Dysprosium

Dysprosium was identified in 1886 by the French chemist Paul-Emile Lecoq de Boisbaudran, after a long struggle to separate it from holmium. Its name comes from the Greek dysprositos, hard to get at, a wry acknowledgement of the difficulty he had faced in isolating it. Dysprosium is a soft, silvery rare-earth metal, important today for the high-temperature performance of neodymium magnets and for control rods in nuclear reactors. Its strong magnetism and appetite for neutrons make dysprosium valuable in magnets that must work hot, as in electric-vehicle and wind-turbine motors, and in reactor control rods, though its scarcity makes it one of the more critical rare earths.

Adding even a few per cent of dysprosium to a neodymium-iron-boron magnet substantially raises its coercivity, its resistance to losing magnetism as it heats up, which is why electric-vehicle traction motors, which run hot under sustained load, depend on dysprosium-doped magnets even though dysprosium itself is scarcer and pricier than the neodymium it reinforces. At extremely low temperatures dysprosium compounds also show some of the largest magnetocaloric effects known, a property explored for magnetic refrigeration, a potentially more efficient alternative to conventional gas-compression cooling.

Dysprosium's name is a rare instance of a chemist commemorating his own frustration. Lecoq de Boisbaudran reached the element only after repeated fractional precipitations, coaxing it apart from its near-identical neighbours, and he marked the ordeal by naming it the hard-to-get-at one. The name belongs to the wider story of the rare earths, whose chemical sameness made their separation one of the most laborious tasks in the history of chemistry, sometimes requiring hundreds or thousands of repeated crystallisations. Dysprosium has no ancient, mythological or alchemical association; its Greek name is a laboratory joke about the sheer obstinacy of the substance, now attached to an element that has become quietly essential to the magnets of electric motors and wind turbines.

Lecoq de Boisbaudran was among the most prolific element-hunters of the century, personally credited with the discovery of gallium in 1875, samarium in 1879 and dysprosium in 1886, a run matched by very few chemists before or since and made possible by his own refinements to spectroscopic and fractional-crystallisation technique. His patience with dysprosium in particular, requiring dozens of repeated precipitations to isolate a barely detectable residue, became something of a legend among later rare-earth chemists confronting their own stubborn separations.