Process for growing calcium fluoride monocrystals

摘要

The invention provides a process for growing UV region 200 nm transmitting calcium fluoride monocrystals, which includes crystallization from the melt, the annealing of the crystals and subsequent cooling, in a vacuum furnace, and which is effected by the continuous transfer of the crucible containing the melt from the crystallization zone into the annealing zone, each of these two zones having its own independent control system for the process parameters, characterized in that there is a temperature drop of 250-450° C. from the crystallization zone to the annealing zone, with a gradient of 8-12° C./cm, the crucible containing the material to be crystallized is moved from the crystallization zone to the annealing zone at a speed of 1-3 mm/hour, it is first kept in the annealing zone at a holding temperature of 1100-1300° C. for 20-40 hours and is then cooled first to 950-900° C. at a rate of 2-40 C./hour and then to 300° C. at a rage of 5-8° C./hour, after which the material is allowed to cool down naturally.