Growth method of calcium fluoride single crystal and used device

Abstract

The invention provides a growth method of a calcium fluoride single crystal and a used device, and belongs to the technical field of new material preparation. The method comprises the following steps:using calcium fluoride as a raw material and adopting a crucible pulling method to obtain a calcium fluoride single crystal, jointly adjusting the temperature of the calcium fluoride single crystal by a side heater arranged on the side surface of the crucible and a bottom heater arranged at the bottom of the crucible in the growth process, and controlling seed crystal fusion and the change of theheating or cooling rate in the crystal growth process. According to the single crystal growth device, the temperature near the seed crystal can be accurately controlled so that the seed crystal welding is controlled; the whole process of the calcium fluoride single crystal growth method is free of lead, zinc and other deoxidants so as to ensure that the prepared calcium fluoride single crystal has no ultraviolet region absorption, the single crystal transmittance is high, the stress birefringence is low, and compared with a single heater growth mode, the yield and the crystal quality of the calcium fluoride single crystal can be effectively improved and thus the crystal is more suitable for being used as an excimer laser window material.

Description

technical field [0001] The invention relates to a growth method and a growth device of a calcium fluoride single crystal, and belongs to the technical field of new material preparation. Background technique [0002] Calcium fluoride, chemical formula CaF 2 , colorless crystal or white powder; insoluble in water, slightly soluble in inorganic acid; react with hot concentrated sulfuric acid to generate hydrofluoric acid. The crystal structure of calcium fluoride belongs to the equiaxed crystal system, which is cubic, octahedral or dodecahedral. Colorless crystal or white powder, natural ore contains impurities, slightly green or purple, glows when heated, density 3.18 g / cm 3 , melting point 1402 ℃, boiling point 2497 ℃, refractive index 1.434, low toxicity. Calcium fluoride has a wide range of uses, and with the advancement of science and technology, the application prospects are becoming more and more broad. At present, it is mainly used in three major industries of metal...

AI Technical Summary

Problems solved by technology

[0003] In the prior art, calcium fluoride can be grown by the crucible drop method or the pulling method. During the growth process of the crucible drop method, the melt contacts the inner wall of the crucible. Since the calcium fluoride single crystal belongs to the cubic crystal system, it is very easy to crystallize. On the surface, it is easy to generate multiple crystal nuclei, and the yield of single crystal is low; during the growth process of the pulling method, the crystal and the crucible wall do not contact, and the seed crystal with good structure can be used for directional growth. The crystal grown by this method has small stress birefringence, single High crystal rate and other advantages, but the growth method with a single heater is commonly used in the pulling method. The temperature gradient in the crystal furnace is uncontrollable, and it is difficult to obtain an ideal temperature range. At the same time, the crystallization rate and crystal orientation of each crystal nucleus are different in the growth process of a single heater Defects such as polycrystals or dislocations

Calcium fluoride windows for excimer lasers have high requirements on the crystal structure, and crystals with structural defects usually have poor performance and cannot be used

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