Beads of a polycrystalline alkali-metal or alkaline-earth metal fluoride, their preparation, and their use for preparing optical single crystals

摘要

The present invention is directed to polycrystalline alkali metal or alkaline earth metal beads, in particular CaF2 beads, having a diameter greater than or equal to 100 mum, advantageously between 100 mum and 2 cm, and an apparent density greater than 60%, advantageously at least 90%, of the theoretical density of said fluoride. The invention is also directed to a process for the preparation of the foregoing alkali metal and alkaline earth fluoride beads, and for the preparation of single crystals of said fluorides using the foregoing polycrystalline beads.