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Method for annealing large-size calcium fluoride crystal

A calcium fluoride, large-size technology, which is applied in the field of annealing large-size calcium fluoride crystals, can solve problems such as crystal cracking, limited crystal growth size, and large thermal stress, so as to improve the laser damage threshold and facilitate thermal stress The effect of releasing and eliminating residual thermal stress

Inactive Publication Date: 2014-03-19
SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the unavoidable mechanical vibration of this method will cause temperature fluctuations at the solid-liquid interface, which is easy to form polycrystalline growth; in the later stage of crystal growth, the temperature gradient at the position of the crystal is large, and it is also easy to generate large thermal stress, resulting in crystal cracking
The temperature gradient method avoids the mechanical disturbance of the crucible drop method, but the fixed temperature field and crucible position also limit the growth size of the crystal

Method used

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  • Method for annealing large-size calcium fluoride crystal

Examples

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Embodiment 1

[0023] CaF grown by pulling method with a size of φ160mm×40mm 2 Put the crystal into a tungsten crucible, use high-purity CaF with a diameter of 2-5mm 2 Buried and covered with crushed crystals to avoid CaF 2 The crystal is in direct contact with the crucible wall and air; then placed in a high vacuum annealing furnace, when the vacuum degree is higher than 5×10 -3 Start to heat up at Pa for vacuum annealing: first raise the temperature to 950°C at a heating rate of 40°C / h, keep the temperature for 24 hours, then lower the temperature to 800°C at a cooling rate of 8°C / h, and then lower the temperature at a cooling rate of 15°C / h Cool down to room temperature, and finally remove the crystals.

Embodiment 2

[0025] CaF grown by pulling method with a size of φ160mm×40mm 2 Put the crystal into a graphite crucible, use high-purity CaF with a diameter of 2-5mm 2 Buried and covered with crushed crystals to avoid CaF 2 The crystal is in direct contact with the crucible wall and air; then placed in a high vacuum annealing furnace, when the vacuum degree is higher than 5×10 -3 When Pa is filled with a mixed gas of high-purity argon and carbon tetrafluoride, the volume fraction of carbon tetrafluoride is 5%, and the inflation pressure is 0.02Mpa; for atmosphere annealing: first, the temperature is raised at a heating rate of 30°C / h to 1000°C, keep the temperature constant for 30 hours, then drop to 850°C at a cooling rate of 6°C / h, then drop to room temperature at a cooling rate of 13°C / h, and finally take out the crystals.

Embodiment 3

[0027] CaF grown by the drop method with a size of φ200mm×60mm 2 Put the crystal into a tungsten crucible, use high-purity CaF with a diameter of 2-5mm 2 Buried and covered with crushed crystals to avoid CaF 2 The crystal is in direct contact with the crucible wall and air; then placed in a high vacuum annealing furnace, when the vacuum degree is higher than 5×10 -3 P a Start to heat up for vacuum annealing: first raise the temperature to 1030°C at a heating rate of 35°C / h, keep the temperature for 35 hours, then lower the temperature to 850°C at a cooling rate of 8°C / h, and then lower the temperature at a cooling rate of 15°C / h to room temperature, and finally remove the crystals.

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Abstract

The invention discloses a method for annealing a large-size calcium fluoride crystal. The method comprises the following steps: putting the calcium fluoride crystal to be annealed into a crucible, burying and covering by use of raw material crushed calcium fluoride crystal, and preventing the crystal from contacting with the crucible and air directly; putting into a vacuum annealing furnace for vacuum annealing or atmosphere annealing; for annealing process, firstly, heating up to 900-1100 DEG C at the heating rate of 20-50 DEG C per hour, then performing heat preservation for 20-60 hours, finally, cooling down to room temperature at the cooling rate less than 20 DEG C per hour. By adopting the method, residual thermal stress in the crystal can be completely eliminated, and the optical property of the large-size calcium fluoride crystal can be well improved.

Description

technical field [0001] The invention relates to a method for annealing large-sized calcium fluoride crystals, specifically, eliminating residual thermal stress in large-sized calcium fluoride crystals and improving optical properties of large-sized calcium fluoride crystals through a reasonable heat treatment process . Background technique [0002] Calcium Fluoride (CaF 2 ) crystal is an important crystal material in functional crystals. Because of its excellent optical and physical and chemical properties, as well as unique structural features, it has always played a very important role in the fields of industrial applications and scientific research. For industrial applications, CaF 2 Crystals have a very wide light transmission range (0.125-10 μm), and are widely used as optical window materials from vacuum ultraviolet to mid-infrared. Also because of its special refractive index and relative dispersion value, it becomes an ideal optical material for apochromatic lense...

Claims

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Application Information

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IPC IPC(8): C30B33/02C30B29/12
Inventor 姜大朋苏良碧王静雅钱小波唐飞吴峰徐军
Owner SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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