Preparation method of large-size trans-stilbene crystal

Abstract

The invention discloses a preparation method of a large-size trans-stilbene crystal, and belongs to the technical field of crystal material preparation. The trans-stilbene (molecular formula: C6H5CH = CHC6H5) crystal is also called stilbene crystal, and is an important neutron detection organic scintillation material. The preparation method provided by the invention is solution-method crystal growth, and comprises the following steps: preparing a solution, measuring a saturation point, and cooling for growth. The solvent ketone reagent adopted by the preparation method has the advantages of high boiling point, small volatility and small harm to human health, the sizes of the prepared large-size trans-stilbene crystal in three directions all exceed 25.4 mm, and the prepared large-size trans-stilbene crystal belongs to inch-level large-size crystal and can meet the requirement of being processed into an inch-level neutron detector.

Description

Technical Field

[0001] The present application relates to a method for preparing large-sized trans-stilbene crystals, belonging to the field of crystal material preparation. Background Art

[0002] Neutron detection technology plays an important role in the fields of basic research in nuclear physics, nuclear proliferation prevention, and nuclear medical imaging. For the development of neutron detection technology, it is particularly important to develop scintillation materials with excellent neutron detection performance. Organic scintillation materials are rich in hydrogen atoms and can convert neutron pulse signals into fluorescence signals based on the nuclear recoil method, thereby realizing neutron detection. Trans-stilbene crystals, also known as stilbene crystals, have a chemical formula of C 6 H 5 CH=CHC 6 H 5 , belongs to the monoclinic system, and is an organic scintillating crystal with excellent comprehensive scintillation performance. Trans-stilbene crystal has the advantages of high luminescence efficiency, short decay time, fast response, high detection efficiency, and excellent neutron / gamma-ray pulse shape discrimination (PSD) performance. It has obvious advantages in fast neutron detection under strong gamma radiation background, and has good application prospects in the field of nuclear radiation detection technology.

[0003] For the practical application of trans-stilbene crystals in the field of neutron detection technology, it is particularly important to develop large-size crystal growth and preparation technology. There are mainly two methods for growing trans-stilbene crystals: melt method and solution method. Due to the high growth temperature and large temperature fluctuations in the melt method, the crystal is subjected to large stress during the growth process, resulting in a large internal defect density of the prepared crystal, poor crystal quality, and difficulty in meeting the requirements of neutron precision detection. Compared with the melt method, the solution method has a lower growth temperature and smaller temperature fluctuations, and the obtained crystal quality is more ideal and has better performance. Therefore, solution method crystal growth is an effective way to prepare high-quality trans-stilbene crystals. The solution method large-size trans-stilbene crystal growth method currently reported mainly uses toluene or anisole as solvent. However, toluene or anisole has problems such as strong volatility, heavy odor, and great health hazards to experimenters, so it is of great significance to develop better reagents for the preparation of trans-stilbene crystals.

[0004] Trans-stilbene is easily soluble in ketone reagents, and ketone reagents such as cyclopentanone, cyclohexanone, and cycloheptanone have high boiling points, are less volatile than toluene or anisole, and are less harmful to the human body. Therefore, ketone reagents such as cyclopentanone, cyclohexanone, and cycloheptanone are expected to replace toluene or anisole as solvents for growing stilbene crystals by solution method. However, there has been no report on the preparation method of growing large-sized trans-stilbene crystals with dimensions exceeding one inch (25.4 mm) in three directions using ketone reagents as solvents. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the solvent used in the existing large-sized trans-stilbene crystal preparation method is highly volatile and harmful to the human body, and provide a method for preparing large-sized trans-stilbene crystals. The solvent ketone reagent used has a higher boiling point, lower volatility and less harm to the human body. And by using the preparation method of the present application, large-sized trans-stilbene crystals with dimensions exceeding one inch (25.4 mm) in three directions can be grown. The crystals are transparent as a whole, have no internal defects or wrapping, and have good crystal quality. It can meet the requirements of processing into inch-level neutron detection devices and has good industrial application prospects.

[0006] According to a first aspect of the present application, a method for preparing large-sized trans-stilbene crystals is provided.

[0007] A method for preparing large-sized trans-stilbene crystals, using a ketone reagent as a solvent and a solution cooling method for crystal growth, comprises the following steps:

[0008] S1. Prepare solution: weigh trans-stilbene raw material and ketone solvent, put them into a growth tank, and then heat them until they are completely dissolved to obtain a crystal growth solution;

[0009] S2. Determine the saturation point: Install a seed crystal rack with seed crystals in the completely dissolved solution, cool it down, and finally determine the saturation point temperature of the solution by observing the dissolution of the seed crystals;

[0010] S3, cooling growth: the solution is heated again until it is completely dissolved, and then cooled to a suitable temperature above the saturation point, and the seed rack loaded with trans-stilbene seed crystals is inserted into the solution in the growth tank; after the seed crystals are slightly dissolved, the temperature is quickly cooled to the saturation point temperature, and the seed crystal rod is rotated; after the seed crystals begin to grow, the temperature is started to be lowered for crystal growth, and finally large-sized trans-stilbene crystals are obtained.

[0011] Optionally, the large-sized trans-stilbene crystals have a dimension in at least one direction exceeding 10 mm.

[0012] Preferably, the dimensions of the large-sized trans-stilbene crystals in three directions are all greater than 10 mm.

[0013] Further preferably, the dimensions of the large-sized trans-stilbene crystals in three directions are all greater than 25.4 mm.

[0014] Optionally, in step S1, the ketone solvent is selected from at least one of cyclopentanone, cyclohexanone and cycloheptanone.

[0015] Optionally, in step S1, the ratio of the mass of the trans-stilbene raw material to the volume of the ketone reagent is 0.15-0.80 g / ml.

[0016] Preferably, in step S1, the ratio of the mass of the trans-stilbene raw material to the volume of the ketone reagent is 0.25-0.65 g / ml.

[0017] More preferably, in step S1, the ratio of the mass of the trans-stilbene raw material to the volume of the solvent is 0.35-0.55 g / ml.

[0018] Optionally, in step S1, the growth tank is placed in a water bath, a stirring rod is installed and stirring is performed, and then the water is heated to 50-85° C. and kept at a constant temperature for 5-300 hours until the substance in the growth tank is completely dissolved.

[0019] Optionally, the ratio of the mass of the trans-stilbene raw material to the volume of the ketone reagent is independently selected from 0.15 g / ml, 0.20 g / ml, 0.25 g / ml, 0.30 g / ml, 0.35 g / ml, 0.40 g / ml, 0.45 g / ml, 0.50 g / ml, 0.55 g / ml, 0.60 g / ml, 0.65 g / ml, 0.70 g / ml, 0.75 g / ml, 0.80 g / ml, or any range between two of them.

[0020] Optionally, S2, determining the saturation point: in a completely dissolved solution, replacing the stirring rod with a seed crystal rack containing seed crystals, cooling the solution at intervals of 0.5°C, and finally determining the saturation point temperature of the solution by observing the dissolution of the seed crystals.

[0021] Optionally, in step S3, the seed crystal is oriented such that an angle between a crystallographic b-axis of the seed crystal and a vertical direction is 0.5 to 45°.

[0022] Preferably, in step S3, the orientation of the seed crystal is such that the angle between the crystallographic b-axis of the seed crystal and the vertical direction is 5 to 15°.

[0023] Specifically, in step S3, the orientation of the seed crystal is such that the angle between the crystallographic b-axis of the seed crystal and the vertical direction is 10°.

[0024] Optionally, in step S3, the orientation of the seed crystal is such that the angle between the crystallographic b-axis of the seed crystal and the vertical direction is independently selected from any value among 0.5°, 1°, 2°, 5°, 7°, 8°, 10°, 12°, 15°, 17°, 20°, 25°, 30°, 35°, 40°, 45° or any range value between two of them.

[0025] In the present application, the seed crystals used can be prepared by the methods of the prior art. For example, they can be prepared by the method of spontaneous nucleation growth. The steps for preparing trans-stilbene crystals by spontaneous nucleation are: weigh 200g of trans-stilbene and 500mL of ketone reagent, put them into a glass growth tank, then put the growth tank into a water bath, install the stirring rod and stir, heat to 60°C, keep the temperature constant for 200 hours, and the trans-stilbene in the growth tank is completely dissolved; then slowly cool to room temperature at 0.5°C / hour, and a large amount of trans-stilbene crystals are precipitated through spontaneous nucleation growth; then rinse and filter with ethanol to collect the trans-stilbene crystals. From the collected crystals, select crystals with regular morphology and transparency as seed crystals. The inventors found that when the seed crystal is oriented in a direction where the angle between the crystallographic b-axis of the seed crystal and the vertical direction is 0.5 to 45°, large-sized, high-quality trans-stilbene crystals can be grown. When the seed crystal is oriented in a direction where the crystallographic b-axis of the seed crystal is parallel to the vertical direction or the crystallographic b-axis of the seed crystal is parallel to the horizontal direction, the grown trans-stilbene crystals are block crystals with obvious defect encapsulation and insufficient thickness. It should also be noted that there are requirements for the orientation of the seed crystal in step S3, and there are no requirements for the orientation of the seed crystal in step S2 for determining the saturation point.

[0026] Optionally, in step S3, the temperature of the solution when the seed crystal rack is inserted is 0.1 to 20° C. higher than the saturation point temperature.

[0027] Preferably, in step S3, the temperature of the solution when the seed rack is inserted is 0.5 to 20.0° C. higher than the saturation point temperature.

[0028] Further preferably, in step S3, the temperature of the solution when the seed rack is inserted is 1.0 to 10.0° C. higher than the saturation point temperature.

[0029] Optionally, the temperature of the solution when the seed rack is inserted is higher than the saturation point temperature and is independently selected from any value among 0.1°C, 0.2°C, 0.5°C, 0.7°C, 1.0°C, 2.0°C, 5.0°C, 7.0°C, 10.0°C, 12.0°C, 15.0°C, 17.0°C, 20.0°C or any range between two thereof.

[0030] Optionally, in step S3, the rotation rate of the seed rod is 1 to 100 revolutions per minute.

[0031] Preferably, in step S3, the rotation rate of the seed rod is 1 to 50 revolutions per minute.

[0032] Further preferably, in step S3, the rotation rate of the seed rod is 5 to 30 revolutions per minute.

[0033] Optionally, the rotation rate of the seed rod is independently selected from any value of 1 rpm, 2 rpm, 5 rpm, 7 rpm, 10 rpm, 15 rpm, 20 rpm, 25 rpm, 30 rpm, 35 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, or any range between two values.

[0034] Optionally, in step S3, the cooling rate for crystal growth is 0.001-50°C / 100 hours.

[0035] Preferably, in step S3, the cooling rate for cooling the crystal growth is 0.005-10°C / 100 hours.

[0036] Further preferably, in step S3, the cooling rate for cooling the crystal growth is 0.01-1.0°C / 100 hours.

[0037] Optionally, the cooling rate for crystal growth is independently selected from 0.001°C / 100 hours, 0.005°C / 100 hours, 0.01°C / 100 hours, 0.05°C / 100 hours, 0.1°C / 100 hours, 0.2°C / 100 hours, 0.5°C / 100 hours, 1.0°C / 100 hours, 5.0°C / 100 hours, 10°C / 100 hours, 20°C / 100 hours, 30°C / 100 hours, 40°C / 100 hours, 50°C / 100 hours, or any range between two of them.

[0038] As a preferred embodiment, the method for preparing large-sized trans-stilbene crystals comprises the following steps:

[0039] (1) Preparing the solution: Weigh trans-stilbene and ketone reagent (see Table 1) according to the set ratio, put them into a glass growth tank, then put the growth tank into a water bath, install a stirring rod and stir, then heat to 50-85°C, keep the temperature constant for 5-300 hours, until the solution is completely dissolved in the growth tank;

[0040] (2) Determination of saturation point: In a completely dissolved solution, replace the stirring rod with a seed crystal rack containing seed crystals, cool down the solution at intervals of 0.5°C, and finally determine the saturation point temperature of the solution by observing the dissolution of the seed crystals.

[0041] (3) Cooling growth: The solution is heated again until it is completely dissolved, and then cooled to 0.5 to 20°C above the saturation point. The stirring rod is removed, and the seed rack loaded with trans-stilbene seed crystals is inserted into the solution in the growth tank. After the seed crystals are slightly dissolved, the temperature is quickly cooled to the saturation point temperature, and the seed crystal rod is rotated at a certain rate. After the seed crystals begin to grow, the temperature is slowly lowered for crystal growth, and the large-sized trans-stilbene crystals are finally obtained.

[0042] According to the second aspect of the present application, there is provided an application of a large-sized trans-stilbene crystal prepared by the above-mentioned preparation method in neutron detection. The dimensions of the prepared large-sized trans-stilbene crystal in three directions are all greater than 25.4 mm, belonging to an inch-level large-sized crystal, which can meet the requirements of being processed into an inch-level neutron detection device.

[0043] Optionally, the large-sized trans-stilbene crystals are mounted on a neutron / gamma ray discrimination system for neutron / gamma ray detection and discrimination.

[0044] The beneficial effects of this application include:

[0045] 1) The method for preparing large-sized trans-stilbene crystals provided in the present application uses a ketone reagent as the solvent, which has the advantages of a higher boiling point, lower volatility and less harm to the human body.

[0046] 2) The method for preparing large-sized trans-stilbene crystals provided in the present application can prepare trans-stilbene crystals with a size of up to 120 mm × 56 mm × 43 mm, with the dimensions in three directions exceeding 25.4 mm. These are inch-scale large-sized crystals that can meet the requirements for processing into inch-scale neutron detectors.

[0047] 3) The method for preparing large-sized trans-stilbene crystals provided in the present application has excellent neutron / gamma pulse shape discrimination (PSD) performance, which meets the application requirements of fast neutron discrimination detection under strong gamma radiation background. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a photograph of trans-diphenylethylene crystal sample 1# in Example 1.

[0049] Figure 2 The powder X-ray diffraction pattern of trans-stilbene crystal sample 1 in Example 2 is

[0050] Figure 3 This is the transmission spectrum of trans-diphenylethylene crystal sample 1# in Example 3.

[0051] Figure 4This is the emission spectrum of trans-stilbene crystal sample 1# in Example 4 under X-ray radiation excitation.

[0052] Figure 5 It is a cylindrical trans-stilbene crystal sample (25.4 mm in diameter, 25.4 mm in height, and polished end face) after processing the trans-stilbene crystal sample 1# in Example 5.

[0053] Figure 6 It is the neutron-gamma pulse shape discrimination (PSD) spectrum of trans-diphenylethylene crystal sample 1# in Example 5.

[0054] Figure 7 This is a photograph of the trans-stilbene crystals in Comparative Example 1.

[0055] Figure 8 This is a photograph of the trans-stilbene crystals in Comparative Example 2. DETAILED DESCRIPTION

[0056] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0057] Unless otherwise specified, the raw materials in the examples of the present application were purchased from commercial sources. The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0058] Among them, trans-stilbene crystals, also known as stilbene crystals, are called Trans-stilbene in English, and their molecular formula is C 6 H 5 CH=CHC 6 H 5 , belongs to the monoclinic crystal system.

[0059] Spontaneous nucleation and growth of trans-stilbene crystals

[0060] Weigh 200g of trans-stilbene and 500mL of ketone reagent, load them into a glass growth tank, then put the growth tank into a water bath, install the stirring rod and stir, heat to 60°C, keep constant temperature for 200 hours, and completely dissolve the trans-stilbene in the growth tank; then slowly cool to room temperature at 0.5°C / hour, and precipitate a large amount of trans-stilbene crystals through spontaneous nucleation growth; then rinse and filter with ethanol to collect trans-stilbene crystals. From the collected crystals, select crystals with regular morphology and transparency as the seed crystals in Example 1. There are requirements for the orientation of the seed crystals in step S3, and there are no requirements for the orientation of the seed crystals in step S2 in order to determine the saturation point.

[0061] Example 1 Growth of large-sized trans-stilbene crystals

[0062] The specific preparation method for growing large-sized trans-stilbene crystals comprises the following steps:

[0063] (1) Preparing the solution: Weigh trans-stilbene and ketone reagent (see Table 1) according to the set ratio, put them into a glass growth tank, then put the growth tank into a water bath, install a stirring rod and stir, then heat to 65°C and keep the temperature constant for 200 hours until the solution is completely dissolved in the growth tank;

[0064] (2) Determination of saturation point: In a completely dissolved solution, replace the stirring rod with a seed crystal rack containing seed crystals, cool down the solution at intervals of 0.5°C, and finally determine the saturation point temperature of the solution by observing the dissolution of the seed crystals.

[0065] (3) Cooling growth: The solution is heated again until it is completely dissolved, then cooled to 5°C above the saturation point, the stirring rod is removed, and the seed rack loaded with trans-stilbene seed crystals is inserted into the solution in the growth tank. After the seed crystals are slightly dissolved, the temperature is quickly cooled to the saturation point temperature, and the seed crystal rod is rotated alternately forward and reverse at a certain rate; after the seed crystals begin to grow, the temperature is slowly lowered for crystal growth, and the large-sized trans-stilbene crystals are finally obtained.

[0066] The sample number, raw material type and amount, solute to solvent ratio, solution heating and dissolution temperature, cooling rate during growth and seed rod rotation rate are shown in Table 1. 6 H 5 CH=CHC 6 H 5 Represents trans-stilbene raw material, C 6 H 10 O represents cyclohexanone reagent, C 5 H 8 O represents cyclopentanone reagent, C 7 H 12 O represents a cycloheptanone reagent.

[0067] Table 1

[0068]

[0069] Figure 1 This is a crystal photo of sample 1# in this example. As can be seen from the figure, the obtained crystal is colorless, transparent as a whole, without internal defects or inclusions, and the crystal quality is good. The crystal mass is 168.4g, the size is 120mm×56mm×43mm, and the dimensions in three directions are all over 25.4mm, which is a large-sized crystal of inch level.

[0070] Example 2 Powder X-ray Diffraction Pattern Test of Trans-stilbene Crystals

[0071] Taking sample 1# as an example, the prepared crystals were ground into powder, and the powder X-ray diffraction (XRD) pattern was tested at room temperature using a powder X-ray diffractometer (model: Bruker D8-Advance). Figure 2 As shown, the powder XRD pattern measured experimentally is consistent with the powder XRD pattern fitted according to the trans-stilbene single crystal structure (CCDC 1275906), indicating that the prepared sample is a trans-stilbene crystal.

[0072] Example 3 Transmission spectrum test of trans-stilbene crystals

[0073] Taking sample 1# as an example, the prepared trans-stilbene crystals were processed into wafers parallel to the crystallographic (001) plane, with a size of 10 mm × 10 mm × 2 mm and double-sided polishing. The transmission spectrum of the wafer was tested using a UV-visible-near infrared spectrometer (model: PerkinElmer Lambda 950). Figure 3 As shown, trans-stilbene crystals have high transmittance in the visible light wavelength range of 400-700 nm, the measured transmittance is greater than 60%, and the ultraviolet cutoff edge is located at 358 nm.

[0074] Example 4 Emission spectrum test of trans-stilbene crystal under X-ray radiation excitation

[0075] Taking sample 1# as an example, the X-rays generated by a tungsten anode X-ray tube were used as the excitation light source to test the radiation fluorescence spectrum. Figure 4 As shown, under the excitation of X-ray radiation, the emission peak of fluorescence is located at 380nm; the fluorescence of this wavelength is within the spectral response range of the photomultiplier tube and is easy to be detected.

[0076] Example 5 Neutron / Gamma Discrimination Performance Test of Trans-Stilbene Crystals

[0077] Taking sample 1# as an example, the prepared trans-stilbene crystal was processed into a polished cylindrical sample with a diameter of 25.4 mm and a height of 25.4 mm ( Figure 5 ),use 252 The neutron / gamma pulse shape discrimination (PSD) performance of the samples was tested using a Cf radiation source. Figure 5 This is a photo of a cylindrical crystal sample after processing. Figure 6 Measured neutron-gamma pulse shape discrimination (PSD) spectrum. Figure 6 In the left figure, trans-stilbene crystals are 252Under the excitation of the Cf radiation source, two charge accumulations appear, the upper one is gamma rays and the lower one is neutrons, and the boundaries between the two charge accumulation beams are clear; in the right figure, the quality factor FOM value obtained based on the PSD fitting curve is 1.28, indicating that the prepared trans-diphenylethylene crystals have good discrimination performance for neutrons and gamma rays.

[0078] Comparative Example 1

[0079] The operation is the same as the preparation process of sample 1#, the only difference is that the orientation of the seed crystal installation is different during the cooling growth, and the crystallographic b axis of the seed crystal is parallel to the vertical direction. The obtained crystal is as follows Figure 7 As shown, it can be seen that when the b-axis is parallel to the vertical direction, the grown crystal is prone to white lines, the crystal quality is poor, and the anisotropy of crystal growth increases. The growth is slower in the direction perpendicular to the (001) direction, the crystal presents a blocky morphology, and the thickness is difficult to reach the inch level.

[0080] Comparative Example 2

[0081] The operation is the same as the preparation process of sample 1#, the only difference is that the orientation of the seed crystal installation is different during the cooling growth, and the crystallographic b axis of the seed crystal is parallel to the horizontal direction. The obtained crystal is as follows Figure 8 As shown, it can be seen that when the b-axis is parallel to the vertical direction, the grown crystal is prone to significant growth stripes, the integrity of the crystal is poor, and the transparency is not high; moreover, the anisotropy of the crystal growth increases, the horizontal growth is faster, and the vertical growth is slower, the crystal presents a blocky morphology, and the thickness is difficult to reach the inch level.

[0082] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing large-sized trans-stilbene crystals, characterized in that: A ketone reagent is used as a solvent and a solution cooling method is used to grow crystals, comprising the following steps: S1. Prepare solution: weigh trans-stilbene raw material and ketone solvent, put them into a growth tank, and then heat them until they are completely dissolved to obtain a crystal growth solution; S2. Determine the saturation point: Install a seed crystal rack with seed crystals in the completely dissolved solution, cool it down, and finally determine the saturation point temperature of the solution by observing the dissolution of the seed crystals; S3, cooling growth: the solution is heated again until it is completely dissolved, and then cooled to a suitable temperature above the saturation point, and the seed rack loaded with trans-stilbene seed crystals is inserted into the solution in the growth tank; after the seed crystals are slightly dissolved, the temperature is quickly cooled to the saturation point temperature, and the seed crystal rod is rotated; after the seed crystals begin to grow, the temperature is started to be lowered for crystal growth, and finally large-sized trans-stilbene crystals are obtained.

2. The preparation method according to claim 1, characterized in that: The large-sized trans-stilbene crystal has a size in at least one direction exceeding 10 mm; Preferably, the dimensions of the large-sized trans-stilbene crystals in three directions are all greater than 10 mm; Further preferably, the dimensions of the large-sized trans-stilbene crystals in three directions are all greater than 25.4 mm.

3. The preparation method according to claim 1, characterized in that: In step S1, the ketone solvent is selected from at least one of cyclopentanone, cyclohexanone and cycloheptanone.

4. The preparation method according to claim 1, characterized in that: In step S1, the ratio of the mass of the trans-stilbene raw material to the volume of the ketone reagent is 0.15 to 0.80 g / ml; Preferably, in step S1, the ratio of the mass of the trans-stilbene raw material to the volume of the ketone reagent is 0.25 to 0.65 g / ml; Further preferably, in step S1, the ratio of the mass of the trans-stilbene raw material to the volume of the solvent is 0.35-0.55 g / ml.

5. The preparation method according to claim 1, characterized in that: In step S3, the seed crystal is oriented such that the angle between the crystallographic b-axis of the seed crystal and the vertical direction is 0.5 to 45°; Preferably, in step S3, the orientation of the seed crystal is such that the angle between the crystallographic b-axis of the seed crystal and the vertical direction is 5 to 15°.

6. The preparation method according to claim 1, characterized in that: In step S3, when the seed crystal rack is inserted, the temperature of the solution is 0.1 to 20° C. higher than the saturation point temperature; Preferably, in step S3, the temperature of the solution when the seed rack is inserted is 0.5 to 20.0° C. higher than the saturation point temperature; Further preferably, in step S3, the temperature of the solution when the seed rack is inserted is 1.0 to 10.0° C. higher than the saturation point temperature.

7. The preparation method according to claim 1, characterized in that: In step S3, the rotation rate of the seed crystal rod is 1 to 100 revolutions per minute; Preferably, in step S3, the rotation rate of the seed rod is 1 to 50 revolutions per minute; Further preferably, in step S3, the rotation rate of the seed rod is 5 to 30 revolutions per minute.

8. The preparation method according to claim 1, characterized in that: In step S3, the cooling rate for crystal growth is 0.001-50°C / 100 hours; Preferably, in step S3, the cooling rate for cooling the crystal growth is 0.005-10°C / 100 hours; Further preferably, in step S3, the cooling rate for cooling the crystal growth is 0.01-1.0°C / 100 hours.

9. Use of large-sized trans-stilbene crystals prepared by the preparation method according to any one of claims 1 to 8 in neutron detection.

10. The use according to claim 9, characterized in that: The large-sized trans-stilbene crystal is installed on a neutron / gamma ray identification system for neutron / gamma ray detection and identification.

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