Transformations of Cerium Tetrafluoride Hydrate under Hydrothermal Conditions: A New Cerium Fluoride Hydrate Ce 3 F 10 ·3H 2 O

The behavior of cerium tetrafluoride hydrate was studied in water at a temperature of 80°C and under hydrothermal treatment at 100, 130, and 220°C for a day. The product of the hydrothermal treatment of CeF 4 ·H 2 O at 100°C was investigated by chemical, thermogravimetric, IR spectroscopic, and X-ray powder diffraction analyses, which identified a new cerium fluoride with the composition, presumably, Ce 3 F 10 ⋅3H 2 O or, most likely, (H 3 O)Ce 3 F 10 ⋅2H 2 O. New compound crystallizes in the space group Fm3̅m with a unit cell parameter of 11.66 Å. Hydrothermal treatment of cerium tetrafluoride hydrate at temperatures above 130°C leads to hydrolysis and reduction of cerium(IV) fluoride compounds to form CeO 2 and CeF 3 .