fusedsilica

Fused silica, also known as fused quartz, is an amorphous form of silicon dioxide (SiO2) produced by melting high-purity silica and rapidly cooling the melt to prevent crystallization. It is distinguished by its very low impurity content and non-crystalline structure, which confer unique optical and thermal properties compared with common glasses.

Production methods involve melting refined silica in electric furnaces or by flame fusion, followed by rapid quenching and annealing to relieve stresses. Common processes include flame fusion and the Verneuil method. The resulting material can be formed into rods, blocks, tubes, or further processed into precise optical components.

Key properties include high optical transmission over a broad wavelength range, from the ultraviolet through the visible and into the near-infrared, with transmission limited primarily by impurities. It has a very low coefficient of thermal expansion, high softening temperature (about 1,700 °C), and good resistance to chemical attack by most acids and bases. However, fused silica is susceptible to attack by hydrofluoric acid and certain alkalis. It exhibits excellent thermal shock resistance for a glass, due to its low thermal expansion and uniform structure, though it remains brittle and can fracture under mechanical stress.

Applications are widespread in optics and photonics, including lenses, prisms, windows, and fiber-optic components, as well as UV optics and laser systems. It is also used in semiconductor processing equipment, laboratory glassware, crucibles, and specialized astronomical instrumentation, where high purity and stable transmission are essential.