A silicon carbide powder with controllable particle size for growing silicon carbide crystals, a synthesis method and application thereof

Abstract

This invention discloses a silicon carbide powder with controllable particle size for silicon carbide crystal growth, its synthesis method, and its applications, relating to the field of semiconductor technology. Silicon carbide powder is prepared by reacting elemental silicon and elemental carbon under vacuum. By adjusting the particle size of elemental silicon, elemental carbon, carbon density, and the carbon-silicon molar ratio, this invention can efficiently control the particle size of the silicon carbide powder to be 4-6 times the particle size of elemental carbon. The synthesis method of this invention has a simple preparation process and produces high-purity silicon carbide powder, overcoming the shortcomings of existing technologies that synthesize SiC powder with uncontrollable, small particle sizes. This method uses simple equipment, has high synthesis efficiency, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to a silicon carbide powder with controllable particle size for silicon carbide crystal growth, its synthesis method, and its application. Background Technology

[0002] In the field of semiconductor technology, wide-bandgap semiconductor materials, represented by silicon carbide (SiC) and gallium nitride (GaN), have become an important cornerstone of modern electronic technology development due to their excellent physical and chemical properties. Among them, SiC has advantages such as high breakdown field strength, high thermal conductivity, high saturated electron drift velocity, and high bonding energy, giving it significant advantages in performance aspects such as breakdown voltage resistance, radiation resistance, and operating temperature.

[0003] Large-particle-size silicon carbide powder (>2000 μm) can be used to improve processing efficiency, while small-particle-size powder (<500 μm) can be used to improve crystal quality. Currently, the preparation process for small-particle-size silicon carbide powder is relatively mature, but the particle size distribution is wide and difficult to control precisely. With the widespread application of SiC substrates in power electronic devices, the market demand for high-quality, large-size silicon carbide crystals is increasing, which in turn drives higher requirements for the quality and particle size controllability of SiC powder. Existing silicon carbide powder preparation processes have significant shortcomings in achieving efficient SiC growth and controllable particle size, severely restricting the flexibility and yield of silicon carbide powder growth.

[0004] Therefore, developing a simple and precisely controllable SiC powder preparation process is of great significance for achieving high-quality, controllable particle size, especially large-size silicon carbide crystals for large-scale production.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a silicon carbide powder with controllable particle size for silicon carbide crystal growth, its synthesis method, and its application, so as to solve the above-mentioned technical problems.

[0007] This invention is implemented as follows:

[0008] In a first aspect, embodiments of the present invention provide a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, comprising the following steps:

[0009] Silicon carbide powder is prepared by reacting elemental silicon and elemental carbon under vacuum.

[0010] The vacuum degree is 1×10 -2 torr to 1×10 2The particle size of elemental silicon is ≤200μm, while that of elemental carbon is 200μm-2000μm; the density of elemental carbon is 0.35g / cm³. 3 -1g / cm 3 The molar ratio of elemental silicon to elemental carbon is (1-1.5):1.

[0011] The particle size of the obtained silicon carbide powder is 4 to 6 times that of the carbon element used.

[0012] Secondly, embodiments of the present invention provide a silicon carbide powder with controllable particle size prepared by the synthesis method described above.

[0013] Thirdly, embodiments of the present invention provide an application of silicon carbide powder with controllable particle size prepared by the aforementioned synthesis method in silicon carbide crystal growth.

[0014] The present invention has the following beneficial effects:

[0015] The method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth provided in this invention can efficiently control the particle size of silicon carbide powder to be 4 to 6 times that of carbon by adjusting the particle size of silicon, the particle size of carbon, the density of carbon, and the carbon-silicon molar ratio. The preparation process of silicon carbide powder is simple and the obtained silicon carbide powder has high purity, which makes up for the shortcomings of the small and uncontrollable particle size of SiC powder synthesized by the prior art. The equipment used in this method is simple, the synthesis efficiency is high, and it is suitable for large-scale industrial production. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 Images showing the morphology of carbon particles and flake graphite: (a) carbon particles, (b) flake graphite;

[0018] Figure 2 Images showing the morphology of the silicon carbide powder prepared in Example 1: (a) small-scale image, (b) particle size test image;

[0019] Figure 3 Images showing the morphology of the silicon carbide powder obtained in Example 2: (a) a small-scale image, and (b) an image of the crucible;

[0020] Figure 4Images showing the morphology of the silicon carbide powder prepared in Example 3: (a) small-scale image, (b) particle size test image;

[0021] Figure 5 Images showing the morphology of the silicon carbide powder prepared in Example 4: (a) small-scale image, (b) micrograph (magnified 5x).

[0022] Figure 6 Images showing the morphology of the silicon carbide powder prepared in Example 5: (a) small-scale image, (b) micrograph (magnified 5x).

[0023] Figure 7 Images showing the morphology of silicon carbide powder obtained in Example 6 (small scale).

[0024] Figure 8 Images showing the morphology of the silicon carbide powder obtained in Example 7 (small scale).

[0025] Figure 9 Images showing the morphology of the silicon carbide powder prepared in Example 8: (a) small-scale image, (b) particle size test image;

[0026] Figure 10 Images showing the morphology of silicon carbide powder obtained in Example 9 (small scale).

[0027] Figure 11 The image shows the morphology of the silicon carbide powder obtained in Example 10 (small scale).

[0028] Figure 12 Images showing the morphology of silicon carbide powder obtained in Example 12: the left image is of the flake graphite produced, and the right image is of the produced material from Example 1;

[0029] Figure 13 Images showing the morphology of the silicon carbide powder prepared in Example 13: (a) small-scale image, (b) microscopic image (magnified 5x).

[0030] Figure 14 This is a schematic diagram of the XRD test results. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0032] In a first aspect, embodiments of the present invention provide a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, comprising the following steps:

[0033] Silicon carbide powder is prepared by reacting elemental silicon and elemental carbon under vacuum.

[0034] The vacuum degree is 1×10 -2 torr to 1×10 2 The particle size of elemental silicon is ≤200μm, while that of elemental carbon is 200μm-2000μm; the density of elemental carbon is 0.35g / cm³. 3 -1g / cm 3 The molar ratio of silicon to carbon is (1-1.5):1.

[0035] The particle size of the obtained silicon carbide powder is 4 to 6 times that of the carbon element used.

[0036] In this embodiment of the invention, the particle size of the carbon element is 20μm-2000μm. The provided synthesis method can efficiently produce silicon carbide powder with small and large particle sizes. Within the set average particle size range, the particle size of the silicon carbide powder is 4 to 6 times that of the carbon element used, and the yield is 45%-60%, which is suitable for large-scale mass production.

[0037] If large-particle carbon is used to prepare silicon carbide, its smaller specific surface area results in fewer adsorbed impurities, which is beneficial for the preparation of high-purity silicon carbide. The large particle size can also avoid excessive densification or deformation of silicon carbide. In addition, the large gaps between large-particles are conducive to achieving a more uniform filling density and reducing lattice defects.

[0038] It should be noted that as the particle size of carbon element increases, the particle size of synthesized silicon carbide shows a stable trend.

[0039] The silicon carbide powder obtained in the embodiments of the present invention has a 4H crystal form and high purity.

[0040] In an optional embodiment, the density of elemental carbon is 0.35 g / cm³. 3 -1g / cm 3 .

[0041] It should be noted that during the synthesis of silicon carbide powder, setting the appropriate carbon density is beneficial for balancing porosity and particle strength, thereby maximizing reaction efficiency. If the carbon density is too low, the carbon will be loosely packed, reducing the overall mechanical strength of the furnace charge, making it prone to collapse at high temperatures, resulting in incomplete reaction and reduced raw material conversion rate. If the carbon density is too high, the packing will be dense, preventing the silicon atmosphere from penetrating into the interior, hindering mass transfer at the reaction interface, causing insufficient internal reaction, forming black-core silicon carbide particles, and leading to a decrease in the reaction rate.

[0042] In an optional embodiment, the molar ratio of elemental silicon to elemental carbon is (1-1.5):1.

[0043] It should be noted that at high temperatures, carbon easily generates CO gas, which adheres to the surface of carbon and hinders the full contact between silicon and carbon, resulting in incomplete carbon reaction. Therefore, the heating device must be evacuated and filled with inert gas.

[0044] Adding an appropriate excess of elemental silicon facilitates sufficient contact between elemental carbon and elemental silicon, pushing the reaction in the forward direction and thus achieving efficient synthesis of silicon carbide.

[0045] In an optional embodiment, the particle size of the obtained silicon carbide powder is 4 to 6 times that of the particle size of the carbon element used.

[0046] It should be noted that the method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth provided by the present invention has a simple preparation process. By adjusting the particle size of silicon, the particle size of carbon, the density of carbon, and the carbon-silicon molar ratio, the particle size of silicon carbide powder can be efficiently controlled to be 4 to 6 times the particle size of carbon, thereby obtaining high-quality, high-purity, large-size silicon carbide powder with controllable particle size.

[0047] In an optional embodiment, the molar ratio of elemental silicon to elemental carbon is (1.05-1.1):1.

[0048] It should be noted that in the reaction C + Si → SiC, the molar ratio of the two reactants is set according to the reaction equation. If one of the reactants is in appropriate excess, it will promote the reaction to move towards the product, which is beneficial to the efficient conversion of the reactants and can effectively inhibit the decomposition of SiC at high temperature. If the molar ratio of carbon is too large, the density of carbon will be too high, which will prevent the silicon atmosphere from penetrating into the interior, resulting in insufficient internal reaction and the formation of black-hearted silicon carbide particles.

[0049] In an optional embodiment, the carbon element is selected from flake graphite or carbon particles, and its structural image can be found in [the image below]. Figure 1 (a) Carbon particles, (b) Flake graphite.

[0050] It should be noted that, in order to ensure the high purity of SiC, in the embodiments of the present invention, both silicon and carbon are selected from high-purity raw materials with a purity greater than 99.999%; if the purity is low, the product obtained will not be silicon carbide for semiconductor crystal growth.

[0051] In the embodiments of the present invention, silicon powder is used as the silicon element.

[0052] In an optional embodiment, the temperature for preparing silicon carbide powder is 1800℃-2400℃, and the time is 5h-30h.

[0053] The time setting can be adjusted reasonably according to the amount of material being processed to ensure that the produced powder reacts fully.

[0054] In an optional implementation, the pressure of the device to be heated is less than 10 during vacuuming. -5 During the torr test, inert gas is introduced; when the pressure reaches 1×10⁻⁶, the gas is filled with inert gas. -2 torr to 1×10 2 During the torr process, the temperature is raised from room temperature to 2000℃-2300℃ to carry out the reaction.

[0055] It should be noted that the vacuum is drawn down to a pressure less than 10. -5 The primary purpose of TORRR (high vacuum environment) is to remove active gas impurities in the system, such as O2, H2O, N2, etc., to avoid oxidation, nitriding, or the formation of other non-target phases, which could damage the integrity of the SiC crystal structure and reduce the purity of the product.

[0056] Inhaling gas at low pressure allows the partial pressure of inert gas to replace residual air, ensuring that the system is dominated by inert gas. In addition, filling with inert gas and controlling the pressure can isolate air, avoid corrosion of crucible materials or heating devices, and extend the service life of the equipment.

[0057] If the pressure is high, the resulting silicon carbide powder will have a small particle size, and the particle size of the silicon carbide powder will be less than 4 times the particle size of the carbon element used. The morphology of the powder will be flocculent, and the silicon carbide powder will be loose and the grain boundaries will be diffuse. When observed under magnification, the boundaries of the silicon carbide powder will be blurred and the crystallization will be incomplete.

[0058] The measurement of the crystal morphology or particle size of silicon carbide powder can be selected according to actual needs; in this embodiment of the invention, the particle size is mainly measured using a ruler, and the morphology is mainly measured by taking pictures with a camera or observing with a conventional microscope.

[0059] It should be noted that silicon carbide powder with a particle size exceeding the range of an electron microscope (the imaging range of an electron microscope is less than 1000 μm) cannot be accurately measured with a microscope. Therefore, in the embodiments of the present invention, the particle size of silicon carbide powder with a particle size greater than 1000 μm is measured using a ruler.

[0060] This invention does not impose any particular limitation on the inert gas; argon or helium can be selected according to actual needs.

[0061] The pressure is 1×10 -2 torr to 1×10 2 During the torr process, raising the temperature from room temperature to 2000℃-2300℃ can reduce the temperature difference within the heating device, avoid local overcooling or overheating, reduce the impact of environmental variables on the synthesis process, and ensure the quality consistency of different batches of products.

[0062] High temperatures are often accompanied by silicon melting (Si melting point 1414℃), while low-pressure environments can reduce the volatilization temperature of silicon and avoid compositional segregation or structural inhomogeneity caused by the liquid phase. High-temperature and low-pressure environments are conducive to suppressing the growth of abnormal grains and obtaining SiC with a uniform microstructure. They can also promote the volatilization of low-boiling-point impurities and improve product purity.

[0063] In an optional embodiment, the internal pressure of the heating device is reduced to less than 10 after evacuation. -5 After torr, the furnace pressure should not exceed 7.5 × 10⁻⁶ within 12 hours under sealed conditions. -2 The test further verifies the airtightness of the heating device; it can effectively prevent external gas from seeping in and internal gas from leaking, reduce the generation of impurities, and improve product yield; in addition, it can ensure the stability of the synthesis process and the reliability of long-term equipment operation.

[0064] In an optional embodiment, elemental silicon and elemental carbon are placed in a crucible for a synthesis reaction, wherein the crucible is made of graphite with an ash content of <5 ppm.

[0065] It should be noted that graphite crucibles are selected because graphite has good thermal conductivity, which allows for rapid and uniform heat transfer, reduces the temperature gradient within the reaction system, and promotes the uniform progress of the Si+C→SiC reaction. Graphite does not react with either silicon or carbon at high temperatures, thus not introducing new impurities. Furthermore, slight volatilization (forming CO) may occur on the surface of the graphite crucible, but excessive loss can be avoided through process control. If carbon is insufficient in the reaction, the graphite crucible can provide a small amount of carbon source.

[0066] In an optional implementation, in order to reduce the loss of graphite in the synthesis process and extend the service life of the graphite crucible, a layer of high-purity carbon powder is spread on the bottom of the crucible before loading silicon and carbon, and the distance between the loading surface and the top of the crucible is maintained at 50mm-150mm. The amount of high-purity carbon powder can be reasonably set according to the actual amount of material being processed.

[0067] In an optional embodiment, the heating device is selected from any one of a high-frequency induction heating furnace, a medium-frequency induction heating furnace, and a graphite resistance heating furnace.

[0068] The heating device can be selected reasonably according to actual needs.

[0069] In summary, the method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth provided by the embodiments of the present invention includes the following steps:

[0070] With a molar ratio (1.05-1.1):1, silicon and carbon are mixed evenly and then placed into a graphite crucible. The crucible is then placed in a graphite resistance heating furnace, and a vacuum is drawn until the internal pressure of the furnace is less than 10. -5After torr, inert helium gas is introduced; wait until the pressure inside the furnace reaches 1×10⁻⁶. -2 torr to 1×10 2 During the torr process, the temperature is raised from room temperature to 1800℃-2400℃ and reacted for 5h-30h. Then, the temperature inside the furnace is lowered to room temperature to obtain silicon carbide powder with controllable particle size for silicon carbide crystal growth.

[0071] Among them, silicon and carbon should be selected reasonably according to actual needs.

[0072] Secondly, embodiments of the present invention provide a silicon carbide powder with controllable particle size prepared by the synthesis method described above.

[0073] Thirdly, embodiments of the present invention provide an application of silicon carbide powder with controllable particle size prepared by the aforementioned synthesis method in silicon carbide crystal growth.

[0074] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0075] Example 1

[0076] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, including the following steps:

[0077] After mixing silicon powder and carbon particles evenly at a molar ratio of 1.05:1, the mixture is placed into a graphite crucible. The crucible is then placed in a graphite resistance heating furnace, and a vacuum is drawn until the internal pressure of the furnace is less than 10 kJ / L. -5 After torr, inert helium gas is introduced; wait until the pressure inside the furnace reaches 1×10⁻⁶. -2 torr to 1×10 2 During the torr process, the temperature is raised from room temperature to 2200℃ and reacted for 25 hours. Then, the temperature inside the furnace is lowered to room temperature to obtain silicon carbide powder.

[0078] The silicon powder has a particle size of 200 μm, the carbon particles have a particle size of 1000 μm, and the carbon particle density is 0.65 g / cm³. 3 The yield of silicon carbide powder was calculated to be 53%.

[0079] This embodiment also measured the particle size of the prepared silicon carbide powder: the average particle size ranged from 4000 μm to 8000 μm, which is about 5 times larger than that of carbon particles. The produced powder showed a relatively complete reaction, and there was no carbon residue inside the particles. The relevant morphology is shown in [reference needed]. Figure 2 (a) Small-scale image, (b) Particle size test image.

[0080] Example 2

[0081] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0082] Silicon powder and carbon particles were mixed evenly at a molar ratio of 1.1:1 and then placed into a graphite crucible; the carbon particles had a particle size of 1000 μm and a particle density of 0.65 g / cm³. 3 The yield of silicon carbide powder was calculated to be 48%.

[0083] The average particle size of the obtained silicon carbide powder ranged from 4000 μm to 8000 μm, which is about 5 times larger than that of carbon particles. The reaction was complete, and the particle size of the silicon carbide powder was close to that of Example 1. However, the crucible was severely corroded, making it unsuitable for large-scale production. The relevant morphology is shown in [reference needed]. Figure 3 (a) Small-scale image, (b) Image of the crucible.

[0084] Example 3

[0085] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0086] Silicon powder and carbon particles were mixed evenly at a molar ratio of 1:1.1 and then placed into a graphite crucible; the carbon particles had a particle size of 1000 μm and a particle density of 0.65 g / cm³. 3 The yield of silicon carbide powder was calculated to be 45%.

[0087] The average particle size of the obtained silicon carbide powder ranges from 4000 μm to 8000 μm, which is about 5 times larger than that of carbon particles. Increasing the carbon particle molar ratio does not affect the particle size. Excess carbon leads to some carbon not participating in the reaction, resulting in black core material and incomplete reaction. Related morphologies are shown in [reference needed]. Figure 4 (a) Small-scale image, (b) Particle size test image.

[0088] Example 4

[0089] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0090] The silicon powder has a particle size of 200 μm, the carbon particles have a particle size of 200 μm, and the carbon particle density is 1.2 g / cm³. 3 The yield of silicon carbide powder was calculated to be 46%.

[0091] The average particle size of the prepared silicon carbide powder ranges from 800μm to 1200μm, which is about 5 times larger than that of carbon particles. The carbon particle density is greater than the set range, so the silicon atmosphere cannot be fully impregnated and the reaction is incomplete, resulting in black core material in the prepared silicon carbide powder. See Figure 5 for specific morphology: (a) small scale image, (b) microscopic image (magnified 5 times).

[0092] Example 5

[0093] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0094] The silicon powder has a particle size of 200 μm, the carbon particles have a particle size of 200 μm, and the carbon particle density is 0.8 g / cm³. 3 The yield of silicon carbide powder was calculated to be 52%.

[0095] The average particle size of the prepared silicon carbide powder ranges from 800μm to 1200μm, which is about 5 times larger than that of carbon particles. The prepared silicon carbide powder crystals have no black cores, and the powder produced has a full reaction. See Figure 6 for specific morphology: (a) small scale image, (b) microscopic image (magnified 5 times).

[0096] Example 6

[0097] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0098] The carbon particles have a diameter of 800 μm and a density of 0.45 g / cm³. 3 The yield of silicon carbide powder was calculated to be 49%.

[0099] The average particle size of the prepared silicon carbide powder ranges from 3000μm to 5000μm, which is about 5 times larger than that of carbon particles. The density is within the set range, the reaction is complete, and there is no black core phenomenon. See Figure 7 for the specific morphology.

[0100] Example 7

[0101] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0102] The carbon particle size is 800 μm, and the carbon particle density is 1.5 g / cm³. 3 The yield of silicon carbide powder was calculated to be 45%.

[0103] The average particle size of the prepared silicon carbide powder ranges from 300μm to 5000μm, which is about 5 times larger than that of carbon particles. The carbon particle density is greater than the set range, so the silicon atmosphere cannot be fully impregnated, the reaction is incomplete, and there are black core materials. See Figure 8 for the specific morphology.

[0104] Example 8

[0105] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0106] The carbon particles have a diameter of 1000 μm and a density of 1.5 g / cm³. 3 The yield of silicon carbide powder was calculated to be 46%.

[0107] The average particle size of the obtained silicon carbide powder ranges from 4000μm to 8000μm, which is about 5 times larger than that of carbon particles. Due to the excessive density of carbon particles, the silicon atmosphere cannot penetrate into the interior, resulting in insufficient reaction of the produced powder and forming black core silicon carbide powder. See Figure 9 for specific morphology: (a) small scale image, (b) particle size test image.

[0108] Example 9

[0109] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0110] The carbon particle size is 2000 μm, and the carbon particle density is 0.8 g / cm³. 3 The yield of silicon carbide powder was calculated to be 49%.

[0111] The average particle size of the prepared silicon carbide powder ranges from 6000μm to 10000μm, which is about 4 times larger than that of carbon particles, indicating a complete reaction. See Figure 10 for specific morphology.

[0112] Example 10

[0113] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0114] The carbon particle size is 2000 μm, and the carbon particle density is 1.5 g / cm³. 3 The yield of silicon carbide powder was calculated to be 47%.

[0115] The average particle size of the prepared silicon carbide powder ranges from 6000μm to 10000μm, which is about 3.5 times larger than that of carbon particles. The carbon particle density is greater than the set range, so the silicon atmosphere cannot be fully impregnated, the reaction is incomplete, and there are black core materials. See Figure 11 for the specific morphology.

[0116] Example 11

[0117] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0118] The carbon particle size is 2500 μm, and the carbon particle density is 0.6 g / cm³. 3 Calculations show that the yield of silicon carbide powder is 40%.

[0119] The average particle size of the prepared silicon carbide powder ranges from 6000μm to 10000μm. The carbon particle size exceeds the set range, limiting the increase in particle size and ensuring sufficient reaction. The specific morphology is similar to that of Example 9.

[0120] Example 12

[0121] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0122] The carbon element used is flake graphite with a particle size of 1000 μm and a density of 0.65 g / cm³. 3 The yield of silicon carbide powder was calculated to be 51%.

[0123] The average particle size of the silicon carbide powder obtained ranges from 4000μm to 8000μm, which is about 5 times larger than that of carbon particles, indicating that the powder reacts fully. See Figure 12 for specific morphology: the left side shows the flake graphite produced, and the right side shows the produced material from Example 1.

[0124] Example 13

[0125] This embodiment provides a method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, which differs from Example 1 only in that:

[0126] When the pressure inside the furnace is 1×10 -2 torr up to 6×10 2 During the torr reaction, the temperature was raised from room temperature to 2200℃ and reacted for 25 hours; the carbon particle size was 200 μm and the carbon particle density was 0.25 g / cm³. 3 Calculations show that the yield of silicon carbide powder is 40%.

[0127] The average particle size of the obtained silicon carbide powder ranges from 500μm to 700μm, which is about 5 times larger than that of carbon particles. The powder is somewhat flocculent, with irregular morphology, incomplete crystallization, and is brittle, resulting in a low yield. See Figure 13 for specific morphology.

[0128] Test Example 1

[0129] This test example performs XRD tests on the silicon carbide powders prepared in Examples 1-4, 6, 8, and 12, respectively. The test results are shown in [Figure 1]. Figure 14 The corresponding icons are 1-7, and icon 75 corresponds to the standard sample.

[0130] XRD test results show that the silicon carbide powder sample is of the standard 4H crystal form.

[0131] Test Example 2

[0132] This test example tested the purity of the silicon carbide powder prepared in Example 1, and the test results are shown in Table 1.

[0133] Table 1 Purity Test Results

[0134]

[0135] As can be seen from the data in Table 1, the purity of the silicon carbide powder prepared in Example 1 is 99.99997%, and its yield is as high as 58%, thus producing silicon carbide powder with controllable particle size with high output and high purity.

[0136] In summary, the molar ratio setting has a relatively small impact on the particle size of silicon carbide powder, but a significant impact on the crystal form, purity, and yield of silicon carbide. Using large-diameter carbon particles with a particle size greater than 1000 μm (1000 μm-2500 μm) can produce silicon carbide powder in the range of 4000 μm-8000 μm, with the average particle size of the produced silicon carbide powder increasing by 3 to 5 times the particle size of the carbon particles used. As the particle size of carbon particles increases, the particle size of silicon carbide powder no longer increases, but the increase factor of particle size and the yield decrease with the increase of carbon particle size. On the other hand, using small-diameter carbon particles with a particle size less than 500 μm increases the average particle size of the produced silicon carbide powder by 6 times the particle size of the carbon particles used. Therefore, by adjusting the particle size of silicon, the particle size of carbon, the density of carbon, and the carbon-silicon molar ratio, this invention can efficiently control the particle size of silicon carbide powder to be 4-6 times that of carbon. The synthesis method of this invention has a simple preparation process and produces silicon carbide powder with high purity, which makes up for the shortcomings of existing technologies that produce SiC powder with uncontrollable small particle size. The equipment used in this method is simple, the synthesis efficiency is high, and it is suitable for large-scale industrial production.

[0137] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for synthesizing silicon carbide powder with controllable particle size for silicon carbide crystal growth, characterized in that, Includes the following steps: Silicon carbide powder is prepared by reacting elemental silicon and elemental carbon under vacuum. The vacuum degree is 1×10 -2 torr to 1×10 2 The silicon particle size is ≤200μm, and the carbon particle size is 200μm-2000μm; the carbon density is 0.35g / cm³. 3 -1g / cm 3 The molar ratio of silicon to carbon is (1.05-1.1):

1. The particle size of the silicon carbide powder obtained is 4 to 6 times that of the carbon element used. The silicon carbide powder is prepared at a temperature of 1800℃-2400℃ for 5h-30h.

2. The synthesis method according to claim 1, characterized in that, The carbon element is selected from flake graphite or carbon particles.

3. The synthesis method according to claim 1, characterized in that, During vacuuming, the pressure of the heating device is less than 10. - 5 During the torr test, inert gas is introduced; when the pressure reaches 1×10⁻⁶, the gas is filled with inert gas. -2 torr to 1×10 2 During torr, the temperature is raised from room temperature to 2000℃-2300℃ to carry out the reaction.

4. The synthesis method according to claim 1, characterized in that, Silicon and carbon were placed in a crucible for a synthesis reaction. The crucible was made of graphite with an ash content of <5 ppm.

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