Device and method for directionally growing fluoride single crystal via lifting small-gradient thermal field

Small gradient temperature field increased the fluoride single crystal growth orientation apparatus and method belongs to the field of crystal growth technique. Low success rate of the prior art, the difference between the crystal quality. Apparatus of the present invention is characterized in that the crucible after the crucible holder disposed at the bottom of a jacketed above; each connection beam connecting two by two the electrode pads, the midpoint of each connecting beams intersect at one point, each of the connecting beams to each other at that point integrally connected, is connected to the lower end of the pulling rod at this point of the respective connecting beams; movable electrode rod and the seal ring fitting. The method of the present invention is characterized in that the lifting rod is connected by a bridge, the electrode holder, the electrode rod pulling up the heating body, rise temperature field, the crucible, seeding tube, the crucible holder, seeding stationary. Growth under this invention is crystalline magnesium fluoride success rate of 95% or more, to reduce the dislocation density of 10 ~ 30 / cm2, and the absorption coefficient is less than 0.2 ~ 7.5μm band 2 × 10E-4 / cm, the crystal quality improve.