| 摘要 |
PROBLEM TO BE SOLVED: To provide a fluoride single crystal which has sufficiently high transmittance in ultraviolet/vacuum ultraviolet (UV/VUV) regions and is excellent in laser resistance and resistance to UV/VUV, to provide a method for heat-treating a fluoride to obtain such a fluoride single crystal, and to provide a method for producing the fluoride single crystal. SOLUTION: The method for heat treating a fluoride includes: an accommodating step for accommodating a fluoride 5 to be treated together with a scavenger having a deoxidation function in an airtight heating furnace 100; a temperature rise starting step for starting temperature rise of the scavenger after reducing the pressure in the heating furnace 100 to be≤1×10<SP>-1</SP>Pa by evacuating the inside of the airtight heating vessel 100; an evacuation stopping step for stopping evacuation of the inside of the heating furnace 100 when the temperature of the scavenger becomes a temperature lower by 20-50°C than the melting point of the scavenger; and an evacuation restarting step for restarting the evacuation of the inside of the heating furnace 100 when the temperature of the scavenger becomes a temperature higher by 20-50°C than the melting point of the scavenger. COPYRIGHT: (C)2011,JPO&INPIT
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