METHOD OF PRODUCING PRETREATED METAL FLUORIDES AND FLUORIDE CRYSTALS

摘要

Provided are pretreated metal fluorides which are reduced in the content of contaminant oxygen and a process for the production of fluoride crystals which are reduced in the content of contaminant oxygen and exhibit excellent optical characteristics such as transparency. A metal fluoride is heated within a temperature range of 300 to 1780 °K in the presence of carbonyl fluoride, preferably in an amount of 1/100 mol or above per mol of the metal fluoride, whereby the oxygen and moisture contained in the metal fluoride used as raw material and a manufacturing furnace are removed.  Thus, a pretreated metal fluoride is obtained.  Then, the pretreated metal fluoride as the raw material is melted by heating, and the obtained melt is subjected to crystal growth procedure according to a pulling-up or pulling-down method.  Thus, a high -quality fluoride crystal is obtained.