A method and fixture for directional zone growth of halide crystals

Abstract

The application discloses a method and a clamp applied to directional zone melting growth of halide crystals, the clamp comprising a quartz plug embedded in the end of a crystal growth container, a circular through hole in the inside of the quartz plug and a seed crystal placing tube embedded in the circular through hole, the axis of the quartz plug and the seed crystal placing tube being coincident, the left side of the seed crystal placing tube being closed and the inside center of the seed crystal placing tube being provided with a seed crystal and a threaded rod connected with the seed crystal through a sleeve, the upper and lower sides of the seed crystal placing tube being respectively screw-connected with first adjustable knobs for adjusting the upper and lower positions of the seed crystal, the end of each of the two first adjustable knobs being fixedly provided with an arc-shaped clamping piece for clamping the seed crystal, the lower side of the seed crystal placing tube being screw-connected with a second adjustable knob for supporting and adjusting the upper and lower positions of the threaded rod, and the threaded rod adjusting the front and back positions of the seed crystal through a transmission device. The application improves the stability and adjustability of clamping the seed crystal, enhances the matching degree of the seed crystal and crystal growth raw materials, and thus improves the seeding effect of the seed crystal.

Description

Technical Field

[0001] This invention relates to the field of halide crystal growth and preparation, and in particular to a method and fixture for directional zone melting growth of halide crystals. Background Technology

[0002] Currently, the main methods for growing halide crystals in China are the crucible lowering method, the Czochralski method, and the zone melting method. The crucible lowering method involves crystal growth in a closed environment, which prevents the placement of seed crystals, resulting in a low single crystal yield and a long growth cycle. The Czochralski method can improve the single crystal yield and optical uniformity by placing seed crystals, but the liquid flow of the melt, vibrations of the transmission device, and temperature fluctuations all affect the crystal quality. Furthermore, the crucible cannot be sealed during growth, leading to easy oxidation and volatilization of the halide material, causing contamination of the instrument. The zone melting method, by adjusting the equipment, allows for the placement of seed crystals, improving the single crystal yield and ensuring halide crystal growth in a closed environment, while also shortening the crystal growth cycle.

[0003] In zone melting directional growth apparatus for halide crystals, the seed crystal is typically placed at one end of a quartz boat or crucible and secured using binding or pin structures to achieve crystal attraction. Chinese utility model patent CN214422780U discloses a zone melting seed crystal clamp. This clamp, designed with a seed crystal holder, inner shaft, cylindrical cavity, internal threads, and external threads, improves the stability of seed crystal connection. However, this seed crystal placement method makes it difficult to adjust the seed crystal position and replace seed crystals of different sizes. It is also difficult to fix the seed crystal in a position that perfectly matches the growth material. Furthermore, impurities are easily introduced during crystal attraction, reducing the purity of the raw material and resulting in poor crystal quality.

[0004] The Chinese invention patent application publication number CN109402724A discloses an undoped and Eu... 2+ The paper describes a directional zone melting growth apparatus and method for doped strontium iodide crystals. It mentions that a seed crystal inoculation process can be used, but does not describe the seed crystal fixing method or mention the seed crystal fixing device. The attached diagram shows that a seed crystal is added to one end of the quartz boat but is not fixed. This method of placing the seed crystal makes it difficult to play a role in crystal attraction. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method and fixture for directional zone melting growth of halide crystals. The method involves placing the seed crystal using a combination structure of a quartz plug and a seed crystal placement tube, which forms a sealed space with the crystal growth container, isolating it from external contact and preventing the deliquescence and oxidation of the raw material, thus ensuring the purity of the raw material. At the same time, it facilitates the movement of the raw material and the high-temperature heating treatment in the early stage, effectively reducing the time required for preparation work before crystal growth, improving the stability and adjustability of the seed crystal clamping, enhancing the compatibility between the seed crystal and the crystal growth raw material, and thus improving the seed crystal attraction effect.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a fixture for directional zone melting growth of halide crystals, including a quartz plug embedded in the end of a crystal growth container, the inner side of the quartz plug having a circular through hole and a seed crystal placement tube embedded in the circular through hole, the axes of the quartz plug and the seed crystal placement tube being coincident, the left side of the seed crystal placement tube being closed and a seed crystal and a threaded rod connected to the seed crystal through a sleeve being placed in the center of the inner side of the seed crystal placement tube (3), the upper and lower sides of the seed crystal placement tube being threadedly connected with first adjustable knobs for adjusting the upper and lower positions of the seed crystal, the ends of the two first adjustable knobs being fixedly provided with arc-shaped clamping pieces for clamping the seed crystal, the lower side of the seed crystal placement tube being threadedly connected with a second adjustable knob for supporting and adjusting the upper and lower positions of the threaded rod, and the threaded rod adjusting the front and rear positions of the seed crystal through a transmission device.

[0007] A further improvement of the technical solution of the present invention is that: the outer 1 / 3-1 / 2 and inner 1 / 2 of the left end of the quartz plug are provided with O-shaped radial grooves, and fluororubber O-rings for sealing are placed in the grooves.

[0008] A further improvement of the technical solution of the present invention is that: an O-shaped radial groove is provided at 1 / 3-1 / 2 of the inner side of the left end of the seed crystal placement tube, and a fluororubber O-ring for fixing the seed crystal is placed in the groove.

[0009] A further improvement of the technical solution of the present invention is that the fluororubber O-ring is made of a high-temperature resistant material.

[0010] A further improvement of the technical solution of the present invention is that the arc-shaped clip is made of ceramic or quartz material.

[0011] A further improvement to the technical solution of the present invention is that the seed crystal placement tube is a ceramic tube or a quartz tube.

[0012] A further improvement of the technical solution of the present invention is that: the transmission device includes a vertical bevel gear that is threadedly connected to the threaded rod, the vertical bevel gear meshing with a horizontal bevel gear, the horizontal bevel gear being fixedly connected to a third adjustable knob, and the third adjustable knob being threadedly connected to the seed crystal placement tube.

[0013] A further improvement of the technical solution of the present invention is that: the transmission device includes a connecting rod movably connected to the end of the threaded rod, and the other end of the connecting rod is movably connected to a vertical moving rod, which moves vertically through the seed crystal placement tube and is locked by a fixing nut.

[0014] A further improvement of the technical solution of the present invention is that: there is at least one second adjustable knob, and the end of the second adjustable knob is an arc surface adapted to the thread of the threaded rod.

[0015] A further improvement to the technical solution of the present invention is: a method for directional zone melting growth of halide crystals, comprising the following steps:

[0016] S1. In a vacuum glove box, thoroughly mix the growth material with anhydrous purity of 99.99%, load it into the crystal growth container, and seal it.

[0017] S2. The crystal growth container containing the raw material is clamped on a high-power resistance wire heater and heated to 100-150°C above the melting point of the raw material. After the raw material is melted, it is cooled to room temperature. The raw material forms a polycrystalline ingot with a reduced volume, and excess voids are generated in the crystal growth container.

[0018] S3. Put an appropriate amount of raw material into the vacuum glove box again and repeat the operation of step S2 until the gap left in the growth container can be used to place the quartz plug.

[0019] S4. After placing the corresponding size fluororubber O-ring in the radial groove of the O-ring on the outside of the quartz plug, press it inward at the opening of the crystal growth container to seal it.

[0020] S5. Place a fluororubber O-ring of the corresponding size in the radial groove of the O-ring inside the quartz plug, and nest the seed crystal placement tube into the inner hole of the quartz plug.

[0021] S6. Place a fluororubber O-ring of the corresponding size in the radial groove of the O-ring inside the seed crystal placement tube, place the seed crystal into the seed crystal placement tube, pass through the fluororubber O-ring set inside the seed crystal placement tube, and extend into the crystal growth container.

[0022] S7. Based on the size of the seed crystal, first adjust the second adjustable knob to coarsely adjust the up and down position of the seed crystal, then adjust the front and back position of the seed crystal through the transmission device, and finally adjust the position of the first adjustable knob and the arc-shaped clamping piece to finely adjust the up and down position of the seed crystal so that the other end of the seed crystal just touches the raw material.

[0023] S8. Place the crystal growth container with the seed crystal in the quartz glass furnace tube and fix it in place. Vacuum the quartz glass furnace tube or introduce an inert or iodine-containing protective gas.

[0024] S9. Activate the moving temperature field as a heating device, so that the temperature of the melting zone is 100-200℃ higher than the melting point of the raw material, and the temperature of the preheating zone and crystallization zone is 50-100℃ lower than the melting point of the raw material. The width of the melting zone is 20-100mm. Set the stepper motor control program to move the moving temperature field from one end of the crystal growth container and the fixture to the other end to carry out directional zone melting growth of the crystal.

[0025] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0026] 1. The clamping structure of the present invention is simple and highly adaptable. It can be placed horizontally or vertically. In addition to directional zone melting, it can also be used for the preparation of halide crystals by the Czochralski method. It improves the stability and adjustability of the seed crystal, enhances the compatibility between the seed crystal and the crystal growth raw material, and thus improves the seed crystal's crystal attraction effect.

[0027] 2. This invention uses a combination structure of a quartz plug and a seed crystal placement tube to place the seed crystal, which can protect the seed crystal and hold seed crystals of different sizes to grow halide crystals of different sizes. At the same time, the position of the seed crystal can be flexibly adjusted. First, the second adjustable knob is adjusted to make a coarse adjustment of the vertical position of the seed crystal. Then, the front and back position of the seed crystal is adjusted through a transmission device. Finally, the position of the first adjustable knob and the arc-shaped clamping piece is adjusted to make a fine adjustment of the vertical position of the seed crystal. This puts the seed crystal in the optimal position for compatibility with the growth raw material, and can better improve the use of the seed crystal for crystal introduction to eliminate misalignment and defects, thereby improving the crystal orientation growth and increasing the single crystal rate of crystal growth.

[0028] 3. After the seed crystal is placed in, the fixture and the crystal growth container can form a sealed space, isolating it from external contact, avoiding the deliquescence and oxidation of the raw material, and ensuring the purity of the raw material; at the same time, it facilitates the movement of the raw material and the high-temperature heating treatment in the early stage, effectively reducing the time required for preparation work before crystal growth.

[0029] 4. This invention allows for multiple feedings before the crystal begins to grow. Since the initial raw material is powder, its volume decreases after melting, causing the crystal growth interface to tilt and preventing contact with the seed crystal, leading to crystal growth failure. In the first melting, cooling yields a crystalline solid with reduced volume. Powdered raw material is then added again, and the melting-crystallization process continues until the growth interface is no longer tilted. This process is then stopped, greatly improving the effectiveness of the seed crystal. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the clamp structure for the first type of transmission device of the present invention;

[0031] Figure 2 This is a schematic diagram of the clamp structure of the second type of transmission device of the present invention;

[0032] Figure 3 This is a schematic diagram of the seed crystal placement tube structure of the present invention;

[0033] Figure 4 This is a schematic diagram of the quartz plug structure of the present invention;

[0034] Figure 5 This is a schematic diagram of the growth device structure for the application of the fixture of this invention;

[0035] Among them, 1. Crystal growth container, 2. Quartz plug, 3. Seed crystal placement tube, 4. Seed crystal, 5. First adjustable knob, 6. Arc-shaped clamp, 7. Fluororubber O-ring, 8. Sleeve, 9. Threaded rod, 10. Vertical bevel gear, 11. Horizontal bevel gear, 12. Second adjustable knob, 13. Third adjustable knob, 14. Connecting rod, 15. Vertical moving rod, 16. Fixing nut; 17. Stepper motor, 18. Roller screw platform, 19. Moving temperature field, 20. Lifting bracket, 21. Lightweight insulation material, 22. Quartz glass furnace tube, 23. Flange, 24. Thermocouple. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to embodiments:

[0037] like Figures 1 to 4 As shown, a fixture for directional zone melting growth of halide crystals includes a crystal growth container 1. Since some halide crystals have low melting points, are prone to deliquescence and oxidation, a transparent quartz tube can be used as the crystal growth container 1 during directional zone melting crystallization. This is beneficial for dynamic or real-time observation of the crystal growth process. Crystal growth can be carried out in an inert or reactive atmosphere, or in a vacuum.

[0038] A quartz plug 2 is embedded at the end of the crystal growth container 1. The quartz plug 2 can be processed into different sizes to correspond to different crystal growth containers 1. O-shaped radial grooves are provided at the outer 1 / 3-1 / 2 and inner 1 / 2 of the left end of the quartz plug 2, and fluororubber O-rings 7 are placed in the grooves for sealing. The inner side of the quartz plug 2 is a circular through hole, and a seed crystal placement tube 3 is embedded in the circular through hole. The seed crystal placement tube 3 is a ceramic tube or quartz tube with high temperature resistance and strong structural stability, which effectively avoids the problem of material volatilization contaminating the crystal during the heating process. The axes of the quartz plug 2 and the seed crystal placement tube 3 coincide. The left side of the seed crystal placement tube 3 is closed, and the seed crystal 4 is placed in the center of the inner side of the seed crystal placement tube (3). The seed crystal 4 is located in the center of the seed crystal placement tube 3. Whether placed horizontally or vertically, it can play a good crystal pulling effect. A threaded rod 9 connected to the seed crystal 4 through a sleeve 8 is also provided in the seed crystal placement tube 3.

[0039] The seed crystal placement tube 3 has an O-shaped radial groove on the inner side of the left end at 1 / 3-1 / 2, and a fluororubber O-ring 7 for fixing the seed crystal 4 is placed in the groove. The seed crystal 4 passes through the fluororubber O-ring 7 and extends into the crystal growth container 1, with a gap between the seed crystal 4 and the fluororubber O-ring 7. The fluororubber O-ring 7 is made of high-temperature resistant material (2500℃) and can remain stable in high-temperature environments. At the same time, the fluororubber O-ring 7 can be processed into different sizes to meet the requirements of nesting and fixing the seed crystal 4. The seed crystal placement tube 3 has first adjustable knobs 5 threaded to the upper and lower sides to adjust the vertical position of the seed crystal 4. The ends of the two first adjustable knobs 5 are fixedly provided with arc-shaped clamping pieces 6 for clamping the seed crystal 4. The arc-shaped clamping pieces 6 are made of high-purity ceramic or quartz. The seed crystal placement tube 3 is threadedly connected to a second adjustable knob 12 that supports and adjusts the vertical position of the threaded rod 9. There is at least one second adjustable knob 12, and the end of the second adjustable knob 12 is an arc surface adapted to the thread of the threaded rod 9. The threaded rod 9 adjusts the front and rear position of the seed crystal 4 through a transmission device.

[0040] The transmission device in this invention has the following two structures:

[0041] The first type of transmission device structure includes a vertical bevel gear 10 threadedly connected to a threaded rod 9. The vertical bevel gear 10 meshes with a horizontal bevel gear 11. The horizontal bevel gear 11 is fixedly connected to a third adjustable knob 13. The third adjustable knob 13 is threadedly connected to a seed crystal placement tube 3. According to the length of the seed crystal 4, the third adjustable knob 13 is adjusted on the outside. The horizontal bevel gear 11 drives the vertical bevel gear 10 to rotate, thereby changing the front and rear position of the threaded rod 9. Thus, the threaded rod 9 drives the adjustment of the front and rear position of the seed crystal 4.

[0042] The second type of transmission device includes a connecting rod 14 movably connected to one end of the threaded rod 9. The other end of the connecting rod 14 is movably connected to a vertical moving rod 15. The vertical moving rod 15 moves vertically through the seed crystal placement tube 3 and is locked by a fixing nut 16. Depending on the length of the seed crystal, the vertical moving rod 15 is pulled or pressed from the outside, thereby changing the position of the threaded rod 9 by driving the connecting rod 14, thus changing the front and rear position of the seed crystal 4. After adjustment, the position of the vertical moving rod 15 is fixed by the fixing nut 16.

[0043] This invention uses a combination structure of a quartz plug 2 and a seed crystal placement tube 3 to place the seed crystal 4, which can protect the seed crystal 4 and hold seed crystals of different sizes to grow halide crystals of different sizes. At the same time, the position of the seed crystal 4 can be flexibly adjusted. First, the second adjustable knob 12 is adjusted to make a coarse adjustment of the vertical position of the seed crystal 4. Then, the front and back position of the seed crystal 4 is adjusted through a transmission device. Finally, the position of the first adjustable knob 5 and the arc-shaped clamp 6 is adjusted to make a fine adjustment of the vertical position of the seed crystal 4, so that the other end of the seed crystal 4 just touches the raw material. The purpose of this is to put the seed crystal 4 in the position with the optimal compatibility with the growth raw material, which can better improve the use of the seed crystal for crystal attraction to eliminate misalignment and defects, thereby better promoting crystal directional growth and improving the single crystal rate of crystal growth.

[0044] Figure 5 The diagram shows a schematic of the growth apparatus structure for the fixture application of the present invention, which is existing technology. The growth apparatus includes a lifting support 20 supporting a quartz glass furnace tube 22, and a ball screw platform 18 controlled by a stepper motor 17. The rotation of the ball screw drives the ball screw platform 18 to move back and forth. A moving temperature field 19 is fixed on the ball screw platform 18, and its movement speed is controlled by the stepper motor 17. Both ends of the quartz glass furnace tube 22 are sealed by flanges 23, forming a closed space that can be filled with inert gas. The crystal growth container 1 is placed inside the quartz glass furnace tube 22.

[0045] A method for directional zone melting growth of halide crystals includes the following steps:

[0046] S1. In a vacuum glove box, thoroughly mix the growth material with anhydrous purity of 99.99%, load it into crystal growth container 1, and seal it.

[0047] S2. The crystal growth container 1 containing the raw material is clamped on a high-power resistance wire heater and heated to 100-150°C above the melting point of the raw material. After the raw material is melted, it is cooled to room temperature. The raw material forms a polycrystalline ingot with a reduced volume, and excess voids are generated in the crystal growth container 1.

[0048] S3. Put an appropriate amount of raw material into the vacuum glove box again and repeat the operation of step S2 until the gap left in the growth container 1 can be used to place the quartz plug 2.

[0049] S4. After placing the fluororubber O-ring 7 of the corresponding size in the radial groove of the O-ring on the outside of the quartz plug 2, press it inward at the opening of the crystal growth container 1 to seal it.

[0050] S5. Place a fluororubber O-ring 7 of the corresponding size in the radial groove of the O-ring inside the quartz plug 2, and nest the seed crystal placement tube 3 into the inner hole of the quartz plug 2.

[0051] S6. Place a fluororubber O-ring 7 of the corresponding size in the radial groove of the O-ring inside the seed crystal placement tube 3, place the seed crystal 4 into the seed crystal placement tube 3, pass through the fluororubber O-ring 7 set inside the seed crystal placement tube 3, and extend into the crystal growth container 1.

[0052] S7. Based on the size of the seed crystal 4, first adjust the second adjustable knob 12 to make a coarse adjustment of the up and down position of the seed crystal 4, then adjust the front and back position of the seed crystal 4 through the transmission device, and finally adjust the position of the first adjustable knob 5 and the arc-shaped clamp 6 to finely adjust the up and down position of the seed crystal 4 so that the other end of the seed crystal 4 just touches the raw material.

[0053] S8. Place the crystal growth container 1 with the seed crystal 4 in the quartz glass furnace tube and fix it. Vacuum the quartz glass furnace tube or introduce an inert or iodine-containing protective gas.

[0054] S9. Activate the moving temperature field as a heating device, so that the temperature of the melting zone is 100-200℃ higher than the melting point of the raw material, and the temperature of the preheating zone and crystallization zone is 50-100℃ lower than the melting point of the raw material. The width of the melting zone is 20-100mm. Set the stepper motor control program to move the moving temperature field from one end of the crystal growth container and the fixture to the other end to carry out directional zone melting growth of the crystal.

[0055] This invention allows for multiple feedings before the actual crystal growth. Since the initial raw material is powder, its volume decreases after melting, causing the crystal growth interface to tilt and preventing contact with the seed crystal, leading to crystal growth failure. In the first melting, cooling yields a reduced-volume crystalline solid. Powdered raw material is then added again, and the melting-crystallization process continues until the growth interface is no longer tilted. This process is then stopped, significantly improving the effectiveness of the seed crystal. After the seed crystal is placed, the fixture and crystal growth container form a sealed space, isolating it from external contact and preventing deliquescence and oxidation of the raw material, thus ensuring its purity. Simultaneously, it facilitates the movement of the raw material and the initial high-temperature heating treatment, effectively reducing the time required for preparation before crystal growth.

[0056] Example 1

[0057] The process for preparing undoped NaI crystals via directional zone melting crystallization includes the following steps:

[0058] First, NaI with a purity ≥ 99.99% is loaded into a crystal growth container 1 with a length of 80 mm, a diameter of 20 mm, and a thickness of 1 mm in a vacuum glove box.

[0059] The crystal growth container 1 containing the raw material is clamped on a high-power resistance wire heater. After heating to melt the raw material, it is cooled to room temperature. The raw material will form a polycrystalline ingot, which will reduce its volume and generate excess voids in the container.

[0060] A quartz plug 2 with an outer diameter of 19.5 mm is selected and coupled to the crystal growth container 1. The seed crystal fixture is assembled, and a square bar-shaped seed crystal of 2 mm × 2 mm × 60 mm is placed in the seed crystal placement tube 3. First, the second adjustable knob 12 is adjusted to make a coarse adjustment of the up and down position of the seed crystal 4. Then, the front and back position of the seed crystal 4 is adjusted through the transmission device. Finally, the position of the first adjustable knob 5 and the arc-shaped clamp 6 are adjusted to make a fine adjustment of the up and down position of the seed crystal 4 so that the other end of the seed crystal 4 just touches the raw material.

[0061] After placing the seed crystal at the port of crystal growth container 1, it is placed in a horizontally positioned quartz glass furnace tube 22 with an inner diameter of 67.86 mm, a length of 1300 mm, and a thickness of 6 mm. The vacuum pump is then turned on to evacuate the quartz glass furnace tube 22 to a vacuum level of 1 × 10⁻⁶. - 2 Pa.

[0062] The moving temperature field 19 is moved to the end where the crystal growth container 1 contacts the fixture. The heating system is turned on, and the temperature is raised to the melting zone temperature of 700°C, so that the raw material in contact with the seed crystal 4 is fully melted, and the temperature of the crystallization zone is maintained at 550°C. The control program of the stepper motor 17 is set so that the melting zone moves from one end of the crystal growth container 1 to the other end at a speed of 2 mm / h. The crystal in the crystal growth container 1 enters the area of ​​the lightweight insulation material 21. The program is set to cool down and perform in-situ annealing of the crystal, so that a complete crystal with the same shape as the crystal growth container 1 can be obtained.

[0063] Example 2

[0064] The process for preparing Tl-doped NaI crystals via directional zone melting crystallization includes the following steps:

[0065] First, in a vacuum glove box, NaI and TlI raw materials with a purity ≥99.99% are thoroughly mixed at a ratio of 250:1, and then placed into a crystal growth container 1 with a length of 100mm, a diameter of 30mm, and a thickness of 1mm.

[0066] The crystal growth container 1 containing the raw material is clamped on a high-power resistance wire heater. After heating to melt the raw material, it is cooled to room temperature. The raw material will form a polycrystalline ingot, which will reduce its volume and generate excess voids in the container.

[0067] A quartz plug 2 with an outer diameter of 29.5 mm is selected and coupled to the crystal growth container 1. The seed crystal fixture is assembled, and a 3 mm × 3 mm × 60 mm square bar seed crystal is placed in the seed crystal placement tube 3. First, the second adjustable knob 12 is adjusted to make a coarse adjustment of the up and down position of the seed crystal 4. Then, the front and back position of the seed crystal 4 is adjusted through the transmission device. Finally, the position of the first adjustable knob 5 and the arc-shaped clamp 6 are adjusted to make a fine adjustment of the up and down position of the seed crystal 4 so that the other end of the seed crystal 4 just touches the raw material.

[0068] A seed crystal is placed at the port of crystal growth container 1, ensuring good contact between the seed crystal and the ingot. It is then placed in a horizontally positioned quartz glass furnace tube 22 with an inner diameter of 67.86 mm, a length of 1300 mm, and a thickness of 6 mm. The vacuum pump is then activated to evacuate the quartz glass furnace tube 22 to a vacuum level of 1 × 10⁻⁶. -2 Pa.

[0069] The moving temperature field 19 is moved back to the end where the crystal growth container 1 contacts the fixture. The heating system is turned on, and the temperature is raised to the melting zone temperature of 700℃, so that the raw material in contact with the seed crystal 4 is fully melted, and the temperature of the crystallization zone is maintained at 550℃. The stepper motor 17 is programmed to move the melting zone from one end of the crystal growth container 1 to the other end at a speed of 2mm / h. The crystal in the crystal growth container 1 enters the area of ​​the lightweight insulation material 21. The cooling program is set to perform in-situ annealing of the crystal, and a complete crystal with the same shape as the crystal growth container 1 is obtained.

[0070] Example 3

[0071] The process for preparing CsI crystals via directional zone melting crystallization includes the following steps:

[0072] First, place CsI raw material with a purity ≥99.99% into a crystal growth container 1 with a length of 80mm, a diameter of 20mm, and a thickness of 1mm in a vacuum glove box.

[0073] The crystal growth container 1 containing the raw material is clamped on a high-power resistance wire heater. After heating to melt the raw material, it is cooled to room temperature. The raw material will form a polycrystalline ingot, which will reduce its volume and generate excess voids in the container.

[0074] A quartz plug 2 with an outer diameter of 19.5 mm is selected and coupled to the crystal growth container 1. The seed crystal fixture is assembled, and a Φ2 mm × 60 mm round bar seed crystal is placed in the seed crystal placement tube 3. First, the second adjustable knob 12 is adjusted to make a coarse adjustment of the up and down position of the seed crystal 4. Then, the front and back position of the seed crystal 4 is adjusted through the transmission device. Finally, the position of the first adjustable knob 5 and the arc-shaped clamp 6 are adjusted to make a fine adjustment of the up and down position of the seed crystal 4 so that the other end of the seed crystal 4 just touches the raw material.

[0075] After placing a seed crystal at the port of the crystal growth container 1 containing the ingot, it is placed in a horizontally positioned quartz glass furnace tube 22 with an inner diameter of 67.86 mm, a length of 1300 mm, and a thickness of 6 mm. The vacuum pump is then turned on to evacuate the quartz glass furnace tube 22 to a vacuum level of 1 × 10⁻⁶. -2 Pa.

[0076] The moving temperature field 19 is moved back to the end where the crystal growth container 1 contacts the fixture. The heating system is turned on, and the temperature is raised to the melting zone temperature of 750°C, so that the raw material at the end in contact with the seed crystal 4 is fully melted, and the crystallization zone temperature is maintained at 520°C. The stepper motor 17 is programmed to move the melting zone from one end of the crystal growth container 1 to the other end at a speed of 2 mm / h. The crystal in the crystal growth container 1 enters the area of ​​the lightweight insulation material 21. The cooling program is set to perform in-situ annealing of the crystal, and a complete crystal with the same shape as the crystal growth container 1 is obtained.

Claims

1. A method for directional zone melting growth of halide crystals, characterized in that: The fixture used includes a quartz plug (2) embedded in the end of the crystal growth container (1). The quartz plug (2) has O-shaped radial grooves at the outer 1 / 3-1 / 2 and inner 1 / 2 of its left end, and fluororubber O-rings (7) for sealing are placed in each groove. The inner side of the quartz plug (2) is a circular through-hole, and a seed crystal placement tube (3) is embedded in the circular through-hole. The axes of the quartz plug (2) and the seed crystal placement tube (3) coincide. The left side of the seed crystal placement tube (3) is closed, and a seed crystal (4) and a threaded rod (9) connected to the seed crystal (4) via a sleeve (8) are placed at the center of the inner side of the seed crystal placement tube (3). The tube (3) has an O-shaped radial groove at 1 / 2-2 / 3 of the inner side of the left end, and a fluororubber O-ring (7) for fixing the seed crystal (4) is placed in the groove. The seed crystal placement tube (3) is threaded with a first adjustable knob (5) for adjusting the up and down position of the seed crystal (4) on the upper and lower sides respectively. The ends of the two first adjustable knobs (5) are fixedly provided with arc-shaped clamping pieces (6) for clamping the seed crystal (4). The seed crystal placement tube (3) is threaded with a second adjustable knob (12) for supporting and adjusting the up and down position of the threaded rod (9). The threaded rod (9) adjusts the front and back position of the seed crystal (4) through a transmission device. The specific method includes the following steps: S1. In a vacuum glove box, thoroughly mix the growth material with anhydrous purity of 99.99% and load it into the crystal growth container (1) and seal it. S2. The crystal growth container (1) containing the raw material is clamped on a high-power resistance wire heater and heated to 100~150 ℃ higher than the melting point of the raw material. After melting the raw material, it is cooled to room temperature. The raw material forms a polycrystalline ingot, which reduces the volume and generates excess voids in the crystal growth container (1). S3. Put an appropriate amount of raw material into the vacuum glove box again and repeat the operation of step S2 until the gap left in the growth container (1) can be used to place the quartz plug (2). S4. After placing a fluororubber O-ring (7) of the corresponding size in the radial groove of the O-ring on the outside of the quartz plug (2), press it inward at the opening of the crystal growth container (1) to seal it. S5. Place a fluororubber O-ring (7) of the corresponding size in the radial groove of the O-ring inside the quartz plug (2), and insert the seed crystal placement tube (3) into the inner hole of the quartz plug (2); S6. Place a fluororubber O-ring (7) of the corresponding size in the radial groove of the O-ring inside the seed crystal placement tube (3), place the seed crystal (4) into the seed crystal placement tube (3), pass through the fluororubber O-ring (7) set inside the seed crystal placement tube (3), and extend into the crystal growth container (1). S7. Based on the size of the seed crystal (4), first adjust the second adjustable knob (12) to make a coarse adjustment of the up and down position of the seed crystal (4), then adjust the front and back position of the seed crystal (4) through the transmission device, and finally adjust the position of the first adjustable knob (5) and the arc-shaped clamp (6) to finely adjust the up and down position of the seed crystal (4) so ​​that the other end of the seed crystal (4) just touches the raw material. S8. Place the crystal growth container (1) after placing the seed crystal (4) in the quartz glass furnace tube and fix it. Vacuum the quartz glass furnace tube or introduce an inert or iodine-containing protective gas. S9. Activate the moving temperature field as a heating device, so that the temperature of the melting zone is 100~200 ℃ higher than the melting point of the raw material, and the temperature of the preheating zone and crystallization zone is 50~100 ℃ lower than the melting point of the raw material. The width of the melting zone is 20~100 mm. Set the stepper motor control program to move the moving temperature field from one end of the crystal growth container and the fixture to the other end to carry out directional zone melting growth of the crystal.

2. The method for directional zone melting growth of halide crystals according to claim 1, characterized in that: The fluororubber O-ring (7) is made of high-temperature resistant material.

3. The method for directional zone melting growth of halide crystals according to claim 1, characterized in that: The seed crystal placement tube (3) is a ceramic tube or a quartz tube.

4. The method for directional zone melting growth of halide crystals according to claim 1, characterized in that: The arc-shaped clip (6) is made of ceramic or quartz.

5. The method for directional zone melting growth of halide crystals according to claim 1, characterized in that: There is at least one second adjustable knob (12), and the end of the second adjustable knob (12) is an arc surface adapted to the thread of the threaded rod (9).

6. The method for directional zone melting growth of halide crystals according to claim 1, characterized in that: The transmission device includes a vertical bevel gear (10) threadedly connected to a threaded rod (9), the vertical bevel gear (10) meshing with a horizontal bevel gear (11), the horizontal bevel gear (11) being fixedly connected to a third adjustable knob (13), and the third adjustable knob (13) being threadedly connected to a seed crystal placement tube (3).

7. The method for directional zone melting growth of halide crystals according to claim 1, characterized in that: The transmission device includes a connecting rod (14) movably connected to the end of the threaded rod (9), and the other end of the connecting rod (14) is movably connected to a vertical moving rod (15). The vertical moving rod (15) moves vertically through the seed crystal placement tube (3) and is locked by a fixing nut (16).

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