Growth apparatus and method for obtaining large-size single crystal material based on solvent evaporation

Abstract

This invention belongs to the field of crystal growth technology, specifically relating to a growth apparatus and method for obtaining large-size single-crystal materials based on solvent evaporation. The evaporation crystal grower consists of a solution evaporation tank, a crystal growth tank, and a funnel-shaped structure connecting the solution evaporation tank and the crystal growth tank. The evaporation crystal grower has an internal cavity for holding the growth solution. The solution evaporation tank has an opening at the top, and the crystal growth tank has a seed-fixing groove at the bottom and a plate-shaped cavity inside. The array-type electric heating temperature control device includes heating elements and temperature-sensing elements, which are arranged in a vertical array on the outside of the evaporation crystal grower. Compared with the prior art, the advantages of this invention are: the plate-shaped cavity inside the crystal growth tank provides a growth space for large-size crystals with specific morphologies; the array-type electric heating temperature control device ensures the entire device operates under static conditions, resulting in high stability, easy and unified control of growth conditions, and convenient operation; and the solvent evaporation method ensures high raw material utilization.

Description

Technical Field

[0001] This invention belongs to the field of crystal growth equipment technology, specifically relating to a growth device and method for obtaining large-size single crystal materials based on solvent evaporation. Background Technology

[0002] Potassium dihydrogen phosphate (KH₂PO₄, abbreviated as KDP) crystal is a high-performance nonlinear optical material with advantages such as a large nonlinear optical coefficient, a wide transmission band, high resistance to laser-induced damage, and ease of growing large-diameter single crystals. It is widely used in the laser field. KDP crystal is the only nonlinear optical crystal to date that can be used in inertial confinement fusion (ICF) engineering. Currently, the main growth methods are the traditional cooling method and the rapid growth method.

[0003] Traditional cooling methods involve cooling the growth solution to achieve a supersaturated state, providing the driving force for crystal growth. Under low supersaturation, the crystal grows along the Z-axis of the solvent at a growth rate of 1-2 mm / day, with a growth cycle of 1-2 years for large-size KDP single crystals. This method, with its long growth cycle and reliance on the crystal growth solvent, is not conducive to improving application efficiency. Rapid growth methods, specifically the "seed crystal" rapid growth method, involve rapid cooling to allow the seed crystal to grow omnidirectionally in a highly supersaturated solution environment, with simultaneous expansion of both conical and cylindrical surfaces. The growth rate is 15-20 mm / day. However, rapid growth methods have drawbacks, including the presence of fan-shaped boundaries in the grown crystal. Furthermore, the lattice distortion near the interface between the conical and cylindrical surfaces of the crystal obtained through rapid growth affects the performance of the passing light beam, leading to reduced crystal utilization. While these two methods yield larger-sized KDP-type single crystals, they have the following drawbacks: First, KDP crystals can only expand and grow along regular crystal shapes. When applied to nonlinear crystal devices, they need to be cut along a specific direction to meet phase-matching conditions. However, mechanical equipment such as wire cutting machines can easily cause irreversible damage to the crystal due to heat accumulation during post-processing. Second, within the conventional growth cooling range, the utilization rate of raw materials in the solution is only 39.5% at most, which means that not all raw materials can be used for crystal growth. Therefore, it requires several times the amount of solution compared to the evaporation method, resulting in significant disadvantages in terms of growth container volume and floor space. Third, although the growth rate is improved to some extent in the rapid growth method, the crystal's conical and cylindrical surfaces expand simultaneously. When cutting along the phase-matching direction, it is easy to generate a lot of edge waste, which seriously reduces the crystal utilization rate. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a growth apparatus and method for obtaining large-size single crystal materials based on solvent evaporation. The method uses a self-designed evaporation crystal grower for directional crystal growth, which can obtain KDP crystals along a certain phase-matching direction at a faster speed with a material utilization rate several times that of traditional cooling growth methods. This reduces the footprint of the crystal grower, saves crystal raw materials, avoids subsequent mechanical cutting, and improves crystal yield.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: a growth device for obtaining large-size single crystal materials based on solvent evaporation method, comprising: an evaporation crystal grower and an array-type electric heating temperature control device. The evaporation crystal grower consists of a solution evaporation pool, a crystal growth tank, and a funnel-shaped structure connecting the solution evaporation pool and the crystal growth tank. The evaporation crystal grower has a cavity for holding the growth solution inside. The solution evaporation pool has an opening at the top. The crystal growth tank has a seed fixing tank at the bottom and a plate-shaped cavity inside. The array-type electric heating temperature control device includes: a heating element and a temperature sensing element. The heating element and the temperature sensing element are arranged in a vertical array on the outside of the evaporation crystal grower.

[0006] Preferably, the spacing between the heating element arrays is no more than 3 cm.

[0007] Preferably, the heating element is a polyimide film heater with a width of no more than 2 cm.

[0008] Preferably, the heating element is connected to a DC power supply, the temperature sensing element is connected to a microcomputer via a temperature transmitter, and the DC power supply is connected to the microcomputer.

[0009] Preferably, the temperature sensing element is a thermistor sensor, which is attached to the outside of the heating element.

[0010] Preferably, the opening of the solution evaporation tank is covered with a semi-permeable membrane, the pore size of which is less than 100 nanometers.

[0011] Preferably, the evaporator crystallizer consists of a front plate and a back plate connected by a flange.

[0012] A method for directional growth of single crystals, comprising the following steps:

[0013] S1. Seed crystals with a specific orientation are placed in the seed crystal fixing tank. The front plate and back plate are assembled and sealed by connecting flanges. Heating elements and temperature sensing elements are arranged in an array on the outside of the evaporation crystal grower.

[0014] S2. A saturated solution of crystal material is injected into the solution evaporation tank and a semi-permeable membrane is covered on top. At the same time, the array-type electric heating temperature control device is adjusted according to the actual growth height of the crystal to meet the growth temperature gradient distribution.

[0015] S3. The solution inside the solution evaporation tank gradually decreases until it is completely consumed, providing growth driving force for the seed crystal in the confined crystal growth tank so that it continues to grow. At the same time, the growth space of the seed crystal is confined in a specific direction until it grows into a large single crystal with a special shape. After the growth is completed, the back plate of the evaporation crystal grower is disassembled and separated to finally obtain the large single crystal product required by the customer.

[0016] Preferably, the temperature gradient distribution of the growth process is controlled as follows: the temperature sensing element detects the temperature and sends the measured temperature data to the microcomputer via the RS485 interface using the Modbus RTU protocol. Based on the received temperature data, the microcomputer controls the output voltage of the DC power supply by writing a program, thereby changing the output power of the heating element and ultimately adjusting the temperature distribution.

[0017] Preferably, the temperature distribution to be achieved by the DC power supply control program is as follows: at a position 12-15 cm above the crystal, the temperature corresponding to a supersaturation of -10% to -15% gradually decreases to the temperature corresponding to a supersaturation of 5-10% at the crystal surface.

[0018] Compared with existing technologies, the advantages of this invention are as follows: the crystal growth tank has a plate-shaped cavity inside, providing a space for the growth of large-sized crystals with specific morphologies, eliminating the need for mechanical cutting and reducing the waste of useless crystals; it is equipped with an array-type electric heating temperature control device, ensuring the entire device operates under static conditions, resulting in high stability, easy and unified control of growth conditions, and convenient operation; and it employs a solvent evaporation method, achieving high raw material utilization. This application not only solves the problems existing in traditional crystal growth technologies but also provides a new approach to the growth of large-sized, high-quality crystals with specific morphologies, possessing unique technical advantages and high market competitiveness. Moreover, it has a simple structure, small equipment size, and low production costs. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the evaporation crystallizer and array-type electric heating temperature control device of the present invention;

[0020] Figure 2 This is a schematic diagram of the seed placement groove and growth direction of the present invention.

[0021] In the diagram: 1. Solution evaporation tank, 2. Growth solution, 3. Main body of crystal growth device, 4. Seed crystal, 5. Front plate, 6. Back plate, 7. Crystal growth tank, 8. Funnel-shaped structure, 9. Thin film heater, 10. Thermistor sensor, 11. Temperature transmitter, 12. DC power supply, 13. Microcomputer, 14. Temperature control device, 15. Rectangular groove. Detailed Implementation

[0022] To facilitate understanding of the present invention, it will be described in more detail below with reference to the accompanying drawings and specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0023] A growth apparatus for obtaining large-size single crystal materials based on solvent evaporation includes: an evaporation crystal grower and an array-type electric heating temperature control device 14. The evaporation crystal grower consists of a solution evaporation pool 1 located above, a crystal growth tank 7 located below, and a funnel-shaped structure 8 connecting the solution evaporation pool 1 and the crystal growth tank 7. The evaporation crystal grower has a cavity for holding the growth solution 2 inside. The solution evaporation pool 1 has an opening at the top, and the bottom of the crystal growth tank 7 has a seed fixing groove. The use of the seed fixing groove can ensure the use of specific tangential seeds and has a certain ability to protect the seed crystal 4 from deformation. The crystal growth tank 7 has a plate-shaped cavity inside, which has a restrictive function and can restrict the growth shape of the single crystal material in one or more directions, which is used to obtain unconventional single crystals such as thin sheets, thereby improving production efficiency. The array-type electric heating temperature control device 14 includes: a heating element and a temperature sensing element, which are arranged in a vertical array outside the evaporation crystal grower. The evaporation crystal grower is referenced. Figure 1 Understanding the main body of the crystal growth apparatus.

[0024] In one embodiment, the spacing between the heating element arrays is no more than 3 cm.

[0025] In one embodiment, the heating element is a polyimide film heater 9 with a width not exceeding 2 cm.

[0026] In one embodiment, the heating element is connected to a DC power supply 12, the temperature sensing element is connected to a microcomputer 13 via a temperature transmitter 11, and the DC power supply 12 is connected to the microcomputer 13.

[0027] In one embodiment, the temperature sensing element is a thermistor sensor 10, which is attached to the outside of the heating element.

[0028] In one embodiment, the opening of the solution evaporation tank 1 is covered with a semi-permeable membrane with a pore size of less than 100 nanometers. This ensures that solvent molecules evaporate and escape while preventing external environmental disturbances to the growth solution 2, thereby improving the stability of the growth process.

[0029] In one embodiment, the evaporation crystal grower consists of a front plate 5 and a back plate 6 connected by a flange. It can be interconnected with the G-shaped clamp and the back plate 6 via a silicone sealing strip, and can be disassembled independently, ensuring an independent and stable crystal growth environment and reducing difficulties during crystal assembly and disassembly.

[0030] A method for directional growth of single crystals, comprising the following steps:

[0031] S1. Seed crystals 4 with a specific orientation are placed in the seed crystal fixing groove. The front plate 5 and the back plate 6 are assembled and sealed by connecting flanges. Heating elements and temperature sensing elements are arranged in an array on the outside of the evaporation crystal grower.

[0032] S2. A saturated solution of crystal material is injected into the solution evaporation tank 1 and a semi-permeable membrane is covered on top. At the same time, the array-type electric heating temperature control device 14 is adjusted according to the actual growth height of the crystal to meet the growth temperature gradient distribution.

[0033] S3. The solution inside the solution evaporation tank 1 gradually decreases until it is completely consumed, providing growth driving force for the seed crystal 4 in the confined crystal growth tank 7 so that it continues to grow. At the same time, the growth space of the seed crystal 4 is confined in a specific direction until it grows into a large single crystal with a special shape. After the growth is completed, the back plate 6 of the evaporation crystal grower is disassembled and separated to finally obtain the large single crystal product required by the customer.

[0034] In one embodiment, the temperature gradient distribution of the growth process is controlled as follows: the temperature sensing element detects the temperature and sends the measured temperature data to the microcomputer 13 via the RS485 interface using the Modbus RTU protocol. Based on the received temperature data, the microcomputer 13 controls the output voltage of the DC power supply 12 by writing a program, thereby changing the output power of the heating element and ultimately adjusting the temperature distribution. This ensures the stability of the growth driving force in the crystal growth environment, reduces the probability of spontaneous nucleation in the solution, and promotes the transport of solute raw materials in the solution to the crystal surface, ensuring that the crystal grows with high quality and complete growth morphology.

[0035] In one embodiment, the DC power supply 12 control program needs to achieve a temperature distribution that gradually decreases from the temperature corresponding to a supersaturation of -10% to -15% at a distance of 12-15 cm above the crystal to the temperature corresponding to a supersaturation of 5-10% at the crystal surface. This temperature distribution can better improve the crystal growth rate and ensure the success rate of crystal growth.

[0036] In this application, multiple polyimide thin-film heaters 9 are arranged in an array outside the evaporation crystal grower and controlled by a DC power supply 12. Each heater is equipped with an NTC10K thermistor sensor 10 and sends temperature data to a microcomputer 13 through a temperature transmitter 11. The microcomputer 13 controls the output of the DC power supply 12 according to the temperature data to change the temperature gradient formed by the heater, thereby controlling the growth driving force distribution, which is beneficial to efficiently obtain a large number of large-size KDP single crystals.

[0037] When using the growth apparatus of this application, the ratio of the cross-sectional area of ​​the solution evaporation tank 1 to the cross-sectional area of ​​the confined crystal growth tank 7 needs to be determined by the solution evaporation rate at the current temperature, so that the replenishment and consumption rate of supersaturation are reasonably configured, ensuring that the growth driving force inside the solution is within a relatively stable range, and effectively improving the growth rate and quality uniformity of the crystal.

[0038] Example 1: Combination Figure 1 Understanding the growth apparatus for obtaining large-size single-crystal materials based on solvent evaporation.

[0039] Solution evaporation tank 1, which is filled with growth solution 2;

[0040] The crystal growth device body 3 has seed crystals 4 installed on the flat groove at the bottom for growth; the crystal growth device body 3 is detachably connected by a front plate 5 and a back plate 6.

[0041] The main body 3 of the crystal growth device can be divided into a growth solution evaporation tank 1 and a confined crystal growth tank 7 due to the difference in longitudinal height. They are connected in the middle by a funnel-shaped structure 8 that gradually tapers. Multiple polyimide thin film heaters 9 are connected to the main body 3 of the crystal growth device and form an array-type electric heating temperature control device 14 consisting of an NTC10K thermistor sensor 10, a temperature transmitter 11, a DC power supply 12, and a microcomputer 13.

[0042] Working principle: When using this invention, the seed crystal 4 for growth is placed on the main body 3 of the growth device. The polyimide thin film heater 9 is connected to the DC power supply 12 for power supply and is attached to the outer surface of the confined crystal growth tank 7 and the bottom of the growth solution evaporation tank 1, forming an array with the same intervals from low to high. An NTC10K thermistor sensor 10 is attached to the outside of each heater and connected to the temperature transmitter 11 through a wire and connected to the microcomputer 13 through an RS485 to USB cable. The NTC10K thermistor sensor 10 can obtain the temperature of the polyimide thin film heater 9 and feed it back to the microcomputer 13 in a timely manner. The microcomputer 13 controls the output voltage of the DC power supply 12 through the serial port according to the real-time temperature data and the height of the crystal, so that there is a temperature distribution that gradually increases from the bottom to the top inside the evaporation crystal grower, thereby forming a supersaturation gradient, promoting the transport of crystal growth raw materials, and allowing the seed crystal 4 to start growing.

[0043] In the above technical solution, a rectangular groove 15 for placing the seed crystal 4 is provided at the bottom center of the front plate 5 and the back plate 6 of the crystal growth body, that is, the seed crystal fixing groove; the rectangular groove 15 has a width of 2mm and a depth of 2mm.

[0044] Working principle: When using this invention, the rectangular groove 15 ensures that the placement position of the seed crystal 4 is more accurate and stable; the seed crystal 4 is accurately placed in the rectangular groove 15, and after placement is completed, the front plate 5 and the back plate 6 of the crystal growth device are connected and sealed by a flange.

[0045] The above technical solution includes a directional growth method to improve the growth quality and utilization rate of large-size KDP single crystals, the specific process of which includes:

[0046] Step 1: Prepare a growth solution 2 with a mass fraction of 24.5% by mixing KH2PO4 powder raw material (analytical grade) and high-purity deionized water (resistivity >17.5MΩ / cm) as solvent. Filter the growth solution 2 using commercially available 0.1μm and 0.05μm polyethersulfone resin microporous filter membranes and a double-layer flat plate filter, and perform a superheat treatment at a temperature 15°C above the saturation point for 24 hours.

[0047] Step 2: Place the seed crystal 4 in the rectangular groove 15 at the bottom of the front plate 5 and the back plate 6. After accurately fixing it, connect the front plate 5 and the back plate 6 with a flange to assemble the crystal growth device body 3. Use an array-type electric heating temperature control device 14, consisting of a polyimide thin film heater 9, an NTC10K thermistor sensor 10, a temperature transmitter 11, a DC power supply 12, and a microcomputer 13, to preheat the crystal growth device body 5 until the seed crystal 4 is preheated to a stable state at a temperature 1°C higher than the set saturation point and maintained for at least 24 hours.

[0048] Step 3: Transfer the growth solution 2 to the solution evaporation tank 1, and adjust the temperature of the polyimide film heater 9 at the bottom of the funnel-shaped solution evaporation tank 1 by the microcomputer 13, so that the growth solution 2 is raised to 6°C above the saturation temperature and begins to evaporate to obtain the growth driving force. The seed crystal 4 grows in a two-dimensional direction in a controlled and stable manner at a certain speed in the confined crystal growth tank 7.

[0049] Step 4: Record and calculate the lateral and longitudinal dimensions of the seed crystal 4. Adjust the temperature of each polyimide film heater 9 according to the actual height of the seed crystal 4. Keep the polyimide film heater 9 at the bottom of the growth solution evaporation tank 1 at 42°C, reduce the polyimide film heater 9 near the crystal surface to 36°C, and set the polyimide film heater 9 at the middle height to have its temperature decrease uniformly from top to bottom according to the gradient. The crystal growth rate should be controlled at 10 mm / day.

[0050] Step 5: After the seed crystal 4 grows to the expected size, the temperature of all polyimide film heaters 9 is slowly reduced at a rate of 0.1℃ / h by the microcomputer 13. Once the temperature reaches ambient temperature, the G-shaped clamps on the outer flange of the crystal growth apparatus body 3 are removed, allowing the front plate 5 and back plate 6 to be disassembled and separated. The seed crystal 4 can then be removed from the growth apparatus body 3, ultimately yielding a 400*400*12mm crystal. 3 Large-sized, thin-film KDP crystals grown along a specific direction.

[0051] Traditional methods for producing 400*400*12mm 3 Large-aperture KDP crystals used in second harmonic converters require a raw material solution weighing over 1790 kg. This design reduces the raw material solution requirement to 35.9 kg. The method described in this application achieves near 100% raw material utilization, rapidly producing large-size oriented crystals that expand and grow along a specific phase-matching direction. This results in faster growth rates and higher utilization rates for large-size KDP crystals while avoiding damage during subsequent machining, thereby increasing crystal yield, shortening the growth cycle, and significantly reducing growth costs. This approach possesses considerable industrial production value and economic benefits.

[0052] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A growth apparatus for obtaining large-size single-crystal materials based on solvent evaporation, characterized in that, include: Evaporation crystallizer and array-type electric heating temperature control device, The evaporation crystal grower consists of a solution evaporation tank, a crystal growth tank, and a funnel-shaped structure connecting the solution evaporation tank and the crystal growth tank. The evaporation crystal grower has a cavity for holding the growth solution inside. The solution evaporation tank has an opening at the top, and the crystal growth tank has a seed fixing groove at the bottom and a plate-shaped cavity inside. The array-type electric heating temperature control device includes: heating elements and temperature sensing elements, the heating elements and the temperature sensing elements are arranged in a vertical array on the outside of the evaporation crystallizer; the interval between the array of heating elements is no more than 3cm; the heating elements are polyimide thin film heaters with a width of no more than 2cm.

2. The growth apparatus for obtaining large-size single crystal materials based on solvent evaporation method according to claim 1, characterized in that, The heating element is connected to a DC power supply, and the temperature sensing element is connected to a microcomputer via a temperature transmitter. The DC power supply is connected to the microcomputer.

3. The growth apparatus for obtaining large-size single crystal materials based on solvent evaporation method according to claim 2, characterized in that, The temperature sensing element is a thermistor sensor, which is attached to the outside of the heating element.

4. The growth apparatus for obtaining large-size single crystal materials based on solvent evaporation method according to claim 1, characterized in that, The opening of the solution evaporation tank is covered with a semi-permeable membrane, the pore size of which is less than 100 nanometers.

5. The growth apparatus for obtaining large-size single crystal materials based on solvent evaporation method according to claim 1, characterized in that, The evaporation crystallizer consists of a front plate and a back plate connected by a flange.

6. A method for directional growth of single crystals using a growth apparatus for obtaining large-size single crystal materials based on solvent evaporation as described in any one of claims 1-5, characterized in that, The steps are as follows: S1. Seed crystals with a specific orientation are placed in the seed crystal fixing tank. The front plate and back plate are assembled and sealed by connecting flanges. Heating elements and temperature sensing elements are arranged in an array on the outside of the evaporation crystal grower. S2. A saturated solution of crystal material is injected into the solution evaporation tank and a semi-permeable membrane is covered on top. At the same time, the array-type electric heating temperature control device is adjusted according to the actual growth height of the crystal to meet the growth temperature gradient distribution. S3. The solution inside the solution evaporation tank gradually decreases until it is completely consumed, providing growth driving force for the seed crystal in the confined crystal growth tank so that it continues to grow. At the same time, the growth space of the seed crystal is confined in a specific direction until it grows into a large single crystal with a special shape. After the growth is completed, the back plate of the evaporation crystal grower is disassembled and separated to finally obtain the large single crystal product required by the customer.

7. The method for directional growth of single crystals according to claim 6, characterized in that, Control of growth temperature gradient distribution: The temperature sensing element detects the temperature and sends the measured temperature data to the microcomputer via the RS485 interface using the Modbus RTU protocol. Based on the received temperature data, the microcomputer controls the DC power supply output voltage through a program, thereby changing the output power of the heating element and ultimately regulating the temperature distribution.

8. The method for directional growth of single crystals according to claim 7, characterized in that, The DC power supply control program needs to achieve the following temperature distribution: at a distance of 12-15cm above the crystal, the temperature gradually decreases from the temperature corresponding to the supersaturation of -10% to -15% to the temperature corresponding to the supersaturation of 5-10% at the crystal surface.

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