Yttrium(III) chloride is an inorganic compound of yttrium and chloride. It exists in two forms, the hydrate (YCl<sub>3</sub>(H<sub>2</sub>O)<sub>6</sub>) and an anhydrous form (YCl<sub>3</sub>). Both are colourless salts that are highly soluble in water and deliquescent.
Solid YCl<sub>3</sub> adopts a cubic structure with close-packed chloride ions and yttrium ions filling one third of the octahedral holes and the resulting YCl<sub>6</sub> octahedra sharing three edges with adjacent octahedra, giving it a layered structure. This structure is shared by a range of compounds, notably AlCl<sub>3</sub>.
YCl<sub>3</sub> is often prepared by the "ammonium chloride route," starting from either Y<sub>2</sub>O<sub>3</sub> or hydrated chloride or oxychloride. or YCl<sub>3</sub>÷6H<sub>2</sub>O. These methods produce (NH<sub>4</sub>)<sub>2</sub>[YCl<sub>5</sub>]:
The pentachloride decomposes thermally according to the following equation:
The thermolysis reaction proceeds via the intermediacy of (NH<sub>4</sub>)[Y<sub>2</sub>Cl<sub>7</sub>].
Treating Y<sub>2</sub>O<sub>3</sub> with aqueous HCl produces the hydrated chloride (YCl<sub>3</sub>÷6H<sub>2</sub>O). When heated, this salt yields yttrium oxychloride rather than reverting to the anhydrous form.
Yttrium chloride is used to make nanocrystals doped with erbium (Er<sup>3+</sup>) and ytterbium (Yb<sup>3+</sup>), such as NaYF<sub>4</sub>:Yb<sup>3+</sup>/Er<sup>3+</sup>.
In electronics and optics, YCl<sub>3</sub> is added to semiconductors, LED materials, and lasers to enhance their performance and stability.