CN-122013297-A - Calcium fluoride crystal preparation device capable of preventing liquid level fluctuation and growth process

CN122013297ACN 122013297 ACN122013297 ACN 122013297ACN-122013297-A

Abstract

The invention relates to the technical field of crystal growth, in particular to a calcium fluoride crystal preparation device capable of preventing liquid level fluctuation and a growth process. The device comprises a bell jar, a crucible, a surrounding type movable heater, a detachable diversion structure and a special connecting device, wherein the inner wall of the crucible is provided with a composite coating to optimize interface performance, the process adopts an atmosphere regulation mode of combining vacuum pumping and inert gas protection, and is matched with a step-by-step temperature rise and reduction strategy to controllably move through the heater to construct a stable temperature gradient. By adopting a temperature field adjusting mode that a crucible is static and a heater is movable, a detachable diversion structure at the mouth of the crucible and a composite coating on the inner wall are matched to stabilize the growth environment, and the process steps of vacuum pumping, inert gas protection and stepwise temperature rise and reduction are combined, so that the directional crystallization of the calcium fluoride melt is realized, and the mechanical vibration interference of the traditional crucible descent method is avoided to improve the crystal quality.

Inventors

ZHEN XIHE
Peng Minglin
ZHOU FANG
ZHOU SONGSONG
HAN SHICHANG
ZHOU CHAO

Assignees

河南微米光学科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260228

Claims (10)

1. The calcium fluoride crystal preparation device capable of preventing liquid level fluctuation is characterized by comprising a bell jar (1), wherein a crucible (2) is arranged in the bell jar (1), a heater (3) is arranged outside the crucible (2) in a surrounding mode, a detachable diversion structure (9) is arranged at the mouth of the crucible (2), the device further comprises a connecting device, the connecting device comprises a first supporting plate (41), a second supporting plate (42), a first supporting rod (51), a second supporting rod (52) and a third supporting rod (53), the first supporting plate (41) is rigidly connected with the bottom of the crucible (2), the upper end of the second supporting rod (52) is rigidly connected with the bottom of the first supporting plate (41), the second supporting rod (52) is fixedly connected with the base of the bell jar (1), the first supporting rod (51), the third supporting rod (53) and the bottom of the heater (3) are rigidly connected, the transmission screw (6) is adaptively connected with the transmission device (7), and the transmission screw (7) is connected with the transmission device and the transmission screw (7) comprises a composite boron nitride coating (10) and the composite water-free coating (10).
2. The calcium fluoride crystal preparation device capable of preventing liquid level fluctuation according to claim 1, wherein the detachable diversion structure (9) is of a hollow cylindrical structure, a diversion ring with an inclination angle of 15-30 degrees is arranged at the bottom of the detachable diversion structure (9), and the detachable diversion structure (9) is in fit and clamping connection with the inner wall of the mouth part of the crucible (2) through an annular buckle.
3. The calcium fluoride crystal preparation device capable of preventing liquid level fluctuation according to claim 1, wherein the thickness of the composite coating (10) is 5-10 mu m, the dispersing agent comprises any one of polyethylene glycol, polyvinylpyrrolidone and polyacrylic acid, and the mass ratio of pyrolytic boron nitride to nano CaF 2 to dispersing agent to absolute ethyl alcohol is 1 (0.05-0.1) (0.005-0.01) (3-5).
4. The calcium fluoride crystal preparation device capable of preventing liquid level fluctuation according to claim 1 is characterized in that a first supporting plate (41) and a second supporting plate (42) of the connecting device are made of high-purity graphite and are 10-15mm in thickness, the first supporting rod (51), the second supporting rod (52) and the third supporting rod (53) are made of molybdenum alloy, the diameter of each supporting rod is 8-12mm, the rigid connection between the first supporting plate (41) and the bottom of the crucible (2) is argon arc welding, and the fixed connection between the second supporting rod (52) and the base of the bell jar (1) is screw fastening connection.
5. The calcium fluoride crystal preparation device capable of preventing liquid level fluctuation according to claim 1, wherein the heater (3) is of an annular surrounding type heating structure and comprises a heating element layer, a heat insulation matrix and an outer protective layer, wherein the heating element layer is arranged from inside to outside, the heating element layer is a tungsten-rhenium alloy heating wire, the heat insulation matrix is a carbon fiber heat insulation material, and the outer protective layer is a silicon nitride coating and has a thickness of 5-8 mu m.
6. The calcium fluoride crystal preparation device capable of preventing liquid level fluctuation according to claim 1 is characterized in that the transmission motor (8) is a servo motor, the control precision is +/-0.01 mm/s, the transmission screw (6) is a ball screw, the screw pitch is 2-4mm, the transmission device (7) is of a gear reduction structure, and the reduction ratio is 1 (10-15).
7. A calcium fluoride crystal growth process for preventing liquid level fluctuation, which adopts the calcium fluoride crystal preparation device for preventing liquid level fluctuation according to any one of claims 1 to 6, and is characterized by comprising the following steps: s1, uniformly mixing high-purity calcium fluoride powder and an ammonium fluoride deoxidizer, and loading the mixture into a crucible (2) with a composite coating (10) on the inner wall, clamping a detachable guide structure (9) at the mouth of the crucible (2) through an annular buckle, closing a bell jar (1), starting a transmission motor (8) to debug the initial position of a heater (3), and ensuring that the heater (3) surrounds the middle area of the crucible (2); S2, starting a vacuum system to vacuumize the inside of the bell jar (1), and detecting the tightness of the furnace body after pressure maintaining, after the tightness is detected to be qualified, heating up for the first time from room temperature, and simultaneously introducing argon as a protective gas to stabilize the pressure in the bell jar (1), and continuing heating up and heat preservation for the second time to completely melt the calcium fluoride raw material; S3, adjusting a transmission motor (8), driving a transmission screw (6) through a transmission device (7) to drive a second supporting plate (42), a first supporting rod (51) and a third supporting rod (53) to synchronously move upwards, further driving a heater (3) to move upwards to enable the liquid level of the melt to form a stable temperature gradient; s4, cooling for the first time after the crystal growth is completed, keeping the argon flow and the furnace chamber pressure stable, continuing cooling to room temperature, closing an argon supply and vacuum system, opening a bell jar (1), removing a detachable diversion structure (9), and taking out the crystal to obtain the calcium fluoride crystal.
8. The calcium fluoride crystal growth process for preventing liquid level fluctuation according to claim 7 is characterized in that in S1, the mass ratio of high-purity calcium fluoride powder to ammonium fluoride deoxidizer is 100 (0.5-1.5), in S2, the pressure of the evacuated bell jar (1) reaches 10 -5 -10 -4 Pa, the dwell time is 15-25min, the first heating rate is 40-50 ℃ per hour, the temperature is 500-600 ℃, the pressure in the bell jar (1) is stabilized at-25-15 Pa, the second heating temperature is 1420-1450 ℃ and the holding time is 3-4h.
9. A calcium fluoride crystal growth process against liquid level fluctuation according to claim 7, wherein in S3, the upward moving rate of the heater (3) is 3-5mm/h.
10. The process for growing calcium fluoride crystals against liquid level fluctuation according to claim 7, wherein in S4, the rate of the first cooling and the second cooling is 18-22 ℃ per hour, and the temperature of the first cooling is 200-300 ℃.

Description

Calcium fluoride crystal preparation device capable of preventing liquid level fluctuation and growth process Technical Field The invention relates to the technical field of crystal growth, in particular to a calcium fluoride crystal preparation device capable of preventing liquid level fluctuation and a growth process. Background The calcium fluoride crystal has excellent deep ultraviolet light transmittance, low refractive index dispersion and good mechanical stability, and has irreplaceable application value in key fields such as high-end optical lenses, laser nuclear fusion devices, ultraviolet detection systems and the like. Currently, the mainstream preparation process of calcium fluoride crystals still takes a crucible descent method as a main principle, and the method drives a crucible to move downwards along a temperature field gradient through a mechanical transmission device so as to realize directional crystallization of a melt. On one hand, the movement of the crucible depends on mechanical transmission components such as a motor, a screw rod and the like, shake generated during the operation of the motor and operation errors of a transmission mechanism can be directly transmitted to the crucible and the liquid level of an internal melt through a supporting structure, so that the crystal liquid level is severely fluctuated, defects such as dislocation, cracks and inclusion are extremely easy to form in the crystal, the optical uniformity and mechanical strength of the crystal are seriously reduced, on the other hand, the interface friction between the crucible and the melt in the traditional process is larger, thermal convection interference is easy to generate in a high-temperature environment, the liquid level instability is further increased, and the finished product crystal yield is lower. The existing improvement scheme focuses on optimizing the precision of a transmission mechanism, but can alleviate the vibration problem to a small extent, but cannot eliminate the interference caused by mechanical transmission fundamentally, and the requirement of heat convection suppression is difficult to be met. Therefore, there is a need to develop a technique for preparing calcium fluoride crystals that can provide a stable growth environment to improve the crystal quality and meet the application requirements of high-end optics for high-purity and low-defect calcium fluoride crystals. Disclosure of Invention Aiming at the problems, the application provides a calcium fluoride crystal preparation device and a growth process for preventing liquid level fluctuation, the application adopts a temperature field adjusting mode that a crucible is static and a heater is movable, the method is matched with a detachable diversion structure at the mouth of the crucible and a composite coating on the inner wall to stabilize the growth environment, and combines the process steps of vacuum pumping, inert gas protection and stepwise temperature rise and reduction to realize the directional crystallization of the calcium fluoride melt, so that the mechanical vibration interference of the traditional crucible descent method is avoided to improve the crystal quality. In order to achieve the above purpose, the application adopts the following technical scheme: the application provides a calcium fluoride crystal preparation device capable of preventing liquid level fluctuation, which comprises a bell jar, wherein a crucible is arranged in the bell jar, a heater is arranged outside the crucible in a surrounding mode, a detachable diversion structure is arranged at the mouth of the crucible, the calcium fluoride crystal preparation device further comprises a connecting device, the connecting device comprises a first supporting plate, a second supporting plate, a first supporting rod, a second supporting rod and a third supporting rod, the first supporting plate is rigidly connected with the bottom of the crucible, the upper end of the second supporting rod is rigidly connected with the bottom of the first supporting plate, the second supporting rod is fixedly connected with the base of the bell jar, the first supporting rod, the third supporting rod and the bottom of the heater are rigidly connected, the second supporting plate is connected with a transmission screw, the transmission screw is in fit connection with a transmission device, the transmission device is connected with a transmission motor, the inner wall surface of the crucible comprises a composite coating, and the composite coating comprises pyrolytic boron nitride, nano CaF 2, a dispersing agent and absolute ethyl alcohol. Preferably, the detachable diversion structure is a hollow cylindrical structure, the bottom of the detachable diversion structure is provided with a diversion ring with an inclination angle of 15-30 degrees, and the detachable diversion structure is in fit and clamping connection with the inner wall of the mouth part of the crucible throu