Polycrystal purification and single crystal growth integrated preparation method of selenium gallium barium

Abstract

The invention discloses a polycrystal purification and single crystal growth integrated preparation method of selenium gallium barium, and belongs to the technical field of inorganic non-metallic material preparation. According to the method, a boron nitride polycrystal boat and a single crystal boat are customized, the polycrystal boat is provided with a horizontal slit for melt filtration and purification, and the single crystal boat is provided with a funnel-shaped structure for promoting single crystal nucleation; the two boats are sealed in a quartz tube after being assembled, and integration of polycrystal purification and single crystal growth is realized through a three-section temperature control program. The temperature is raised to 1050-1070 DEG C in the polycrystal purification stage, and the temperature gradient is maintained at 2-4 DEG C / cm; and the temperature is reduced step by step in the single crystal growth stage to complete crystal condensation. According to the method, the technological process is simplified, the preparation period is shortened to 15-20 days, the size of the obtained single crystal reaches 30mm * 7mm * 150mm, the 4-micron infrared transmittance is close to the theoretical limit (69.7%), and the method is suitable for preparing medium and long infrared laser devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic non-metallic raw material purification and crystal growth, and specifically relates to an integrated preparation method for polycrystalline purification and single crystal growth of barium gallium selenide. Background Art

[0002] Barium gallium selenide (BaGa4Se7, abbreviated as BGSe) is a new type of infrared nonlinear crystal with independent intellectual property rights in China. It has a wide light transmission band (0.47~18μm), a high damage threshold (557 MW / cm 2 @1.06μm) and suitable birefringence (0.07-0.11, meeting the 2μm pump non-critical phase matching NCPM) and other advantages. It can be pumped by 1-2μm near-infrared laser and output 3-5μm and 8-12μm medium and long infrared lasers, which has important applications in environmental monitoring, medical diagnosis and national defense security.

[0003] Many institutions at home and abroad are actively conducting research on the preparation of this crystal. For example, in 2011, the Russian State Kubai University used the Bridgman method to grow BGSe crystals for the first time; in 2018, the American BAE system company used the horizontal temperature gradient condensation method to grow 25×15×150mm 3 In 2022, the Institute of Physics and Chemistry of the Chinese Academy of Sciences reported on the growth of φ40mm BGSe crystals using the vertical Bridgman method. In 2024, the Anguang Institute of the Chinese Academy of Sciences reported on the polycrystalline synthesis and purification of BGSe.

[0004] As the requirements for crystal quality increase, the purity of polycrystalline raw materials has gradually become more important. The purity of the metal Ba element currently available on the market is generally not higher than 99.9%. In addition, the alkaline earth metal Ba is relatively active and is easily oxidized during the weighing, tube loading and sealing processes. These factors will affect the purity of the polycrystalline raw materials. The current main solution to the BGSe raw material purity problem is to purify the polycrystalline raw materials before single crystal growth. Relatively speaking, this technical solution has an additional polycrystalline purification process, which makes the preparation of BGSe crystals complicated, costly and long. Based on previous exploratory research, we have invented a preparation method that integrates polycrystalline purification and single crystal growth of the infrared nonlinear material BGSe. Summary of the Invention

[0005] The present invention aims to provide an integrated method for polycrystal purification and single crystal growth of barium gallium selenide. The method involves first melting the synthesized polycrystal material and separating the impurities through precipitation to purify the raw material. The purified melt is then flowed into a growth boat for single crystal growth. The entire polycrystal purification and single crystal growth process is completed simultaneously within a sealed quartz tube, resulting in an integrated production process.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for preparing polycrystalline gallium barium selenide by purification and single crystal growth, comprising the following steps:

[0008] 1. Polycrystalline Boat Preparation

[0009] Custom boron nitride polycrystalline boats are sized (20-30 mm wide, 10-15 mm high, and 150-200 mm long) with a wall thickness of 2-3 mm. A 5-15 mm long, 0.5-1 mm wide horizontal slit is cut at one end to allow the melt to flow out to the growth boat. The lower edge of the slit is 0.5-0.8 mm from the bottom. The bottom of the polycrystalline boat features a rectangular 1 mm boss (tenon) that snaps into the upper edge (mortise) of the single crystal boat, allowing the two boats to be assembled together.

[0010] 2. Polycrystalline boat loading

[0011] The BGSe polycrystalline material synthesized in the early stage is ground to a particle size of 1-2 mm and then loaded into a polycrystalline boat. The amount of raw materials is filled according to the demand, but not exceeding the capacity of the polycrystalline boat.

[0012] 3. Single Crystal Boat Preparation

[0013] Custom boron nitride single crystal boats are available with dimensions of (20-30) mm wide, (10-15) mm high, and (200-250) mm long, with a wall thickness of 2-3 mm. One end of the boat is designed with a funnel shape to facilitate single crystal nucleation and growth. The angle between the funnel's slope and the tube wall is 120°, and the inner diameter of the funnel's tapered neck is 4-6 mm, with a length of 30-40 mm.

[0014] 4. Boat assembly

[0015] Place the loaded polycrystalline boat on top of the single crystal boat, and use the convex rectangular platform (tenon) to clamp the polycrystalline boat into the opening (mortise) on the single crystal boat to fix the two together;

[0016] 5. Quartz Tube Preparation

[0017] Select a quartz tube with dimensions of (35-50) mm x (300-350) mm and a wall thickness of 2-3 mm. Deionize the quartz tube and dry it.

[0018] 6. Quartz tube loading and sealing

[0019] Place the polycrystalline boat and single crystal boat kit into the quartz tube, with the "funnel-shaped" end of the single crystal boat facing the bottom of the quartz tube. Connect the placed quartz tube to the exhaust table and evacuate to 10 -3 Pa, oxyhydrogen flame seal.

[0020] 7. Furnace loading

[0021] The charged and sealed quartz tube is placed in the furnace of a horizontal three-stage furnace, close to the range near the linear temperature gradient, which is convenient for polycrystalline melting and purification and single crystal condensation growth.

[0022] 8. Polycrystalline purification

[0023] The three furnace sections (high temperature zone, gradient zone, and low temperature zone) were raised to 1020-1030°C, 970-1000°C, and 920-960°C, respectively, at a rate of 50-100°C / h, with a temperature gradient of approximately 2-4°C / cm. The three furnace sections were then raised to 1050-1070°C, 1020-1050°C, and 980-1020°C, respectively, over 24-48 hours, maintaining a temperature gradient of 2-4°C / cm.

[0024] 9. Single Crystal Growth

[0025] After maintaining the three furnace temperatures at 1050-1070°C, 1020-1050°C, and 980-1020°C for 24-48 hours, the high-temperature melt is allowed to stand. Over the next 10-15 days, the three furnace temperatures are lowered to 1020-1030°C, 970-1000°C, and 920-960°C, respectively, to complete single crystal growth through temperature gradient condensation.

[0026] 10. Cooling

[0027] After the crystal growth is completed, the entire furnace is slowly cooled to room temperature over 2-3 days and the crystal rod is taken out.

[0028] The above method can be used to obtain BGSe crystals. By adjusting the growth parameters (such as the amount of polycrystalline material, the size of the boron nitride boat, and the growth cycle), single crystals of the desired size can be obtained.

[0029] Beneficial effects:

[0030] This invention achieves integrated production of polycrystalline purification and single crystal growth. This preparation method designs technical solutions for raw material purification and single crystal growth, exploring purification and growth temperature control procedures and parameters. The slit design of the polycrystalline boat is used for impurity separation and melt flow control. The dimensions of the polycrystalline boat and single crystal boat are matched to ensure the melt flow path. By first melting the polycrystalline raw material, the slit structure of the polycrystalline boat is used to precipitate and filter impurities and separate the BGSe melt. The "funnel"-shaped growth boat is then used to complete seed crystal formation, shoulder placement, and uniform single crystal growth. This simplifies the process flow, shortens the preparation cycle, and improves preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the boron nitride boat for polycrystalline purification in the present invention;

[0032] Figure 2 This is a schematic diagram of a boron nitride boat for single crystal growth;

[0033] Figure 3 Schematic diagram of the placement of the polycrystal purification and single crystal growth boats and the temperature field distribution in the present invention, wherein 1 is the high-temperature melting curve, 2 is the low-temperature condensation curve, and the temperature range between curves 1 and 2 can be understood as the temperature condensation curves at different stages; 3 is the polycrystal purification boat, the dotted line portion in the figure; 4 is the single crystal growth boat, the solid line portion in the figure; the abscissa represents position, the ordinate represents temperature, and Tm represents the melting point of the BGSe crystal (approximately 1020°C);

[0034] Figure 4 is the BGSe single crystal prepared in Example 1;

[0035] Figure 5 is the infrared transmittance curve of BGSe crystal. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. However, the following embodiments are intended only to explain the present invention, and the scope of protection of the present invention should include the entire contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement the entire contents of the claims of the present invention.

[0037] Example 1, an integrated preparation method for polycrystalline purification and single crystal growth of BGSe:

[0038] Preparation of polycrystalline boat: Customized boron nitride polycrystalline boat with dimensions of 30mm×15mm×200mm, 3mm wall thickness, and a 15mm long × 0.8mm wide horizontal slit machined on the right end of the boat, with the lower edge of the slit 0.8mm from the bottom. The horizontal slit of the polycrystalline boat is used for melt filtration and purification. The bottom of the polycrystalline boat has a rectangular 1mm boss structure with a length and width of approximately 197mm×23.8mm, slightly smaller than the inner diameter of the single crystal boat (see Figure 1 ).

[0039] Polycrystalline boat loading: The BGSe polycrystalline material synthesized in the early stage is ground into 1-2mm particles and then loaded into the polycrystalline boat. The filling amount is about 90% of the volume of the polycrystalline boat.

[0040] Prepare single crystal boat: Customize the boron nitride single crystal boat with the size of 30mm×15mm×250mm and the wall thickness of 3mm. The left end of the single crystal boat is designed to be funnel-shaped to facilitate the nucleation and growth of single crystals (see Figure 2 The angle between the slope of the "funnel" and the tube wall is 120°, the inner diameter of the "funnel" at the narrow neck is 6mm, and the length is 40mm.

[0041] Boat assembly: align the ends of the polycrystalline boat with the slits and the "funnel" of the single crystal boat. Insert the polycrystalline boat into the upper edge of the single crystal boat through the rectangular boss structure at the bottom. Then, assemble the two boats together. Figure 3As shown in the polycrystalline purification boat 3 and the single crystal growth boat 4.

[0042] Quartz tube preparation: Use a quartz tube with a size of φ50mm×350mm and a wall thickness of 3mm. Ultrasonic cleaning with deionized water twice, drying at 80℃ for 2h, horizontally install the boron nitride boat assembly into the quartz outer tube, and install the funnel-shaped end of the single crystal boat into the quartz tube. Connect the quartz tube to the exhaust table and evacuate to 10 -3 Pa, hydrogen-oxygen flame sealing. Place the sealed quartz tube into a horizontal three-section furnace. The furnace zones are positioned from left to right: high temperature zone, gradient zone, low temperature zone (see Figure 3 ).

[0043] Polycrystalline purification: The three furnace temperatures of the high temperature zone, gradient zone and low temperature zone were raised to 1030℃, 1000℃ and 960℃ respectively (gradient of about 4℃ / cm) at a rate of 50℃ / h, close to Figure 3 The low temperature condensation curve 2 in the figure is shown. Then the temperature is gradually increased over 48 hours, and the three furnace temperatures are respectively increased to 1070℃, 1050℃, and 1020℃, which is close to Figure 3 The high temperature melting curve 1 gradually melts the polycrystalline material, and the temperature gradient is maintained at about 4℃ / cm.

[0044] Single crystal growth: a) Days 1-3: The temperatures of the three furnace sections were lowered to 1062°C in the high-temperature zone, 1040°C in the gradient zone, and 1005°C in the low-temperature zone; b) Days 4-7: The temperatures of the three furnace sections were lowered to 1050°C in the high-temperature zone, 1020°C in the gradient zone, and 980°C in the low-temperature zone; c) Days 8-15: The temperatures of the three furnace sections were lowered to 1020°C in the high-temperature zone, 970°C in the gradient zone, and 920°C in the low-temperature zone. At this point, the melt was completely condensed and crystallized.

[0045] Cooling: After crystallization is completed, slowly cool it down to room temperature over 3 days and take out the crystal rod.

[0046] Figure 4 The BGSe crystal grown in this embodiment has a size of approximately 30 mm × 7 mm × 150 mm; Figure 5 Infrared transmittance curve of the crystal. The crystal has good infrared transmittance at 2500cm -1 The transmittance near (4μm) is 69.1%, close to the transmittance limit of 69.7%.

[0047] Example 2, an integrated preparation method for polycrystalline purification and single crystal growth of BGSe:

[0048] Preparation of polycrystalline boat: Customized boron nitride polycrystalline boat with dimensions of 20mm×10mm×150mm, wall thickness of 2mm, and a horizontal slit of 10mm long and 0.5mm wide was machined on the right end of the boat, with the lower edge of the slit 0.5mm from the bottom. The bottom of the polycrystalline boat has a rectangular 1mm boss structure with dimensions of approximately 148mm×15.8mm, slightly smaller than the inner diameter of the single crystal boat (see Figure 1 ).

[0049] Polycrystalline boat loading: The BGSe polycrystalline material synthesized in the early stage is ground into 1-2mm particles and then loaded into the polycrystalline boat. The filling amount is about 90% of the volume of the polycrystalline boat.

[0050] Prepare single crystal boat: Customize the boron nitride single crystal boat with the size of 20mm×10mm×200mm and the wall thickness of 2mm. The left end of the single crystal boat is designed to be funnel-shaped to facilitate the nucleation and growth of single crystals (see Figure 2 The angle between the slope of the "funnel" and the tube wall is 120°, the inner diameter of the thin neck of the "funnel" is 4mm, and the length is 30mm.

[0051] Boat assembly: align the ends of the polycrystalline boat with the slits and the "funnel" of the single crystal boat. Insert the polycrystalline boat into the upper edge of the single crystal boat through the rectangular boss structure at the bottom. Then, assemble the two boats together. Figure 3 As shown in the polycrystalline purification boat 3 and the single crystal growth boat 4.

[0052] Quartz tube preparation: Use a quartz tube with a size of φ35mm×300mm and a wall thickness of 2mm. Ultrasonic cleaning with deionized water twice, drying at 80℃ for 2h, horizontally install the boron nitride boat assembly into the quartz outer tube, and install the funnel-shaped end of the single crystal boat into the quartz tube. Connect the quartz tube to the exhaust table and evacuate to 10 -3 Pa, hydrogen-oxygen flame sealing. Place the sealed quartz tube into a horizontal three-section furnace. The furnace zones are positioned from left to right: high temperature zone, gradient zone, low temperature zone (see Figure 3 ).

[0053] Polycrystalline purification: The three furnace temperatures of the high temperature zone, gradient zone and low temperature zone were raised to 1020℃, 970℃ and 920℃ respectively (gradient of about 2℃ / cm) at a rate of 100℃ / h, close to Figure 3 The low temperature condensation curve 2 in the figure is shown. Then the temperature is gradually increased over 24 hours, and the three furnace temperatures are respectively increased to 1050℃, 1020℃, and 980℃, which is close to Figure 3 The high temperature melting curve 1 gradually melts the polycrystalline material, and the temperature gradient is maintained at about 2℃ / cm.

[0054] Single crystal growth: a) Days 1-2: The three-stage furnace temperatures were lowered to 1045°C in the high-temperature zone, 1012°C in the gradient zone, and 966°C in the low-temperature zone; b) Days 3-6: The three-stage furnace temperatures were lowered to 1037°C in the high-temperature zone, 1000°C in the gradient zone, and 955°C in the low-temperature zone; c) Days 7-10: The three-stage furnace temperatures were lowered to 1020°C in the high-temperature zone, 970°C in the gradient zone, and 920°C in the low-temperature zone. The melt was completely condensed and crystallized.

[0055] Cooling: After crystallization is completed, slowly cool it down to room temperature over 2 days and take out the crystal rod.

[0056] The infrared transmittance of the BGSe crystal grown in this example is basically consistent with the test results of the sample in Example 1 ( Figure 5 ), at 2500cm -1 The transmittance near (4μm) is 69.0%, close to the transmittance limit of 69.7%, and the optical quality of the crystal is good.

[0057] Example 3, an integrated preparation method for polycrystalline purification and single crystal growth of BGSe:

[0058] Preparation of polycrystalline boat: Customized boron nitride polycrystalline boat with dimensions of 25mm×12.5mm×150mm, wall thickness of 2.5mm, and a horizontal slit of 12.5mm long and 0.6mm wide was machined on the right end of the boat, with the lower edge of the slit 0.6mm from the bottom. The bottom of the polycrystalline boat has a rectangular 1mm boss structure with dimensions of approximately 148mm×19.8mm, slightly smaller than the inner diameter of the single crystal boat (see Figure 1 ).

[0059] Polycrystalline boat loading: The BGSe polycrystalline material synthesized in the early stage is ground into 1-2mm particles and then loaded into the polycrystalline boat. The filling amount is about 80% of the volume of the polycrystalline boat.

[0060] Prepare single crystal boat: Customize the boron nitride single crystal boat with the size of 25mm×12.5mm×200mm and the wall thickness of 2.5mm. The left end of the single crystal boat is designed to be funnel-shaped to facilitate the nucleation and growth of single crystals (see Figure 2 The angle between the slope of the "funnel" and the tube wall is 120°, the inner diameter of the "funnel" at the narrow neck is 5mm, and the length is 35mm.

[0061] The end of the polycrystalline boat with the slit is aligned with the end of the single crystal boat with the "funnel". The polycrystalline boat is inserted into the upper edge of the single crystal boat through the rectangular boss structure at the bottom. The two boats are fixed together. Figure 3 As shown in the polycrystalline purification boat 3 and the single crystal growth boat 4.

[0062] Quartz tube preparation: Use a quartz tube with a size of φ45mm×300mm and a wall thickness of 2.5mm. Ultrasonic cleaning with deionized water twice, drying at 80℃ for 2h, horizontally install the boron nitride boat assembly into the quartz outer tube, and install the funnel-shaped end of the single crystal boat into the quartz tube. Connect the quartz tube to the exhaust table and evacuate to 10 -3 Pa, hydrogen-oxygen flame sealing. Place the sealed quartz tube into a horizontal three-section furnace. The furnace zones are positioned from left to right: high temperature zone, gradient zone, low temperature zone (see Figure 3 ).

[0063] Polycrystalline purification: The three furnace temperatures of the high temperature zone, gradient zone and low temperature zone were raised to 1025℃, 985℃ and 940℃ respectively (gradient of about 3℃ / cm) at a rate of 75℃ / h, close to Figure 3 The low temperature condensation curve 2 in the figure is shown. Then the temperature is gradually increased over 48 hours, and the three furnace temperatures are raised to 1060℃, 1035℃, and 1000℃ respectively, which is close to Figure 3 The high temperature melting curve 1 gradually melts the polycrystalline material, and the temperature gradient is maintained at about 3℃ / cm.

[0064] Single crystal growth: a) Days 1-3: The temperatures of the three furnace sections were lowered to 1054°C in the high-temperature zone, 1027°C in the gradient zone, and 990°C in the low-temperature zone; b) Days 4-7: The temperatures of the three furnace sections were lowered to 1045°C in the high-temperature zone, 1015°C in the gradient zone, and 973°C in the low-temperature zone; c) Days 8-15: The temperatures of the three furnace sections were lowered to 1025°C in the high-temperature zone, 985°C in the gradient zone, and 940°C in the low-temperature zone. The melt was completely condensed and crystallized.

[0065] Cooling: After crystallization is completed, slowly cool it down to room temperature over 2 days and take out the crystal rod.

[0066] The infrared transmittance of the BGSe crystal grown in this example is basically consistent with the test results of the sample in Example 1 ( Figure 5 ), at 2500cm -1 The transmittance near (4μm) is 69.2%, close to the transmittance limit of 69.7%, and the optical quality of the crystal is good.

[0067] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing polycrystalline gallium barium selenide by purification and single crystal growth, characterized in that: The following steps are involved: (1) Preparation of a boron nitride polycrystalline boat: A horizontal slit is provided at one end of the polycrystalline boat, the slit is 5-15 mm long and 0.5-1 mm wide, the lower edge of the slit is 0.5-0.8 mm from the bottom of the boat, and a boss structure is provided at the bottom of the polycrystalline boat; (2) Loading the polycrystalline boat: Grind the selenium gallium barium polycrystalline material into 1-2 mm particles and then load it into the polycrystalline boat; (3) Preparation of a boron nitride single crystal boat: One end of the single crystal boat is a funnel-shaped structure, the angle between the funnel slope and the tube wall is 120°, the inner diameter of the funnel neck is 4-6 mm, and the length is 30-40 mm; (4) Boat assembly: The boss structure of the polycrystalline boat is engaged and fixed with the mortise and tenon of the single crystal boat to connect the polycrystalline boat with the single crystal boat; (5) Quartz tube sealing: Place the assembled boat into the quartz tube and evacuate to 10 -3 Pa rear seal; (6) Polycrystalline purification: Place the quartz tube in a horizontal three-stage furnace and heat it up in stages to 1050-1070°C in the high temperature zone, 1020-1050°C in the gradient zone, and 980-1020°C in the low temperature zone. The temperature gradient is 2-4°C / cm and maintained for 24-48 hours. (7) Single crystal growth: Cool down in stages to 1020-1030℃ in the high temperature zone, 970-1000℃ in the gradient zone, and 920-960℃ in the low temperature zone. The cooling cycle is 10-15 days. (8) Cooling: Cool to room temperature in 2-3 days to obtain a barium gallium selenide single crystal.

2. The method according to claim 1, characterized in that The dimensions of the polycrystalline boat are 20-30 mm in width, 10-15 mm in height, 150-200 mm in length, and 2-3 mm in wall thickness.

3. The method according to claim 1, characterized in that The size of the single crystal boat is 20-30 mm in width, 10-15 mm in height, 200-250 mm in length, and 2-3 mm in wall thickness.

4. The method according to claim 1, wherein The dimensions of the quartz tube are 35-50 mm in diameter, 300-350 mm in length, and 2-3 mm in wall thickness.

5. The method according to claim 1, wherein The heating rate in step (6) is 50-100°C / h.

6. The method according to claim 1, characterized in that The single crystal growth in step (7) is divided into three stages: The first stage: high temperature zone 1062-1045℃, gradient zone 1040-1012℃, low temperature zone 1005-966℃, maintain for 1-3 days; The second stage: high temperature zone 1050-1037℃, gradient zone 1020-1000℃, low temperature zone 980-955℃, maintain for 3-7 days; The third stage: high temperature zone 1020℃, gradient zone 970℃, low temperature zone 920℃, maintain for 8-15 days.

7. The method according to claim 1, characterized in that The loading amount of the polycrystalline boat is 80-90% of the boat volume.

8. The method according to claim 1, characterized in that The quartz tube is ultrasonically cleaned with deionized water and dried before loading.

9. The method according to claim 1, characterized in that The horizontal slits provided on the polycrystalline boat are used for melt filtering and purification.

10. The method according to claim 1, characterized in that The funnel-shaped structure of the single crystal boat is used to promote single crystal nucleation and isodiametric growth.

Images