Abstract: A method for preparing polycrystalline fluoride ceramics using powder of fluoride ceramics nanocrystallites as starting material, wherein the method includes: (a) Optionally, a pre-processing step at a temperature ranging from 100° C. to 300° C. at vacuum of 10-5 mbar (10-3 Pa) to 10-8 mbar (10-6 Pa) for 30 minutes to 10 hours, (b) Applying a uniaxial pressure in the range from 1 to 200 MPa, at or around ambient temperature, to obtain a pre-compacted sample, (c) Applying to the pre-compacted of step b) a hydrostatic pressure by Cold Isostatic Pressing, to obtain a pre-compacted sample, (d) Loading the pre-compacted sample from step (c) into a die and submitting the sample to a uniaxial compression in combination with electric field-assisted sintering, under vacuum equal to or higher than 5 Pa. Polycrystalline fluoride ceramics obtained by this method find use in IR devices.