Dysprosium

Dysprosium is a bright, silvery lanthanide with the configuration [Xe]4f10 6s2. Like its neighbours it forms the Dy3+ ion almost exclusively, and the close similarity in size and charge among the heavy lanthanides is what made it so hard to separate. Its partly filled 4f shell carries a large magnetic moment, and the metal orders magnetically when cold: it is ferromagnetic below about 85 K and has a helical magnetic structure between 85 and 179 K.

Dysprosium's main job today is in neodymium-iron-boron magnets. Adding a few percent of dysprosium raises the magnets' coercivity, their resistance to being demagnetised, especially at the 100–200 °C reached inside electric-vehicle motors and wind-turbine generators. Because supply is concentrated in a few deposits, dysprosium is regularly listed as a critical raw material. Its isotopes also absorb neutrons well, so dysprosium oxide and titanate are used in reactor control rods, and its iodide gives metal-halide lamps an intense white light.

Discovery

French chemist Paul-Émile Lecoq de Boisbaudran identified dysprosium in 1886 in a sample of holmium oxide. He separated it by repeatedly dissolving the oxide in acid and precipitating it with ammonia, needing more than 30 attempts before he succeeded. He named it from the Greek dysprositos, 'hard to get at'. A reasonably pure metal was not obtained until the 1950s, when Frank Spedding's group at Iowa State University developed ion-exchange separation.