Thulium

Thulium (Tm), atomic number 69, is a silvery-gray rare earth metal belonging to the lanthanide series. With an atomic weight of 168.93422 u, thulium has a melting point of 1545°C (2813°F), boiling point of 1950°C (3542°F), and density of 9.32 g/cm3. Thulium is one of the least abundant rare earth elements in nature, typically occurring in trace amounts in minerals like fluorocarbonates and monazite.

Thulium finds relatively few applications in electronics, but it does play roles in certain niche areas. It is used as a doping agent in some solid-state lasers, particularly tunable diode-pumped solid-state lasers that emit near-infrared light around 1.9-2.0 microns wavelength, used in medicine and dentistry, especially for soft tissue surgical procedures.

Additionally, thulium is applied in making portable X-ray devices where the isotope Tm-170 serves as the X-ray source. Thulium also finds use in specialized optical equipment and as a control rod material in nuclear reactors.

While not as widely applied as some other rare earths, thulium remains important in scientific research and certain high-tech applications. Its rarity and cost often limit its use, but thulium remains an indispensable material in the aforementioned niche markets.