PRODUCTION OF FLUORIDE BULK SINGLE CRYSTAL

摘要

PROBLEM TO BE SOLVED: To provide a production process that produces fluoride bulk single crystal of high quality from a fluoride raw material of a low purity (for example, 99.9 wt.% purity) more simply than the conventional process. SOLUTION: The powdery fluoride raw material is heated in the range from the room temperature up to a prescribed temperature over 500 deg.C under a high vacuum condition higher than 106 torr to remove moisture and oxygen in the raw materials in the furnace. After the raw material is molten, a flon gas is introduced into the single crystal-producing furnace so that the flon gas is allowed to contact with the impurities occurring on the surfaces of the melt and the solution and the impurities distributing in the melt and in the solution for a sufficient time to allow the flon gas to react with the impurities until the impurities are removed. The resultant purified melt or solution is subjected to the single crystal-growing process thereby producing the objective fluoride bulk single crystal.