Gadolinium(III) iodide can be obtained by the reaction between gadolinium(III) oxide and hydroiodic acid, crystallizing into the hydrate form. The hydrate form can be heated with ammonium iodide to form the anhydrous form.Kutscher, J.; Schneider, A. Preparation of anhydrous lanthanide halides, especially iodides. Inorganic and Nuclear Chemistry Letters, 1971. 7 (9): 815-819.
