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Czochralski method growth process of sodium nitrate monocrystalline

A technology of sodium nitrate and pulling method, which is applied in the direction of single crystal growth, single crystal growth, crystal growth, etc. It can solve the problem of unsatisfactory crystal integrity, purity and crystallization degree, high temperature field and growth process control requirements, and difficult Obtaining large-sized complete single crystals and other problems, achieving the effects of reducing crystal pollution, simple and convenient process, and small thermal stress

Inactive Publication Date: 2015-11-18
SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] The difficulty in the preparation of sodium nitrate single crystal lies in (1) the raw material is easy to deliquescence, and bubbles are easy to be generated during the crystallization process; (2) there is an abnormal phase transition point at 275°C and a decomposition point at 380°C, which requires less control over the temperature field and growth process High; (3) The crystal is easy to crack, and it is difficult to obtain a large-sized complete single crystal
At present, there are few reports on the growth technology of sodium nitrate single crystals, and the obtained crystals are not ideal in terms of integrity, purity and crystallinity.
For example, Chinese patent CN101892514A discloses a growth process of sodium nitrate single crystal by the crucible drop method, and a single crystal of sodium nitrate is grown, but the growth cycle of this process is long, the prepared crystal is easy to crack, and the crystallinity is low

Method used

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  • Czochralski method growth process of sodium nitrate monocrystalline

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0037] (1) Using spectrally pure sodium nitrate (≥99.99%) as a raw material, after roasting at 120° C. for 2 hours to remove water, charge in a drying oven;

[0038] (2) Use size Φ50×60mm 3, a cylindrical platinum crucible with a wall thickness of 2.0mm, put the raw materials into the crucible, then put the crucible into the pulling furnace, raise the furnace temperature to 350°C after 2 hours, and then keep it warm for 2 hours to completely melt the raw materials. Slowly lower the furnace temperature and gradually shake down the seed rod, the size of the seed crystal is 3×3×80mm 3 , not targeted. When the furnace temperature is controlled at 310°C, the automatic pulling device is turned on to start crystal growth, the pulling rate is 2.0mm / h, and the temperature gradient of the growth interface is 20°C / cm;

[0039] (3) Slowly adjust the heating power, and after completing the shouldering and equal diameter processes, lift the crystal out of the melt. Cool the furnace body ...

Embodiment 2

[0041] (1) Using spectroscopically pure sodium nitrate (≥99.99%) as a raw material, after dewatering by roasting at 150°C for 1 hour, charging in a drying oven;

[0042] (2) Use size Φ50×60mm 3 , A cylindrical platinum crucible with a wall thickness of 2.0mm, put the raw materials into the crucible, then put the crucible into the pulling furnace, raise the furnace temperature to 380°C after 3 hours, and then keep it warm for 2 hours to completely melt the raw materials. Slowly lower the furnace temperature and gradually shake down the seed rod, the size of the seed crystal is 4×4×70mm 3 , with an orientation of . When the furnace temperature is controlled at 310°C, the automatic pulling device is turned on to start crystal growth, the pulling rate is 2.0mm / h, and the temperature gradient of the growth interface is 20°C / cm;

[0043] (3) Slowly adjust the heating power, and after completing the shouldering and equal diameter processes, lift the crystal out of the melt. Cool t...

Embodiment 3

[0045] (1) Using spectroscopically pure sodium nitrate (≥99.99%) as a raw material, after dewatering by roasting at 100°C for 3 hours, charging in a drying oven;

[0046] (2) Use size Φ50×60mm 3 , a cylindrical platinum crucible with a wall thickness of 2.0mm, put the raw materials into the crucible, then put the crucible into the pulling furnace, raise the furnace temperature to 360°C after 3 hours, and then keep it warm for 2 hours to completely melt the raw materials. Slowly lower the furnace temperature and gradually shake down the seed rod, the size of the seed crystal is 5×5×50mm 3 , with an orientation of . When the furnace temperature is controlled at 320° C., the automatic pulling device is turned on to start crystal growth, the pulling rate is 3.0 mm / h, the growth interface temperature gradient is 25° C. / cm, and other process operations are the same as in Example 2 (3).

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Abstract

The invention relates to a czochralski method growth process of sodium nitrate monocrystalline. The czochralski method growth process includes the following steps that sodium nitrate is put into a crucible after being dried at the temperature of 100 DEG C to 200 DEG C for 2 hours to 5 hours; the crucible with the sodium nitrate is placed in a lifting furnace, the temperature of the furnace rises to 350 DEG C to 450 DEG C 2 to 5 hours later and remains for 1 hour to 2 hours, the sodium nitrate in the crucible is completely melted, and heating power is lowered slowly; when the temperature of the furnace is controlled in the range of from 250 DEG C to 350 DEG C, seed crystals are soaked in the melt, the seed crystals are rotated and lifted and begin to grow, the lifting speed ranges from 1.0 mm / h to 10 mm / h, the rotating rate ranges from 10 r / min to 20 r / min, the temperature gradient of the solid-liquid interface ranges from 10 DEG C / cm to 30 DEG C / cm; according to the crystal growth tendency, the heating power is slightly adjusted, the shouldering and isometrical processes are finished, growth is completed, the crystals are lifted and taken out to be separated from the melt, and the furnace body is cooled to the room temperature at the cooling rate of 20 DEG C / h to 50 DEG C / h; the thermal stress of the crystals is small, and cracking of the crystals can be reduced.

Description

technical field [0001] The invention relates to a pulling growth process of sodium nitrate crystals, in particular to a pulling growth process of sodium nitrate crystals for optical components, and belongs to the technical field of crystal growth. Background technique [0002] Sodium nitrate single crystal (NaNO 3 ) belongs to the hexagonal crystal system, space group R3c-, density 2.26g / cm 3 , Melting point 306.8℃, easy to deliquescence, soluble in water and liquid ammonia, slightly soluble in ethanol, glycerin and acetone. Negative uniaxial crystal with large birefringence, good optical uniformity, light transmission range between 0.2 and 2 μm, can be used in optical isolators, optical circulators, beam shifters and various optical polarizing prisms. The birefringence of sodium nitrate is larger than that of calcite, which is beneficial to simplify the structure of the device, and has low cost and high light transmittance, so it is more suitable for various polarizing de...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C30B29/22C30B15/00
Inventor 陈良熊巍周尧袁晖
Owner SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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