Characteristics: A silvery-white rare earth metal that is malleable and ductil and soft enough to be cut with a knife. Terbium is never found in nature as a free element, however, is contained in many minerals such as: cerite, gadolinite, monazite, xenotime and euxenite. It reacts slowly with water and soluble in dilute acids. The salts are colorless. It is highly reactive and should be handled in an inert atmosphere or vacuum.
Derivation: Most separation processes for terbium salt from the rare-earth salt solution is ion exchange. In this process, rare-earth ions are sorbed onto suitable ion-exchange resins by exchange with hydrogen, ammonium or cupric ions present in the resin. The rare earth ions are then selectively washed out by a suitable complexing agent. As with other rare earths, terbium metal is produced by reducing the anhydrous chloride or fluoride with calcium metal. Calcium and tantalum impurities can be removed by vacuum re-melting, distillation, amalgam formation or zone melting.
Terbium is used as a dopant in calcium fluoride, calcium tungstate and strontium molybdate, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cells which operate at elevated temperatures.
Hazards: As with the other lanthanides, terbium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail.