Silicaglas

Silicaglas, commonly known as fused silica or silica glass, is an amorphous form of silicon dioxide (SiO2) with very high purity. It is produced by melting silica-rich materials and cooling the liquid to a rigid, non-crystalline solid. The term is used in German- and some European-language sources to distinguish this high-purity glass from ordinary soda-lime glass.

Properties include broad optical transparency, extending from the ultraviolet through the visible and into the near-infrared. The refractive index is around 1.46 at 589 nm, with excellent transmission and very low autofluorescence. Thermal properties are notable for an extremely low coefficient of thermal expansion (approximately 0.5 × 10^-6 per kelvin at room temperature) and a high melting point near 1713°C, which gives good thermal stability and resistance to thermal shock under controlled conditions. Chemically, silicaglas is highly inert to most acids and bases but is attacked by hydrofluoric acid. It is also characterized by low impurity content, which reduces scattering and absorption in precision optical applications.

Manufacturing approaches include the classical Verneuil flame-fusion process and other high-purity melting techniques; sol-gel methods and chemical vapor deposition are used to produce specialised shapes and layers. Purification is critical to minimize metallic and hydroxyl contaminants that can absorb UV light or increase losses in optical systems.

Applications are broad in optics and industry: lenses and windows for UV to near-IR, high-power laser components, UV lithography optics, fiber-optic cores and preforms, and crucibles or labware that require chemical inertness and stability at elevated temperatures. Silicaglas remains favored where minimal impurities, high transparency, and thermal stability are essential, though its cost is higher than that of common borosilicate and soda-lime glasses.

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