Potassium chloride crystal growth method for ultraviolet chip film substrate

Abstract

The invention provides a potassium chloride crystal growth method for an ultraviolet chip film substrate, and belongs to the field of crystal growth processes, the growth method is a method for growing a large-section potassium chloride crystal in an atmospheric environment by adopting a Czochralski method, and the growth method comprises the steps of raw material purification, charging, heating, seeding, shouldering, shouldering, equal-diameter growth, pull-off, annealing and the like. According to the method, the large-section high-quality potassium chloride crystal with the diameter phi of 110-150 mm can be obtained. The obtained crystal test shows that the transmittance of the potassium chloride crystal in the infrared band is greater than 91%, the XRD shows that the crystal is high in purity and free of impure peaks, and the crystal has great application value in the fields of ultraviolet chip film substrates, infrared windows and the like.

Description

Technical Field

[0001] The invention relates to the field of crystal growth, and in particular to a method for growing potassium chloride crystals for ultraviolet chip film substrates. Background Art

[0002] Potassium chloride crystals have the characteristics of simple structure, low melting point, wide transmission band, high transmittance, easy growth and low cost, and have always been the preferred material for multifunctional crystal development, theoretical and experimental research. Potassium chloride crystals have been widely used in optical windows, infrared prisms, devices, filters, optical lenses, various cell windows, FTIR spectroscopy, membrane-based separation, ultraviolet and infrared optical components, etc.

[0003] At present, the growth methods of potassium chloride crystals include the Czochralski method, the crucible descent method and the temperature gradient method. Among them, the Czochralski method is one of the most commonly used methods for growing crystals from the melt. Since the crystal growth process is visible, the crystal growth process can be accurately grasped. The crystal does not contact the crucible wall, which can reduce the defects and thermal stress of crystal growth. The Czochralski method for growing potassium chloride crystals includes raw material purification, charging, heating, seeding, shoulder release, shoulder retraction, equal diameter growth, pulling, annealing, etc. For potassium chloride crystals used for ultraviolet chip thin film substrates, the raw material purity, circulating water temperature, pulling speed, rotation speed, etc. of the crystal are crucial to the crystal quality, especially for the growth of large-sized potassium chloride crystals. The axial temperature gradient and the shape of the solid-liquid interface are very critical. Only by fully studying the relevant theories and processes in the crystal growth process can we ensure the growth of high-quality, large-sized potassium chloride crystals. Summary of the invention

[0004] Aiming at the problems existing in the growth process of large-size and high-quality potassium chloride crystals, the invention reduces the structural defects in the crystal growth process and further improves the crystal growth quality. The invention provides a potassium chloride crystal growth method for an ultraviolet chip thin film substrate.

[0005] The potassium chloride crystal growth method provided by the present invention adopts the following technical scheme:

[0006] A method for growing potassium chloride crystals for ultraviolet chip thin film substrates, comprising the following steps: S1), raw material purification: KOH and NH 4 Cl is added to the HCl solution, and the mixed solution is concentrated and evaporated at a certain temperature to obtain a solid mixture. The solid mixture is placed in a quartz container and vacuum dehydrated to obtain a dehydrated product. The product is then calcined at a high temperature in an inert atmosphere to obtain a raw material for crystal growth;

[0007] S2), pressing the raw material obtained in step S1) into a cylindrical block on a pressure testing machine, and sintering the pressed block at a temperature of 300° C. for 24 h for subsequent crystal growth;

[0008] S3) along <100> The potassium chloride crystal is cut into a rectangular crystal blank of a certain size as a seed crystal;

[0009] S4), placing the seed crystal obtained in step S3) in the groove at the bottom end of the seed crystal rod, fixing it with a seed crystal chuck, placing the material block obtained in step S2) in a quartz crucible with a constant temperature field heater installed at the bottom, wherein the constant temperature field heater at the bottom of the quartz crucible is 8-12 cm away from the bottom of the quartz crucible, adjusting the heater, quartz crucible, and seed crystal rod to be in the same straight line, covering the furnace of the pulling furnace with a heat-insulating quartz plate, setting a heating program, heating from room temperature to a certain temperature at a heating rate of 3-5 ° C / h, and keeping the temperature constant for 2 h;

[0010] S5) Growing single crystals by Czochralski method to obtain large-section potassium chloride crystals with a diameter of Φ110 mm-150 mm.

[0011] Further, the Czochralski process comprises the following steps:

[0012] Place the pressed material block into a quartz crucible with a constant temperature field heater installed at the bottom, where the constant temperature field heater at the bottom of the quartz crucible is 8-12 cm away from the bottom of the quartz crucible. Adjust the heater, quartz crucible, and seed crystal rod to be in the same straight line. Cover the furnace with a heat-insulating quartz plate, set a heating program, and heat up from room temperature to a certain temperature at a heating rate of 3-5℃ / h, and keep the temperature constant for 2 hours.

[0013] Turn on the pulling furnace and start the heating system in the pulling furnace. After the temperature reaches 780 °C, keep the temperature constant for 2 hours. When the block in the quartz crucible is completely melted and the melt flow line is clear and stable, slowly put the seed crystal in. After the seed crystal contacts the melt surface, perform the necking process to reduce the seed crystal diameter by 6 mm-8 mm.

[0014] Adjust the temperature and start crystal growth. The seed crystal direction is <100> , the crystal growth process includes the following steps:

[0015] ① Shoulder release: When releasing the shoulder, the cooling rate is 0.8 ℃ / h-1 ℃ / h, the pulling rate is 0.6 mm / h~0.8 mm / h, and the crystal rotation rate is 7 r / min~9 r / min;

[0016] ② Equal diameter growth: During the equal diameter growth process, the cooling rate, pulling speed and rotation speed should be kept constant. The cooling rate is 0.5 ℃ / h-1 ℃ / h, the pulling speed is 0.8 mm / h~1.1 mm / h, and the rotation speed is 6 r / min~8 r / min;

[0017] ③ Finishing: When the crystal grows to a certain length, it enters the finishing stage. The finishing process is exactly the opposite of the shoulder release process. The cooling program is adjusted to the heating program with a heating rate of 5 ℃ / h-10 ℃ / h for 2 hours. Finally, the pulling speed and rotation speed are reduced to 0 to end the crystal growth.

[0018] ④ Cooling annealing, keeping the temperature at 710-720 ℃ for 64 h-72 h, and then cooling to room temperature at a rate of 10 ℃ / h-20 ℃ / h; high-quality large-sized potassium chloride crystals are obtained, and the transmittance of the crystals is greater than 91%.

[0019] Preferably, the inert atmosphere is one or both of nitrogen and argon.

[0020] Preferably, the block has a diameter of Φ120 mm-180 mm and a thickness of 15 mm-30 mm.

[0021] Preferably, the quartz crucible has a diameter of 250 mm and a height of 150 mm.

[0022] Preferably, the furnace of the pulling furnace is circular, with a diameter of 300 mm, a height of 500 mm, and a thickness of 15 mm.

[0023] Preferably, in the Czochralski process: the melt is superheated and maintained for more than 2 h before the Czochralski growth process is carried out.

[0024] Through the above design scheme, the present invention can bring the following beneficial effects:

[0025] The invention provides a method for growing potassium chloride crystals for ultraviolet chip thin film substrates. By purifying raw materials and optimizing the growth process, potassium chloride crystals with high quality and few defects are grown. The crystal diameter can reach Φ110mm-150mm, and the crystal transmittance is greater than 91.8%.

[0026] The potassium chloride crystals grown by the invention can be processed into crystal elements and can be used for ultraviolet chip thin film substrate materials, infrared windows and FTIR spectroscopy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a photo of potassium chloride crystals grown by the present invention;

[0028] Figure 2 This is a photo of potassium chloride crystals grown at a high cooling rate according to the present invention;

[0029] Figure 3 This is a photo of potassium chloride crystals grown and covered with quartz sand according to the present invention;

[0030] Figure 4is an XRD spectrum of potassium chloride crystals grown by the present invention, wherein the abscissa 2θ (°) represents the diffraction angle, the ordinate Intensity (au) represents the diffraction intensity, Pure KCl represents pure potassium chloride crystals, PDF#72-1540 represents a standard card of potassium chloride, and (200), (220), (222), (400), (420), (422) represent the crystal phase corresponding to each peak;

[0031] Figure 5 3 is the transmission spectrum of the potassium chloride crystal grown by the present invention, in which the abscissa Wavelength (μm) represents the wavelength, and the ordinate Transmittance represents the transmittance. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with examples and drawings. The specific description below is illustrative rather than restrictive and should not be used to limit the protection scope of the present invention.

[0033] Example 1: A method for growing potassium chloride crystals for ultraviolet chip thin film substrates.

[0034] KOH and NH 4 Cl is weighed according to the stoichiometric ratio and added to the HCl solution. The mixed solution is concentrated and evaporated at 100 °C to obtain a solid mixture. The solid mixture is placed in a quartz container and vacuum dehydrated at 210 °C to obtain a dehydrated product. The product is then calcined at 400 °C in a nitrogen atmosphere to obtain a raw material for crystal growth;

[0035] The obtained raw materials were pressed into Φ 120 mm × 20 mm blocks on a pressure testing machine, and the pressed blocks were sintered at 300 °C for 24 h for subsequent crystal growth.

[0036] along <100> The potassium chloride crystal was cut into a 45 mm × 12 mm × 8 mm cuboid crystal blank as a seed crystal;

[0037] Place the seed crystal obtained in the step into the groove at the bottom end of the seed crystal rod and fix it with a seed crystal chuck. Place the obtained material block into a quartz crucible with a constant temperature field heater installed at the bottom, wherein the constant temperature field heater at the bottom of the quartz crucible is 8 cm away from the bottom of the quartz crucible. Adjust the heater, quartz crucible, and seed crystal rod to be in the same straight line. Cover the furnace with a heat-insulating quartz plate, set a heating program, and heat from room temperature to 780 ° C at a heating rate of 5 ° C / h, and keep the temperature constant for 2 h;

[0038] Seeding and necking: When the block in the quartz crucible is completely melted and the melt flow line is clear and stable, slowly put the seed crystal in. After the seed crystal contacts the melt surface, the necking process is performed to reduce the seed crystal diameter by 7 mm. Adjust the temperature and start crystal growth. The seed crystal direction is <100> ;

[0039] Shoulder release: When releasing the shoulder, the cooling rate is 0.8 ℃ / h, the pulling rate is 0.6 mm / h, the crystal rotation rate is 7 r / min, and the constant temperature time is 3 h;

[0040] Equal diameter growth: During the equal diameter growth process, the cooling rate, pulling speed and rotation speed are kept constant, the cooling rate is 0.6 ℃ / h, the pulling speed is 0.8 mm / h, and the rotation speed is 6 r / min;

[0041] Finishing: When the crystal grows to the required length, the finishing stage is carried out. The cooling program is adjusted to the heating program, and the heating rate is 9 ℃ / h for 2 hours. Finally, the pulling speed and rotation speed are reduced to 0 to end the crystal growth.

[0042] Annealing was carried out by keeping the temperature at 720 °C for 64 h, and then cooling to room temperature at a rate of 15 °C / h to obtain potassium chloride crystals with a diameter of Φ112 mm. Figure 1 shown.

[0043] Example 2: A method for growing potassium chloride crystals for ultraviolet chip thin film substrates.

[0044] KOH and NH 4 Cl is weighed according to the stoichiometric ratio and added to the HCl solution. The mixed solution is concentrated and evaporated at 130 °C to obtain a solid mixture. The solid mixture is placed in a quartz container and vacuum dehydrated at 230 °C to obtain a dehydrated product. The product is then calcined at 430 °C in an inert atmosphere to obtain a raw material for crystal growth;

[0045] The obtained raw materials were pressed into Φ130 mm×15 mm blocks on a pressure testing machine, and the pressed blocks were sintered at 300 °C for 24 h for subsequent crystal growth.

[0046] along <100> The potassium chloride crystal was cut into a 50 mm × 15 mm × 10 mm cuboid crystal blank as a seed crystal;

[0047] Place the seed crystal obtained in the step into the groove at the bottom end of the seed crystal rod and fix it with a seed crystal chuck. Place the obtained material block into a quartz crucible with a constant temperature field heater installed at the bottom, wherein the constant temperature field heater at the bottom of the quartz crucible is 9 cm away from the bottom of the quartz crucible. Adjust the heater, quartz crucible, and seed crystal rod to be in the same straight line. Cover the furnace with a heat-insulating quartz plate, set a heating program, and heat from room temperature to 785°C at a heating rate of 4°C / h, and keep the temperature constant for 2 hours.

[0048] Seeding and necking: When the block in the quartz crucible is completely melted and the melt flow line is clear and stable, slowly put the seed crystal in. After the seed crystal contacts the melt surface, the necking process is performed to reduce the seed crystal diameter by 7 mm. Adjust the temperature and start crystal growth. The seed crystal direction is <100> ;

[0049] Shoulder release: When releasing the shoulder, the cooling rate is 0.9 ℃ / h, the pulling rate is 0.7 mm / h, and the crystal rotation rate is 8 r / min;

[0050] Equal diameter growth: During the equal diameter growth process, the cooling rate, pulling speed and rotation speed are kept constant, the cooling rate is 0.8 ℃ / h, the pulling speed is 0.9 mm / h, and the rotation speed is 7 r / min;

[0051] Finishing: When the crystal grows to the required length, the finishing stage is carried out. The cooling program is adjusted to the heating program, and the heating rate is 8 ℃ / h for 2 hours. Finally, the pulling speed and rotation speed are reduced to 0 to end the crystal growth.

[0052] Annealing was performed by keeping the temperature at 715 °C for 68 h and then cooling to room temperature at a rate of 20 °C / h to obtain potassium chloride crystals with a diameter of Φ120 mm.

[0053] Example 3: A method for growing mixed potassium chloride crystals for ultraviolet chip thin film substrates.

[0054] KOH and NH 4 Cl is weighed according to the stoichiometric ratio and added to the HCl solution. The mixed solution is concentrated and evaporated at 140 °C to obtain a solid mixture. The solid mixture is placed in a quartz container and vacuum dehydrated at 250 °C to obtain a dehydrated product. The product is then calcined at 480 °C in an inert atmosphere to obtain a raw material for crystal growth;

[0055] The obtained raw materials were pressed into Φ150 mm×25 mm blocks on a pressure testing machine, and the pressed blocks were sintered at 300 °C for 24 h for subsequent crystal growth.

[0056] along <100> The potassium chloride crystal was cut into a 55 mm × 16 mm × 12 mm cuboid crystal blank as a seed crystal;

[0057] Place the seed crystal obtained in the step into the groove at the bottom end of the seed crystal rod and fix it with a seed crystal chuck. Place the obtained material block into a quartz crucible with a constant temperature field heater installed at the bottom, wherein the constant temperature field heater at the bottom of the quartz crucible is 10 cm away from the bottom of the quartz crucible. Adjust the heater, quartz crucible, and seed crystal rod to be in the same straight line. Cover the furnace with a heat-insulating quartz plate, set a heating program, and heat from room temperature to 790 ° C at a heating rate of 5 ° C / h, and keep the temperature constant for 2 h;

[0058] Seeding and necking: When the block in the quartz crucible is completely melted and the melt flow line is clear and stable, slowly put the seed crystal in. After the seed crystal contacts the melt surface, the necking process is carried out to reduce the seed crystal diameter by 8mm. Adjust the temperature and start crystal growth. The seed crystal direction is <100> ;

[0059] Shoulder release: When releasing the shoulder, the cooling rate is 1 ℃ / h, the pulling rate is 0.8 mm / h, and the crystal rotation rate is 9 r / min;

[0060] Equal diameter growth: During the equal diameter growth process, the cooling rate, pulling speed and rotation speed are kept constant, the cooling rate is 1℃ / h, the pulling speed is 1 mm / h, and the rotation speed is 8 r / min;

[0061] Finishing: When the crystal grows to the required length, the finishing stage is carried out. The cooling program is adjusted to the heating program, and the heating rate is 7 ℃ / h for 2 hours. Finally, the pulling speed and rotation speed are reduced to 0 to end the crystal growth.

[0062] Annealing was performed by keeping the temperature at 710 °C for 72 h and then cooling to room temperature at a rate of 25 °C / h to obtain potassium chloride crystals with a diameter of Φ130 mm.

[0063] Comparative Example 1

[0064] Example 1 was repeated, except that the cooling rate was changed from 15 °C / h to 30 °C / h, and the other conditions remained unchanged. The resulting crystal cracked as shown in FIG. Figure 2 shown.

[0065] Comparative Example 2

[0066] Example 1 was repeated, except that during the cooling annealing process, quartz sand was covered on the crystal surface, and the crystal surface transmittance was reduced. Figure 3 shown.

Claims

1. A method for growing potassium chloride crystals for ultraviolet chip thin film substrates, characterized in that: The steps include: S1), raw material purification: KOH and NH4Cl with a purity of 99.9% are added to the HCl solution, and the mixed solution is concentrated and evaporated at a certain temperature to obtain a solid mixture, and the solid mixture is placed in a quartz container for vacuum dehydration to obtain a dehydrated product, and then the product is calcined at a high temperature in an inert atmosphere to obtain a raw material for crystal growth; S2), pressing the raw material obtained in step S1) into a cylindrical block on a pressure testing machine, and sintering the pressed block at a temperature of 300 ° C for 24 h for subsequent crystal growth; S3) <100> The potassium chloride crystal is cut into a rectangular crystal blank of a certain size as a seed crystal; S4), placing the seed crystal obtained in step S3) in the groove at the bottom end of the seed crystal rod, fixing it with a seed crystal chuck, placing the material block obtained in step S2) in a quartz crucible with a constant temperature field heater at the bottom, adjusting the heater, quartz crucible, and seed crystal rod to be in the same straight line, covering the furnace of the pulling furnace with a heat-insulating quartz plate, setting a heating program, heating from room temperature to a certain temperature, and keeping the temperature constant for 2 hours; S5) Growing single crystals by Czochralski method to obtain large-section potassium chloride crystals.

2. A method for growing potassium chloride crystals for ultraviolet chip thin film substrates according to claim 1, characterized in that: In step S1), the evaporation temperature is 90°C to 140°C, the vacuum dehydration temperature is 200°C to 250°C, and the calcination temperature is 400°C to 500°C; the inert atmosphere is one or both of nitrogen and argon.

3. A potassium chloride crystal growth method for a UV chip thin film substrate according to claim 1, characterized in that: In step S2), the block has a diameter of 120 mm-180 mm and a thickness of 15 mm-30 mm.

4. A potassium chloride crystal growth method for a UV chip thin film substrate according to claim 1, characterized in that: In step S3), the size of the seed crystal is 45 mm-55 mm×10 mm-16 mm×8 mm-12 mm.

5. A potassium chloride crystal growth method for a UV chip thin film substrate according to claim 1, characterized in that: In step S4), the diameter of the quartz crucible is 250 mm and the height is 150 mm; the constant temperature field heater is 8-12 cm away from the bottom of the quartz crucible; the furnace of the pulling furnace is circular, with a diameter of 300 mm, a height of 500 mm and a thickness of 15 mm.

6. A potassium chloride crystal growth method for a UV chip thin film substrate according to claim 1, characterized in that: In step S5), during the process of growing the single crystal by the Czochralski method, the cooling rate during shoulder release is 0.8 °C / h-1 °C / h, the pulling rate is 0.6 mm / h-0.8 mm / h, and the crystal rotation rate is 7 r / min-9 r / min.

7. A method for growing potassium chloride crystals for ultraviolet chip thin film substrates according to claim 1, characterized in that: In step S5), when the diameter is constant during the single crystal growth process using the Czochralski method, the cooling rate is 0.5°C / h-1°C / h, the pulling speed is 0.8 mm / h-1.1 mm / h, and the rotation speed is 6 r / min-8 r / min.

8. The method for growing potassium chloride crystals for ultraviolet chip thin film substrate according to claim 1, characterized in that: In step S5), when the shoulder is contracted during the single crystal growth process using the Czochralski method, the cooling program is adjusted to a heating program with a heating rate of 5°C / h-10°C / h for 2 hours, and finally the pulling speed and rotation speed are reduced to 0 to end the crystal growth.

9. The method for growing potassium chloride crystals for ultraviolet chip thin film substrates according to claim 1, characterized in that: In step S5), during the annealing process of growing the single crystal by the Czochralski method, the temperature is kept constant at 710-720 °C for 64 h-72 h, and then cooled to room temperature at a rate of 10-20 °C per hour.

10. The method for growing potassium chloride crystals for ultraviolet chip thin film substrate according to claim 1, characterized in that: In step S5), the diameter of the crystal obtained by growing the single crystal by the Czochralski method is Φ110 mm-150 mm, and its transmittance is greater than 91%.

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