Low bubble expansion rate quartz crucible and method of making same

Abstract

This invention provides a method for preparing a quartz crucible with low bubble expansion rate, belonging to the field of quartz crucible production technology. The method includes: S1, pouring quartz sand into a mold and using centrifugal molding to form a crucible bubble layer and a transparent layer, wherein the crucible bubble layer uses coarse-grained quartz sand, and the crucible transparent layer uses fine-grained quartz sand; S2, inserting the formed quartz sand along with the mold into a melting chamber and starting a vacuum pump to evacuate to a predetermined pressure; S3, igniting an arc in the mold, and during the formation of the crucible transparent layer, performing a first stage of high-temperature melting on the quartz sand using a first preset power; S4, in the later stage of melting, performing a second stage of high-temperature melting on the quartz sand using a second preset power, and after the second stage of high-temperature melting, removing the mold to obtain a quartz crucible with low bubble expansion rate. This invention, through the combination of quartz sand particle size matching and melting power adjustment, ultimately prepares a quartz crucible with low bubbles and low bubble expansion rate.

Description

Technical Field

[0001] This invention relates to the field of quartz crucible manufacturing technology, specifically to a quartz crucible with low bubble expansion rate and its preparation method. Background Technology

[0002] With the rapid development of the semiconductor and photovoltaic industries towards higher efficiency, larger size, and lower cost, the requirements for the quality of monocrystalline silicon materials have reached unprecedented levels. As a core consumable in the Czochralski (CZ) single crystal growth process, the performance of the quartz crucible directly determines the success or failure and quality of the crystal. During the arc melting process, traditional quartz crucibles inevitably trap and generate a large number of tiny bubbles due to the high-temperature reaction. These bubbles pose multiple fatal risks in the high-temperature crystal pulling environment: First, the bursting of bubbles releases the accumulated metallic impurities (such as Na and K), contaminating the silicon melt and leading to abnormal crystal resistivity and a decrease in minority carrier lifetime; second, encountering bubbles at the crystal growth interface can cause lattice misalignment, resulting in defects such as dislocations, and even edge breakage; third, bubbles significantly reduce the high-temperature strength and viscosity of the crucible, making it prone to deformation due to the hydrostatic pressure of the molten silicon during long-term crystal pulling, disrupting thermal field stability and causing process control failure. The widespread adoption of high-efficiency N-type solar cell technologies (such as TOPCon and HJT) has placed extremely stringent demands on the purity and perfection of the substrate silicon material. Any minute defects or contamination can drastically affect the conversion efficiency of the final device. Therefore, traditional crucibles with high bubble content have become a bottleneck restricting product yield and quality improvement.

[0003] Against this backdrop, the development of low-bubble quartz crucibles has become a key technological breakthrough in overcoming industry bottlenecks. Currently, the main methods involve using high-vacuum melting processes, precision layer control technology, and ultra-high-purity raw materials (such as synthetic quartz sand) to construct a dense, low-bubble transparent layer on the inner surface of the crucible. This ensures that when the crucible comes into contact with the molten silicon, there are no sources of impurity release or defect induction points, thus providing a crucial foundation for growing ultra-high-quality, ultra-low-defect-density monocrystalline silicon. While these technologies significantly improve the quality of monocrystalline silicon, existing quartz crucibles typically use quartz sand of the same particle size for both the bubble layer and the transparent layer. This results in large gaps between the particles in the transparent layer, making it easier for air to be trapped at high temperatures, forming interstitial bubbles. Consequently, a layer of bubbles remains on the crucible surface that cannot be effectively removed. Therefore, a method for preparing quartz crucibles that can effectively remove bubbles from the crucible surface is needed. Summary of the Invention

[0004] In view of this, the present invention provides a quartz crucible with low bubble expansion rate and its preparation method, so as to solve the technical problem that existing quartz crucible preparation methods cannot effectively remove bubbles on the surface of the crucible.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A method for preparing a quartz crucible with low bubble expansion rate includes the following steps:

[0007] S1. Pour quartz sand into the mold and use centrifugal molding to shape the quartz sand to form the crucible bubble layer and the crucible transparent layer of the quartz crucible. The crucible bubble layer uses coarse-grained quartz sand, and the surface of the crucible transparent layer uses fine-grained quartz sand to achieve the preset thickness.

[0008] S2. The formed quartz sand, along with the mold, is inserted into the melting chamber, and the vacuum pump is started to evacuate the air to the predetermined pressure to increase the efficiency of bubble extraction.

[0009] S3. Initiate an arc in the mold. During the melting stage of the transparent layer of the crucible, use the first preset power to perform the first stage of high-temperature melting on the quartz sand, so that the quartz sand is fully melted.

[0010] S4. In the later stage of melting, the quartz sand is subjected to a second stage of high-temperature melting with the second preset power to increase the viscosity of the quartz sand and reduce the bubble accumulation at the R part; after the second stage of high-temperature melting is completed, the mold is removed to obtain a quartz crucible with low bubble expansion rate.

[0011] Preferably, in step S1, the surface layer of the transparent layer of the crucible is made of fine-grained quartz sand for 1-3 mm.

[0012] Preferably, in step S1, the particle size of the coarse-grained quartz sand is 100-400 μm.

[0013] Preferably, in step S1, the particle size of the fine-grained quartz sand is 50-150 μm.

[0014] Preferably, in step S3, the first preset power is 3250-3900kW.

[0015] Preferably, in step S4, the second preset power is 1050-1400kW.

[0016] Preferably, the transparent layer formation stage of the crucible is 0-4 min, and the later melting stage is 4-18 min.

[0017] Preferably, in step S2, the predetermined pressure is -0.09 MPa.

[0018] Preferably, in step S2, the number of vacuum pumps is multiple, and the multiple vacuum pumps are connected in parallel.

[0019] The present invention also provides a quartz crucible with low bubble expansion rate, which is prepared by the preparation method of the quartz crucible with low bubble expansion rate as described above.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] In preparing the quartz crucible, this invention first pours coarse-grained quartz sand into a mold and centrifugally forms a crucible bubble layer on the inner wall of the mold. The high density and numerous pores in the coarse-grained quartz sand structure enhance the crucible's heat retention and allow for more uniform inward radiation of heat from the graphite thermal field. Next, fine-grained quartz sand is poured into the mold and centrifugally forms a transparent layer on the inner wall of the bubble layer. The high packing density of the fine-grained quartz sand results in fewer air particles remaining between them, facilitating the formation of a dense and uniform structure during melting. This significantly reduces microbubbles and impurities, thereby lowering the bubble expansion rate and reducing the risk of bubble expansion and rupture at high temperatures, releasing impurities. Then, during the transparent layer formation stage, the melting power is increased to fully melt the quartz sand. Simultaneously, the vacuum pump's negative pressure is increased to improve the efficiency of quartz sand bubble extraction and ensure more thorough bubble removal. Finally, in the later stages of melting, the melting power is reduced to increase the viscosity of the quartz sand, reducing its movement and ultimately weakening bubble aggregation at the R-position. Therefore, this invention effectively removes bubbles from the crucible surface by adjusting the particle size of the quartz sand and regulating the melting power of the high-vacuum melting process, thereby reducing the source of expandable gas at high temperatures. This results in the preparation of a quartz crucible with low bubbles and low bubble expansion rate, which provides a crucial foundation for the growth of ultra-high quality, ultra-low defect density monocrystalline silicon. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method for preparing the low bubble expansion rate quartz crucible of the present invention.

[0023] Figure 2 The diagram shows the distribution of the number of bubbles in section R of the embodiment.

[0024] Figure 3 This is a comparative diagram showing the distribution of the number of bubbles in section R.

[0025] Figure 4 The cross-sectional bubble distribution diagram is shown in the example.

[0026] Figure 5 This is a comparative cross-sectional bubble distribution diagram.

[0027] Figure 6 This is a schematic diagram of the expansion of bubbles in the cross-section after calcination, as shown in the example.

[0028] Figure 7 This is a schematic diagram showing the expansion of bubbles in the cross-section after calcination, as a comparative example. Detailed Implementation

[0029] The technical solutions and effects of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] Please refer to Figure 1 A method for preparing a quartz crucible with low bubble expansion rate includes the following steps:

[0031] S1. Pour quartz sand into the mold and use centrifugal molding to shape the quartz sand to form the crucible bubble layer and the crucible transparent layer of the quartz crucible. The crucible bubble layer uses coarse-grained quartz sand, and the surface of the crucible transparent layer uses fine-grained quartz sand to achieve the preset thickness.

[0032] S2. The formed quartz sand, along with the mold, is inserted into the melting chamber, and the vacuum pump is started to evacuate the air to the predetermined pressure to increase the efficiency of bubble extraction.

[0033] S3. Initiate an arc in the mold. During the melting stage of the transparent layer of the crucible, use the first preset power to perform the first stage of high-temperature melting on the quartz sand, so that the quartz sand is fully melted.

[0034] S4. In the later stage of melting, the quartz sand is subjected to a second stage of high-temperature melting with the second preset power to increase the viscosity of the quartz sand and reduce the bubble accumulation at the R part; after the second stage of high-temperature melting is completed, the mold is removed to obtain a quartz crucible with low bubble expansion rate.

[0035] In preparing the quartz crucible, this invention first pours coarse-grained quartz sand into a mold and centrifugally forms a crucible bubble layer on the inner wall of the mold. The high density and numerous pores in the coarse-grained quartz sand structure enhance the crucible's heat retention and allow for more uniform inward radiation of heat from the graphite thermal field. Next, fine-grained quartz sand is poured into the mold and centrifugally forms a transparent layer on the inner wall of the bubble layer. The high packing density of the fine-grained quartz sand results in fewer air particles remaining between them, facilitating the formation of a dense and uniform structure during melting. This significantly reduces microbubbles and impurities, thereby lowering the bubble expansion rate and reducing the risk of bubble expansion and rupture at high temperatures, releasing impurities. Then, during the transparent layer formation stage, the melting power is increased to fully melt the quartz sand. Simultaneously, the vacuum pump's negative pressure is increased to improve the efficiency of quartz sand bubble extraction and ensure more thorough bubble removal. Finally, in the later stages of melting, the melting power is reduced to increase the viscosity of the quartz sand, reducing its movement and ultimately weakening bubble aggregation at the R-position. Therefore, this invention effectively removes bubbles from the crucible surface by adjusting the particle size of the quartz sand and regulating the melting power of the high-vacuum melting process, thereby reducing the source of expandable gas at high temperatures. This results in the preparation of a quartz crucible with low bubbles and low bubble expansion rate, which provides a crucial foundation for the growth of ultra-high quality, ultra-low defect density monocrystalline silicon.

[0036] Furthermore, during the high-temperature melting process, the migration path of bubbles in the melt is as follows: nucleation occurs first on the inner wall of the transparent layer of the crucible, then the entire crucible wall thickness is traversed, passing through the channels of the crucible bubble layer, and finally escaping from the free surface of the melt. When gas-liquid inclusions in the quartz sand rupture upon heating, releasing gas, if the crucible bubble layer and the crucible transparent layer use the same particle size, the pore distribution between particles is uniform, lacking a pore gradient structure from fine to coarse. This hinders the migration path of bubbles from the crucible transparent layer to the crucible bubble layer during high-temperature melting, preventing the bubbles from directionally escaping along the pressure gradient. Consequently, the bubbles remain 1-3 mm above the surface of the crucible transparent layer, forming microbubbles that contaminate the silicon melt. Moreover, with the same particle size, the melt fluidity is consistent, preventing bubbles from escaping from the surface of the crucible transparent layer due to viscous resistance and surface tension. Based on this, the present invention uses fine-grained quartz sand at a predetermined thickness on the surface of the transparent layer of the crucible. This allows the quartz sand to be densely packed, forming a low-porosity, high-viscosity, dense layer. This significantly reduces the frequency of gas-liquid inclusion rupture and gas release during the initial melting stage, suppressing bubble formation at the source. Furthermore, the fine particles restrict melt flow, making it difficult for bubbles to aggregate and grow on the surface of the transparent layer, thus reducing the number of microbubbles. Simultaneously, the present invention uses coarse-grained quartz sand in the bubble layer of the crucible, forming a porous network with high porosity and low viscosity. Driven by thermal buoyancy, bubbles migrate directionally along a pore gradient from the inside out and from dense to sparse, being captured by the outer layer rather than remaining at the transparent layer interface, further reducing bubble aggregation on the surface of the transparent layer.

[0037] Further, in step S1, the surface 1-3 mm of the transparent layer of the crucible uses fine-grained quartz sand. Specifically, the transparent layer of the crucible in this invention uses high-purity quartz sand of the same purity, wherein the surface 1-3 mm of the transparent layer, i.e., the portion closest to the inner surface of the crucible, uses fine-grained quartz sand, while the portion near the bubble layer of the crucible uses coarse-grained quartz sand. The transparent layer of the quartz crucible is typically 3-5 mm thick. The presence of the transparent layer reduces the bubble density in the contact area between the crucible and the solution, thereby improving the success rate of single crystal growth and the quality of the crystal rod. During the use of the crucible, the inner surface in contact with the molten silicon continuously melts into the molten silicon, and the microbubbles in the transparent layer continuously grow. The bubbles near the innermost surface burst, releasing quartz microparticles and microbubbles along with the molten silicon. These impurities, in the form of microparticles and microbubbles, flow throughout the entire silicon melt along with the molten silicon, directly affecting the crystallization of silicon and the quality of single crystal silicon. The innermost layer of the crucible refers to the part of the transparent layer of the crucible that is 1-3 mm from the inner surface. Therefore, the present invention uses fine-grained quartz sand in this part to further reduce the generation of bubbles on the surface. Since finer-grained quartz sand is more difficult and more expensive to process, coarse-grained quartz sand is used in the part near the bubble layer of the crucible, thereby reducing the bubble on the surface of the crucible while reducing the processing difficulty and cost of quartz sand.

[0038] Further, in step S1, the particle size of the coarse-grained quartz sand is 100-400 μm. Since the crucible bubble layer of the quartz crucible does not directly contact the high-temperature molten silicon, the requirements for the purity and impurities of the quartz sand are relatively low. Generally, lower-cost natural quartz sand is used, and coarse-grained natural quartz sand is easier to obtain and cheaper. Furthermore, this invention uses coarse-grained quartz sand because, on the one hand, the structure formed by coarse-grained quartz sand has more pores and a higher bubble density, which helps to enhance the heat preservation effect of the quartz crucible and allows the heat source from the graphite thermal field to radiate more evenly inward; on the other hand, the coarse-grained stacked structure provides better resistance to deformation, supporting the overall structure of the quartz crucible and preventing the quartz crucible from collapsing at high temperatures. Preferably, the particle size of the coarse-grained quartz sand in this invention is 200-300 μm.

[0039] Because quartz sand of different particle sizes has different bulk densities and melting rates, coarse-grained quartz sand has a lower bulk density than fine-grained quartz sand, resulting in more air trapped between the particles. Therefore, coarse-grained quartz sand leaves more air bubbles in the transparent layer during the vacuum melting stage. Furthermore, coarse-grained quartz sand melts more slowly than fine-grained quartz sand, and due to the lower temperature during the arc ignition stage, it is more likely to leave air bubbles on the inner surface of the crucible under high vacuum melting conditions. Based on this, this invention uses fine-grained quartz sand in the transparent layer of the quartz crucible during preparation. The particle size of the fine-grained quartz sand is 50-150 μm, preferably 75-150 μm. Because fine-grained quartz sand melts faster and the arc ignition stage temperature is lower, it is less likely to leave air bubbles on the inner surface of the crucible under high vacuum melting conditions. Furthermore, finer particle size also means smaller gaps between particles, resulting in smaller microbubbles formed by air in the gaps and a smaller bubble expansion rate. As a result, they need a longer time to grow to the point of breaking through the inner surface during the crystal pulling process, making it less likely for foreign particles to enter the silicon melt and avoiding problems such as dislocations, black chips, or perforated wafers during the growth of single crystal silicon.

[0040] In some embodiments, fine-grained quartz sand is obtained by screening. Specifically, the raw ore is first coarsely crushed using a jaw crusher, then further crushed using a cone crusher or impact crusher, followed by grinding the quartz sand to 0.1-0.5 mm using a ball mill or rod mill to release inclusions. Finally, the quartz sand of the target particle size is separated by a vibrating screen, hydrocyclone, or air classification system, removing coarse particles and fine clay powder. In some embodiments, fine-grained quartz sand can also be obtained by vibratory ball milling. Specifically, the surface dust and foreign matter of the quartz sand raw material are first removed, and the blocky quartz sand is cut into block samples ≤5 mm using a cutting machine (large particles of powdered quartz sand can be directly screened to remove them). No additional drying or cooling treatment is required; the sample is directly loaded into a grinding jar of the same material according to the required sample volume, and grinding balls of the corresponding size are added, ready for subsequent high-efficiency grinding. Then, a vibratory ball mill is used to drive grinding balls of the same material through high-frequency vibration to impact, grind and shear the quartz sand solid sample at high speed, so as to completely break the crystal structure and particle agglomerates of the quartz sand and obtain quartz sand of the target particle size.

[0041] Because the coarse and fine quartz sand used in this invention have significantly different particle sizes, the mixing area between them has a large particle size range, making it impossible to form effective mechanical interlocking. This significantly reduces the interfacial bonding strength, leading to thermal stress concentration and weakening the overall mechanical properties of the crucible. Furthermore, the large gaps between the coarse quartz sand particles prevent the fine quartz sand from completely filling them, causing gas retention during melting and forming a network of interconnected pores, which becomes a channel for stress concentration and crack propagation. Additionally, the significant difference in their thermal expansion coefficients generates shear stress during heating / cooling, inducing interfacial debonding. Therefore, in some embodiments, the transparent layer of the quartz crucible of this invention is designed as a three-layer structure, including a portion of the transparent layer near the bubble layer, a transition layer, and a surface layer of the transparent layer, wherein the thickness of the transition layer is 1 mm. Each layer contains quartz sand of the same purity, but the particle size decreases sequentially from the portion of the transparent layer near the bubble layer to the surface layer. Specifically, the transparent layer of the crucible near the bubble layer uses coarse-grained quartz sand of 100-400 μm, the transition layer uses medium-grained quartz sand of 150-200 μm, and the surface 1-3 mm of the transparent layer uses fine-grained quartz sand of 50-150 μm. This increases the gradual particle size distribution in the transition layer, allowing the medium-grained quartz sand to fill the spaces between the coarse-grained quartz sand, reducing gas retention during melting, forming effective mechanical interlocking, improving interfacial bonding strength, reducing thermal stress concentration, and ultimately improving the overall mechanical properties of the quartz crucible.

[0042] Furthermore, in step S3, the first preset power is 3250-3900kW. During the formation stage of the transparent layer in the crucible, that is, 0-4 minutes after the arc is ignited in the melting furnace, an electric arc is ignited through the graphite electrode to convert electrical energy into heat energy, and the resulting high temperature melts the quartz sand. In this process, because the surface layer of the transparent layer of the crucible is made of fine-grained quartz sand, which melts faster, increasing the melting power to 3250-3900kW during this stage allows for more complete melting of the quartz sand. This promotes the rupture of gas-liquid inclusions within the quartz sand, reducing residual gas in incompletely fused areas. Furthermore, increasing the melting power raises the local temperature, reducing the viscosity of the molten quartz and promoting the rise and escape of internal microbubbles. The increased power further alters the thermal gradient, enhancing convection within the melt and accelerating bubble migration and rupture to the surface. Finally, the vacuum environment helps to remove gas, resulting in a cleaner removal of bubbles from the transparent layer of the crucible. This ensures that the area of ​​the quartz crucible in direct contact with the molten silicon is virtually bubble-free, fundamentally preventing the expansion and rupture of bubbles on the inner wall at high temperatures. Fewer bubbles mean less total expandable gas per unit volume, effectively reducing the bubble expansion rate of the quartz crucible.

[0043] Further, in step S4, the second preset power is 1050-1400kW. In the later stages of melting, specifically the 4-18 min melting phase, most of the quartz sand has melted. The viscosity of the quartz melt decreases significantly with increasing temperature. If high power is maintained in the later stages, it will lead to localized overheating, resulting in excessively low melt viscosity, which is detrimental to forming a uniform and dense inner layer structure. Therefore, reducing the melting power in the later stages of melting can increase the viscosity of the quartz sand, reduce its movement, and ultimately weaken the bubble aggregation at location R. Simultaneously, reducing the melting power slows down the melting rate and prolongs the melt holding time, allowing bubbles more time to escape or be extracted by the vacuum system, reducing the density of inner layer bubbles, thereby obtaining a more uniform and dense transparent crucible layer. Furthermore, quartz material softens at high temperatures. If high-power heating continues, the crucible wall may collapse or develop holes due to localized overheating, affecting the structural integrity of the finished product.

[0044] Furthermore, in step S2, the predetermined pressure is -0.09 MPa. Removing air from the melting chamber via a vacuum system reduces oxygen content, decreases impurity reactions in the quartz sand at high temperatures, and facilitates stable arc ignition. Quartz sand raw materials often contain trace amounts of adsorbed water, crystal water, and air. During high-temperature melting, these gases expand to form bubbles. The solubility of gases in the melt is proportional to the partial pressure of the gases above. Increasing the vacuum level in the melting chamber significantly reduces the total ambient pressure, thereby lowering the partial pressure of dissolved gases in the molten quartz sand. This causes these gases to precipitate from the melt and be removed, reducing gas residue in the molten quartz sand. Additionally, the vacuum environment inhibits bubble nucleation and growth, making it easier for existing microbubbles to break or merge and float due to the internal and external pressure difference. This reduces the bubble content in the final product, decreases the source of bubble expansion, and consequently reduces the gas expansion rate of the quartz crucible.

[0045] Furthermore, in step S2, multiple vacuum pumps are used, and these pumps are connected in parallel. Because the melting power is increased during the formation of the transparent layer in the crucible, the quartz sand melts faster when the melting power is higher, and the trapped gases and volatile impurities are released more quickly. If the vacuum system's pumping speed is insufficient at this time, it may cause pressure fluctuations in the furnace or re-dissolution of impurities, affecting the crucible's purity and microbubble density. Therefore, this invention uses multiple vacuum pumps to increase the vacuum system's pumping speed during the formation of the transparent layer, in conjunction with the higher melting power, resulting in higher efficiency and more thorough bubble removal from the quartz crucible. In some embodiments, multiple vacuum pumps are connected in parallel. Since the melting power differs between the formation of the transparent layer and the later melting stages, different numbers of vacuum pumps can be controlled to maintain stable pressure within the melting chamber, thereby precisely controlling the vacuum level within the melting chamber.

[0046] The present invention also provides a quartz crucible with low bubble expansion rate, which is prepared by the preparation method of the quartz crucible with low bubble expansion rate as described above.

[0047] The following specific experimental examples further illustrate the technical solution and effects of the present invention. It should be noted that the following experimental examples are only for further explanation of the present invention and do not limit the technical solution of the present invention.

[0048] Example

[0049] First, coarse-grained natural quartz sand with an average particle size of 250 μm is poured into a mold, and centrifugal molding is used to form a crucible bubble layer on the inner wall of the mold. Then, coarse-grained high-purity quartz sand with an average particle size of 250 μm is poured into the mold, and centrifugal molding is used to form a 2 mm transparent layer on the inner wall of the crucible bubble layer. Next, fine-grained high-purity quartz sand with an average particle size of 100 μm is poured into the mold, and centrifugal molding is used to form a 3 mm transparent layer on the surface. The molded quartz sand, along with the mold, is placed into the melting chamber, and the vacuum pump is activated to evacuate the air to -0.09 MPa. An arc is initiated on the mold, and during the first stage of transparent layer formation (0-4 minutes), the quartz sand is melted at a first-stage high-temperature melting power of 3250 kW. During the later melting stage (4-18 minutes), the quartz sand is melted at a second-stage high-temperature melting power of 1050 kW. After the second stage of high-temperature melting is completed, the electric arc is turned off, and the mold is sent out of the melting chamber after the furnace temperature has cooled down. It is then further cooled down in the workshop by natural cooling for about 10 to 20 minutes. After cooling, the crucible is removed from the mold, resulting in the quartz crucible of the embodiment.

[0050] Comparative Example

[0051] First, coarse-grained natural quartz sand with an average particle size of 250 μm is poured into a mold, and centrifugal molding is used to form a crucible bubble layer on the inner wall of the mold. Then, coarse-grained high-purity quartz sand with an average particle size of 250 μm is poured into the mold, and centrifugal molding is used to form a crucible transparent layer on the inner wall of the crucible bubble layer. The molded quartz sand, along with the mold, is placed into the melting chamber, and a vacuum pump is started to evacuate the air to -0.07 MPa. An arc is ignited in the mold, and during the formation of the crucible transparent layer, the quartz sand is melted at a first stage of high temperature at a melting power of 2500 kW. In the later stage of melting, the quartz sand is melted at a second stage of high temperature at a melting power of 1500 kW. After the second stage of high-temperature melting is completed, the arc is turned off, and after the furnace temperature cools down, the mold is sent out of the melting chamber and further cooled by natural cooling in the workshop for about 10-20 minutes. After cooling, the crucible is removed from the mold to obtain a comparative quartz crucible. Other melting process parameters are the same as in the example.

[0052] Since the bubbles in the R-section are more easily affected by the particle size of the quartz sand, making them easier to analyze, the R-sections of the quartz crucibles in the examples and comparative examples were selected for testing. The number of bubbles and their expansion in the transparent layer of the R-section were analyzed and compared. First, the number of bubbles in the 0-2mm transparent layer of the R-section was analyzed using a bubble meter, as shown below. Figure 2 and Figure 3 The bubble distribution diagram shown illustrates that the quartz crucible in the embodiment has fewer bubbles in the transparent layer of section R, while the comparative quartz crucible has more bubbles in the transparent layer of section R. The bubble distribution in the transparent layer cross-section was then observed by slicing the quartz crucibles, yielding the following results: Figure 4 and Figure 5 The cross-sectional bubble distribution diagram shown illustrates that the quartz crucible slices in the embodiment have fewer bubbles in the transparent layer cross-section, while the quartz crucible slices in the comparative example have more bubbles. Finally, the quartz crucible slices were calcined to observe the expansion of bubbles in the transparent layer cross-section, yielding the following results: Figure 6 and Figure 7 The image shown. See also... Figure 4 and Figure 6 The images show that the quartz crucible slices in the embodiment have a low bubble expansion rate after calcination, while referring to... Figure 5 and Figure 7 The images show that the comparative quartz crucible slices exhibit a larger bubble expansion rate after calcination. The above results demonstrate that selecting quartz sand of different particle sizes for the bubble layer and the transparent layer of the crucible, combined with increasing the melting power in the early stages of melting and decreasing it in the later stages, can effectively reduce bubbles on the surface of the transparent layer of the quartz crucible and lower the bubble expansion rate.

[0053] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for preparing a quartz crucible with low bubble expansion rate, characterized in that, Includes the following steps: S1. Pour quartz sand into the mold and use centrifugal molding to shape the quartz sand to form the crucible bubble layer and the crucible transparent layer of the quartz crucible. The crucible bubble layer uses coarse-grained quartz sand, and the surface of the crucible transparent layer uses fine-grained quartz sand to achieve the preset thickness. S2. The formed quartz sand, along with the mold, is inserted into the melting chamber, and the vacuum pump is started to evacuate the air to the predetermined pressure to increase the efficiency of bubble extraction. S3. Initiate an arc in the mold. During the melting stage of the transparent layer of the crucible, use the first preset power to perform the first stage of high-temperature melting on the quartz sand, so that the quartz sand is fully melted. S4. In the later stage of melting, the quartz sand is subjected to a second stage of high-temperature melting with the second preset power to increase the viscosity of the quartz sand and reduce the bubble accumulation at the R part; after the second stage of high-temperature melting is completed, the mold is removed to obtain a quartz crucible with low bubble expansion rate.

2. The method for preparing a low-bubble expansion rate quartz crucible according to claim 1, characterized in that, In step S1, the surface layer of the transparent layer of the crucible, 1-3 mm thick, is made of fine-grained quartz sand.

3. The method for preparing a low-bubble expansion rate quartz crucible according to claim 2, characterized in that, In step S1, the particle size of the coarse-grained quartz sand is 100-400 μm.

4. The method for preparing a low-bubble expansion rate quartz crucible according to claim 3, characterized in that, In step S1, the particle size of the fine-grained quartz sand is 50-150 μm.

5. The method for preparing a low-bubble expansion rate quartz crucible according to any one of claims 1-4, characterized in that, In step S3, the first preset power is 3250-3900kW.

6. The method for preparing a low-bubble expansion rate quartz crucible according to claim 5, characterized in that, In step S4, the second preset power is 1050-1400kW.

7. The method for preparing a low-bubble expansion rate quartz crucible according to claim 6, characterized in that, The formation stage of the transparent layer in the crucible is 0-4 min, and the later stage of melting is 4-18 min.

8. The method for preparing a low-bubble expansion rate quartz crucible according to claim 1, characterized in that, In step S2, the predetermined pressure is -0.09 MPa.

9. The method for preparing a low-bubble expansion rate quartz crucible according to claim 8, characterized in that, In step S2, there are multiple vacuum pumps connected in parallel.

10. A quartz crucible with low bubble expansion rate, characterized in that, It is prepared using the method for preparing a low bubble expansion rate quartz crucible as described in any one of claims 1-9.

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