Synthesizer for mass production of SiC powder by optimizing high-temperature area position and SiC powder production method

Abstract

The invention relates to a synthesis device for mass production of SiC powder by optimizing a high-temperature area position and a SiC powder production method.According to the synthesis device, a graphite structure is additionally arranged at the bottom of a crucible barrel, a hollow cavity structure is arranged in a graphite base, the crucible barrel and the graphite base are coaxially arranged, and the central axes of the crucible barrel and the graphite base coincide; the heat preservation layer is arranged outside the crucible barrel, so that the position of a high-temperature area is improved, the radial temperature gradient is optimized, cracking of the bottom of the crucible and growth of SiC particles are effectively prevented, the axial temperature gradient is adjusted and controlled through process setting, the discharging ratio of large-particle-size SiC powder can be increased, and synthesis of high-purity, large-batch and low-carbon-impurity-content SiC powder is facilitated.

Description

Technical Field

[0001] This invention relates to a synthesis apparatus and a method for mass production of SiC powder by optimizing the location of high-temperature regions, belonging to the field of SiC powder preparation technology. Background Technology

[0002] Silicon carbide (SiC) is a third-generation wide bandgap semiconductor material. Due to its excellent properties such as large bandgap, high thermal conductivity, high critical breakdown electric field strength, high saturation carrier drift velocity and low dielectric constant, it has attracted widespread attention in recent years.

[0003] Currently, physical vapor transport (PVT) is the mainstream technology for preparing SiC single crystals. As the core raw material for PVT, the market demand for SiC powder continues to rise with the widespread application of SiC single crystals in semiconductors, new energy, and other fields. At present, the industry mainly uses an improved self-propagating synthesis process combined with a single-coil PVT synthesis system to prepare SiC powder. However, this method has two major technical bottlenecks: first, the amount synthesized in a single batch is limited, making it difficult to meet the needs of large-scale production; second, the carbon impurity content in the product is relatively high, affecting the quality of subsequent single crystal growth. Therefore, developing a SiC powder synthesis technology that combines high purity, low carbon impurities, and large-scale preparation capabilities is of significant practical importance for promoting the development of the third-generation semiconductor industry.

[0004] To address the aforementioned problems, patent document CN114832764A discloses a device for producing silicon carbide powder with a large loading capacity and its synthesis method. This structure includes a dual-coil induction heater, a crucible, and a heat-insulating structure, with graphite rings or graphite pillars added inside the crucible. During operation, the silicon carbide powder raw materials are mixed, and segmented heating is employed. The dual-coil induction heaters are independently controlled, and their relative positions are adjustable, which facilitates the control of the axial temperature gradient and the improvement of the radial temperature gradient. However, this device still has a high-temperature zone, which is difficult to control, prone to crystallization, leading to difficulties in material handling, and limited temperature and temperature gradient control range, thus hindering the further application of the dual-coil synthesis furnace.

[0005] Given the limited research on the synthesis of SiC powder using dual-coil induction heating technology, there is an urgent need to develop a novel dual-coil high-temperature furnace synthesis device that can optimize the position of the high-temperature zone, so as to facilitate the large-scale and efficient preparation of SiC powder. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a synthesis apparatus and a method for mass production of SiC powder by optimizing the location of high-temperature regions.

[0007] The synthesis apparatus of the present invention adds a graphite structure to the bottom of the crucible, which improves the position of the high-temperature zone, optimizes the radial temperature gradient, effectively prevents cracking at the bottom of the crucible and the growth of SiC particles, and can increase the output ratio of large-particle-size SiC powder by controlling the axial temperature gradient through process settings, which is beneficial to synthesizing high-purity, large-volume SiC powder with low carbon impurity content.

[0008] This invention is achieved through the following technical solution:

[0009] A synthesis apparatus for mass production of SiC powder with optimized high-temperature region location. The synthesis apparatus includes a crucible cylinder with an opening at the top and a crucible cover at the opening. A graphite base is provided at the bottom of the crucible cylinder and is in contact with it. The graphite base has a hollow cavity structure inside. The crucible cylinder and the graphite base are arranged coaxially with their central axes coinciding. An insulation layer is provided on the outside of the crucible cylinder.

[0010] According to a preferred embodiment of the present invention, the graphite base has a convex shape, and the longitudinal section of the internal cavity structure of the graphite base has a convex shape that is smaller at the top and larger at the bottom.

[0011] According to a preferred embodiment of the present invention, the height of the cavity structure accounts for 80-90% of the total height of the graphite base.

[0012] According to a preferred embodiment of the present invention, the graphite base has a sidewall structure with an axially gradient.

[0013] According to a preferred embodiment of the present invention, the height of the graphite base is 100-300 mm, the wall thickness of the graphite base is 10-30 mm, the long outer diameter of the graphite base is greater than the outer diameter of the crucible tube, and the short outer diameter is less than or equal to the outer diameter of the crucible tube.

[0014] According to a preferred embodiment of the present invention, the thickness of the crucible tube is 10-30 mm, the height of the crucible tube is 550-750 mm, and the diameter of the crucible tube is 300-550 mm.

[0015] According to a preferred embodiment of the present invention, an upper insulation layer is provided at the top of the crucible cylinder, a lower insulation layer is provided at the bottom of the graphite base, an outer insulation layer is provided on the outer side wall of the crucible cylinder and the outer side wall of the graphite base, and a dual medium-frequency induction heating coil is provided on the outer side of the insulation layer.

[0016] According to a preferred embodiment of the present invention, the dual intermediate frequency induction heating coil includes an upper induction coil and a lower induction coil, which are independently controlled and whose relative positions are adjustable. The upper and lower induction coils are respectively connected to an external high-frequency AC power supply.

[0017] According to a preferred embodiment of the present invention, an upper temperature measuring hole is provided penetrating the upper insulation layer, and a lower temperature measuring hole is provided penetrating the lower insulation layer.

[0018] In existing high-temperature synthesis devices for SiC powder, under the action of high-frequency alternating current, the induced current is mainly concentrated on the surface of the crucible, thus the heat is mainly concentrated in the surface area. However, this invention features a hollow graphite base at the bottom of the crucible, which is in contact with the base. This effectively concentrates heat in the bottom region of the crucible, shifting the high-temperature zone to the bottom. Therefore, the graphite base structure of this invention optimizes the location of the high-temperature zone. The hollow shape design helps reduce the radial temperature gradient at the bottom of the crucible and optimizes the transport path of gaseous components, effectively preventing cracking at the bottom of the crucible and the growth of SiC particles. Furthermore, the device can handle a loading capacity of over 100 kg with a high yield, and the SiC powder produced using this device has high purity and low carbon inclusion content.

[0019] A method for mass production of silicon carbide powder based on the above-mentioned synthesis apparatus includes the following steps:

[0020] S1. Raw material pretreatment:

[0021] Silicon powder and carbon powder are dry ball-milled and mixed at a molar ratio of 1:1 to 1:2 to obtain a uniformly mixed material.

[0022] S2. Crucible activation treatment:

[0023] The synthesis apparatus was heated by dual intermediate-frequency induction heating coils and activated by high-temperature dry firing under an argon protective atmosphere. The temperatures at the top and bottom of the crucible were measured through the upper and lower temperature measuring holes, respectively, and denoted as T. top and T bot ;

[0024] S3. Vacuum synthesis process:

[0025] 1) Vacuum purification stage:

[0026] The mixture obtained in S1 was loaded into the activated crucible, and a vacuum was drawn to achieve a vacuum level of 10. -5 -10 - 6 mbar;

[0027] 2) β-SiC synthesis stage:

[0028] The temperature was raised to 1200-1600℃ and held for 10 hours to complete the solid-phase diffusion reaction and generate β-SiC crystal phase. During this period, the temperature uniformity of the reaction interface was ensured by dynamically balancing the thermal field distribution in the upper and lower regions, and free carbon inclusions were suppressed.

[0029] 3) α-SiC crystal form transformation stage:

[0030] Maintain an argon flow rate of 20-300 sccm and adjust the pressure inside the crucible to 10-200 mbar. Adjust the power of the upper and lower coils, raise the temperature to 2000-2400℃, and control T. bot -T top The temperature difference is 150-200℃, and it is maintained for 15 hours to promote the transformation of β-SiC into α-SiC, and the decomposition of SiC and the transport of gaseous components occur.

[0031] S4. Cool down by filling with argon gas and then allowing it to cool naturally to room temperature.

[0032] According to a preferred embodiment of the present invention, in step S2, the high-temperature dry-firing process parameters are as follows: heating the crucible body to 1800-2400℃, heating time of 10-30min, argon flow rate of 10-500ccm, and furnace pressure of 10-200mbar.

[0033] According to a preferred embodiment of the present invention, in step 1), the mechanical vacuum pump and the molecular pump group are started sequentially to perform gradient vacuuming on the synthesis apparatus, wherein the mechanical pump evacuates for 1-10 hours to reduce the furnace pressure to 10. -1 -10 -2 mbar, then the molecular pump continues to pump for 1-10 hours to achieve a vacuum of 10 mbar inside the device. -5 -10 -6 mbar.

[0034] According to a preferred embodiment of the present invention, in step 2), 20-300 sccm of high-purity argon gas is introduced, and the power of the upper and lower induction coils is adjusted to raise the temperature of the material to 1200-1600℃ at a rate of 80-120℃ / min and maintain Ttop=Tbot±5℃.

[0035] According to a preferred embodiment of the present invention, in step S4, the cooling rate is to cool to 350-450°C within 5-15 hours.

[0036] The present invention employs a two-stage temperature field matching crystal evolution process to ultimately obtain α-SiC powder with a particle size distribution D50 ≥ 50 μm, a crystal purity > 99.8%, and a free carbon content < 200 ppm.

[0037] By using the device and method of the present invention, temperature and temperature gradient can be adjusted within a wide range, which is suitable for the needs of various product processes. It can also prevent the formation of a cold zone at the junction of the upper and lower coils due to power mismatch during the adjustment process, which would otherwise lead to crucible corrosion.

[0038] Technical features and advantages of the present invention:

[0039] 1. The device of the present invention has a graphite base with an internal cavity structure at the bottom of the crucible cylinder and the base is in contact with the graphite base. This can adjust the position of the high temperature zone to the bottom of the crucible, reduce the radial temperature gradient, and suppress the transport of gaseous components to the bottom of the crucible, thereby improving the yield of SiC powder. On the other hand, it reduces the risk of crucible cracking and extends the service life of the crucible.

[0040] 2. The apparatus of this invention has a graphite base with an internal cavity structure at the bottom of the crucible cylinder, which is in contact with the base. Heating is achieved using upper and lower induction coils, allowing for control of the axial temperature gradient and synthesis of SiC powder within the crucible. Compared to existing synthesis apparatuses, this invention allows for temperature and temperature gradient control over a wider range, suitable for various product processes. Furthermore, it prevents cold zones at the junction of the upper and lower coils due to power mismatch, thus preventing corrosion. Using this apparatus for SiC powder synthesis allows for a single loading of over 100 kg with a high yield, effectively reducing costs. The resulting SiC powder is characterized by high purity, large batch production, and low carbon inclusion content. GDMS testing shows low concentrations of impurities such as B, Al, Ti, and Mn, meeting the requirements for SiC single crystal production.

[0041] 3. The high-purity SiC powder synthesized using the method of this invention can effectively increase SiC powder yield and significantly reduce costs. It reduces the carbon impurity content in the powder, increases the proportion of large particles, and is suitable for large-scale production. The produced high-purity SiC powder meets the requirements for SiC crystal growth. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the apparatus for synthesizing high-purity SiC powder according to Embodiment 1 of the present invention.

[0043] In the diagram: 11 Upper induction coil, 12 Lower induction coil, 21 Upper insulation layer, 22 Outer insulation layer, 23 Lower insulation layer, 31 Crucible lid, 32 Crucible cylinder, 33 Graphite base, 4 Carbon silicon powder mixture raw material, 51 Upper temperature measuring hole, 52 Lower temperature measuring hole.

[0044] Figure 2 This is a simulation diagram of the temperature field of the crucible in the synthesis apparatus for synthesizing high-purity SiC powder without using a graphite base, which is shown in Comparative Example 1.

[0045] Figure 3 This is a simulation diagram of the temperature field of the crucible in the synthesis apparatus of Example 1. Detailed Implementation

[0046] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution will be further described in detail below with reference to the accompanying drawings in the embodiments of the present invention. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0047] Example 1

[0048] A synthesis apparatus for mass production of SiC powder with optimized high-temperature region location, the structure of which is as follows: Figure 1 As shown, the synthesis apparatus includes a crucible cylinder 32 with an opening at the top and a crucible cover 31 at the opening. A graphite base 33 is located at the bottom of the crucible cylinder and is in contact with it. The graphite base has a convex shape, and the longitudinal section of the internal cavity structure of the graphite base is a convex structure with a smaller top and a larger bottom. The crucible cylinder and the graphite base are arranged coaxially with their central axes coinciding. The height of the cavity structure accounts for 80% of the total height of the graphite base. The graphite base has a sidewall structure with axial gradient changes. The height of the graphite base is 100 mm, the wall thickness of the graphite base is 10 mm, the long outer diameter of the graphite base is greater than the outer diameter of the crucible cylinder, and the short outer diameter is less than or equal to the outer diameter of the crucible cylinder. The thickness of the crucible cylinder is 10 mm, the height of the crucible cylinder is 550 mm, and the diameter of the crucible cylinder is 300 mm.

[0049] The top of the crucible cylinder is provided with an upper insulation layer 21, the bottom of the graphite base is provided with a lower insulation layer 23, and the outer side wall of the crucible cylinder and the side wall of the graphite base are provided with an outer insulation layer 22. A dual medium-frequency induction heating coil is provided outside the insulation layer. The dual medium-frequency induction heating coil includes an upper induction coil 11 and a lower induction coil 12. The upper and lower induction coils are independently controlled and their relative positions are adjustable. The upper and lower induction coils are respectively connected to a high-frequency AC power supply. An upper temperature measuring hole 51 is provided through the upper insulation layer, and a lower temperature measuring hole 52 is provided through the lower insulation layer.

[0050] Example 2

[0051] A synthesis apparatus for mass production of SiC powder with optimized high-temperature region location, the structure of which is as follows: Figure 1As shown, the synthesis apparatus includes a crucible cylinder 32 with an opening at the top and a crucible lid 31 at the opening. A graphite base 33 is located at the bottom of the crucible cylinder and is in contact with it. The graphite base has a convex shape, and the longitudinal section of the internal cavity structure of the graphite base is a convex structure with a smaller top and a larger bottom. The crucible cylinder and the graphite base are arranged coaxially with their central axes coinciding. The height of the cavity structure accounts for 85% of the total height of the graphite base. The graphite base has a sidewall structure with axial gradient changes. The height of the graphite base is 200 mm, the wall thickness of the graphite base is 20 mm, the long outer diameter of the graphite base is greater than the outer diameter of the crucible cylinder, and the short outer diameter is less than or equal to the outer diameter of the crucible cylinder. The thickness of the crucible cylinder is 20 mm, the height of the crucible cylinder is 650 mm, and the diameter of the crucible cylinder is 450 mm.

[0052] The top of the crucible cylinder is provided with an upper insulation layer 21, the bottom of the graphite base is provided with a lower insulation layer 23, and the outer side wall of the crucible cylinder and the side wall of the graphite base are provided with an outer insulation layer 22. A dual medium-frequency induction heating coil is provided outside the insulation layer. The dual medium-frequency induction heating coil includes an upper induction coil 11 and a lower induction coil 12. The upper and lower induction coils are independently controlled and their relative positions are adjustable. The upper and lower induction coils are respectively connected to a high-frequency AC power supply. An upper temperature measuring hole 51 is provided through the upper insulation layer, and a lower temperature measuring hole 52 is provided through the lower insulation layer.

[0053] Example 3

[0054] A synthesis apparatus for mass production of SiC powder with optimized high-temperature region location, the structure of which is as follows: Figure 1 As shown, the synthesis apparatus includes a crucible cylinder 32 with an opening at the top and a crucible cover 31 at the opening. A graphite base 33 is located at the bottom of the crucible cylinder and is in contact with it. The graphite base has a convex shape, and the longitudinal section of the internal cavity structure of the graphite base is a convex structure with a smaller top and a larger bottom. The crucible cylinder and the graphite base are arranged coaxially with their central axes coinciding. The height of the cavity structure accounts for 90% of the total height of the graphite base. The graphite base has a sidewall structure with axial gradient changes. The height of the graphite base is 300 mm, the wall thickness of the graphite base is 30 mm, the long outer diameter of the graphite base is greater than the outer diameter of the crucible cylinder, and the short outer diameter is less than or equal to the outer diameter of the crucible cylinder. The thickness of the crucible cylinder is 30 mm, the height of the crucible cylinder is 750 mm, and the diameter of the crucible cylinder is 550 mm.

[0055] Comparative Example 1

[0056] The synthesis apparatus for producing SiC powder is the same as that described in Example 1, except that:

[0057] The bottom of the crucible tube was not provided with a graphite base, but otherwise it was carried out in accordance with Example 1.

[0058] Experimental example:

[0059] Temperature field simulation was performed on the SiC powder synthesis device. Figure 2 This is a simulation diagram of the temperature field of the crucible in the synthesis apparatus for synthesizing high-purity SiC powder without a graphite base, as shown in Comparative Example 1. Figure 3 This is a temperature field simulation diagram using the device of Example 1. Figure 2 , Figure 3 The comparison reveals that the device of the present invention has a graphite base with an internal cavity structure at the bottom of the crucible cylinder, which is in contact with the base. This effectively adjusts the high-temperature zone, which is beneficial to reducing the radial temperature gradient at the bottom of the crucible and optimizing the gas phase transport path.

[0060] Example 4

[0061] The method for mass production of silicon carbide powder based on the synthesis apparatus of Example 1 includes the following steps:

[0062] 1) Ingredients: Silicon powder with a purity of 99.9999% and carbon powder with a purity of 99.9999%. Weigh 70,000g of silicon powder and 30,000g of carbon powder into a plastic bucket. Mix the silicon and carbon raw materials thoroughly to obtain a mixture. Prepare the mixture for use.

[0063] 2) Dry firing: The crucible and graphite base are assembled in the synthesis furnace. The synthesis furnace is heated by dual medium-frequency induction heating coils, and the heating temperature is controlled at 2380℃. The argon flow rate is 200ccm, and the furnace pressure is 100mbar. The temperature is measured by upper temperature measuring and lower orifice temperature measuring, and is recorded as T. top and T bot The graphite crucible has been pretreated to reduce impurities;

[0064] 3) Synthesis: Transfer the prepared materials to a graphite crucible; assemble the graphite base, graphite cylinder, and graphite top cover and place them in the synthesis furnace;

[0065] Phase 1: Vacuuming with a mechanical pump for 2 hours, followed by vacuuming with a molecular pump for 2 hours, controlling the vacuum pressure inside the furnace to 10. -5 mabr.

[0066] Second stage: Introduce argon gas at a flow rate of 200 sccm, adjust the power of the upper and lower coils, and control the temperature T of the upper and lower temperature measuring holes. top and T bot The same conditions apply, and the temperature is raised to 1400℃ and maintained for 10 hours.

[0067] Third stage: Introduce argon gas at a flow rate of 200 sccm, maintaining a furnace pressure of 100 mbar. Adjust the power of the upper and lower coils, setting the upper coil temperature to 2100℃, and control T... bot -T top Set the temperature to 200℃ and maintain for 10 hours.

[0068] Fourth stage: Cool down to 400℃ within 10 hours, fill with argon gas, and then let it cool naturally to room temperature.

[0069] After cooling, the powder was taken out for observation and it was found that a very small amount of carbonization occurred at the edges, the bottom of the particles were small and dense, and the top particles were larger.

[0070] The synthesized SiC powder was subjected to GDMS testing, and the results are shown in Table 1. The impurity content was very low, meeting the requirements for crystal growth.

[0071] Table 1 GDMS Test Results

[0072]

[0073] As can be seen from Table 1, this invention can achieve high single-batch production while obtaining SiC powder with low content of test impurity elements, meeting the requirements for crystal growth and effectively reducing synthesis costs. By adding a graphite base structure at the bottom, it is beneficial to increase the uniformity of the radial temperature gradient. By adopting a segmented synthesis method and controlling the temperature of the upper and lower coils, the axial gradient is reduced in the first-order reaction, which is beneficial to the more complete reaction. In the second-order reaction, the axial temperature gradient is increased, which is beneficial to the increase of the large particle output ratio.

[0074] In summary, the high-purity SiC powder synthesized using the apparatus of this invention can effectively increase SiC powder yield and significantly reduce costs. It reduces the carbon impurity content in the powder and increases the proportion of large particles. The structure is simple, suitable for large-scale production, and the produced high-purity SiC powder meets the requirements for SiC crystal growth.

[0075] According to some embodiments of the present invention, the graphite materials such as graphite crucibles described in the present invention are preferably purified to reduce the introduction of foreign impurities.

[0076] In the description of this invention, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0077] The main innovation of this invention lies in the addition of a graphite base structure, which adjusts the high-temperature zone to the bottom of the crucible and reduces the radial temperature gradient, thereby suppressing the transport of gaseous components to the bottom of the crucible, especially the center of the bottom, and reducing the risk of crucible cracking.

[0078] By using the method and structure of this invention, the axial temperature gradient is controlled by adjusting the power of the upper and lower coils. The synthesis process adopts a low axial temperature gradient in the early stage, which is conducive to the full reaction and reduces the occurrence of carbon inclusions. The method of high axial temperature gradient in the later stage can improve the output ratio of large particle SiC powder.

[0079] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A synthesis apparatus for mass production of SiC powder with optimized high-temperature region location, the synthesis apparatus comprising a crucible cylinder, an opening at the top of the crucible cylinder, a crucible cover at the opening, a graphite base at the bottom of the crucible cylinder in contact with it, the graphite base having a hollow cavity structure inside, the crucible cylinder and the graphite base being arranged coaxially with their central axes coinciding, and an insulation layer being provided on the outside of the crucible cylinder.

2. The synthesis apparatus according to claim 1, characterized in that, The graphite base has a convex shape, and the longitudinal section of the internal cavity structure is a convex structure that is smaller at the top and larger at the bottom.

3. The synthesis apparatus according to claim 2, characterized in that, The height of the cavity structure accounts for 80-90% of the total height of the graphite base.

4. The synthesis apparatus according to claim 1, characterized in that, The graphite base has a sidewall structure with axial gradient variation. The height of the graphite base is 100-300mm, the wall thickness of the graphite base is 10-30mm, the long outer diameter of the graphite base is greater than the outer diameter of the crucible tube, and the short outer diameter is less than or equal to the outer diameter of the crucible tube.

5. The synthesis apparatus according to claim 1, characterized in that, The thickness of the crucible tube is 10-30 mm, the height of the crucible tube is 550-750 mm, and the diameter of the crucible tube is 300-550 mm.

6. The synthesis apparatus according to claim 1, characterized in that, The top of the crucible cylinder is provided with an upper insulation layer, the bottom of the graphite base is provided with a lower insulation layer, the outer side wall of the crucible cylinder and the side wall of the graphite base are provided with an outer insulation layer, and a dual medium-frequency induction heating coil is provided on the outside of the insulation layer.

7. The synthesis apparatus according to claim 6, characterized in that, The dual medium-frequency induction heating coil includes an upper induction coil and a lower induction coil. The upper and lower induction coils are independently controlled and their relative positions are adjustable. The upper and lower induction coils are respectively connected to a high-frequency AC power supply. An upper temperature measuring hole is provided through the upper insulation layer, and a lower temperature measuring hole is provided through the lower insulation layer.

8. A method for mass production of silicon carbide powder based on the synthesis apparatus of claim 1, comprising the following steps: S1. Raw material pretreatment: Silicon powder and carbon powder are dry ball-milled and mixed at a molar ratio of 1:1 to 1:2 to obtain a uniformly mixed material. S2. Crucible activation treatment: The synthesis apparatus was heated by dual intermediate-frequency induction heating coils and activated by high-temperature dry firing under an argon protective atmosphere. The temperatures at the top and bottom of the crucible were measured through the upper and lower temperature measuring holes, respectively, and denoted as T. top and T bot ; S3. Vacuum synthesis process: 1) Vacuum purification stage: The mixture obtained in S1 was loaded into the activated crucible, and a vacuum was drawn to achieve a vacuum level of 10. -5 -10 -6 mbar; 2) β-SiC synthesis stage: The temperature was raised to 1200-1600℃ and held for 10 hours to complete the solid-phase diffusion reaction and generate β-SiC crystal phase. During this period, the temperature uniformity of the reaction interface was ensured by dynamically balancing the thermal field distribution in the upper and lower regions, and free carbon inclusions were suppressed. 3) α-SiC crystal form transformation stage: Maintain an argon flow rate of 20-300 sccm and adjust the pressure inside the crucible to 10-200 mbar. Adjust the power of the upper and lower coils, raise the temperature to 2000-2400℃, and control T. bot -T top The temperature difference is 150-200℃, and it is maintained for 15 hours to promote the transformation of β-SiC into α-SiC, and the decomposition of SiC and the transport process of gas phase components occur. S4. Cool down by filling with argon gas and then allowing it to cool naturally to room temperature.

9. The production method according to claim 8, characterized in that, In step S2, the high-temperature dry-firing process parameters are as follows: the crucible body is heated to 1800-2400℃, the heating time is 10-30min, the argon flow rate is 10-500ccm, and the furnace pressure is 10-200mbar.

10. The production method according to claim 8, characterized in that, In step S3, step 1), the mechanical vacuum pump and the molecular pump group are started sequentially to perform gradient vacuuming of the synthesis apparatus, wherein the mechanical pump is used for 1-10 hours to reduce the furnace pressure to 10. -1 -10 - 2 mbar, then the molecular pump continues to pump for 1-10 hours to achieve a vacuum of 10 mbar inside the device. -5 -10 -6 In step S2), 20-300 sccm of high-purity argon gas is introduced, and the power of the upper and lower induction coils is adjusted to raise the temperature of the material to 1200-1600℃ at a rate of 80-120℃ / min and maintain Ttop=Tbot±5℃. In step S4, the cooling rate is to cool down to 350-450℃ within 5-15 hours.

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