Terbium(III) chloride (TbCl<sub>3</sub>) is a chemical compound. In the solid state TbCl<sub>3</sub> has the YCl<sub>3</sub> layer structure. Terbium(III) chloride frequently forms a hexahydrate.
The hexahydrate of terbium(III) chloride can be obtained by the reaction of terbium(III) oxide and hydrochloric acid:
It can also be obtained by direct reaction of the elements:
Terbium(III) chloride is a white, hygroscopic powder. It crystallizes in an orthorhombic plutonium(III) bromide crystal structure with space group Cmcm (No. 63). It can form a complex Tb(gly)<sub>3</sub>Cl<sub>3</sub>÷3H<sub>2</sub>O with glycine.
The hexahydrate plays an important role as an activator of green phosphors in color TV tubes and is also used in specialty lasers and as a dopant in solid-state devices.
Terbium(III) chloride causes hyperemia of the iris.