METHOD FOR PRODUCING METAL FLUORIDE SINGLE CRYSTAL AND AS-GROWN SINGLE CRYSTAL OF METAL FLUORIDE PRODUCED BY THE METHOD

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a metal fluoride single crystal from which an as-grown single crystal, in which scattering bodies are very few and from which an optical material having a large diameter can be cut in a high yield, can be produced.;SOLUTION: The metal fluoride single crystals such as calcium fluoride and the like are produced by the method that the metal fluoride single crystal is grown by bringing a seed crystal into contact with the molten liquid surface of a raw metal fluoride and by pulling it according to a single crystal pulling method. The depth of the molten liquid of the raw metal fluoride is kept at least in a certain period from the beginning to the end of the pulling, favorably the period, where the depth is 0.65 times or less to the cylindrical diameter of the as-grown single crystal, is prepared as the practically whole period of the pulling of the cylindrical part of the as-grown single crystal.;COPYRIGHT: (C)2006,JPO&NCIPI