| 摘要 |
PROBLEM TO BE SOLVED: To provide a fluoride raw material (powder) purification method which is high in productivity, low in production cost, and useful for producing a fluoride crystal having high transmittance to excimer laser and excellent durability to high output laser. SOLUTION: The vacuum degree in a furnace is kept in the range of 0.01-1 Pa in a temperature range where a fluorine-based gas is generated from a solid scavenger during heating and temperature rise before the fluoride raw material is melted in a purification process thereof. Thereby, it becomes possible to feed the fluorine-based gas to the whole raw material in a short period of time to thereby fluorinate the whole raw material even for a large amount of powdery fluoride raw material. COPYRIGHT: (C)2006,JPO&NCIPI
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