| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to maintain the position of the solid-liquid bound ary to a raw material put into a crucible and the temperature gradient in a direction perpendicular to the solid-liquid boundary constant by setting the part near the solid-liquid boundary of the raw material put into the crucible in such a manner that the solid angle viewed from a heater side does not change as the crucible moves. SOLUTION: The crucible 3 comprises a material, such as carbon, which does not react with the raw material 4 of the crystal to be formed. CaF2 which is the raw material 4 is contained in the crucible 3. As the crucible 3 moves, the part near the solid-liquid boundary of the raw material 4 put into the crucible 3 is constituted so that the solid angle viewed from the heater 1a and 1b side does not change. According to such constitution, the positional relations between the heaters 1a and 1b and the raw material 4 put into the crucible 3 do not change and, therefore, the position of the solid-liquid boundary of the raw material 4 put into the crucible 3 and the temperature gradient in the direction perpendicular to the solid-liquid boundary may be maintained constant. Consequently, the production of a single crystal having the excellent homogeneity of refractive indices is made possible.
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