Method for growing large-size fluoride crystals through top seed crystal kyropoulos method

Abstract

The invention discloses a method for growing large-size fluoride crystals through a top seed crystal kyropoulos method. The method comprises the following steps: weighing and mixing fluoride crystals and deoxidant powder, and pressing a mixture to form a block; drying the pressed block; putting the block into a crucible, sequentially installing thermal field components and installing seed crystals; vacuumizing, and heating to smelt the material until observing that the block is molten; descending the seed crystals to contact with a melting liquid level so as to slightly melt the seed crystals, pulling seed crystal rods and growing the block on the seed crystals in a condensation manner; after finishing crystal seeding, entering a shouldering period at power reduction, maintaining the crystals rotating and keeping the crystal pulling speed in the period, gradually increasing the diameters of the crystals in an upward pulling process, and entering an isometrical growth period until the crystal growth is finished; and cooling and annealing after the crystal weight reaches the feed weight. The method is low in growth cost and short in growth period; the method is suitable for large-size fluoride crystals, and the fluoride crystals grow in a vacuum condition without oxygen impurities; and the growth process is visible and controllable, so that the crystal quality is improved.

Description

technical field [0001] The invention relates to a method for growing large-sized fluoride crystals by the top seed crystal kyrophoroplasty method. Background technique [0002] Alkaline-earth fluoride crystal is a traditional crystal material. Because of its excellent optical and physical and chemical properties, as well as unique structural characteristics, it has always played a very important role in both industrial applications and scientific research. And with the development of human science and technology, new application prospects are constantly emerging. In terms of industrial applications, alkaline earth fluoride crystals have a wide range of transmission wavelengths and are used as window materials in the vacuum ultraviolet to infrared bands. At the same time, the low refractive index and low dispersion characteristics make alkaline earth fluoride crystals become excellent achromatic and apochromatic lens materials, and are widely used in ultraviolet lithography,...

AI Technical Summary

Problems solved by technology

However, this method cannot observe seed crystal inoculation and the entire growth process, and cannot be adjusted in real time during the growth process, and the growth cycle is long (in 2003, Schott Lithotec, Germany, successfully grew Φ350mm×100mm CaF2 crystals by using the improved crucible drop method. , the growth period is 2 months);

[0006] The temperature gradient method can avoid the complex convection and temperature fluctuation of the solid-liquid interface caused by the interference of the irregular mechanical vibration source, so the quality of the grown crystal and the single crystal rate are better than the crucible drop method, but due to the crystal growth process Completely relying on diffusion transport, the crystal growth is relatively slow, and there is no relative movement between the growing crystal and the temperature field, which limits the height of the crystal; at the same time, the method uses a fully enclosed crucible, and the entire growth process is invisible; and its heating method uses graphite heating, The crucible is generally a graphite crucible, and the volatilization of graphite will affect the quality of the growing crystal;