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Process for growing sodium nitrate monocrystal by Bridgman method

A crucible descending method and sodium nitrate technology, applied in the direction of single crystal growth, single crystal growth, crystal growth, etc., can solve the problem that the crystal size, purity and degree of crystallization are not ideal, the temperature field and growth process control requirements are high, and it is difficult to obtain Large-scale complete single crystal and other problems, to achieve the effect of small thermal stress, simple and convenient process, and high yield

Active Publication Date: 2012-05-30
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 size, purity and crystallization degree.

Method used

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  • Process for growing sodium nitrate monocrystal by Bridgman method
  • Process for growing sodium nitrate monocrystal by Bridgman method
  • Process for growing sodium nitrate monocrystal by Bridgman method

Examples

Experimental program
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Effect test

Embodiment 1

[0037] (1) Analytical sodium nitrate (≥99.0%) is used as a raw material, and after dehydration is roasted at 200°C for 2 hours, it is charged in a drying oven;

[0038] (2) Adopt size Ф10×100mm 3 , a cylindrical quartz glass crucible with a wall thickness of 1.5mm, compact the raw materials into the crucible, then put the crucible into the downcomer, raise the furnace temperature to 370°C after 5 hours, then keep it warm for 4 to 6 hours and gradually increase Downpipe, when the temperature at the bottom of the crucible reaches the melting point of sodium nitrate, turn on the descending device to start crystal growth, the descending rate is 0.4mm / h, and the temperature gradient at the growth interface is 5°C / cm;

[0039] (3) After the growth is completed, turn off the power supply, let the furnace body cool down to room temperature naturally, take out the quartz glass crucible, and peel the crystal from the crucible to obtain a colorless sodium nitrate single crystal. In this...

Embodiment 2

[0041] (1) Analytical sodium nitrate (≥99.0%) is used as a raw material, and after dehydration is roasted at 200° C. for 3 hours, it is charged in a drying oven;

[0042] (2) Adopt size Ф20×200mm 3 , a cylindrical platinum crucible with a wall thickness of 0.12 mm, the furnace temperature is controlled at 370° C., the rate of descent is 0.4 mm / h, and the temperature gradient at the growth interface is 5° C. / cm. Other process conditions and operations are the same as in Example 1. In this embodiment, one furnace can grow 4 sodium nitrate crystals.

Embodiment 3

[0044] (1) Analytical sodium nitrate (≥99.0%) is used as a raw material, and after dehydration is roasted at 200°C for 2 hours, it is charged in a drying oven;

[0045] (2) Adopt size Ф25×200mm 3, a cylindrical platinum crucible with a wall thickness of 0.14 mm, the furnace temperature is controlled at 370° C., the rate of descent is 0.6 mm / h, and the temperature gradient at the growth interface is 5° C. / cm. Other process conditions and operations are the same as in Example 1. In the present embodiment, one furnace can grow 6 sodium nitrate crystals.

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Abstract

The invention relates to a method for growing a sodium nitrate monocrystal with large dimension and high quality by a Bridgman method, belonging to the technical field of crystal growth and comprising the following steps: adopting analytically pure sodium nitrate as a raw material, adopting a monolayer taper base platinum crucible or arc bottom quartz glass crucible for containing materials and utilizing a Bridgman furnace which adopts a silicon carbide rod or silicon-molybdenum rod as a heating element to carry out crystal growth, wherein the growth furnace temperature is 350-380 DEG C, the growth rate is 0.2-1.0mm / h, and the growth interface temperature gradient is 5-15 DEG C / cm. The growth process of the Bridgman method is simple and has the advantages that crystal growth can be carried out according to established conditions, the temperature field is stable, the radial temperature gradient is small, crystal cleavage can be effectively reduced, and sodium nitrate monocrystals with different specifications can be simultaneously grown in the same furnace.

Description

technical field [0001] The invention relates to a growth process of sodium nitrate crystals by a crucible drop method, in particular to a growth process of a sodium nitrate crystal by a crucible drop method 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, circulators 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 ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C30B11/00C30B29/10
Inventor 袁晖熊巍陈良周尧
Owner SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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