What Is Dysprosium?

Dysprosium is a rare earth element with atomic number 66 and chemical symbol Dy, belonging to the lanthanide series of the periodic table. It is a soft, malleable silvery-white metal with a density of 8.54 g/cm³, a melting point of approximately 1,412 °C, and one of the highest magnetic susceptibilities of any element. The name derives from the Greek word dysprositos, meaning hard to get at, a reference to the difficulty of isolating it from its ore mixture. Dysprosium occurs in minerals such as xenotime and monazite, and commercial production is concentrated primarily in ionic clay deposits in southern China.

Los Alamos National Laboratory's periodic table entry for dysprosium records seven naturally occurring stable isotopes with mass numbers ranging from 156 to 164. The isotope ¹⁶⁴Dy, the most abundant at approximately 28 percent of natural dysprosium, carries the largest thermal neutron capture cross-section of any stable isotope, exceeding 2,600 barns, a property that drives its use in nuclear technology. This combination of unusual magnetic and nuclear properties makes dysprosium technologically significant in a narrow but demanding set of applications.

Magnetic Properties and Permanent Magnets

The primary commercial use of dysprosium is as an additive to neodymium-iron-boron (NdFeB) permanent magnets, the most energetically dense class of permanent magnets in production use. Pure NdFeB magnets lose coercivity at elevated temperatures, limiting their use in environments above roughly 80 °C. Adding dysprosium in concentrations of 1 to 10 weight percent raises the magnetic coercivity, allowing the magnets to retain their alignment and resist demagnetization at temperatures up to 220 °C or higher. The U.S. Department of Energy rare earth permanent magnets supply chain assessment identifies dysprosium as a critical material because it has no commercially viable substitute in high-temperature NdFeB applications, and because supply is geographically concentrated in a single region. The traction motors of electric vehicles and the generators of direct-drive wind turbines are the two largest consumers, and both require magnets that operate reliably at elevated temperatures over long service lives.

Nuclear and Radiation Applications

Dysprosium's exceptionally large neutron absorption cross-section makes it valuable in nuclear reactor control and safety systems. Dysprosium oxide-nickel cermets (ceramic-metal composites) are used in control rod designs where the material must absorb neutrons efficiently without significant dimensional swelling under sustained irradiation flux. Dysprosium titanate (Dy₂TiO₅) has been studied as an absorber material for control rods in pressurized water reactors, with the IAEA assessment of dysprosium titanate as an absorber material noting its resistance to swelling under irradiation and its stable neutron efficiency over multi-year reactor campaigns. Dysprosium is also used in neutron dosimetry, where irradiated dysprosium foils are analyzed after exposure to quantify fast neutron fluence in reactor and shielding experiments.

Applications

Dysprosium has applications in a range of fields, including:

• Electric vehicle traction motors, where high-coercivity NdFeB magnets containing dysprosium enable compact, high-temperature-capable drive units
• Wind power generation, where direct-drive turbine generators require large permanent magnets with stable magnetic properties across wide temperature ranges
• Nuclear reactor control, where dysprosium-containing control rods and burnable absorbers regulate neutron flux
• Neutron dosimetry and activation analysis, where irradiated dysprosium foils quantify neutron fluence in research and industrial reactors
• Magnetostrictive actuators and sensors, where dysprosium-iron alloys such as Terfenol-D exhibit large magnetostrictive strains useful in precision positioning systems