On November 20-21, 2025, the "2025 Ninth National Quartz Conference & Exhibition," hosted by China Powder Network, was grandly held in Xuzhou, Jiangsu! On site at the conference, a reporter from China Powder Network had the privilege of inviting Zhou Yang, Head of Quartz Materials at Longi Green Energy Technology Co., Ltd., to be a guest on the "Dialogue" segment.
China Powder Network: Hello, Mr. Zhou, thank you very much for accepting our interview. As the head of quartz materials at the world's leading photovoltaic wafer manufacturer, what do you believe are the most critical technical indicators for photovoltaic-grade quartz crucibles? Mr. Zhou: Based on current practical applications, the core technical indicators for photovoltaic-grade quartz crucibles primarily revolve around three aspects: appearance requirements, intrinsic quality, and purity standards. Appearance requirements: Firstly, they must conform to the dimensional standards of the thermal field design to ensure a good fit with the thermal field; secondly, the crucible itself must be free from visible defects that affect usability, such as bubbles, impurities, or black spots visible to the naked eye. Intrinsic quality: The core is ensuring the stability of the crystal pulling process. On one hand, the crucible must possess sufficient strength to avoid abnormalities during pulling; on the other hand, the bubble expansion rate needs to be controlled to prevent wire breakage caused by bubble rupture; simultaneously, the external bubble layer must have good erosion resistance to reduce crystallization issues on the outer wall, lower the risk of pulling abnormalities, and improve pulling outcomes. Purity standards: The key lies in low impurity and low hydroxyl content. Low impurities and low hydroxyl levels prevent adverse effects on silicon ingot quality and can further help enhance it.
China Powder Network: So, what standards must a quartz crucible meet to be considered qualified? How are these indicators directly related to which core stages of monocrystalline silicon production? Mr. Zhou: The primary qualification standard for quartz crucibles is meeting customer requirements. As a customized product, they must align with the drawing specifications for monocrystalline production, while also guaranteeing pulling duration, reducing breakage rates, and ensuring high stability. These indicators are closely linked to the core stages of monocrystalline silicon production, mainly manifesting in two phases: Charging/Melting stage: This stage places high demands on the crucible's high-temperature viscosity and strength; insufficient crucible strength can lead to issues like edge collapse. Furthermore, the uniformity of the crucible's structure affects the melting efficiency of the silicon feedstock. Uniform distribution of the bubble layer leads to more even heat conduction, facilitating melting and thereby reducing energy consumption during the charging process. Seed crystal dipping/necking stage: This stage requires stable temperatures to ensure the smooth growth of the crystal ingot. Particularly given the current stringent requirement for "zero breakage" in monocrystalline silicon production, controlling bubble rupture in the crucible becomes critical. Additionally, the low-impurity characteristics of the crucible can reduce the introduction of impurities during silicon melt erosion, mitigating issues like high oxygen content in the silicon ingot and short lifespan. It is noteworthy that although quartz crucibles are single-use containers for monocrystalline pulling, their impact on production far exceeds the basic attributes of a mere "container."
China Powder Network: As N-type technology imposes stricter requirements on wafer quality and continuous feeding technology demands crucible lifespans of several hundred hours, what do you believe is the ultimate bottleneck currently constraining the performance of high-end quartz crucibles? Mr. Zhou: The industry has made some progress in developing high-lifespan crucibles, which can basically meet the requirements for pulling duration. Simultaneously, with upgrades in purification technology, the purity of quartz sand is continuously improving. However, considering the ultimate demands of future industry pulling processes, the core bottlenecks restricting high-end quartz crucible performance can be summarized as two points: Low-impurity control of the raw material, which is the prerequisite for ensuring the basic quality of the crucible; and control of the oxygen content in the silicon ingot during the pulling process, which is the more critical ultimate bottleneck. This is because the oxygen element in the silicon ingot during pulling mainly originates from the quartz crucible, including both the hydroxyl groups within the crucible itself and oxygen generated from impurity reactions. Therefore, how to reduce the oxygen supply from the crucible to the silicon ingot and lower the ingot's oxygen content is the core direction for high-end quartz crucible research and development.
China Powder Network: As a wafer leader, what unique systems or standards does Longi have in place for quartz material procurement verification and supply chain cooperation to address these challenges and ensure supply security? Mr. Zhou: Longi has established a four-step verification system for supplier onboarding, ensuring material quality and supply stability through full-process control. The specific流程 is as follows: Quartz sand preliminary research and crucible trial production: First, preliminary research is conducted on the quartz sand provided by the supplier, followed by trial crucible production. Key tests include impurity element content, particle size, etc., while parameters like crucible appearance, microscopic inclusions, and deformation are used to judge if the quartz sand meets usage requirements and its applicable tier. Small-batch trial production and pulling verification: If initial testing is qualified, small-batch trial production of crucibles for specific usage tiers is conducted, and they are simultaneously sent to pulling bases for practical application verification. Pilot-scale volume verification: After successful small-batch trials, the process moves to the pilot stage, expanding crucible production volume and verification scale based on the small batch, focusing on assessing stability under mass production conditions. Incremental stability verification: After pilot-stage qualification, post-introduction incremental verification is conducted. The core is evaluating the batch-to-batch stability of the quartz sand to ensure it can meet Longi's supply demands over the long term.
China Powder Network: Continuous Czochralski (CCz) single crystal technology imposes extremely strong lifespan requirements on quartz crucibles. Does this mean we need to redefine quartz materials? Is Longi exploring or evaluating entirely new solutions like synthetic quartz crucibles or composite structure crucibles? Mr. Zhou: Continuous Czochralski technology has indeed driven an upgrade in the positioning and technological innovation of quartz crucibles. This change is mainly reflected in three dimensions: Positioning upgrade: Quartz crucibles have evolved from initially being "simple containers ensuring successful melting and seeding" to becoming "core reactors meeting the demands of long-duration crystal pulling." They now need to withstand higher temperatures and longer durations of silicon melt erosion, while possessing stronger mechanical strength and resistance to thermal stress impact to cope with abnormalities like edge collapse, bulging, and sinking. Material innovation: There is a shift from reliance on natural sand towards "functionally graded design," which involves rationally blending natural sands according to different tier requirements, and even introducing synthetic sand to enhance performance. Technology upgrade: The technology has progressed from early "simple fusion molding merely satisfying forming and short-duration pulling" to "integrated调控 of microstructure and performance" to adapt to the needs of long-duration pulling.
China Powder Network: We have observed that used quartz crucibles themselves have become a valuable "urban mineral." As an advocate of green energy, what specific practices and plans does Longi have regarding the recycling, treatment, and resource utilization of waste quartz crucibles? Mr. Zhou: Longi has already initiated phased practices in the resource utilization of waste quartz crucibles and has formulated long-term plans,具体 divided into three stages: Initial stage: For waste sand generated during the crucible production process, the common industry practice is to purify it a second time for use as insulating sand; meanwhile, crucible fragments, cutting waste, etc., are mostly used as raw materials in downstream industries like construction materials and ceramics. Current practice: As quartz sand resources become increasingly scarce, we have started the deep recycling of waste crucibles. Through processes like crushing, grinding, and acid washing purification, the treated material is used in the production of the outer layers of quartz crucibles. Future plan: The plan is to further enhance purification technology so that recycled materials can substitute for mid-layer and inner-layer raw materials, ultimately achieving full circular utilization of quartz sand resources.
China Powder Network: So, you mentioned earlier that there are plans to use synthetic quartz sand in crucibles. In which layer of the quartz crucible is synthetic quartz sand intended to be used? Mr. Zhou: Due to its higher purity, which better suits the preparation needs of silicon ingots requiring "high quality and low impurities," the industry currently predominantly uses synthetic quartz sand for the inner layer of quartz crucibles. However, the results of current verification in this area are not particularly ideal within the industry. Note: Images are for non-commercial use; please inform us if there are any copyright issues for deletion! To join the powder industry exchange group, please add the WeChat of China Powder Network's editorial department: 18553902686.
Massive information, precise interpretation, all on the Sina Finance App.
Comments