Judgment method and application of high-purity quartz sand for preparing low-bubble photovoltaic quartz crucible

Abstract

The invention provides a judgment method and application of high-purity quartz sand for preparing a low-bubble photovoltaic quartz crucible, and the judgment method comprises the following steps: detecting attribute indexes of the high-purity quartz sand, including chemical components, tap density and gas-liquid inclusion content; calculating the detected attribute index of the high-purity quartz sand according to a calculation formula to obtain a bubble content index; the impurity element content and bubble content indexes in the high-purity quartz sand are graded, and the high-purity quartz sand is comprehensively judged according to the impurity element content grade and the bubble content index grade. Reliable and quantifiable raw material screening standards are provided for the quartz crucible manufacturing industry, inferior quartz sand can be accurately screened out, the product yield of the low-bubble photovoltaic quartz crucible can be remarkably increased, the service life of the low-bubble photovoltaic quartz crucible can be remarkably prolonged through application and popularization of the low-bubble photovoltaic quartz crucible, the stability and safety of a downstream monocrystalline silicon drawing process are effectively guaranteed, and the production cost is reduced. The method is of great significance in promoting cost reduction, efficiency improvement and high-quality development of a photovoltaic industry chain.

Description

TECHNICAL FIELD

[0001] The present application relates to the application technical field of high-purity quartz material, in particular to a determination method and application of high-purity quartz sand for preparing low-bubble photovoltaic quartz crucibles. BACKGROUND

[0002] High-purity quartz sand is the core basic raw material for preparing photovoltaic single-crystal silicon quartz crucibles, and the quality thereof directly determines the performance and defect level of the quartz crucible. The quartz crucible is generally of a multi-layer structure, the outer layer being a bubble composite layer for heat preservation and maintaining mechanical stability of the crucible, and the inner layer being a bubble depletion layer for preventing the influence of bubbles on the silicon liquid. Among the many defects, too high a bubble content is one of the most critical factors leading to deterioration and even failure of the quartz crucible. In the high-temperature crystal pulling process, the dissolution of the inner wall of the crucible will release the bubbles in the bubble depletion layer of the quartz crucible to the silicon melt, seriously damaging the solid-liquid interface stability of single-crystal growth, and being the main cause of dislocation and even broken wire climbing of the crystal bar. Therefore, controlling the physicochemical properties of high-purity quartz sand from the source is a prerequisite for preparing high-performance quartz crucibles.

[0003] At present, there are significant defects in the evaluation of high-purity quartz sand in the industry, and it is impossible to effectively screen and determine the raw materials suitable for "low-bubble" crucibles. The existing methods mostly focus on isolated detection of a single index, such as only analyzing the chemical composition and inclusion content of high-purity quartz, and the correlation with the final "low-bubble" target is not strong enough.

[0004] The fundamental dilemma of the current technology is that a quantitative prediction system based on the intrinsic characteristics of quartz sand aimed at achieving the "low-bubble" target has not been established. The industry is well aware that bubbles are caused by inclusions and other defects, but there is a lack of quantitative standards for what size of inclusion content, particle size distribution and morphology combination can ensure that the crucible reaches the "low-bubble" level, leading to a serious disconnection between raw material screening and the final crucible performance. Due to the lack of the above-mentioned causal relationship and characterization technology, the industry urgently needs a comprehensive determination standard specially designed for "low-bubble" crucible raw materials. Without this standard, it is impossible to accurately exclude high-purity quartz sand with high-bubble risk from the source, resulting in poor production stability and low yield of high-end low-bubble crucibles.

[0005] In summary, it is necessary to establish a determination method and standard for high-purity quartz sand for low-bubble photovoltaic quartz crucibles, which is the key to breaking through the bottleneck of high-end quartz crucible preparation technology and improving the quality of the basic materials of the photovoltaic industry chain in China. SUMMARY

[0006] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art. For example, one objective of this invention is to provide a method for determining the purity of high-purity quartz sand used in preparing low-bubble photovoltaic quartz crucibles; another objective of this invention is to provide an application of the method for determining the purity of high-purity quartz sand used in preparing low-bubble photovoltaic quartz crucibles.

[0007] To achieve the above objectives, the present invention provides a method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles, the method comprising: 1) Test the property indicators of high-purity quartz sand; 2) Calculate the bubble content index w by using the formula to obtain the property index of high-purity quartz sand obtained from the test; 3) The impurity element content and bubble content index w in high-purity quartz sand are classified, and the high-purity quartz sand is comprehensively judged based on the impurity element content level and bubble content index level.

[0008] Alternatively, the property indicators of the high-purity quartz sand described in step 1) include: chemical composition, tap density, gas-liquid inclusion content, and loss on ignition.

[0009] Optionally, the chemical composition refers to the content of impurity elements in the high-purity quartz sand; the gas-liquid inclusion content refers to the area ratio of dark regions caused by gas-liquid inclusions in the high-purity quartz sand under a microscope and / or the liquid phase content and gas phase content of the gas-liquid inclusions; the loss on ignition is the loss on ignition of the high-purity quartz sand sample after calcination at 1050℃±50℃ for more than 1 hour.

[0010] Alternatively, the calculation formula in step 2) includes formulas (1) and (2): w=20(1.48-x)+5y+10z (1) w=20(1.48-x)+2(a+b)+10z (2) In equations (1) and (2), x represents the tap density, with units of g / cm³. 3 When x > 1.48, x = 1.48 is taken; when the content of gas-liquid inclusions is taken as the proportion of the dark area caused by gas-liquid inclusions under a microscope, it is calculated using formula (1), where y represents the percentage of the dark area caused by inclusions in the high-purity quartz sand sample; when the content of gas-liquid inclusions is taken as the liquid phase content and gas phase content of gas-liquid inclusions, it is calculated using formula (2), where a is the gas phase content of gas-liquid inclusions, in cm 3 / 100g, b is the liquid phase content of the gas-liquid inclusions, in g / 100g; z is the loss on ignition of high-purity quartz sand.

[0011] Optionally, the impurity element content levels mentioned in step 3) include grade a, grade b, and grade c, wherein: Grade A requires the following conditions to be met simultaneously: Al content is 5.0~12.0ppm, total Li, Na and K content is less than 1.5ppm, Ti content is less than 2.0ppm, Fe and Ba content are both less than 0.5ppm, Ca content is less than 0.8ppm, Mg content is less than 0.3ppm, Mn, Cu and Cr content are all less than 0.1ppm, B content is less than 0.1ppm, P content is less than 0.4ppm, Ge content is less than 0.5ppm, Ni content is less than 0.05ppm, and Zr content is less than 0.9ppm; Grade B requires the following conditions to be met simultaneously: Al content is 12.0~15.0 ppm or less than 5 ppm, total Li, Na, and K content is less than 2.0 ppm, Ti content is less than 2.5 ppm, Fe and Ba content are both less than 0.5 ppm, Ca content is less than 1.0 ppm, Mg content is less than 0.3 ppm, Mn, Cu, and Cr content are all less than 0.1 ppm, B content is less than 0.1 ppm, P content is less than 0.4 ppm, Ge content is less than 0.9 ppm, and Ni content is less than 0.05 ppm; Grade C requires the following conditions to be met simultaneously: Al content is 15.0~18.0 ppm or less than 5 ppm, total Li, Na and K content is less than 3.0 ppm, Ti content is less than 4.0 ppm, Fe and Ba content are both less than 0.5 ppm, Ca content is less than 1.2 ppm, Mg content is less than 0.3 ppm, Mn, Cu and Cr content are all less than 0.1 ppm, B content is less than 0.1 ppm, P content is less than 0.4 ppm, Ge content is less than 0.9 ppm, and Ni content is less than 0.05 ppm.

[0012] Optionally, the bubble content index grade mentioned in step 3) includes grade A, grade B and grade C, wherein when w < 0.19, it is judged as grade A; when 0.19 ≤ w < 0.8, it is judged as grade B; and when 0.8 ≤ w < 1.1, it is judged as grade C.

[0013] Alternatively, in the comprehensive determination described in step 3), the applicable strata of high-purity quartz sand may be further divided according to the following rules: If both the impurity element index and the bubble index meet the grade A standard, then the quartz sand is determined to be suitable for preparing the inner layer of the low-bubble photovoltaic quartz crucible. If one of the impurity element content level and the bubble content index level meets level a and the other meets level b, or both meet level b, then the quartz sand is determined to be suitable for preparing the middle layer of the low-bubble photovoltaic quartz crucible. If one of the impurity element content level and the bubble content index level meets grade a, grade b or grade c, while the other only meets grade c, then the quartz sand is determined to be suitable for preparing the outer layer of the low bubble photovoltaic quartz crucible. If either the impurity element content level or the bubble content index level fails to meet the above-mentioned grade C standard, then the quartz sand is deemed unsuitable for preparing the low-bubble photovoltaic quartz crucible.

[0014] Alternatively, if the bubble content index is classified as Grade A, then the bubble content of the quartz crucible is less than 6 cm. 3 / kg; if the bubble content index is classified as grade b, then the bubble content of the quartz crucible is ≥6cm. 3 / kg and <9cm 3 / kg; if the bubble content index is classified as grade C, then the bubble content of the quartz crucible is ≥9cm. 3 / kg and ≤15cm 3 / kg.

[0015] Another aspect of the present invention provides an application of a method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles, wherein the determination method is the aforementioned method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles.

[0016] Alternatively, the determination method can be applied to the manufacturing process of low-bubble photovoltaic quartz crucibles to perform quality grading and suitability screening of high-purity quartz sand raw materials from different batches or sources, determining whether they are suitable for preparing the inner, middle, or outer layer of the low-bubble photovoltaic quartz crucible, or unsuitable as high-purity quartz sand for the low-bubble photovoltaic quartz crucible.

[0017] Alternatively, when the determination result is that it is not suitable as high-purity quartz sand for the low-bubble photovoltaic quartz crucible, it can be purified again or the particle size distribution can be changed for optimization, and the optimized high-purity quartz sand can be determined again.

[0018] Compared with the prior art, the beneficial effects of the present invention include at least one of the following: (1) This invention constructs a multi-dimensional quantitative index system and a comprehensive judgment model. This invention innovatively considers multiple indicators such as chemical composition, tap density, inclusion content and volatile substance content in a coordinated manner, and introduces a bubble content evaluation index formula. By weighted calculation, it comprehensively quantifies the influence of high-purity quartz sand on crucible bubbles, overcoming the limitations and subjectivity of single index judgment.

[0019] (2) This invention establishes a classification and application criterion based on quantitative grading. By setting strict threshold ranges for bubble content evaluation indicators and impurity element indicators, this invention clearly defines the raw material grades applicable to the preparation of the inner, middle, and outer layers of low-bubble photovoltaic quartz crucibles. This determination method accurately matches the sand sample quality with the crucible layer function, is highly operable and repeatable, and provides a reliable technical basis for the accurate grading, targeted application, and quality control of high-purity quartz sand. Attached Figure Description

[0020] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 A schematic flowchart of the method for determining the high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles according to the present invention is shown. Detailed Implementation

[0021] In the following sections, an exemplary embodiment of the present invention will be used to describe in detail a method for determining high-purity quartz sand for preparing low-bubble photovoltaic quartz crucibles and its application.

[0022] Exemplary Example 1 This exemplary embodiment provides a method for determining the purity of quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles. The determination process is as follows: Figure 1 As shown. The determination method includes detecting and analyzing the property indicators of high-purity quartz sand, namely chemical composition, tap density, gas-liquid inclusion content, and loss on ignition, and calculating the bubble content index according to the calculation formula. Then, the high-purity quartz sand is comprehensively judged based on the impurity element content level and the bubble content index level. If both indicators are grade A (impurity element content level is grade A and bubble content index level is grade A), it can be used as the inner layer sand for preparing low-bubble photovoltaic quartz crucibles; if one indicator is not grade A, and neither indicator contains grade C (e.g., impurity element content level is grade A and bubble content index level is grade B, impurity element content level is grade B...). If one of the indicators is grade B and the bubble content is grade C, it can be used as the middle layer sand for preparing low-bubble photovoltaic quartz crucibles; if one indicator is grade C (e.g., impurity element content grade B and bubble content grade C, impurity element content grade C and bubble content grade C, etc.), it can be used as the outer layer sand for preparing low-bubble photovoltaic quartz crucibles; if the impurity element content grade and the bubble content grade do not meet the grade C criteria, it cannot be used as raw material for preparing high-purity quartz sand for low-bubble photovoltaic quartz crucibles, or it needs to be further purified or its particle size distribution optimized, and the optimized high-purity quartz sand should be re-evaluated.

[0023] Specifically, the determination method may include the following steps: S1. Test the property indicators of high-purity quartz sand.

[0024] In this embodiment, the property indicators of the high-purity quartz sand include: chemical composition, tap density, gas-liquid inclusion content, and loss on ignition.

[0025] In this embodiment, the chemical composition refers to the content of impurity elements in the high-purity quartz sand; the gas-liquid inclusion content refers to the area ratio of dark regions caused by gas-liquid inclusions in the high-purity quartz sand under a microscope and / or the liquid phase content and gas phase content of the gas-liquid inclusions; the loss on ignition is the loss on ignition of the high-purity quartz sand sample after calcination at 1050℃±50℃ for more than 1 hour.

[0026] S2. Calculate the bubble content index w by using the formula to obtain the property index of high-purity quartz sand obtained from the test.

[0027] In this embodiment, the calculation formula includes formula (1) and formula (2): w=20(1.48-x)+5y+10z (1) w=20(1.48-x)+2(a+b)+10z (2) In equations (1) and (2), x represents the tap density, with units of g / cm³. 3 When x > 1.48, x = 1.48 is taken; when the content of gas-liquid inclusions is taken as the proportion of the dark area caused by gas-liquid inclusions under a microscope, it is calculated using formula (1), where y represents the percentage of the dark area caused by inclusions in the high-purity quartz sand sample; when the content of gas-liquid inclusions is taken as the liquid phase content and gas phase content of gas-liquid inclusions, it is calculated using formula (2), where a is the gas phase content of gas-liquid inclusions, in cm 3 / 100g, b is the liquid phase content of the gas-liquid inclusions, in g / 100g; z is the loss on ignition of high-purity quartz sand.

[0028] The primary source of bubbles in quartz crucibles is the porosity between quartz particles. Bulk density directly relates to bubble formation and suppression during crucible preparation, and is a key factor determining the final crucible quality. Low bulk density of the quartz sand indicates a large number of voids between powder particles. During high-temperature sintering, these voids are filled with air, forming initial bubble sources. More seriously, low bulk density is often accompanied by poor flowability and uneven filling, leading to localized loose areas within the crucible mold. During melting, these areas evolve into macroscopic bubble clusters or structural defects. These bubbles expand, migrate, or merge under the extreme temperatures of subsequent crystal pulling, severely disrupting the uniformity of the crucible's inner wall. This can not only ignite single crystal growth failure but also increase the risk of crucible breakage. Therefore, optimizing the particle size distribution and morphology of the quartz sand to increase its bulk density is a core technological approach to achieve tight packing, reduce bubble generation at the source, and prepare high-performance, long-life quartz crucibles. Experiments show a significant non-linear negative correlation between quartz sand bulk density and crucible bubble content. In the region of low tap density (below 1.48 g / cm³), the bubble content decreases rapidly with increasing tap density, indicating that at this stage, tap density is the main controlling factor affecting bubble formation. As tap density further increases, its influence on bubble content gradually weakens. When the tap density exceeds 1.48 g / cm³, the bubble content essentially stabilizes and no longer changes significantly with tap density. Since higher tap density has a significant impact on bubbles, a coefficient of 20 was selected after verification and calculation. Furthermore, when the tap density exceeds 1.48 g / cm³, the influence of bulk density on crucible bubble content weakens; therefore, 1.48 was chosen as the minuend and threshold.

[0029] Currently, the main raw material for quartz crucibles is natural quartz sand. Inclusions are common in natural minerals, and in quartz, they originate from its natural formation process: when crystals grow from hydrothermal fluids in a geological environment, rapid growth, crystal surface defects, or microcracks caused by later tectonic stress can trap and seal the ore-forming fluids inside the crystal. Over long geological periods, these inclusions form primary and secondary gas-liquid inclusions. These inclusions are widespread in quartz and become a fatal defect in the formation of bubbles during the quartz crucible melting process. Because high-purity quartz has extremely low impurity element content, after meeting predetermined limits for impurity elements, the inclusions inside are mainly gas-liquid inclusions. During crucible manufacturing, gas-liquid inclusions have a significant impact on bubble formation within the crucible. Firstly, when the quartz sand is heated, the internal pressure of the inclusions increases dramatically with temperature. This extreme pressure causes cracks in the quartz, and the released gas and the formation of microcracks are important sources of bubbles. Secondly, at high temperatures, liquid water rapidly vaporizes, interacting with the gas within the inclusions and further contributing to their bursting. Finally, impurity ions (such as Na+) contained in the liquid phase of the inclusions... , K Cl-) will react with quartz (SiO) A reaction occurs, producing new gas, for example, 2NaCl + SiO₂. +H O(g) Na SiO +2HCl(g), where g represents gas, further increases the number and size of bubbles. Due to the unavoidable and harmful nature of gas-liquid inclusions in quartz sand, their content is limited to avoid a significant increase in bubble content caused by gas-liquid inclusions. After verification and calculation, a coefficient of 5 was chosen as the variable for the proportion of dark areas caused by inclusions, and a coefficient of 2 was chosen when calculating the gas or liquid phase content in the gas-liquid inclusions.

[0030] Loss on ignition (LOI) refers to the percentage of mass lost by a high-purity quartz sand sample after ignition under specific high-temperature conditions (1050±50℃). This indicator is essentially a comprehensive quantitative representation of the total amount of all volatile substances in the sample. These volatile components mainly originate from the following sources: a) structural hydroxyl groups (-OH) adsorbed on the surface of quartz particles; b) inclusions released from shallow gas-liquid inclusions at high temperatures (such as water, CO2, etc.); c) residual flotation agents (such as amines, sulfonates, etc.) or acid leaching agents (such as organic acids, inorganic acids, etc.) that may remain during the raw material purification process. In the ultra-high temperature environment (>2000℃) of quartz crucible arc melting, the rapid release of these volatile components directly leads to bubble formation. The specific mechanism includes: dehydration condensation reaction of adjacent silanol groups on the quartz surface (Si-OH+HO-Si→Si-O-Si+H). O↑) generates water vapor; shallow inclusions burst due to thermal rupture, causing their contents to volatilize; organic residues undergo thermal decomposition and carbonization, producing CO2, H2O, and other gaseous products; inorganic residues volatilize. Due to the extremely rapid heating rate during arc melting, these gases do not have time to diffuse slowly and instantly form high-pressure bubbles inside the high-viscosity molten quartz. If the total amount of gas generated is too large, macroscopic bubble defects will form, severely damaging the crucible's density and optical homogeneity. Therefore, strictly controlling the loss on ignition to an extremely low level of no more than 0.02% is a key means of limiting the source of bubbles from the raw materials. This threshold was established based on extensive process experiment analysis, showing that within this range, the uncontrolled generation of bubbles caused by the concentrated release of volatile substances can be effectively avoided, thus ensuring the stability of the melting process and ultimately providing a core raw material guarantee for the preparation of low-bubble, long-life, high-performance quartz crucibles. Verification calculations selected a loss on ignition calculation coefficient of 10.

[0031] S3. The impurity element content and bubble content index w in high-purity quartz sand are classified, and the high-purity quartz sand is comprehensively judged based on the impurity element content level and bubble content index level.

[0032] In this embodiment, the impurity element content levels include grade a, grade b, and grade c, wherein: Grade A requires the following conditions to be met simultaneously: Al content is 5.0~12.0ppm, total Li, Na and K content is less than 1.5ppm, Ti content is less than 2.0ppm, Fe and Ba content are both less than 0.5ppm, Ca content is less than 0.8ppm, Mg content is less than 0.3ppm, Mn, Cu and Cr content are all less than 0.1ppm, B content is less than 0.1ppm, P content is less than 0.4ppm, Ge content is less than 0.5ppm, Ni content is less than 0.05ppm, and Zr content is less than 0.9ppm; Grade B requires the following conditions to be met simultaneously: Al content is 12.0~15.0 ppm or less than 5 ppm, total Li, Na, and K content is less than 2.0 ppm, Ti content is less than 2.5 ppm, Fe and Ba content are both less than 0.5 ppm, Ca content is less than 1.0 ppm, Mg content is less than 0.3 ppm, Mn, Cu, and Cr content are all less than 0.1 ppm, B content is less than 0.1 ppm, P content is less than 0.4 ppm, Ge content is less than 0.9 ppm, and Ni content is less than 0.05 ppm; Grade C requires the following conditions to be met simultaneously: Al content is 15.0~18.0 ppm or less than 5 ppm, total Li, Na and K content is less than 3.0 ppm, Ti content is less than 4.0 ppm, Fe and Ba content are both less than 0.5 ppm, Ca content is less than 1.2 ppm, Mg content is less than 0.3 ppm, Mn, Cu and Cr content are all less than 0.1 ppm, B content is less than 0.1 ppm, P content is less than 0.4 ppm, Ge content is less than 0.9 ppm, and Ni content is less than 0.05 ppm.

[0033] Among them, different categories of impurity elements have significant differences in their occurrence state and elemental properties, resulting in varying mechanisms and degrees of influence on bubble formation. These elements are categorized into alkali metals, amphoteric elements, transition metals, alkaline earth metals, and non-metallic elements, with their influence mechanisms explained separately. Alkali metal elements (such as Na, K, and Li) often exist as adsorbed salts on the particle surface or enter lattice defects through ion substitution. When their content is high, they can directly vaporize or decompose at high temperatures, releasing gases and becoming a source of bubbles, with a very serious impact. Amphoteric elements (such as Al) mainly enter the quartz lattice in isomorphous form, replacing silicon atoms in silicon-oxygen tetrahedra, or exist as fine mineral inclusions. When Al enters the lattice in isomorphous form, alkali metal ions need to be introduced to maintain charge balance; therefore, high Al content is often accompanied by high alkali metal content, indirectly exacerbating the vaporization process of alkali metals at high temperatures. When Al exists as fine mineral inclusions (such as feldspar and mica), microcracks will form at the interface during heating due to the difference in thermal expansion coefficients between the mineral and the quartz matrix. When the temperature reaches the melting point of these minerals (e.g., potassium feldspar approximately 1150℃, sodium feldspar approximately 1100℃, and mica approximately 1300℃), the minerals melt and undergo violent vaporization, while thermal decomposition reactions occur simultaneously (e.g., carbonates decompose to release CO2, and layered silicates and clay minerals dehydroxylate to release H2O). At this time, the external quartz melt is in a high-viscosity state, trapping the gas within and preventing its escape, ultimately forming bubble defects with a severe impact. Transition metal elements (such as Fe, Cr, Cu, and Ni) mostly exist as fine mineral inclusions or surface oxides. When they exist as mineral inclusions, their impact mechanism is the same as described above, involving both vaporization and decomposition; simultaneously, the valence state changes of these elements at high temperatures trigger gas release, further contributing to bubble formation and a severe impact. Alkaline earth metal elements (such as Ca and Mg) can exist both within mineral inclusions and can be adsorbed onto the quartz surface through ion exchange. When present as mineral inclusions, their influence mechanism involves the combined effects of vaporization and thermal decomposition; when present as surface adsorption, they mainly participate indirectly in bubble formation and stabilization by affecting the viscosity and crystallization behavior of molten quartz, with a moderate degree of influence. Non-metallic elements (such as B and P) are typically present in low concentrations in quartz, and their impact on bubble formation is relatively limited when they do not exist as independent minerals. In determining the quality of high-purity quartz sand for low-bubble quartz crucibles, strict control of alkali metal (Na, K, Li) and aluminum (Al) content is crucial for suppressing bubble formation. Furthermore, the restriction of each impurity element is not only based on its impact on bubble formation but also requires comprehensive consideration of preventing crucible crystallization, softening and collapse, and contamination of the silicon solution. Therefore, a holistic qualification threshold system with coordinated multi-element indicators is needed for comprehensive judgment.

[0034] In this embodiment, the bubble content index grades include grade A, grade B, and grade C. When w < 0.19, it is judged as grade A; when 0.19 ≤ w < 0.8, it is judged as grade B; and when 0.8 ≤ w < 1.1, it is judged as grade C.

[0035] In this embodiment, during the comprehensive determination, the applicable strata for high-purity quartz sand are further divided according to the following rules: If both the impurity element index and the bubble index meet the grade A standard, then the quartz sand is determined to be suitable for preparing the inner layer of the low-bubble photovoltaic quartz crucible. If one of the impurity element content level and the bubble content index level meets level a and the other meets level b, or both meet level b, then the quartz sand is determined to be suitable for preparing the middle layer of the low-bubble photovoltaic quartz crucible. If one of the impurity element content level and the bubble content index level meets grade a, grade b or grade c, while the other only meets grade c, then the quartz sand is determined to be suitable for preparing the outer layer of the low bubble photovoltaic quartz crucible. If either the impurity element content level or the bubble content index level fails to meet the above-mentioned grade C standard, then the quartz sand is deemed unsuitable for preparing the low-bubble photovoltaic quartz crucible.

[0036] In this embodiment, comprehensive judgment is the core of the quality decision-making process for the entire method. This step makes the final determination based on two key dimensions: impurity element index and bubble content index. Regarding the impurity element index, the aim is to ensure that the chemical purity of the quartz sand meets stringent grade requirements, fundamentally guaranteeing the stability and low crystallization tendency of the quartz glass at high temperatures. Regarding the bubble content index, this is an integrated quantitative parameter whose value is influenced by the synergistic effect of three key physical properties: tap density, inclusion content, and loss on ignition. It scientifically reflects the potential risk of bubble generation during the melting process of the quartz sand. Finally, based on the grade combination of the two indicators, the applicable layer of the quartz sand is precisely determined: the highest quality (e.g., double-A grade) is used in the inner layer directly in contact with the molten silicon to provide high purity and minimal bubble protection; medium quality is used in the middle layer; and quality meeting basic requirements is used in the outer layer supporting the structure. This graded application strategy ensures the overall performance of the quartz crucible while optimizing the allocation of raw material resources and maximizing cost-effectiveness. Meanwhile, this invention aims to eliminate any single performance deficiency, provide objective and clear pass / rejection criteria for raw material acceptance, and ultimately systematically ensure the low bubble rate, excellent high-temperature performance and long life of quartz crucibles from the source.

[0037] In this embodiment, if the bubble content index is classified as Grade A, then the bubble content of the quartz crucible is less than 6 cm. 3 / kg; if the bubble content index is classified as grade b, then the bubble content of the quartz crucible is ≥6cm. 3 / kg and <9cm 3 / kg; if the bubble content index is classified as grade C, then the bubble content of the quartz crucible is ≥9cm. 3 / kg and ≤15cm 3 / kg.

[0038] Exemplary Example 2 This exemplary embodiment provides an application of a method for determining high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles, wherein the determination method is the determination method described in Exemplary Embodiment 1; In this embodiment, the determination method can be applied to the manufacturing process of low-bubble photovoltaic quartz crucibles to perform quality grading and suitability screening of high-purity quartz sand raw materials from different batches or sources, and to determine whether they are suitable for preparing the inner, middle or outer layer of the low-bubble photovoltaic quartz crucible, or not suitable as high-purity quartz sand for the low-bubble photovoltaic quartz crucible.

[0039] In this embodiment, when the determination result is that it is not suitable as high-purity quartz sand for the low-bubble photovoltaic quartz crucible, it can be purified again or the particle size distribution can be changed for optimization, and the optimized high-purity quartz sand can be determined again.

[0040] To better understand the exemplary embodiments of the present invention described above, further explanation is provided below with reference to specific examples.

[0041] Example 1 This example uses the determination method for high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles described in this invention to determine the high-purity quartz sand. The determination method includes: Step 1: Indicator Detection a) Chemical composition analysis: 1.0000g of high-purity quartz sand was weighed, completely digested with hydrofluoric acid, and then dilute nitric acid was added to completely dissolve the digestion residue. The solution was brought to a final volume of 25mL. Three parallel samples and three blank samples were prepared for simultaneous digestion and analysis. The final test result was the average value of the parallel samples minus the average value of the blank samples. The final calculated content of impurity elements in the high-purity quartz sand is shown in Table 1.

[0042] Table 1. Impurity element content of high-purity quartz sand 1 (μg / g)

[0043] Note: - indicates below the detection limit.

[0044] b) Tapped density: The high-purity quartz sand was tested using a tapped density meter. The high-purity quartz sand sample was placed in the graduated cylinder of the instrument and mechanically vibrated under the set parameters until the volume remained constant. The mass of the sample was weighed and divided by the volume after vibration. The average value was taken after three measurements, yielding a tapped density of 1.471 cm³. 3 / g.

[0045] c) Bubble content analysis: High-purity quartz sand 1 was placed on a glass slide and evenly distributed in a single layer. Liquid paraffin was added as an impregnation oil. Twenty microscopic images of quartz sand particles were acquired using a polarizing microscope at 100x magnification. The total area of ​​the quartz sand particle region and the area of ​​the dark region caused by inclusions in the images were statistically analyzed, and the average value of all images was calculated. The proportion of the dark region caused by inclusions was found to be 0.97%.

[0046] d) Loss on ignition determination: Weigh 100.000g or more of high-purity quartz sand sample 1, calcine it in a high-temperature furnace at 1100℃ for 1h, and accurately weigh the mass after cooling. Calculate the loss on ignition of the sample by the mass difference before and after calcination. Set up three parallel samples and calculate the average loss on ignition as 0.012%.

[0047] Step 2: Calculation of bubble content index w w=20(1.48-1.471)+5×0.97%+10×0.012%=0.189.

[0048] Step 3: Indicator Classification and Comprehensive Judgment The impurity element content of high-purity quartz sand sample 1 all meet the Class A limit thresholds for impurity elements; the comprehensive judgment index for bubble content, w=0.189, satisfies the Class A limit for bubble content. Therefore, this quartz sand can be used as the inner layer sand for low-bubble quartz crucibles.

[0049] Example 2 This example uses the determination method for high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles described in this invention to determine the high-purity quartz sand. The determination method includes: Step 1: Indicator Detection a) Chemical composition analysis: 1.0000g of the high-purity quartz sand 2 was weighed, completely digested with hydrofluoric acid, and then dilute nitric acid was added to completely dissolve the digestion residue. The solution was brought to a final volume of 25mL. Three parallel samples and three blank samples were set up for simultaneous experiments and analysis. The final test result was the average value of the parallel samples minus the average value of the blank samples. The final calculated content of impurity elements in the high-purity quartz sand 2 is shown in Table 2.

[0050] Table 2. Impurity element content of high-purity quartz sand 2 (μg / g)

[0051] Note: - indicates below the detection limit.

[0052] b) Tapped density: The high-purity quartz sand was tested using a tapped density meter. The high-purity quartz sand sample was placed in the graduated cylinder of the instrument and mechanically vibrated under the set parameters until the volume remained constant. The mass of the sample was weighed and divided by the volume after vibration. The average value was taken after three measurements, yielding a tapped density of 1.429 cm³. 3 / g.

[0053] c) Inclusion content analysis: High-purity quartz sand was placed on a glass slide and evenly distributed in a single layer. Liquid paraffin was added as an impregnation oil. Ten microscopic images of quartz sand particles were acquired using a polarizing microscope at 100x magnification. The total area of ​​the quartz sand particle region and the area of ​​the dark region caused by inclusions in the images were statistically analyzed, and the average value of all images was calculated. The dark region area of ​​inclusions accounted for 0.01%.

[0054] d) Loss on ignition determination: Weigh 100.000g of high-purity quartz sand sample and calcine it in a high-temperature furnace at 1100℃ for 1h. After cooling, accurately weigh the mass after calcination. Calculate the loss on ignition of the sample by the mass difference before and after calcination. Set up three parallel samples and calculate the average loss on ignition as 0.018%.

[0055] Step 2: Calculation of bubble content index w w=20(1.48-1.429)+5×0.01%+10×0.018%=1.022.

[0056] Step 3: Indicator Classification and Comprehensive Judgment The impurity element content of sample 2, which is of high purity quartz sand, meets the threshold limit for impurity element type b, while the bubble content index w=1.022 meets the threshold limit for high purity quartz sand type c. Therefore, it can be used as the outer layer sand for low bubble quartz crucibles.

[0057] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles, characterized in that, The determination method includes: 1) Test the property indicators of high-purity quartz sand; 2) Calculate the bubble content index w by using the formula to obtain the property index of high-purity quartz sand obtained from the test; 3) The impurity element content and bubble content index w in high-purity quartz sand are classified, and the high-purity quartz sand is comprehensively judged based on the impurity element content level and bubble content index level.

2. The method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles according to claim 1, characterized in that, The property indicators of the high-purity quartz sand mentioned in step 1) include: chemical composition, tap density, gas-liquid inclusion content, and loss on ignition; Wherein, the chemical composition refers to the content of impurity elements in the high-purity quartz sand; the gas-liquid inclusion content refers to the area ratio of dark regions caused by gas-liquid inclusions in the high-purity quartz sand under a microscope and / or the liquid phase content and gas phase content of the gas-liquid inclusions; and the loss on ignition is the loss on ignition of the high-purity quartz sand after calcination at 1050℃±50℃ for more than 1 hour.

3. The method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles according to claim 1, characterized in that, The calculation formulas mentioned in step 2) include formulas (1) and (2): w=20(1.48-x)+5y+10z (1) w=20(1.48-x)+2(a+b)+10z (2) In equations (1) and (2), x represents the tap density, with units of g / cm³. 3 When x > 1.48, x = 1.48 is taken; when the content of gas-liquid inclusions is taken as the proportion of the dark area caused by gas-liquid inclusions under a microscope, it is calculated using formula (1), where y represents the percentage of the dark area caused by inclusions in the high-purity quartz sand sample; when the content of gas-liquid inclusions is taken as the liquid phase content and gas phase content of gas-liquid inclusions, it is calculated using formula (2), where a is the gas phase content of gas-liquid inclusions, in cm 3 / 100g, b is the liquid phase content of the gas-liquid inclusions, in g / 100g; z is the loss on ignition of high-purity quartz sand.

4. The method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles according to claim 1, characterized in that, The impurity element content levels mentioned in step 3) include grade A, grade B, and grade C, wherein, Grade A requires the following conditions to be met simultaneously: Al content is 5.0~12.0ppm, total Li, Na and K content is less than 1.5ppm, Ti content is less than 2.0ppm, Fe and Ba content are both less than 0.5ppm, Ca content is less than 0.8ppm, Mg content is less than 0.3ppm, Mn, Cu and Cr content are all less than 0.1ppm, B content is less than 0.1ppm, P content is less than 0.4ppm, Ge content is less than 0.5ppm, Ni content is less than 0.05ppm, and Zr content is less than 0.9ppm; Grade B requires the following conditions to be met simultaneously: Al content is 12.0~15.0 ppm or less than 5 ppm, total Li, Na, and K content is less than 2.0 ppm, Ti content is less than 2.5 ppm, Fe and Ba content are both less than 0.5 ppm, Ca content is less than 1.0 ppm, Mg content is less than 0.3 ppm, Mn, Cu, and Cr content are all less than 0.1 ppm, B content is less than 0.1 ppm, P content is less than 0.4 ppm, Ge content is less than 0.9 ppm, and Ni content is less than 0.05 ppm; Grade C requires the following conditions to be met simultaneously: Al content is 15.0~18.0 ppm or less than 5 ppm, total Li, Na and K content is less than 3.0 ppm, Ti content is less than 4.0 ppm, Fe and Ba content are both less than 0.5 ppm, Ca content is less than 1.2 ppm, Mg content is less than 0.3 ppm, Mn, Cu and Cr content are all less than 0.1 ppm, B content is less than 0.1 ppm, P content is less than 0.4 ppm, Ge content is less than 0.9 ppm, and Ni content is less than 0.05 ppm.

5. The method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles according to claim 1, characterized in that, The bubble content index grades mentioned in step 3) include grade A, grade B, and grade C, wherein, When w < 0.19, it is classified as Grade A; When 0.19 ≤ w < 0.8, it is classified as grade b; When 0.8 ≤ w < 1.1, it is judged as grade C.

6. The method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles according to claim 1, characterized in that, In the comprehensive determination described in step 3), the applicable strata for high-purity quartz sand are further divided according to the following rules: If both the impurity element index and the bubble index meet the grade A standard, then the quartz sand is determined to be suitable for preparing the inner layer of the low-bubble photovoltaic quartz crucible. If one of the impurity element content level and the bubble content index level meets level a and the other meets level b, or both meet level b, then the quartz sand is determined to be suitable for preparing the middle layer of the low-bubble photovoltaic quartz crucible. If one of the impurity element content level and the bubble content index level meets grade a, grade b or grade c, while the other only meets grade c, then the quartz sand is determined to be suitable for preparing the outer layer of the low bubble photovoltaic quartz crucible. If either the impurity element content level or the bubble content index level fails to meet the above-mentioned grade C standard, then the quartz sand is deemed unsuitable for preparing the low-bubble photovoltaic quartz crucible.

7. The method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles according to claim 1, characterized in that, If the bubble content index is classified as Grade A, then the bubble content of the quartz crucible is less than 6 cm. 3 / kg; if the bubble content index is classified as grade b, then the bubble content of the quartz crucible is ≥6cm. 3 / kg and <9cm 3 / kg; if the bubble content index is classified as grade C, then the bubble content of the quartz crucible is ≥9cm. 3 / kg and ≤15cm 3 / kg.

8. An application of a method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles, characterized in that, The determination method is the determination method for high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles as described in any one of claims 1-7; The determination method can be applied to the manufacturing process of low-bubble photovoltaic quartz crucibles to classify and screen the suitability of high-purity quartz sand raw materials from different batches or sources, and determine whether they are suitable for preparing the inner, middle or outer layer of the low-bubble photovoltaic quartz crucible, or unsuitable as high-purity quartz sand for the low-bubble photovoltaic quartz crucible.

9. The application of the method for determining the purity of high-purity quartz sand used in the preparation of low-bubble photovoltaic quartz crucibles according to claim 8, characterized in that, When the determination result is that it is not suitable as high-purity quartz sand for the low-bubble photovoltaic quartz crucible, it can be purified again or the particle size distribution can be changed for optimization, and the optimized high-purity quartz sand can be determined again.

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