Terbium Discovered in 1843, terbium is a soft, ductile, malleable and silvery element of the lanthanide series . Other sources of terbium are oxide mixtures found in xenotime and euxenite . Terbium is extremely reactive when exposed to air or oxygen and must be kept in an inert atmosphere.
Terbium is used in special lasers and as a dopant in solid-state devices.