Per Teodor Cleve, a Swedish chemist, discovered thulium in 1879. Cleve started by removing all of the known contaminants from erbia: the oxide of erbium. He obtained two new compounds: one green, which he named ´thulia´ for Thule in Scandinavia, and the other brown, which he named ´holmia´ for Stockholm.
Thulium is the least abundant of the rare earth elements.
Pure thulium metal has a bright, silvery lustre. It is reasonably stable in air, but the metal must be protected from moisture. The element is silvery grey, soft, malleable and ductile, and can be cut with a knife. Thulium is primarily obtained through solvent extraction processes from clay deposits in China.
Applications of Thulium:
- Opto-electronics and Electronics: Because of its scarcity and its high cost, thulium does not have many practical applications. It has been used to create laser lights, but production costs have been too high for commercial use. Similarly to yttrium, thulium has been used in high temperature superconductors. Thulium potentially has use in ferrites, a type of ceramic magnet used in microwave equipment.
- Medicine: Portable x-ray devices use thulium isotopes that are made in nuclear reactors for a radiation sources. These have proven valuable in medical and dental technology in areas where electric power is not available.