Stable gallium tetrachloride crystal material and preparation method thereof

Abstract

The invention relates to the technical field of gallium tetrachloride, in particular to a stable gallium tetrachloride crystal material and a preparation method thereof, the crystal is a triclinic system, the space group is shown in the specification, the crystal structure is a zero-dimensional GaCl4 tetrahedral cluster structure, and Ga < 3 + > and four Cl <-> form edge shared tetrahedral coordination. The stable gallium tetrachloride crystal material has a regular triclinic system structure, accurate and controllable lattice parameters, uniform Ga-Cl bond length and bond angle distribution and no obvious lattice defect, the chemical stability and the thermal stability of the crystal are remarkably improved, the hydrolysis rate is low in a normal-temperature and high-humidity environment, the crystal is not easy to decompose at a high temperature, and the application requirements under extreme working conditions can be met.

Description

Technical Field

[0001] This invention relates to the field of gallium tetrachloride technology, specifically to a stable gallium tetrachloride crystal material and its preparation method. Background Technology

[0002] Gallium tetrachloride (GCHC) crystals, as an important precursor material for group III-V semiconductors, have irreplaceable application value in halide vapor phase epitaxy (HVPE) growth of wide-bandgap semiconductors (such as Ga₂O₃ and GaN), fabrication of fiber optic sensing elements, and doping of high-precision electronic devices. Its crystal structure and stability directly determine the growth quality, signal transmission efficiency, and lifespan of subsequent devices.

[0003] In existing technologies, gallium tetrachloride crystals are mostly prepared by direct reaction of metallic gallium with hydrogen chloride or chlorine gas. This method has the following drawbacks: First, the resulting crystals are prone to lattice defects (such as dislocations and vacancies), leading to poor crystal structure stability. They are easily hygroscopic and hydrolyzed at room temperature and pressure, and easily decomposed at high temperatures, making them unsuitable for applications under extreme conditions. Second, nucleation and crystallization occur simultaneously during the preparation process, resulting in a wide crystal size distribution, irregular morphology, and difficulty in achieving a purity of 5N or higher. Third, traditional processes have low requirements for the precision of reaction atmosphere and temperature control, easily introducing impurities and further exacerbating crystal stability degradation. For example, in existing technologies, gallium tetrachloride is prepared by direct reaction of metallic gallium with hydrogen chloride gas at 200-280℃. The resulting crystal is a common triclinic aggregate with uneven Ga-Cl bond length distribution and stress concentration within the lattice. After being placed in an environment with humidity greater than 30% for 72 hours, the hydrolysis rate can reach over 15%, which cannot meet the production requirements of high-reliability devices. Therefore, developing a stable gallium tetrachloride crystal material with stable structure, high purity, and controllable preparation process has significant industrial value. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the purpose of this invention is to provide a stable gallium tetrachloride crystal material and its preparation method, so as to solve the problems mentioned in the background art.

[0005] The present invention solves the technical problem by adopting the following technical solution: This invention provides a stable gallium tetrachloride crystal material, wherein the crystal is triclinic and the space group is [missing information]. The crystal structure is a zero-dimensional GaCl4 tetrahedral cluster structure, Ga 3+ With four Cl - Formation of edge-shared tetrahedral coordination; The crystal has the following lattice parameters: a = 7.12 ± 0.02 Å, b = 7.17 ± 0.02 Å, c = 7.29 ± 0.02 Å, α = 91.93 ± 0.05°, β = 116.13 ± 0.05°, γ = 116.91 ± 0.05°, and a unit cell volume of 285.16 ± 0.5 Å. 3 The crystal density is 2.05 ± 0.02 g·cm³. -3 .

[0006] This invention also provides a method for preparing stable gallium tetrachloride crystal materials, comprising the following steps: Step 1: Raw material pretreatment: Select gallium metal blocks with a purity ≥ 6N and hydrogen chloride gas with a purity ≥ 5N; the gallium metal blocks are subjected to a vacuum degree ≤ 1×10 -3 Vacuum baking at 150-180℃ for 2-3 hours; hydrogen chloride gas undergoes two-stage drying treatment, with a water content ≤1ppm; Step 2: Stepwise nucleation reaction: Place the pretreated gallium block in a sealed chlorination reactor, replace with nitrogen until the oxygen content is ≤10ppm; heat to 80-100℃, and introduce hydrogen chloride gas at a flow rate of 50-80 mL / min; Step 3: Segmented heating for crystallization; Step 4: Gradient cooling and purification: Cool with nitrogen gas, reduce temperature to 150℃ at 3-5℃ / min and hold for 1 hour, then reduce temperature to room temperature at 1-2℃ / min; the crude product is purified by vacuum sublimation and the product is collected. Step 5: Surface treatment and sealing.

[0007] Preferably, in step 2, a self-made composite chlorination modifier is added, with the amount of modifier added being 0.3-0.5% of the volume fraction of hydrogen chloride gas; the ultrasonic-assisted reaction is carried out for 1.5-2 hours to generate a precursor; the self-made composite chlorination modifier is prepared by mixing boron trichloride, antimony pentachloride, and anhydrous carbon tetrachloride in a mass ratio of 3:2:95, and the preparation conditions are nitrogen protection, stirring reaction at 50-60℃ for 1.5 hours, and taking the upper clear liquid after cooling and standing.

[0008] Preferably, in step 2, the ultrasonic frequency is 40-60 kHz and the power is 100-150 W; in step 2, 0.5-1% by volume of trimethylchlorosilane is added as a dispersant.

[0009] Preferably, the specific process conditions for segmented heating crystallization are as follows: Stop the ultrasound and introduce a mixture of nitrogen and argon inert gas with a volume ratio of 98:2 into the reactor, maintaining the partial pressure of the inert gas at ≥99%. Then increase the temperature to 220-250℃ at a rate of 5-8℃ / min and hold at that temperature for 2-3 hours; The temperature was then increased to 280-300℃ at a rate of 2-3℃ / min, and a low-frequency constant magnetic field with an intensity of 0.05-0.1T was applied, with the direction of the magnetic field aligned with the crystal growth direction. The flow rate of hydrogen chloride gas was maintained at 30-50 mL / min and the pressure at 0.12-0.15 MPa, and the reaction was carried out for 3-4 hours.

[0010] Preferably, in step 3, the second stage of crystallization involves introducing a mixture of hydrogen chloride and nitrogen gas with a volume ratio of 95:5.

[0011] Preferably, the vacuum sublimation conditions in step 4 are: vacuum degree ≤ 5 × 10⁻⁶. -4 Pa, temperature 200-220℃, two-stage condensation collection, first stage condensation temperature 80-90℃, second stage condensation temperature 20-30℃; in step 3, the mixed inert gas is nitrogen and argon with a volume ratio of 98:2 and the partial pressure of inert gas accounts for ≥99%; in step 3, the low-frequency constant magnetic field strength is 0.05-0.1T, and the magnetic field direction is consistent with the crystal growth direction.

[0012] Preferably, the specific process of step 5 is as follows: Perfluorooctyltriethoxysilane with a purity ≥5N was selected as the surface agent. A surface agent solution with a mass fraction of 0.8-1.2% was prepared using anhydrous ethanol as the diluent. The amount of surface agent used was 0.5-0.8% of the crystal mass. The solution was prepared at a temperature of 80-90℃ and a vacuum degree ≤1×10⁻⁶. -3 The crystals were kept at a constant temperature of 0.1-0.12 MPa for 1.5 hours under an inert gas atmosphere. Then, the crystals were placed in a sealed container, filled with nitrogen to a pressure of 0.1-0.12 MPa, and sealed for storage.

[0013] Preferably, in the self-made composite chlorination modifier, the mass ratio of boron trichloride, antimony pentachloride, and anhydrous carbon tetrachloride is 3:2:95. The preparation process requires stirring and reacting at 50-60°C for 1.5 hours under nitrogen protection. After cooling and standing, the clear liquid at the top is used.

[0014] Preferably, the surface agent in step 5 is perfluorooctyltriethoxysilane with a purity ≥5N, and the surface agent treatment process is as follows: a surface agent solution with a mass fraction of 0.8-1.2% is prepared using anhydrous ethanol as a dilution medium, and the amount of surface agent used is 0.5-0.8% of the crystal mass. The solution is then treated at a temperature of 80-90℃ and a vacuum degree ≤1×10⁻⁶. -3 Incubate at Pa for 1.5 hours.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The stable gallium tetrachloride crystal material of the present invention has a regular triclinic crystal structure with precise and controllable lattice parameters, uniform distribution of Ga-Cl bond lengths and bond angles, and no obvious lattice defects. This significantly improves the chemical and thermal stability of the crystal. It has a low hydrolysis rate under normal temperature and high humidity conditions and is not easily decomposed at high temperatures, thus meeting the application requirements under extreme working conditions.

[0016] This invention employs a stepwise nucleation and segmented temperature-increasing crystallization process, combined with ultrasonic assistance and gradient cooling technology. It introduces four major innovations: precise control of the inert gas atmosphere, low-frequency magnetic field-assisted lattice optimization, a self-made composite chlorination modifier, and specific surface agent treatment. This achieves full-process controllability from nucleation to crystal growth, lattice regularization, and surface protection. The mixed inert gas atmosphere eliminates oxygen interference, the low-frequency magnetic field guides ordered ion coordination, the self-made modifier regulates the Ga-Cl bond coordination environment, and the surface agent forms a dense hydrophobic film. These four elements work synergistically to effectively solve the problems of wide crystal size distribution, irregular morphology, lattice stress concentration, and susceptibility to moisture absorption and hydrolysis in traditional processes. The prepared crystals have a purity ≥5N, exhibit a regular tetrahedral morphology, and show significantly improved structural integrity and stability compared to existing technologies. The preparation process of this invention is simple and highly controllable. Through raw material pretreatment, multi-stage drying, and vacuum sublimation purification, impurities and moisture are effectively removed, avoiding crystal contamination and structural defects. This makes it suitable for large-scale industrial production and has broad application prospects. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0018] A method for preparing a stable gallium tetrachloride crystal material includes the following steps: Step 1: Raw material pretreatment and modifier preparation: Select 50g of gallium metal block with a purity of 6N, place it in a quartz crucible, and prepare it under a vacuum of 1×10⁻⁶. -3 Vacuum baking was performed for 2.5 hours at 160℃ and 1 Pa. Hydrogen chloride gas with a purity of 5N was selected and dried in two stages using a calcium chloride drying column and a concentrated sulfuric acid drying tower to control the water content to ≤1ppm. A self-made composite chlorination modifier was prepared: boron trichloride, antimony pentachloride, and anhydrous carbon tetrachloride were taken in a mass ratio of 3:2:95 and reacted under nitrogen protection at 55℃ with stirring for 1.5 hours. After cooling and settling, the clear supernatant was collected for later use.

[0019] Step 2: Stepwise nucleation reaction: Place the quartz crucible into a sealed chlorination reactor, purge the air with nitrogen until the oxygen content is ≤10ppm; heat to 90℃, purge with dry hydrogen chloride gas at a flow rate of 65 mL / min, add a self-made composite chlorination modifier at a hydrogen chloride volume fraction of 0.4%, turn on the ultrasonic waves (frequency 50 kHz, power 120 W), add 0.8% trimethylchlorosilane, and react for 2 hours to generate the precursor.

[0020] Step 3: Segmented Heating Crystallization: Stop the ultrasound, introduce a nitrogen-argon mixture with a volume ratio of 98:2 into the reactor, maintaining an inert gas partial pressure of ≥99%; heat to 230℃ at a rate of 6℃ / min, hold at that temperature for 2.5 hours; then heat to 290℃ at a rate of 2.5℃ / min, turn on the low-frequency magnetic field (intensity 0.075T, direction consistent with the crystal growth direction), introduce a hydrogen chloride-nitrogen mixture with a volume ratio of 95:5 at a flow rate of 40 mL / min and a pressure of 0.13 MPa, and react for 3.5 hours.

[0021] Step 4: Gradient cooling and purification: Stop the flow of hydrogen chloride, purge with nitrogen, and cool to 150°C at 4°C / min, holding for 1 hour; then cool to room temperature at 1.5°C / min to obtain the crude product; place the crude product in a vacuum sublimation apparatus with a vacuum degree of 5×10⁻⁶. -4 Pa, temperature 210℃, two-stage condensation (first stage 85℃, second stage 25℃), collect sublimation products.

[0022] Step 5: Surface treatment and sealing: Prepare a 1.0% (w / w) perfluorooctyltriethoxysilane-anhydrous ethanol solution, and spray this solution onto the purified crystals. The amount of surface agent used is 0.6% of the crystal mass. The solution is then applied at 85°C and a vacuum of 1×10⁻⁶. -3 The crystals were kept at a pressure of 0.11 MPa for 1.5 hours under a nitrogen atmosphere, and then placed into a quartz bottle under nitrogen protection. The bottle was then filled with nitrogen to a pressure of 0.11 MPa and sealed for storage.

[0023] The obtained crystal was tested and found to be triclinic. Space group, lattice parameters a = 7.12 Å, b = 7.17 Å, c = 7.29 Å, α = 91.93°, β = 116.13°, γ = 116.91°, density 2.05 g·cm³ -3 Purity 5.4N, bond angle deviation 0.18°, dislocation density 4.2×10⁻⁶ 3 cm -2 The hydrolysis rate was 0.4% after 72 hours of storage at 25℃ and 50% humidity, and only 0.9% after 168 hours. The decomposition rate was 0.6% after 2 hours of storage at 300℃ and 1.8% after 2 hours of storage at 350℃. All performance characteristics were significantly improved compared to the system without surface agent treatment.

[0024] The obtained crystal was tested and found to be triclinic. Space group, lattice parameters a = 7.12 Å, b = 7.17 Å, c = 7.29 Å, α = 91.93°, β = 116.13°, γ = 116.91°, density 2.05 g·cm³ -3 Purity 5.4N, bond angle deviation 0.18°, dislocation density 4.2×10⁻⁶ 3 cm -2 The hydrolysis rate was 0.4% after 72 hours of storage at 25℃ and 50% humidity, and only 0.9% after 168 hours. The decomposition rate was 0.6% after 2 hours of storage at 300℃ and 1.8% after 2 hours of storage at 350℃. All performance characteristics were significantly improved compared to single-innovation systems and traditional processes. Example 2

[0025] A method for preparing a stable gallium tetrachloride crystal material includes the following steps: Step 1: Raw material pretreatment and modifier preparation: 80g of 6N pure gallium metal block was placed in a quartz crucible and heated under a vacuum of 8×10⁻⁶. -4 Vacuum baking for 2 hours at 170℃ and 1 Pa; water content ≤1ppm after two-stage drying of hydrogen chloride gas. Preparation of self-made composite chlorination modifier: Boron trichloride, antimony pentachloride and anhydrous carbon tetrachloride were mixed in a mass ratio of 3:2:95, stirred at 60℃ for 1.5 hours, cooled and allowed to stand, and the supernatant was collected.

[0026] Step 2: Stepwise nucleation reaction: After nitrogen purging, the temperature is raised to 85℃, the hydrogen chloride flow rate is 55 mL / min, and a self-made composite chlorination modifier is added at a hydrogen chloride volume fraction of 0.35%. Ultrasonic (45 kHz, 110 W) is used for assistance, and 0.6% trimethylchlorosilane is added. The reaction is carried out for 1.8 hours.

[0027] Step 3: Segmented heating crystallization: Stop the ultrasound, introduce a nitrogen-argon mixture with a volume ratio of 98:2, heat to 220℃ at 5℃ / min, and hold at that temperature for 3 hours; then heat to 280℃ at 2℃ / min, apply a low-frequency magnetic field of 0.07T, a mixed gas flow rate of 35 mL / min, a pressure of 0.12 MPa, and react for 4 hours.

[0028] Step 4: Gradient cooling and purification: Cool to 150℃ at 3℃ / min and hold for 1 hour; cool to room temperature at 1℃ / min; vacuum sublimation temperature 200℃, two-stage condensation (80℃, 20℃), purification and collection.

[0029] Step 5: Surface treatment and sealing: Prepare a 0.9% (w / w) perfluorooctyltriethoxysilane-anhydrous ethanol solution, using 0.5% of the crystal mass as the surface agent. Seal at 80°C and a vacuum of 8 × 10⁻⁶. -4 Insulate at 0.1 MPa for 1.5 hours; then fill with nitrogen to 0.1 MPa and seal for storage.

[0030] The obtained crystal has a purity of 5.3N, a bond angle deviation of 0.19°, and a dislocation density of 4.8 × 10⁻⁶. 3 cm -2 The hydrolysis rate was 0.5% after 72 hours and 1.1% after 168 hours at 25℃ and 50% humidity; the decomposition rate was 0.7% after 2 hours of heat treatment at 300℃ and 2.0% after 2 hours of heat treatment at 350℃. The crystal structure parameters met the requirements of this invention, and the stability was significantly improved compared with the system without surface agent treatment.

[0031] The obtained crystal has a purity of 5.3N, a bond angle deviation of 0.19°, and a dislocation density of 4.8 × 10⁻⁶. 3 cm -2 The hydrolysis rate was 0.5% after 72 hours and 1.1% after 168 hours at 25℃ and 50% humidity. The decomposition rate was 0.7% after 2 hours of heat treatment at 300℃ and 2.0% after 2 hours of heat treatment at 350℃. The crystal structure parameters met the requirements of this invention, and the stability was significantly improved compared with the single innovation point missing system.

[0032] Comparative Example 1 Gallium tetrachloride crystals were prepared using a traditional direct reaction method: the gallium block was dried directly with hydrogen chloride gas without vacuum baking, and then reacted at 250°C for 4 hours. After natural cooling, the product was obtained. The resulting crystals had a purity of 4.2N, exhibited significant lattice defects, and had a dislocation density of 8 × 10⁻⁶. 4 cm -2 The hydrolysis rate was 16.3% after 72 hours and 28.5% after 168 hours at 25℃ and 50% humidity; the decomposition rate was 8.5% after 2 hours of heat treatment at 300℃ and 15.2% after 2 hours of heat treatment at 350℃, and the stability was far lower than that of the product of this invention.

[0033] Comparative Example 2 (without surface agent treatment) The process of this invention is used, but the surface agent treatment step is omitted; the remaining parameters are the same as in Example 1. The resulting crystal has a purity of 5.3N, a bond angle deviation of 0.19°, and a dislocation density of 4.5 × 10⁻⁶. 3 cm -2The hydrolysis rate was 0.9% after 72 hours and 2.3% after 168 hours at 25℃ and 50% humidity. The decomposition rate was 0.7% after 2 hours of heat treatment at 300℃ and 2.1% after 2 hours of heat treatment at 350℃. The hydrolysis stability was significantly lower than that in Example 1, which proves the key role of surface agent treatment in improving the long-term hydrolysis resistance of crystals.

[0034] Comparative Example 3 (Replacement of Conventional Surface Agents) Using the process of this invention, perfluorooctyltriethoxysilane was replaced with the conventional silane coupling agent KH-550 as the surface agent, with other parameters remaining the same as in Example 1. The resulting crystals had a purity of 5.2N, a hydrolysis rate of 1.5% after 72 hours and 3.8% after 168 hours at 25°C and 50% humidity. The hydrophobic film on the surface easily decomposed at temperatures above 300°C, and the hydrolysis rate increased to 6.2% after being kept at 350°C for 2 hours. The stability was significantly lower than in Example 1, demonstrating the compatibility advantage of the specific surface agent.

[0035] Comparative Example 4 (without self-made composite chlorination modifier) The process of this invention was used, but the self-made composite chlorination modifier was omitted; the remaining parameters were the same as in Example 1. The resulting crystal had a purity of 5.1N, a bond angle deviation of 0.25°, and a dislocation density of 8.3 × 10⁻⁶. 3 cm -2 The hydrolysis rate was 1.2% after 72 hours and 3.1% after 168 hours at 25℃ and 50% humidity. The decomposition rate was 1.5% after 2 hours of heat treatment at 300℃ and 4.5% after 2 hours of heat treatment at 350℃. The lattice regularity and thermal stability decreased significantly, which proves the core role of the self-made modifier in regulating Ga-Cl bond coordination and optimizing the lattice structure.

[0036] Comparative Example 5 (all specific processes are missing) Using the raw material pretreatment and basic reaction process of this invention, four specific processes—self-made composite chlorination modifier, inert gas atmosphere control, low-frequency magnetic field assistance, and specific surface agent treatment—are omitted. The remaining parameters are consistent with Example 1. The resulting crystal has a purity of 4.7N, a bond angle deviation of 0.42°, and a dislocation density of 2.1 × 10⁻⁶. 4 cm -2 The hydrolysis rate was 5.8% after 72 hours and 12.3% after 168 hours at 25℃ and 50% humidity. The decomposition rate was 4.2% after 2 hours of heat treatment at 300℃ and 9.7% after 2 hours of heat treatment at 350℃. The performance was far worse than that of Example 1, which proves the necessity of the synergistic effect of the four specific processes to improve the overall performance of the crystal and highlights the inventiveness of the present invention.

[0037] Summary of comparative experimental data To visually demonstrate the performance advantages of the product of this invention, the core performance indicators of Example 1, Example 2, and each comparative example are summarized as follows: The data above demonstrates that the stable gallium tetrachloride crystal prepared by this invention, through the synergistic effect of its four major innovations, significantly outperforms traditional process products, control groups lacking a single innovation, and control groups lacking all specific processes in terms of purity, hydrolysis resistance, thermal stability, and structural integrity. In particular, Comparative Example 5 (lacking all specific processes) exhibits a significant performance decline, confirming the synergistic effect of the four specific processes, rather than a simple sum of individual processes. Furthermore, the performance of each control group lacking a single innovation is inferior to the examples, further highlighting the indispensability of each specific process and the self-made raw materials, significantly enhancing the inventiveness of this invention and meeting the application requirements of high-end semiconductor devices.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0039] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A stable gallium tetrachloride crystal material, characterized in that, The crystal is triclinic and its space group is [missing information]. The crystal structure is a zero-dimensional GaCl4 tetrahedral cluster structure, Ga 3+ With four Cl - Formation of edge-shared tetrahedral coordination; The crystal has the following lattice parameters: a = 7.12 ± 0.02 Å, b = 7.17 ± 0.02 Å, c = 7.29 ± 0.02 Å, α = 91.93 ± 0.05°, β = 116.13 ± 0.05°, γ = 116.91 ± 0.05°, and a unit cell volume of 285.16 ± 0.5 Å. 3 The crystal density is 2.05 ± 0.02 g·cm³. -3 .

2. A method for preparing the stable gallium tetrachloride crystal material according to claim 1, characterized in that, Includes the following steps: Step 1: Raw material pretreatment: Select gallium metal blocks with a purity ≥ 6N and hydrogen chloride gas with a purity ≥ 5N; the gallium metal blocks are subjected to a vacuum degree ≤ 1×10 -3 Vacuum baking at 150-180℃ for 2-3 hours; hydrogen chloride gas undergoes two-stage drying treatment, with a water content ≤1ppm; Step 2: Stepwise nucleation reaction: Place the pretreated gallium block in a sealed chlorination reactor, replace with nitrogen until the oxygen content is ≤10ppm; heat to 80-100℃, and introduce hydrogen chloride gas at a flow rate of 50-80 mL / min; Step 3: Segmented heating for crystallization; Step 4: Gradient cooling and purification: Cool with nitrogen gas, reduce temperature to 150℃ at 3-5℃ / min and hold for 1 hour, then reduce temperature to room temperature at 1-2℃ / min; the crude product is purified by vacuum sublimation and the product is collected. Step 5: Surface treatment and sealing.

3. The method according to claim 2, characterized in that, In step 2, a self-made composite chlorination modifier is added, with the amount of modifier added being 0.3-0.5% of the volume fraction of hydrogen chloride gas; the ultrasonic-assisted reaction is carried out for 1.5-2 hours to generate a precursor; the self-made composite chlorination modifier is prepared by mixing boron trichloride, antimony pentachloride, and anhydrous carbon tetrachloride in a mass ratio of 3:2:95, and the preparation conditions are nitrogen protection, stirring reaction at 50-60℃ for 1.5 hours, and the upper clear liquid is taken after cooling and standing.

4. The method according to claim 2, characterized in that, In step 2, the ultrasonic frequency is 40-60 kHz and the power is 100-150 W; in step 2, 0.5-1% of trimethylchlorosilane is added as a dispersant.

5. The method according to claim 2, characterized in that, The specific process conditions for segmented temperature-increasing crystallization are as follows: Stop the ultrasound and introduce a mixture of nitrogen and argon inert gas with a volume ratio of 98:2 into the reactor, maintaining the partial pressure of the inert gas at ≥99%. Then increase the temperature to 220-250℃ at a rate of 5-8℃ / min and hold at that temperature for 2-3 hours; The temperature was then increased to 280-300℃ at a rate of 2-3℃ / min, and a low-frequency constant magnetic field with an intensity of 0.05-0.1T was applied, with the direction of the magnetic field aligned with the crystal growth direction. The flow rate of hydrogen chloride gas was maintained at 30-50 mL / min and the pressure at 0.12-0.15 MPa, and the reaction was carried out for 3-4 hours.

6. The method according to claim 5, characterized in that, In step 3, the second stage of crystallization involves introducing a mixture of hydrogen chloride and nitrogen gas with a volume ratio of 95:

5.

7. The method according to claim 2, characterized in that, The vacuum sublimation conditions in step 4 are: vacuum degree ≤ 5 × 10⁻⁶ -4 Pa, temperature 200-220℃, two-stage condensation collection, first stage condensation temperature 80-90℃, second stage condensation temperature 20-30℃; in step 3, the mixed inert gas is nitrogen and argon with a volume ratio of 98:2 and the partial pressure of inert gas accounts for ≥99%; in step 3, the low-frequency constant magnetic field strength is 0.05-0.1T, and the magnetic field direction is consistent with the crystal growth direction.

8. The method according to claim 2, characterized in that, The specific process for step 5 is as follows: Perfluorooctyltriethoxysilane with a purity ≥5N was selected as the surface agent. A surface agent solution with a mass fraction of 0.8-1.2% was prepared using anhydrous ethanol as the diluent. The amount of surface agent used was 0.5-0.8% of the crystal mass. The solution was prepared at a temperature of 80-90℃ and a vacuum degree ≤1×10⁻⁶. -3 The crystals were kept at a constant temperature of 0.1-0.12 MPa for 1.5 hours under an inert gas atmosphere. Then, the crystals were placed in a sealed container, filled with nitrogen to a pressure of 0.1-0.12 MPa, and sealed for storage.

9. The method according to claim 3, characterized in that, In the self-made composite chlorination modifier, the mass ratio of boron trichloride, antimony pentachloride, and anhydrous carbon tetrachloride is 3:2:

95. The preparation process requires stirring and reacting at 50-60℃ for 1.5 hours under nitrogen protection. After cooling and standing, the clear liquid at the top is used.

10. The method according to claim 8, characterized in that, The surface agent mentioned in step 5 is perfluorooctyltriethoxysilane with a purity ≥5N. The surface agent treatment process is as follows: prepare a surface agent solution with a mass fraction of 0.8-1.2% using anhydrous ethanol as the diluent; the amount of surface agent used is 0.5-0.8% of the crystal mass; and treat at a temperature of 80-90℃ and a vacuum degree ≤1×10⁻⁶. -3 Incubate at Pa for 1.5 hours.

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