Thulium is a chemical element having an atomic number 69 with the symbol Tm, It was discovered in 1879, along with holmium, by Per Teodor Cleve, who named the oxide thulia after an ancient name for Scandinavia. It is found in small amounts in such rare-earth minerals as laterite ionic clays, xenotime, and euxenite and in products of nuclear fission. Tm is one of the rarest of the rare-earth elements.
Its abundance in Earth’s crust is nearly the same as those of antimony and iodine. It is the 13th element in the lanthanide series in the periodic table. The element is barely traced purely in nature but it is traced in minute amounts in minerals with other rare earth metals.
Natural Tm is wholly composed of the stable isotope thulium-169. They range in mass from 144 to 179, and their half-lives range from more than 300 nanoseconds (thulium-178) to 1.92 years (thulium-171). Bombarded by neutrons, natural Tm becomes radioactive Tm-170 (128.6-day half-life), which ejects soft gamma radiation with wavelength commensurate with laboratory hard X-ray sources. Only one allotropic (structural) form is known for thulium.
Uses of Thulium
- It is used for laser manufacturing and for surgical purposes.
- It is used as a source of radiation from portable X-ray devices and in nuclear reactions.
- Despite being slightly expensive, superconductors of high temperature use thulium.
- It is used for manufacturing ferrites, ceramic magnetic materials for microwave items.
- Pure Tm metal has a bright, silvery luster, which tarnishes on exposure to air. The metal can be cut with a knife, as it has a Mohs hardness of 2 to 3; it is malleable and ductile.
- It is ferromagnetic below 32K, antiferromagnetic between 32 and 56.
- It has two major allotropes, the tetragonal α-Tm and the more stable hexagonal β-Tm.