Crucible and preparation method thereof

Abstract

The invention provides a crucible and a preparation method thereof, and relates to the technical field of silicon rod preparation, the method comprises the following steps: providing a crucible base body of a first type material, and performing surface treatment on the inner wall surface of the crucible base body to obtain a to-be-bonded area; providing an initial coating raw material of a second type material, wherein the phase of the initial coating raw material comprises solid particles; performing homogenization treatment on the initial coating raw material to obtain a target coating raw material; the average particle size of the target coating raw material is smaller than that of the initial coating raw material; the target coating raw materials are fused through the fusion spraying technology, and the to-be-combined area is coated with the fused target coating raw materials; and cooling the target coating raw material to form the compact crucible coating which is in a metallurgical bonding state with the to-be-bonded area. The compact coating of the crucible has good high temperature resistance and stability, and effectively avoids stripping or falling at high temperature, so that the stability of the compact coating is favorably maintained, and the durability and the stability of the crucible are further improved.

Description

Technical Field

[0001] The present application relates to the technical field of silicon rod preparation, and in particular to a crucible and a method for preparing the same. Background Art

[0002] With the increasing development of the photovoltaic and semiconductor markets, silicon wafers, as one of the key materials, have higher and higher quality requirements. At present, the photovoltaic industry mostly uses the Czochralski method to prepare single crystal silicon. During the crystal pulling process, a crucible is required to hold molten high-temperature silicon liquid, making the crucible one of the key equipment to ensure the quality of crystal pulling. This requires the crucible to be resistant to high temperatures, non-polluting to silicon materials, and have a long service life.

[0003] However, traditional quartz crucibles have a tendency to turn into silicon dioxide crystals under long-term high-temperature working conditions, which is commonly known as "crystallization". After the quartz crucible crystallizes, the strength of the crucible will be reduced, which is easy to cause deformation and have an adverse effect on crystal pulling. In the related art, in order to ensure the quality of crystal pulling, quartz crucibles are usually used as consumables and need to be replaced frequently, which seriously reduces production efficiency. In addition, as the reserves of high-purity (purity greater than 99.99%) quartz sand used to prepare quartz crucibles are gradually consumed, it becomes increasingly difficult to obtain related resources, further affecting the stable supply of silicon wafers and cost control in the photovoltaic industry.

[0004] Thus, how to improve the crucible and its preparation method to ensure the quality of crystal pulling, improve production efficiency and reduce preparation costs has become one of the research directions in this field. Summary of the invention

[0005] The purpose of the present application is to provide a crucible and a method for preparing the same in view of the deficiencies in the above-mentioned prior art, by providing a crucible substrate of silicon nitride and an initial coating raw material of quartz, and performing surface treatment on the inner wall of the crucible substrate and homogenizing the initial coating raw material, so as to facilitate obtaining a dense crucible coating metallurgically bonded to the inner wall of the crucible substrate by means of a melt spraying process, effectively improve the bonding strength between the dense crucible coating and the crucible substrate, avoid the problem of easy peeling of the dense crucible coating during use, thereby reducing the cost of the crucible material while ensuring its reliability, thereby ensuring the quality of crystal pulling and reducing manufacturing costs.

[0006] To achieve the above object, the present application provides a method for preparing a crucible, comprising:

[0007] Providing a crucible base of a first type of material, and performing surface treatment on the inner wall surface of the crucible base to obtain a region to be bonded;

[0008] Providing an initial coating material of a second type of material, wherein the initial coating material comprises solid particles;

[0009] Performing a homogenization process on the initial coating raw material to obtain a target coating raw material; the average particle size of the target coating raw material is smaller than the average particle size of the initial coating raw material;

[0010] The target coating material is melted and applied to the area to be bonded by using a melt spraying process;

[0011] Cooling the target coating raw material to form a crucible dense coating in a metallurgical bonded state with the area to be bonded;

[0012] Among them, the first type of material includes: silicon nitride; the second type of material includes: quartz.

[0013] Optionally, the inner wall surface of the crucible substrate is subjected to surface treatment to obtain a region to be bonded, including:

[0014] Performing ultrasonic cleaning on the inner wall surface of the crucible base;

[0015] performing a drying process on the crucible base after ultrasonic cleaning;

[0016] Performing sandblasting on the inner wall surface of the crucible base after the drying treatment, including: using sandblasting particles with an average particle size of 22 mesh to 40 mesh, and spraying them onto the inner wall surface of the crucible base at a spray pressure of 0.3 MPa to 0.6 MPa to obtain a to-be-treated area with a preset surface roughness;

[0017] in,

[0018] The temperature of the drying process includes: 60℃~100℃;

[0019] The duration of drying treatment includes: 1h~2h;

[0020] The surface roughness of the inner wall surface of the crucible substrate after the surface treatment is in the range of 2.2 μm to 2.4 μm.

[0021] Optionally, a homogenization process is performed on the initial coating raw material to obtain a target coating raw material, comprising:

[0022] Provides preset amounts of dispersants and thickeners;

[0023] The initial coating raw material, dispersant and thickener are mixed to obtain a mixed grinding material; wherein the mass ratio of the dispersant to the mixed grinding material includes: 0.6% to 1%; the mass ratio of the thickener to the mixed grinding material includes: 1.5% to 2.5%;

[0024] The mixed grinding material and the solvent are mixed, and grinding balls are added to perform ball milling to obtain a coating slurry; wherein the mass ratio of the mixed grinding material, the grinding balls and the solvent includes: (1-2): (1.5-3): (1-3);

[0025] Performing spray granulation treatment on the coating slurry, and screening out coating particles that meet a preset average particle size range as target coating raw materials;

[0026] The average particle size of the initial coating raw material is 100 μm to 200 μm; the average particle size of the target coating raw material is 50 μm to 100 μm.

[0027] Optionally, the dispersant includes: 0.6wt.% to 1.0wt.% of ammonium citrate; the thickener includes: 1.5wt.% to 2.5wt.% of gum arabic; and the solvent includes: deionized water.

[0028] Optionally, the grinding balls include first type zirconia balls and second type zirconia balls; wherein the diameter of the first type zirconia balls includes: 6mm~10mm; the diameter of the second type zirconia balls includes: 3mm~5mm; the mass ratio of the first type zirconia balls to the second type zirconia balls includes: (2~8): (3~7).

[0029] Optionally, a melt spraying process is used to melt the target coating raw material and apply it to the area to be bonded, including:

[0030] A plasma spraying process is used to melt the target coating raw material, and the molten target coating raw material is directly sprayed and fully penetrated into the to-be-bonded area of ​​the crucible substrate;

[0031] Among them, in the plasma spraying process, the spraying power includes: 30kW~40kW; the feeding rate includes: 10%~20%; the argon flow rate includes: 30SLPM~35SLPM; the hydrogen flow rate includes: 10SLPM~15SLPM; the injection pressure of the front cooling gas includes: 2bar~6bar; the spraying distance includes: 80mm~120mm.

[0032] Optionally, cooling the target coating raw material to form a crucible dense coating in a metallurgical bonding state with the to-be-bonded area comprises:

[0033] The molten target coating raw material is cooled by natural cooling or low-temperature annealing to form a crucible dense coating that is metallurgically bonded to the area to be bonded; wherein the thickness of the crucible dense coating is 1 mm to 5 mm.

[0034] Optionally, before the target coating material is melted and coated on the to-be-bonded area by the melt spraying process, the method further comprises:

[0035] The crucible base is subjected to a preheating treatment, wherein the temperature of the crucible base after the preheating treatment includes: 200°C to 300°C.

[0036] The present application also provides a crucible, which is obtained by using any of the above-mentioned methods for preparing a crucible, and the crucible comprises:

[0037] A crucible base of the first type of material; the surface roughness of the inner wall of the crucible base includes: 2.2μm to 2.4μm;

[0038] The second type of crucible dense coating is arranged on the inner wall surface of the crucible base and is metallurgically bonded to the crucible base;

[0039] Among them, the first type of material includes: silicon nitride; the second type of material includes: quartz.

[0040] Optionally, the thickness of the dense coating of the crucible includes: 1 mm to 5 mm.

[0041] The present application also provides an application of the above-mentioned crucible in a process of preparing silicon material.

[0042] The beneficial effects of this application include:

[0043] By providing a crucible substrate of a first type of material (such as silicon nitride), and surface treating the inner wall surface of the crucible substrate, this surface treatment is intended to enhance the bonding strength between the crucible substrate and the subsequent coating, and the treated surface becomes the area to be bonded to the coating, ensuring that the contact surface is uniform and has sufficient adhesion. When preparing the coating material, an initial coating raw material of a second type of material (such as quartz) is provided, and the physical phase of the initial coating raw material includes solid particles. By homogenizing the initial coating raw material, the particle size of the raw material is reduced to make its distribution more uniform. After homogenization, the average particle size of the target coating raw material obtained is smaller than that of the initial coating raw material, which can improve the density and uniformity of the subsequent coating obtained, ensuring good adhesion performance under high temperature conditions. Next, the treated target coating raw material is melted and coated on the area to be bonded of the crucible substrate by a melt spraying process. Finally, the target coating is solidified by cooling treatment, and a crucible dense coating with excellent bonding strength and dense structure is formed. Among them, through high-temperature melting and cooling treatment, it is ensured that the target coating material and the area to be bonded of the crucible substrate are metallurgically bonded to form a dense and firm bonding layer. This metallurgical bonding state significantly improves the high temperature resistance and stability of the dense coating of the crucible, avoids peeling or falling off at high temperatures, thereby effectively maintaining the stability of the dense coating of the crucible, and further improves the durability, stability and service life of the crucible. In general, this dense coating of the crucible not only effectively reduces the use of quartz sand and reduces the preparation cost of the crucible, but also provides better protection for the crystal pulling process when the crucible is in contact with molten silicon, ensuring the purity of the molten silicon and thus ensuring the quality of the crystal pulling. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 A schematic flow chart of a method for preparing a crucible provided in some embodiments of the present application;

[0046] Figure 2 A schematic diagram of a process of step S10 provided in some embodiments of the present application;

[0047] Figure 3 A schematic diagram of a process of step S30 provided in some embodiments of the present application;

[0048] Figure 4 A schematic flow chart of another method for preparing a crucible provided in some embodiments of the present application;

[0049] Figure 5 This is a schematic diagram of the structure of a crucible provided in some embodiments of the present application.

[0050] Description of reference numerals:

[0051] 100-crucible base; 200-crucible dense coating. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0053] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. It should be noted that, in the absence of conflict, the various features in the embodiments of the present application can be combined with each other, and the combined embodiments are still within the scope of protection of the present application.

[0054] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in the drawings.

[0055] In the description of the present application, it should be noted that the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0056] like Figure 1 As shown, the present application provides a method for preparing a crucible, comprising:

[0057] S10: providing a crucible base 100 of a first type of material, and performing surface treatment on the inner wall surface of the crucible base 100 to obtain a region to be bonded;

[0058] S20: providing an initial coating raw material of a second type of material, wherein the initial coating raw material comprises solid particles;

[0059] S30: performing a homogenization process on the initial coating raw material to obtain a target coating raw material; the average particle size of the target coating raw material is smaller than the average particle size of the initial coating raw material;

[0060] S40: melt the target coating raw material and apply it to the area to be bonded by using a melt spraying process;

[0061] S50: Cooling the target coating material to form a crucible dense coating 200 that is metallurgically bonded to the to-be-bonded area. The first type of material includes silicon nitride, and the second type of material includes quartz.

[0062] Here, the inventors have found through research that during the melt spraying process, when the target coating raw material size is too small (for example, the particle size is less than 50nm), it will be blown away during the spraying process; and when the target coating raw material size is too large (for example, the particle size is greater than 100nm), it will fall during the spraying process and leave the spraying range. That is, target coating raw materials that are too large or too small cannot be effectively melted in the melt spraying process, and thus pores are easily generated during the spraying process. The inventors have further found through research that when the particle size range of the target coating raw material is 50μm to 100μm, its degree of melting in the melt spraying is high, and it can be completely transformed into droplets and spread on the crucible substrate 100. Based on this, the target coating raw material after the homogenization treatment can ensure that it is fully heated and melted during the spraying process, reducing the presence of unmelted and semi-melted target coating raw materials, so as to facilitate the preparation of a crucible dense coating 200.

[0063] Specifically, the present application first provides a crucible substrate 100 of a first type of material (such as silicon nitride), and performs surface treatment on the inner wall surface of the crucible substrate 100. This surface treatment is intended to enhance the bonding strength between the crucible substrate 100 and the subsequent coating. The treated surface becomes the area to be bonded to the coating, ensuring that the contact surface is uniform and has sufficient adhesion. When preparing the coating material, an initial coating raw material of a second type of material (such as quartz) is provided, and the physical phase of the initial coating raw material includes solid particles. By homogenizing the initial coating raw material, the particle size of the raw material is reduced to make its distribution more uniform. After homogenization, the average particle size of the target coating raw material obtained is smaller than that of the initial coating raw material, which can improve the density and uniformity of the subsequent coating obtained, ensuring good adhesion performance under high temperature conditions. Next, the treated target coating raw material is melt-coated to the area to be bonded of the crucible substrate 100 by a melt spraying process. Finally, the target coating is solidified by cooling treatment, and a crucible dense coating 200 with excellent bonding strength and dense structure is formed. Among them, through high-temperature melting and cooling treatment, it is ensured that the target coating material and the band bonding area of ​​the crucible substrate 100 are metallurgically bonded to form a dense and firm bonding layer. This metallurgical bonding state significantly improves the high temperature resistance and stability of the crucible dense coating 200, avoids peeling or falling off at high temperatures, thereby effectively maintaining the stability of the crucible dense coating 200, and further improving the durability, stability and service life of the crucible. In general, this crucible dense coating 200 not only effectively reduces the use of quartz sand and reduces the preparation cost of the crucible, but also provides better protection for the crystal pulling process when the crucible is in contact with molten silicon, ensuring the purity of the molten silicon, and thus ensuring the quality of the crystal pulling.

[0064] For example, the size of the crucible base 100 may be 14 to 36 inches, and further, may be 28 to 36 inches.

[0065] It is understandable that the present application does not limit the order of implementation of S10 and S30, and S10 and S30 can be performed simultaneously, or S10 can be completed first and then S30, or S30 can be completed first and then S10. However, it should be noted that S40 and S50 need to be implemented in sequence after both S010 and S030 are completed.

[0066] See also Figure 2 In some embodiments, the inner wall surface of the crucible base 100 is subjected to surface treatment to obtain the area to be bonded. The specific operation includes:

[0067] S11: performing ultrasonic cleaning on the inner wall surface of the crucible base 100;

[0068] S12: performing a drying process on the crucible base 100 after ultrasonic cleaning;

[0069] S13: performing sandblasting on the inner wall surface of the crucible base 100 after the drying treatment, including: using sandblasting particles with an average particle size of 22 mesh to 40 mesh, and spraying them onto the inner wall surface of the crucible base 100 at a spray pressure of 0.3 MPa to 0.6 MPa to obtain a to-be-treated area with a preset surface roughness.

[0070] in,

[0071] Acetone or anhydrous ethanol solution can be used as the cleaning solution in the ultrasonic cleaning step;

[0072] The temperature of the drying process includes: 60°C to 100°C; illustratively, the temperature of the drying process includes 60°C, 70°C, 80°C, 90°C or 100°C.

[0073] The duration of the drying process includes: 1 hour to 2 hours; illustratively, the duration of the drying process includes 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, 1.9 hours or 2 hours.

[0074] Compressed air can be used as the blasting power. The blasting particles can be any one of silicon carbide, corundum or quartz sand.

[0075] The surface roughness of the inner wall surface of the crucible base 100 after the surface treatment is in the range of 2.2 μm to 2.4 μm; for example, the surface roughness is 2.2 μm, 2.3 μm or 2.4 μm.

[0076] See also Figure 3 In some embodiments, a homogenization process is performed on the initial coating raw material to obtain a target coating raw material, including:

[0077] S31: providing a preset amount of dispersant and thickener;

[0078] S32: mixing the initial coating raw material, the dispersant and the thickener to obtain a mixed abrasive; wherein the mass ratio of the dispersant to the mixed abrasive comprises: 0.6% to 1%; the mass ratio of the thickener to the mixed abrasive comprises: 1.5% to 2.5%;

[0079] S33: mixing the mixed abrasive with the solvent, and adding grinding balls to perform ball milling to obtain a coating slurry; wherein the mass ratio of the mixed abrasive, the grinding balls and the solvent comprises: (1-2): (1.5-3): (1-3);

[0080] S34: performing spray granulation treatment on the coating slurry, and screening out coating particles that meet a preset average particle size range as target coating raw materials.

[0081] Specifically, adding a dispersant to the initial coating material helps the initial coating material to be dispersed in the solvent, and adding a thickener can change the flow properties of the solvent, making it easier for the grinding balls to grind the initial coating material in the coating slurry. For example, the dispersant includes ammonium citrate; the thickener includes gum arabic.

[0082] It can be understood that the specific amount of dispersant and thickener provided is determined by matching the mixed grinding material to be prepared. For example, the mass ratio of dispersant to the mixed grinding material includes: 0.6% to 1%; for example, the mass ratio of dispersant to the mixed grinding material includes 0.6%, 0.7%, 0.8%, 0.9% or 1%. The mass ratio of thickener to the mixed grinding material ranges from 1.5% to 2.5%; for example, the mass ratio of thickener to the mixed grinding material ranges from 1.5%, 1.8%, 2.0%, 2.2%, 2.4% or 2.5%.

[0083] Grinding balls usually include type I zirconia balls and type II zirconia balls. Type I zirconia balls mainly impact and squeeze the coating slurry, while type II zirconia balls grind the coating slurry through grinding and multiple impacts. Therefore, selecting grinding balls of different diameters can achieve a better coordination between the two, achieving an ideal grinding effect of reducing the coating slurry and then grinding it.

[0084] For example, the diameter of the first type zirconia ball includes: 6mm-10mm; for example, the diameter of the first type zirconia ball includes 6mm, 7mm, 8mm, 9mm or 10mm. The diameter of the second type zirconia ball includes: 3mm-5mm; for example, the diameter of the second type zirconia ball includes 3mm, 4mm or 5mm.

[0085] For example, the mass ratio of the first type zirconia balls to the second type zirconia balls includes: (2-8): (3-7), for example, the mass ratio of the first type zirconia balls to the second type zirconia balls includes 2:3, 2:5, 2:7, 4:3, 4:5, 4:7, 8:3, 8:5 or 8:7.

[0086] See also Figure 4 In some embodiments, before the target coating material is melted and coated on the to-be-bonded area by the melt spraying process, the preparation method further comprises:

[0087] S35: performing a preheating treatment on the crucible base 100; wherein the temperature of the crucible base 100 after the preheating treatment includes: 200°C to 300°C.

[0088] The purpose of the preheat treatment is to make the crucible substrate 100 have a suitable temperature state during the coating process, reduce the temperature difference between the molten target coating raw material and the crucible substrate 100, so as to prevent the adverse effects of thermal stress caused by the drastic temperature difference during the spraying process, improve the bonding strength between the target coating raw material and the substrate surface, and improve the uniformity and density of the crucible dense coating 200, thereby avoiding cracks or falling off of the crucible dense coating 200 during the cooling process.

[0089] The following examples respectively describe in detail the preparation process of crucibles of different sizes.

[0090] Embodiment 1:

[0091] In this embodiment, a 28-inch silicon nitride crucible is selected as the crucible base 100 .

[0092] The inner wall surface of the crucible substrate 100 is ultrasonically cleaned three times with acetone and anhydrous ethanol; and the crucible substrate 100 after ultrasonic cleaning is dried at 60°C for a total of 1 hour, thereby removing dirt and residual sandblasting particles on the inner wall surface of the crucible substrate 100, reducing the contamination of the interface between the inner wall surface of the crucible substrate 100 and the crucible dense coating 200, and reducing the influence of dirt on the bonding strength between the inner wall surface of the crucible substrate 100 and the crucible dense coating 200; then, sandblasting particles with an average particle size of 22 mesh are used and sprayed onto the inner wall surface of the crucible substrate 100 at a spray pressure of 0.3 MPa, and a treated area with a surface roughness of 2.2 μm is obtained on the inner wall surface of the crucible substrate 100, thereby improving its mechanical properties and cleanliness, increasing the adhesion between the inner wall surface of the crucible substrate 100 and the crucible dense coating 200, and extending the durability of the crucible dense coating 200.

[0093] An initial coating raw material with a particle size of 100 μm is selected, and ammonium citrate as a dispersant and gum arabic as a thickener are added to the initial coating raw material to prepare a mixed grinding material, wherein the mass ratios of ammonium citrate and gum arabic to the mixed grinding material are 0.6% and 1.5%, respectively; the mixed grinding material is mixed with deionized water, and grinding balls are added to perform ball milling treatment to obtain a coating slurry; wherein the grinding balls include a first type zirconia ball with a diameter of 6 mm and a second type zirconia ball with a diameter of 3 mm, and the mass ratio of the first type zirconia ball to the second type zirconia ball is 2:3, and the mass ratio of the mixed grinding material, the grinding balls and the deionized water is 1:1.5:1, that is, the mass ratio of the initial coating raw material, the grinding balls and the deionized water is 0.979:1.5:1; the coating slurry is added to a polytetrafluoroethylene ball mill, and after ball milling with the grinding balls for 3 days, a spray drying device is used for spray granulation, and a vibration screening instrument is used to screen out the target coating raw material that meets the preset average particle size range, has uniform size distribution, high sphericity and good fluidity.

[0094] The crucible base 100 is preheated, and the temperature of the crucible base 100 after the preheating is 200°C.

[0095] The target coating material is melted by a plasma spraying process, and the molten target coating material is directly sprayed and fully penetrated into the to-be-bonded area of ​​the crucible substrate 100. Specifically, under the conditions of a spraying distance of 80 mm, a spraying power of 30 kW, a powder feeding rate of 10%, an argon flow rate of 30 SLPM, a hydrogen flow rate of 10 SLPM, and a front cooling gas injection pressure of 2 bar, the target coating material is melted at a high temperature of a plasma arc by a plasma spraying method, and the molten target coating material is sprayed at a high speed onto the inner wall surface of the preheated crucible substrate 100.

[0096] The molten target coating material is cooled by natural cooling or low-temperature annealing to form a crucible dense coating 200 that is metallurgically bonded to the area to be bonded. The crucible dense coating 200 has a thickness of 3 mm and takes 3.5 hours to prepare. The obtained crucible dense coating 200 has a high bonding strength with the inner wall of the crucible substrate 100 and has no cracking or deformation at high temperatures (1500°C).

[0097] Embodiment 2:

[0098] In this embodiment, a 32-inch silicon nitride crucible is selected as the crucible base 100 .

[0099] The inner wall surface of the crucible substrate 100 is ultrasonically cleaned three times with acetone and anhydrous ethanol; and the crucible substrate 100 after ultrasonic cleaning is dried at 80°C for a total of 1.5 hours, thereby removing dirt and residual sandblasting particles on the inner wall surface of the crucible substrate 100, reducing the pollution of the interface between the inner wall surface of the crucible substrate 100 and the crucible dense coating 200, and reducing the influence of dirt on the bonding strength between the inner wall surface of the crucible substrate 100 and the crucible dense coating 200; then, sandblasting particles with an average particle size of 30 mesh are sprayed onto the inner wall surface of the crucible substrate 100 at a spray pressure of 0.5 MPa, and a to-be-treated area with a surface roughness of 2.3 μm is obtained on the inner wall surface of the crucible substrate 100, thereby improving its mechanical properties and cleanliness, increasing the adhesion between the inner wall surface of the crucible substrate 100 and the crucible dense coating 200, and extending the durability of the crucible dense coating 200.

[0100] An initial coating raw material with a particle size of 150 μm is selected, and ammonium citrate as a dispersant and gum arabic as a thickener are added to the initial coating raw material to prepare a mixed grinding material, wherein the mass ratios of ammonium citrate and gum arabic to the mixed grinding material are 0.8% and 2%, respectively; the mixed grinding material is mixed with deionized water, and grinding balls are added to perform ball milling to obtain a coating slurry; wherein the grinding balls include a first type zirconia ball with a diameter of 8 mm and a second type zirconia ball with a diameter of 4 mm, and the mass ratio of the first type zirconia ball to the second type zirconia ball is 1:1, and the mass ratio of the mixed grinding material, the grinding balls and the deionized water is 3:4:4, that is, the mass ratio of the initial coating raw material, the grinding balls and the deionized water is 2.916:4:4; the coating slurry is added to a polytetrafluoroethylene ball mill, and after ball milling with the grinding balls for 3 days, a spray drying device is used for spray granulation, and a vibration screening instrument is used to screen out the target coating raw material that meets the preset average particle size range, has uniform size distribution, high sphericity and good fluidity.

[0101] The crucible base 100 is preheated, and the temperature of the crucible base 100 after the preheating is 250°C.

[0102] The target coating material is melted by a plasma spraying process, and the molten target coating material is directly sprayed and fully penetrated into the to-be-bonded area of ​​the crucible substrate 100. Specifically, under the conditions of a spraying distance of 100 mm, a spraying power of 35 kW, a powder feeding rate of 15%, an argon flow rate of 32 SLPM, a hydrogen flow rate of 13 SLPM, and a front cooling gas injection pressure of 4 bar, the target coating material is melted at a high temperature of a plasma arc by a plasma spraying method, and the molten target coating material is sprayed at a high speed onto the inner wall surface of the preheated crucible substrate 100.

[0103] The molten target coating material is cooled by natural cooling or low-temperature annealing to form a crucible dense coating 200 that is metallurgically bonded to the area to be bonded. The crucible dense coating 200 has a thickness of 4 mm and takes 5.5 hours to prepare. The obtained crucible dense coating 200 has a high bonding strength with the inner wall of the crucible substrate 100 and has no cracking or deformation at high temperatures (1500°C).

[0104] Embodiment 3:

[0105] In this embodiment, a 36-inch silicon nitride crucible is selected as the crucible base 100 .

[0106] The inner wall surface of the crucible substrate 100 is ultrasonically cleaned three times with acetone and anhydrous ethanol; and the crucible substrate 100 after ultrasonic cleaning is dried at 100°C for a total of 2 hours, thereby removing dirt and residual sandblasting particles on the inner wall surface of the crucible substrate 100, reducing the pollution of the interface between the inner wall surface of the crucible substrate 100 and the crucible dense coating 200, and reducing the influence of dirt on the bonding strength between the inner wall surface of the crucible substrate 100 and the crucible dense coating 200; then, sandblasting particles with an average particle size of 40 mesh are sprayed onto the inner wall surface of the crucible substrate 100 at a spray pressure of 0.6 MPa, and a to-be-treated area with a surface roughness of 2.4 μm is obtained on the inner wall surface of the crucible substrate 100, thereby improving its mechanical properties and cleanliness, increasing the adhesion between the inner wall surface of the crucible substrate 100 and the crucible dense coating 200, and extending the durability of the crucible dense coating 200.

[0107] An initial coating raw material with a particle size of 200 μm is selected, and ammonium citrate as a dispersant and gum arabic as a thickener are added to the initial coating raw material to prepare a mixed grinding material, wherein the mass ratios of ammonium citrate and gum arabic to the mixed grinding material are 1% and 2.5%, respectively; the mixed grinding material is mixed with deionized water, and grinding balls are added to perform ball milling treatment to obtain a coating slurry; wherein the grinding balls include a first type zirconia ball with a diameter of 10 mm and a second type zirconia ball with a diameter of 5 mm, and the mass ratio of the first type zirconia ball to the second type zirconia ball is 8:7, and the mass ratio of the mixed grinding material, the grinding balls and the deionized water is 2:3:3, that is, the mass ratio of the initial coating raw material, the grinding balls and the deionized water is 1.93:3:3; the coating slurry is added to a polytetrafluoroethylene ball mill, and after ball milling with the grinding balls for 3 days, a spray drying device is used for spray granulation, and a vibration screening instrument is used to screen out the target coating raw material that meets the preset average particle size range, has uniform size distribution, high sphericity and good fluidity.

[0108] The crucible base 100 is preheated, and the temperature of the crucible base 100 after the preheating is 300°C.

[0109] The target coating material is melted by a plasma spraying process, and the molten target coating material is directly sprayed and fully penetrated into the to-be-bonded area of ​​the crucible substrate 100. Specifically, under the conditions of a spraying distance of 120 mm, a spraying power of 40 kW, a powder feeding rate of 20%, an argon flow rate of 35 SLPM, a hydrogen flow rate of 15 SLPM, and a front cooling gas injection pressure of 6 bar, the target coating material is melted at a high temperature of a plasma arc by a plasma spraying method, and the molten target coating material is sprayed at a high speed onto the inner wall surface of the preheated crucible substrate 100.

[0110] The molten target coating material is cooled by natural cooling or low-temperature annealing to form a crucible dense coating 200 that is metallurgically bonded to the area to be bonded. The crucible dense coating 200 has a thickness of 5 mm and takes 7 hours to prepare. The obtained crucible dense coating 200 has a high bonding strength with the inner wall of the crucible substrate 100 and has no cracking or deformation at high temperatures (1500°C).

[0111] It can be seen that the crucible dense coating 200 and the inner wall surface of the crucible base 100 in the crucible prepared by Examples 1 to 3 are tightly combined, ensuring that the crucible dense coating 200 will not fall off during the high-temperature use of the crucible, thereby protecting the inner wall of the crucible and improving the durability, stability and service life of the crucible.

[0112] Embodiment 4~6:

[0113] Embodiments 4 to 6 provide a crucible, and the preparation methods thereof correspond to the aforementioned embodiments 1 to 3, respectively. Figure 5 As shown, by preparing a crucible dense coating 200 of a second type of material on the inner wall surface of a crucible base 100 of a first type of material, and enhancing the bonding strength between the inner wall surface of the crucible base 100 and the crucible dense coating 200, the crucible is free from cracking and deformation at high temperatures and can be reused, thereby effectively reducing the amount of quartz used, reducing the material cost of the crucible and improving production efficiency.

[0114] It should be understood that due to the mismatch in thermal expansion coefficients of silicon nitride and quartz, there will be thermal stress accumulation at the interlayer joints. The thicker the coating, the more serious the thermal stress accumulation, resulting in reduced interlayer bonding strength. Therefore, the thicker the coating, the lower the bonding strength. Specifically, the thickness of the crucible dense coating 200 in the crucibles of Examples 4 to 6 is 3 to 5 mm, and the bonding strength between the crucible dense coating 200 and the crucible substrate 100 is about 30-50 MPa. Among them, in Example 4, the bonding strength between the 3 mm thick crucible dense coating 200 and the crucible substrate 100 is about 45 MPa; in Example 5, the bonding strength between the 4 mm thick crucible dense coating 200 and the crucible substrate 100 is about 40 MPa; in Example 6, the bonding strength between the 5 mm thick crucible dense coating 200 and the crucible substrate 100 is about 30 MPa.

[0115] It should also be understood that in addition to the coating thickness affecting the interlayer bonding strength, the particle size of the target coating raw material will also have a certain impact on the interlayer bonding strength. According to the test results of the inventor of this case: if a target coating raw material of 50-75μm is selected, in Example 4, the bonding strength between the 3mm thick crucible dense coating 200 and the crucible substrate 100 is about 50Mpa; in Example 5, the bonding strength between the 4mm thick crucible dense coating 200 and the crucible substrate 100 is about 45MPa; in Example 6, the bonding strength between the 5mm thick crucible dense coating 200 and the crucible substrate 100 is about 35MPa. If a target coating raw material of 75-100 μm is selected, in Example 4, the bonding strength between the 3 mm thick crucible dense coating 200 and the crucible substrate 100 is approximately 40 MPa; in Example 5, the bonding strength between the 4 mm thick crucible dense coating 200 and the crucible substrate 100 is approximately 35 MPa; in Example 6, the bonding strength between the 5 mm thick crucible dense coating 200 and the crucible substrate 100 is approximately 25 MPa.

[0116] The crucible is used in the process of preparing silicon materials. By preparing a crucible dense coating 200 on the inner wall surface of the crucible base 100 and enhancing the bonding strength between the inner wall surface of the crucible base 100 and the crucible dense coating 200, the crucible is free from cracking and deformation during the silicon material production process and can be reused, thereby extending the service life of the crucible, thereby effectively reducing the amount of quartz used and alleviating the current situation of quartz sand in short supply.

[0117] Comparative Example 1:

[0118] This comparative example provides an application of a crucible in a process of preparing silicon material. The crucible corresponds to the crucible base 100 of the above embodiment, and the inner wall surface of the crucible does not have a crucible dense coating 200 .

[0119] It should be understood that since the crucible is prone to cracking and deformation during the preparation of silicon materials, the crucible needs to be replaced frequently. After the inner wall surface of the crucible substrate 100 is combined with the crucible dense coating 200, the crucible can be used 3 to 5 times by only re-preparing the crucible dense coating 200 on the inner wall surface of the crucible substrate 100. Specifically, when the crucible in Comparative Example 1 is used to prepare a single crystal silicon rod, the crucible can only be used once and then scrapped, and its service life is about 200 to 300 hours; when the crucible in Example 4 is used to prepare a single crystal silicon rod, the crucible can be reused 3 times; when the crucible in Example 5 is used to prepare a single crystal silicon rod, the crucible can be reused 4 times; when the crucible in Example 4 is used to prepare a single crystal silicon rod, the crucible can be reused 5 times.

[0120] It should also be understood that during the preparation of silicon material, as the temperature rises, impurities such as oxygen and carbon will inevitably enter the silicon material, resulting in the inevitable introduction of impurities into the silicon material, making it difficult to ensure the purity requirements of the silicon material. However, after the inner wall surface of the crucible base 100 is combined with the crucible dense coating 200, the content of impurities in the silicon material will be significantly reduced, and the purity of the silicon material will be improved. Specifically, when a single crystal silicon rod is prepared using a crucible,

[0121] The metal impurity content in the silicon rod prepared by the crucible in Comparative Example 1 is about 150-200 ppm;

[0122] The metal impurity content in the silicon rod prepared by the crucible in Example 4 is about 30 ppm;

[0123] The metal impurity content in the silicon rod prepared by the crucible in Example 5 is about 20 ppm;

[0124] The metal impurity content in the silicon rod prepared by using the crucible in Example 6 was about 15 ppm.

[0125] In summary, if continuous direct-pull single crystal technology is used to pull single crystal silicon rods, a 5 mm thick crucible dense coating 200 is selected to be prepared. Under long-term operation, the metal impurity content in the pulled single crystal silicon rod can be effectively controlled; if direct-pull single crystal technology is used to pull single crystal silicon rods, a 4 mm thick crucible dense coating 200 is selected to be prepared. It can ensure that the metal impurity content in the single crystal silicon rods pulled in one furnace meets the standard; if the manufacturer introduces the impurity gettering technology after slicing, a 3 mm thick crucible dense coating 200 can be selected to be prepared. Although there are a small amount of metal impurities in the pulled single crystal silicon rods, the metal impurity content can be reduced by impurity gettering.

[0126] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a crucible, characterized in that: include: Providing a crucible base (100) of a first type of material, and performing surface treatment on the inner wall surface of the crucible base (100) to obtain a region to be bonded; Providing an initial coating material of a second type of material, wherein the initial coating material comprises solid particles; Performing a homogenization process on the initial coating raw material to obtain a target coating raw material; the average particle size of the target coating raw material is smaller than the average particle size of the initial coating raw material; Using a melt spraying process to melt the target coating raw material and apply it to the area to be bonded; Cooling the target coating raw material to form a crucible dense coating (200) that is metallurgically bonded to the area to be bonded; Among them, the first type of material includes: silicon nitride; the second type of material includes: quartz.

2. The method for preparing a crucible according to claim 1, characterized in that: The inner wall surface of the crucible base (100) is subjected to surface treatment to obtain a region to be bonded, comprising: Performing ultrasonic cleaning on the inner wall surface of the crucible base (100); performing a drying process on the crucible base (100) after ultrasonic cleaning; Performing sandblasting on the inner wall surface of the crucible base (100) after the drying treatment, comprising: using sandblasting particles with an average particle size of 22 mesh to 40 mesh, and spraying them onto the inner wall surface of the crucible base (100) at a spray pressure of 0.3Mpa to 0.6Mpa, so as to obtain a to-be-treated area with a preset surface roughness; in, The temperature of the drying process includes: 60°C to 100°C; The duration of the drying process includes: 1h to 2h; The surface roughness of the inner wall of the crucible base (100) after the surface treatment is in the range of 2.2 μm to 2.4 μm.

3. The method for preparing a crucible according to claim 1, characterized in that: The initial coating raw material is subjected to a homogenization process to obtain a target coating raw material, comprising: Provides preset amounts of dispersants and thickeners; The initial coating raw material, the dispersant and the thickener are mixed to obtain a mixed grinding material; wherein the mass ratio of the dispersant to the mixed grinding material includes: 0.6% to 1%; the mass ratio of the thickener to the mixed grinding material includes: 1.5% to 2.5%; The mixed abrasive is mixed with a solvent, and grinding balls are added to perform ball milling to obtain a coating slurry; wherein the mass ratio of the mixed abrasive, the grinding balls and the solvent comprises: (1-2): (1.5-3): (1-3); Performing a spray granulation process on the coating slurry, and screening out coating particles that meet a preset average particle size range as target coating raw materials; Wherein, the average particle size of the initial coating raw material includes: 100 μm to 200 μm; the average particle size of the target coating raw material includes: 50 μm to 100 μm.

4. The method for preparing a crucible according to claim 3, characterized in that , The dispersant comprises: 0.6wt.% to 1.0wt.% of ammonium citrate; The thickener comprises: 1.5wt.% to 2.5wt.% of gum arabic; The solvent includes: deionized water.

5. The method for preparing a crucible according to claim 3, characterized in that: The grinding balls include first-type zirconia balls and second-type zirconia balls; wherein the diameter of the first-type zirconia balls includes: 6mm~10mm; the diameter of the second-type zirconia balls includes: 3mm~5mm; the mass ratio of the first-type zirconia balls to the second-type zirconia balls includes: (2~8): (3~7).

6. The method for preparing a crucible according to claim 3, characterized in that: The target coating raw material is melted and coated on the area to be bonded by a melt spraying process, comprising: Using a plasma spraying process to melt the target coating raw material, and directly spraying and fully penetrating the molten target coating raw material into the to-be-bonded area of ​​the crucible substrate (100); Among them, in the plasma spraying process, the spraying power includes: 30kW~40kW; the feeding rate includes: 10%~20%; the argon flow includes: 30SLPM~35SLPM; the hydrogen flow includes: 10SLPM~15SLPM; the injection pressure of the front cooling gas includes 2bar~6bar; and the spraying distance includes 80mm~120mm.

7. The method for preparing a crucible according to claim 6, characterized in that: Cooling the target coating raw material to form a crucible dense coating (200) in a metallurgical bonding state with the to-be-bonded area, comprising: The molten target coating raw material is cooled by natural cooling or low-temperature annealing to form a crucible dense coating (200) that is metallurgically bonded to the area to be bonded; wherein the thickness of the crucible dense coating (200) is 1 mm to 5 mm.

8. The method for preparing a crucible according to any one of claims 1 to 7, characterized in that: Before the target coating material is melted and coated on the to-be-bonded area by a melt spraying process, the method further comprises: The crucible base (100) is subjected to a preheating treatment; wherein the temperature of the crucible base (100) after the preheating treatment is within a range of 200°C to 300°C.

9. A crucible obtained by the method for preparing a crucible according to any one of claims 1 to 8, characterized in that: The crucible comprises: A crucible base (100) of a first type of material; the surface roughness of the inner wall of the crucible base (100) comprises: 2.2 μm to 2.4 μm; A crucible dense coating (200) of a second type of material, disposed on the inner wall surface of the crucible base (100) and in a metallurgical bonding state with the crucible base (100); Among them, the first type of material includes: silicon nitride; the second type of material includes: quartz.

10. The crucible according to claim 9, characterized in that The thickness of the crucible dense coating (200) ranges from 1 mm to 5 mm.

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