The name Dysprosium is derived from the Greek ‘dysprositos’, meaning hard to get. Dysprosium was identified in 1886, in Paris, by Paul Émile Lecoq de Boisbaudran. Its discovery came as a result of research into Yttrium oxide, first made in 1794, and from which other rare earths (aka Lanthanoids) were subsequently to be extracted, namely Erbium in 1843, then Holmium in 1878, and finally Dysprosium. De Boisbaudran’s method had involved endless precipitations carried out on the marble slab of his fireplace at home. Pure samples of Dysprosium were not available until Frank Spedding and co-workers at Iowa State University developed the technique of ion-exchange chromatography around 1950. From then on it was possible to separate the rare earth elements in a reliable and efficient manner, although that method of separation has now been superseded by liquid-liquid exchange technology.
In common with many other Lanthanides, Dysprosium is found in the minerals monazite and bastnaesite. It is also found in smaller quantities in several other minerals such as xenotime and fergusonite. As a pure metal it is little used because it reacts readily with water and air. It tarnishes slowly in air at room temperature and dissolves in both dilute and concentrated acids. It takes only small amounts of impurities to affect the metal’s physical properties, but it is generally soft enough to be cut with a knife. It has low toxicity.
Like other heavier Lanthanides, Dysprosium has a lot of unpaired electrons, giving both the metal and its ions a high magnetic susceptibility. Since it is resistant to demagnetisation at high temperatures, Dysprosium’s main use is in alloys for Neodymium-based magnets. This property is important for magnets used in motors or generators. These magnets are used in wind turbines and electrical vehicles, so demand for Dysprosium is growing rapidly. Other key applications that harness its magnetic properties are applications in data storage devices such as compact discs.
Terfenol-D (a Terbium, Iron and Dysprosium alloy) expands or contracts in the presence of a magnetic field and is used in ships’ sonar systems and in sensors and transducers.
Dysprosium has a high thermal neutron absorption cross-section, meaning that it is very good at absorbing neutrons. For this reason, a Dysprosium oxide-Nickel cermet (a composite material of ceramic and metal) is used in nuclear reactor control rods. It readily absorbs neutrons and does not swell or contract when bombarded with neutrons for long periods, stopping fission reactions getting out of control.
Dysprosium, when combined with Vanadium and other rare earth elements, has been used in the production of laser materials. Dysprosium-Cadmium chalcogenides have been used for studying chemical reactions, as they are sources of Radium.
Art and Design
Dysprosium is also used in medium source rare-earth lamps (MSRs) in the film industry. These lamps produce an intense white light.
Terfenol-D is used in a speaker called the ‘SoundBug’, which turns any flat surface into a speaker.