Yttrium sesquioxide, Y₂O₃

Yttrium sesquioxide, or yttria, Y₂O₃, is a pure white powder of density 4.84 at 15° C. It is feebly diamagnetic.

Yttria absorbs carbon dioxide from the air, liberates ammonia from ammonium salts, and dissolves readily in acids.

When dissolved in molten calcium chloride and cooled, yttria assumes the crystalline state, crystallising in trapezohedra.