An Organic Crystal Growth Method Based on the Control of the Inner Wall Angle of the Crucible

Abstract

This invention relates to the field of organic functional crystal growth technology, specifically a method for growing organic crystals based on the control of the included angle of the inner wall of a crucible. The method employs a quartz crucible with an axisymmetric conical inner cavity, and controls the included angle β of the inner wall of the crucible to be 10°–30°, preferably 15°–20°. After loading the organic crystal raw material into the crucible, a vacuum of 1×10⁻⁶ is applied. ‑2 After being sealed by welding, and after passing the pre-growth inspection and sealing, the melt is placed in a Bridgman crystal growth furnace for heating and melting and held at that temperature for 24 hours. The axial temperature gradient is controlled, and the melt is directionally solidified and grown from bottom to top at a rate of 1-1.5 mm / h. The organic single crystal is then slowly cooled to obtain the organic single crystal. This invention optimizes the melt flow field and solid-liquid interface by adjusting the crucible angle, reduces the radial temperature gradient, reduces defects such as crystal cracks and dislocations, and improves crystal integrity and optical uniformity. The process is simple, has good repeatability, and is suitable for large-size, high-quality growth of organic scintillation crystals and organic optoelectronic crystals.

Description

Technical Field

[0001] This invention relates to the field of organic functional crystal growth technology, specifically an organic crystal growth method based on the control of the angle between the inner walls of a crucible. Background Technology

[0002] Organic scintillation crystals and organic optoelectronic crystals are core organic functional crystal materials. Currently, these organic functional crystals are generally grown using the Bridgman process. During the growth process, straight-walled cylindrical crucibles or fixed-angle cone crucibles are conventionally used as crystal growth containers. In the actual growth process, the uniformity of the temperature field distribution inside the melt is a key factor affecting the crystal forming quality. Traditional crucible structures cannot specifically control the melt flow field and crystallization interface, making it difficult to maintain a stable state during the crystal growth process.

[0003] Existing organic crystal growth techniques only optimize crystal growth quality by controlling the cooling rate or axial temperature gradient. There is limited research on the influence of crucible geometry on melt flow field distribution and solid-liquid interface morphology. During crystal growth, uneven temperature field distribution within the melt can induce thermal stress and convection disturbances at the solid-liquid interface, leading to defects such as dislocations, cracks, and growth streaks within the crystal. This significantly reduces the optical uniformity and performance of organic crystals. Currently, there is a lack of effective technical means to improve the growth quality of organic crystals from the perspective of crucible structure optimization. Therefore, in view of the above situation, there is an urgent need to develop an organic crystal growth method based on the control of the crucible inner wall angle to overcome the shortcomings in current practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide an organic crystal growth method based on the control of the angle between the inner walls of the crucible, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An organic crystal growth method based on the controlled angle of the crucible inner wall includes the following steps:

[0007] S1: A crucible with an axially symmetric conical internal cavity and an included angle β of 15° to 20° between the inner walls of the crucible;

[0008] S2: After loading the organic crystal raw material into the crucible, vacuum it and seal it;

[0009] S3: Place the properly sealed crucible into the Bridgman crystal growth furnace, heat and melt it, and keep it at the desired temperature;

[0010] S4: Adjust the axial temperature gradient inside the furnace to enable directional solidification and growth of the melt;

[0011] S5: Slowly cool the grown crystal to obtain an organic single crystal.

[0012] As a further aspect of the present invention: in step S1, the crucible is made of quartz.

[0013] As a further aspect of the present invention: In step S2, after evacuation, the vacuum level inside the crucible reaches 1×10⁻⁶. -2 Pa.

[0014] As a further aspect of the present invention: in step S3, the heat preservation time after the raw material is heated and melted is 24 hours.

[0015] As a further aspect of the present invention: in step S4, the melt undergoes directional solidification and growth from bottom to top at a speed of 1 to 1.5 mm / h.

[0016] As a further aspect of the present invention: in step S3, after the sealed crucible passes the pre-growth inspection and is sealed, the heating and melting operation is then carried out.

[0017] As a further aspect of the present invention: in step S5, the organic single crystal is an organic scintillation crystal or an organic photoelectric crystal.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] This invention utilizes a crucible with an axisymmetric conical internal cavity and adjusts the included angle β of the inner wall to regulate the rate of change of the cross-sectional area of ​​the melt along the axial direction, optimize the natural convection intensity, flow path, and solid-liquid interface morphology inside the melt, and reduce the radial temperature gradient. This reduces the generation of internal cracks, dislocations, oxidation-induced defects, and growth streaks in the crystal, effectively improving the integrity, optical uniformity, and subsequent cutting and processing performance of organic crystals.

[0020] The growth process of this invention is simple and reproducible, and can be applied to the large-size, high-quality growth of organic scintillation crystals and organic optoelectronic crystals. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the 22° inner wall included angle conical crucible structure in Comparative Example 1 of the present invention.

[0022] Figure 2 This is a photograph of the crystal obtained by growing in a conical crucible with an inner wall angle of 22° in Comparative Example 1 of the present invention.

[0023] Figure 3 This is a schematic diagram of the cone-shaped crucible structure with an inner wall angle of 15° to 20° in Embodiment 1 of the present invention.

[0024] Figure 4 This is a photograph of the crystal obtained by growing in a cone-shaped crucible with an inner wall angle of 15° to 20° in Example 1 of the present invention.

[0025] In the figure: 1-the opening end of the crucible, 2-the middle end of the cylindrical crucible, 3-the tip of the cone of the crucible, 4-the cylindrical plug. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0028] Please see Figures 1-4 The present invention provides an organic crystal growth method based on the control of the included angle of the inner wall of the crucible. The crucible has an axially symmetric conical structure. The conical crucible includes, from top to bottom, a crucible opening end 1, a crucible cylindrical middle end 2, and a crucible conical tip portion 3. A cylindrical plug 4 is detachably provided on the crucible opening end 1.

[0029] By precisely controlling the included angle β of the crucible inner wall, which characterizes the included angle between two relative generatrices, the melt flow field, temperature field, and solid-liquid interface morphology during the organic crystal growth process are optimized. This solves the technical problem of defects easily generated during the growth of organic crystals in traditional straight-walled crucibles / fixed cone-angle crucibles from the perspective of crucible structure.

[0030] The conical crucible is made of quartz, with the diameter of the upper opening being larger than that of the lower opening. The included angle β of the inner wall of the axisymmetric conical structure is 10° to 30°, preferably 15° to 20°. This angle range can adjust the rate of change of the cross-sectional area of ​​the melt along the axial direction, optimize the natural convection intensity, flow path, and solid-liquid interface morphology inside the melt, reduce the radial temperature gradient, reduce internal crystal cracks, dislocations, and oxidation-induced defects, and improve crystal integrity, optical uniformity, and subsequent processing performance.

[0031] The overall process steps of the organic crystal growth method based on the controlled angle of the crucible inner wall in this invention are as follows:

[0032] Step 1: Place the organic crystal raw material (such as solid p-terphenyl raw material) into an axisymmetric conical crucible with an inner wall angle β of 10° to 30°;

[0033] Step 2: Evacuate the crucible to a vacuum level of 1×10⁻⁶. -2 After Pa, it is welded and sealed to form a closed growth environment;

[0034] Step 3: After pre-growth treatment, the sealing performance of the crucible is checked. Once it is confirmed that the crystal is free of oxidation, it can be used for formal growth.

[0035] Step 4: Place the crucible in the Bridgman crystal growth furnace, heat it to a temperature higher than the melting point of the raw material and hold it at that temperature for 24 hours to allow the raw material to fully melt and form a homogeneous melt.

[0036] Step 5: Adjust the axial temperature gradient according to the crystal melting point, thermal conductivity and crystallization characteristics, and move the crucible or temperature zone at a speed of 1 to 1.5 mm / h to make the melt solidify and grow directionally from bottom to top along the axial direction.

[0037] Step 6: After crystal growth is complete, slowly cool the crystal to room temperature to obtain a high-quality organic single crystal.

[0038] This method is simple, reproducible, and suitable for large-size, high-quality growth of organic scintillation crystals and organic optoelectronic crystals.

[0039] To fully verify the effectiveness of the technical solution of the present invention, comparative examples and preferred embodiments are set up below for comparison and explanation. All embodiments use the same organic crystal raw materials, the same Bridgman crystal growth furnace and the same process parameters without crucible structure, only changing the included angle β of the inner wall of the crucible.

[0040] Comparative Example 1: Using a conical crucible with an inner wall angle β=22°, organic crystals were grown according to the following steps:

[0041] 1. Raw material loading: The organic crystal raw material is loaded into an axisymmetric conical quartz crucible with an inner wall angle of 22°;

[0042] 2. Vacuum sealing: The crucible is evacuated to achieve an internal vacuum level of 1×10⁻⁶. -2 Pa, and then the open end of the crucible is welded and sealed to form a closed growth environment;

[0043] 3. Sealing inspection: The pre-growth treatment is performed on the welded crucible to test its sealing performance; if the pre-grown crystal does not oxidize, the sealing is deemed to meet the requirements.

[0044] 4. Raw material melting: Place a qualified crucible in a Bridgman crystal growth furnace, heat it to a temperature higher than the melting point of the raw material, and hold it at that temperature for 24 hours to completely melt the raw material and form a homogeneous melt;

[0045] 5. Directional growth: The axial temperature gradient inside the furnace is controlled (based on the melting point and crystallization point of terphenyl, the high temperature zone is set to 230℃ and the low temperature zone to 180℃), and the crucible / temperature zone is moved at a speed of 1mm / h. The melt is directionally solidified and grown into organic single crystals from bottom to top along the axial direction.

[0046] 6. Cooling and Shaping: After the crystal growth is completed, it is slowly cooled to room temperature to obtain organic crystals.

[0047] The resulting crystal has many internal cracks and local structural defects, poor overall integrity, and is prone to breakage during subsequent processing. The crystal quality cannot meet the requirements for high-performance applications.

[0048] Example 1: Using a conical crucible with an inner wall angle β = 15°~20°, and selecting the same raw materials and process parameters as in Example 1, organic crystals were grown according to the following steps:

[0049] 1. Raw material loading: The organic crystal raw material is loaded into an axisymmetric conical quartz crucible with an inner wall angle of 15° to 20°;

[0050] 2. Vacuum sealing: Evacuate the crucible to a vacuum level of 1×10⁻⁶. -2 Pa, the welding seal forms a stable and closed growth environment;

[0051] 3. Sealing Inspection: The sealing performance of the ampoules was verified through pre-growth treatment. The specific procedure was as follows: Solid p-terphenyl was used as the raw material and kept at 230℃ for 24 hours until the raw material was fully melted and uniformly mixed. Growth was then carried out at a growth rate of 5-6 mm / h, followed by rapid cooling at a rate of 10-15℃ / min. After cooling, the crystal color and weld seal condition were observed: if the crystal body color was normal and no yellowing was observed, and no crystal precipitation occurred near the weld seal, it indicated good sealing performance, no oxidation of the crystals, and compliance with subsequent growth requirements.

[0052] 4. Raw material melting: Place in a Bridgeman furnace and heat to a temperature higher than the melting point of the raw material, hold for 24 hours until completely melted;

[0053] 5. Directional growth: By controlling the axial temperature gradient and moving the crucible / temperature zone at a speed of 1 mm / h, the melt solidifies directionally from bottom to top.

[0054] 6. Cooling and shaping: Slowly cool to room temperature to obtain high-quality organic single crystals; perform diamond wire cutting on the crystals to obtain crystal slices.

[0055] The resulting organic crystal has a complete overall morphology, a significantly reduced number of internal cracks, and no obvious through cracks. Its structural uniformity and mechanical integrity are far superior to those of Example 1. It is suitable for diamond wire cutting and has excellent processing applicability and practical value.

[0056] Since the optimal included angle range is 15° to 20°, the rate of change of the melt cross-sectional area can be precisely controlled, the flow field and solid-liquid interface can be optimized, the radial temperature gradient can be reduced, crystal defects can be significantly reduced, and crystal quality and processing performance can be improved.

[0057] In summary, the included angle β of the crucible inner wall is the core parameter that determines the growth quality of organic crystals. Controlling it within the preferred range of 15° to 20° can significantly improve the crystal growth environment and achieve large-size, high-quality, and high-stability growth of organic functional crystals. When the included angle deviates from this preferred range, crystal defects increase significantly and the growth quality decreases drastically.

[0058] It should be noted that, in this invention, although the specification describes the embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for growing organic crystals based on the angle control of the inner wall of a crucible, characterized in that, Includes the following steps: S1: A crucible with an axially symmetric conical internal cavity and an included angle β of 15° to 20° between the inner walls of the crucible; S2: After loading the organic crystal raw material into the crucible, vacuum it and seal it; S3: Place the properly sealed crucible into the Bridgman crystal growth furnace, heat and melt it, and keep it at the desired temperature; S4: Adjust the axial temperature gradient inside the furnace to enable directional solidification and growth of the melt; S5: Slowly cool the grown crystal to obtain an organic single crystal.

2. The organic crystal growth method based on crucible inner wall angle control according to claim 1, characterized in that, In step S1, the crucible is made of quartz.

3. The organic crystal growth method based on crucible inner wall angle control according to claim 1, characterized in that, In step S2, the vacuum degree inside the crucible reaches 1 x 10 -2 Pa after vacuumizing.

4. The organic crystal growth method based on crucible inner wall angle control according to claim 1, characterized in that, In step S3, the holding time after the raw material is heated and melted is 24 hours.

5. The organic crystal growth method based on crucible inner wall angle control according to claim 1, characterized in that, In step S4, the melt undergoes directional solidification and growth from bottom to top at a rate of 1 to 1.5 mm / h.

6. The organic crystal growth method based on crucible inner wall angle control according to claim 1, characterized in that, In step S3, after the sealed crucible passes the pre-growth inspection and is sealed, it is then heated and melted.

7. The organic crystal growth method based on crucible inner wall angle control according to claim 1, characterized in that, In step S5, the organic single crystal is an organic scintillation crystal or an organic photoelectric crystal.

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