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Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO₂ and a molecular weight of 60.08 g/mol. It is one of the most abundant chemical compounds in the Earth's crust, occurring naturally in a wide variety of crystalline and amorphous mineral forms.

SiO₂ has a giant covalent network structure in which each silicon atom is tetrahedrally bonded to four oxygen atoms, and each oxygen atom bridges two silicon atoms, forming a highly cross-linked three-dimensional lattice. This architecture imparts exceptional hardness, a very high melting point, low thermal expansion, strong electrical insulating properties, and broad chemical inertness.

Silicon dioxide occurs in two principal structural categories: crystalline and amorphous. The most common crystalline forms are α-quartz (stable at room temperature), tridymite, and cristobalite (both stable at high temperatures), as well as high-pressure polymorphs such as coesite and stishovite. Amorphous silica occurs naturally as opal and diatomaceous earth, and is synthetically manufactured as fumed silica, precipitated silica, silica gel, colloidal silica, and fused silica.

Silicon dioxide is among the most widely used industrial raw materials. Its major applications span:

• Construction: As the primary constituent of sand and gravel, it is used in cement, concrete, mortar, and glass, representing approximately 95% of the commercial use of silica sand
• Glass manufacturing: Mixed with lime and soda ash to produce flat glass, container glass, and specialty glasses (e.g., borosilicate glass for Pyrex, high-purity fused silica for optical and aerospace applications)
• Ceramics and refractories: Used in tiles, porcelain, and refractory bricks for high-temperature furnace linings
• Electronics and semiconductors: Serves as a gate dielectric, passivation layer, and electrical insulator in integrated circuits and silicon wafer fabrication; optical fibers are drawn from high-purity fused silica
• Oil & gas: High-purity crystalline silica is used as a proppant in hydraulic fracturing (fracking) to hold open rock fractures and enhance hydrocarbon recovery
• Catalysis and petrochemicals: Amorphous silica (silica gel) is widely used as a catalyst support and carrier, and as a desiccant and adsorbent for gas drying and purification in refinery and gas processing operations
• Food and pharmaceuticals: Used as an anti-caking agent (food additive E551) in powdered foods and spices, and as an excipient in tablet manufacturing
• Rubber and plastics: Precipitated silica reinforces synthetic rubber in tire manufacturing and serves as a functional filler in polymer compounds

References

1. Wikipedia. Silicon dioxide (Page version Feb 23, 2026)
2. Shandong Unikem Industry (May 27, 2025). The Multifaceted Applications of Silicon Dioxide
3. Princeton University. Silica, SiO₂, Quartz, Tridymite, Crystobalite. From: Askland, "The Science and Engineering of Materials," PWS (1994)
4. AZO Materials (Dec 13, 2001). Silica - Silicon Dioxide (SiO₂)
5. AlfatestLab (Oct 5, 2020). An introduction to Silicon dioxide (silica) forms and applications
6. Elchemy (Feb 21, 2025). What Is Silica Used For? Industrial Applications and Benefits for Manufacturers
7. Vizag Chemicals International, Silicon dioxide, silica distributors, manufacturers, exporters, and suppliers in India