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

Abstract

The invention discloses a device and a method for directionally growing fluoride single crystal via lifting a small-gradient thermal field, which belongs to the technical field of crystal growth. The prior art has low success rate and bad crystal quality. The device disclosed by the invention is characterized in that a crucible is installed on the upper side of the bottom part of an insulating sleeve via a crucible pedestal; electrode holders which are opposite two by two are connected via connection beams, the middle points of the connection beams are intersected on one point, and the connection beams are connected on the point to form a complete body; the low ends of pulling rods are connected with the connection beams on the point; and electrode rods are dynamically matched with sealing rings. The method disclosed by the invention is characterized in that the pulling rods pull the heating bodies via the connection beams, the electrode holders and the electrode rods, later the thermal field is lifted, and finally the crucible, small crystal tubes, the crucible pedestal and small crystals are static. The success rate of the magnesium fluoride crystals grown according to the invention is over 95%, the dislocation density is reduced to 10-30 / cm<2>, the absorption coefficient at the wave band of 0.2-7.5 micrometers is smaller than 2*10E-4 / cm, and the quality of the crystals is fully improved.

Description

technical field [0001] The invention relates to a device and method for directional growth of a fluoride single crystal with a small gradient temperature field rising, which grows a fluoride in a specific direction such as a magnesium fluoride single crystal under vacuum conditions, and belongs to the technical field of crystal growth. Background technique [0002] Fluoride single crystal is a crystal material with anisotropy and birefringence properties, and is mainly used in polarizing elements in the ultraviolet band. Due to the requirements of birefringence characteristics, the cutting of the crystal must be carried out in a specific direction. If the crystal fails to grow in the predetermined direction, the cutting loss will be large and the utilization rate will be low. In order to improve the utilization rate, the crystal must be grown directionally. The existing method for directional growth of fluoride single crystal is a seed drop method. The method grows crystal...

AI Technical Summary

Problems solved by technology

Since the melting of the seed crystal cannot be observed in real time during the crystal growth process, it is impossible to detect whether the seed crystal melts according to the predetermined requirements in time, and the crystal growth result cannot be known until the crystal growth process is completely completed. If it fails, it will inevitably cause serious waste of raw materials and electric energy.

Such a low success rate and such serious waste have resulted in the price of magnesium fluoride single crystal blanks with a specific direction on the market as high as 10,000 yuan / kg, which affects the application of this material in a wider range of fields

[0006] Although there is still a success rate of 50-60% in the directional growth of fluoride crystals by the existing seed drop method, there are still problems in crystal quality.

Due to the existence of water-cooled drop rods, there are phenomena such as temperature fluctuations, unstable temperature fields, and excessive temperature gradients. The negative consequences of these phenomena are that the shape of the solid-liquid interface is not an ideal flat and slightly convex interface, which in turn leads to the formation of a large number of internal defects in the crystal. , the dislocation density reaches 60~100 / cm 2 , the absorption coefficient reaches 5×10E-4 / cm, such quality is difficult to meet the requirements of high-end polarizing prisms

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