1. Core raw material minerals of silicon materials
The preparation of silicon materials (polysilicon or monocrystalline silicon) depends on high-purity silicon elements, and its raw materials mainly come from the following three natural minerals:
1. Quartzite
- The silicon dioxide (SiO2) content exceeds 90%, and the texture is hard, which needs to be crushed and purified.
- Typical deposits are distributed in Xinjiang, China, Arkansas, the United States, etc., with global reserves of about 30 billion tons (according to USGS 2022 data).
2. Quartz sand
- Natural sedimentary sand, with a SiO2 content of 95%-99%, few impurities, can be directly used for metallurgical grade silicon (industrial silicon) production.
- Australia and Indonesia are the main production areas of high-quality quartz sand, accounting for more than 40% of the global supply.
3. Vein quartz
- A high-purity mineral formed by hydrothermal deposits, with a SiO₂ content of more than 99.5%, it is an ideal raw material for electronic-grade silicon materials.
- The vein quartz mine in Donghai, Jiangsu, China is famous for its ultra-high purity, supporting 70% of the domestic demand for high-end silicon materials.
2. Other potential silicon sources and their application limitations
In addition to the above mainstream minerals, some silicon-containing minerals have not yet been used on a large scale due to technical or economic factors:
- Feldspar: The SiO₂ content is about 60%-70%, requiring a complex purification process, and is currently only used in the low-end ceramic industry.
- Clay minerals: mainly aluminosilicates, with high energy consumption for silicon extraction, but Japanese scholars are studying its nano-silicon extraction technology (2021 "Nature Materials" paper).
- Biosilicon: Rice husk ash contains 90% SiO₂, and Brazil has built a pilot production line, but the production capacity is limited.
3. Impact of ore selection on silicon material quality and cost
1. Purity difference: The electronic-grade silicon material produced by vein quartz has a purity of 99.9999% (6N), while quartz sand is usually used for metallurgical-grade silicon with a purity of 99%-99.9% (2N-3N).
2. Energy consumption comparison: Quartzite purification requires a high temperature of more than 1700℃, which is 20% higher than the energy consumption of quartz sand process (International Energy Agency 2023 report).
3. Geographical factors: The comprehensive cost of transporting African quartz sand to China for processing is 15%-30% higher than that of local vein quartz, but environmental protection approval is simpler.