Crystal growth method for obtaining flat solid-liquid interface, and apparatus thereof

The invention relates to a method for growing fluoride crystals under a vacuum condition through a descending technology, and an apparatus thereof. The electrode of the heating unit of the apparatus is positioned above the heating unit, and the electrode of the heating unit traverses through a heat insulation layer, and is leaded to the outside of a furnace body by the outer side of the heat insulation layer. The electrode of the heating unit is leaded from a position far from a cold zone and hot zone interface above a crucible, so influence of the heat conduction of the electrode on the structure of a temperature field in a solid-liquid interface when the electrode is connected to the lower portion of the heating unit is avoided. The lowest equipotential ring of the heating unit provides an axial uniform and symmetric temperature field. Temperature gradient required by the growth of the crystals can be obtained through cold rap formed in the solid-liquid interface due to a graphite separator plate with a heat dissipation screen, so the solid-liquid interface maintains a flat interface or an upward slightly convex interface in the whole crystal growth process, and high-quality fluoride crystals with the inside containing few defects grow.