s. Dysprosium belongs to a series of elements called rare earths , lanthanides , or "4f elements." The occurrence of dysprosium is low: 4.5 ppm (parts per million), that is, 4.5 grams per metric ton in Earth's crust, and 2 × 10−7 ppm in seawater. Two minerals that contain many of the rare earth elements (including dysprosium) are commercially important: monazite (found in Australia, Brazil, India, Malaysia, and South Africa) and bastnasite (found in China and the United States). As a metal , dysprosium is reactive and yields easily oxides or salts of its triply oxidized form (Dy3+ ion).
Dysprosium or its compounds are used in small quantities in several high-technological applications owing to their thermal, magnetic, and optical properties. For instance, dysprosium is susceptible to large magnetization and is a part of special magnetic alloys (e.g., those used for data storage on CDs). A cermet (a combination of a heat resistant ceramic with a metal) of dysprosium oxide and nickel enables the control of nuclear reactors, as it easily absorbs neutrons. Dysprosium is put into mercury-vapor lamps and several materials used to generate lasers, to enhance their optical properties. Dysprosium-cadmium chalcogenides are a source of infrared radiation. Some special purpose eyeglasses (e.g., those worn by glassblowers) contain dysprosium.
see also Cerium; Erbium; Europium, Gadolinium; Holmium; Lanthanides; Lanthanum; Lutetium; Neodymium; Praseodymium; Promethium; Samarium; Terbium; Thulium; Ytterbium.