METHOD FOR PRODUCING METAL FLUORIDE SINGLE CRYSTAL USING METAL FLUORIDE SINGLE CRYSTAL PULLING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide a method for reducing intake or remnant of a metal component constituting a solid scavenger into or in a crystal, that is one factor deteriorating the internal transmittance of a metal fluoride single crystal used in an optical member or the like.;SOLUTION: A scavenging reaction, and melting and crystallization of a raw material are performed so that a solid scavenger or its melt are not brought into contact with a raw material metal fluoride 19 or its melt 23. For example, a double-structure crucible is used, and the solid scavenger is accommodated in a member 22 having a recessed part, which is provided below an opening part shielding member 15 attached to the outer wall of an inner crucible 2. Thereby, the scavenger is not directly brought into contact with the raw material metal fluoride 19 accommodated in an outer crucible 1 and a semi-closed space formed by the outer crucible 1, the inner crucible 2 and the opening part shielding member 15 is filled with the gasified scavenger and the gasified scavenger stays in the space for a long period of time. Accordingly, the efficiency of the scavenging reaction is not lowered. Further, the scavenger is not brought into contact with the melt 23 of the raw material metal fluoride 19 even in melting and crystallization processes.;COPYRIGHT: (C)2009,JPO&INPIT