Material Category: Fused Silica

Fused Silica Glass Overview

Vitreous Silica is the generic term used to describe all types of silica glass, which manufacturers either refer to as Fused Silica or Synthetic Quartz. It is a noncrystalline glass form of silicon dioxide (quartz and sand) and is manufactured by melting naturally occurring crystalline silica, such as sand or rock crystal. It is unique from other types of glasses because it is manufactured using a single ingredient.

Fused silica, often referred to as synthetic quartz, is created by using high purity silica sand that has been manufactured from SiCL4, resulting in a transparent glass with an ultra-high purity and improved optical transmission. However, depending on the manufacturing process, water bubbles can get caught in the glass and result in a translucent appearance.

Fused silica glass has very high viscosity, which means that it can be formed, cooled, and annealed without crystallizing.

It is known for:

  • Extreme hardness
  • Resistance to high temperature
  • Extensive optical transmission in the ultraviolet spectrum, but some infrared fused silica glasses are available
  • Permeability
  • Low coefficient of thermal expansion (CTE)
  • High chemical purity
  • High corrosion resistance
  • Excellent electrical insulation qualities
  • Low refractive index variations
  • Low birefringence values
  • Large size capabilities
  • State-of-the-art homogeneity levels

Available Materials

Based upon customer demand, Sydor Optics offers Fused Silica made from the following substrate materials. Of course, if you don’t see a material you need, please contact a Sales Engineer, who will gladly discuss additional options that may be available.

Fused Silica

Fused Silica Properties

Principle Uses of Fused Silica

Compared to other types of glass, fused silica is efficient at transmitting waves on the ultraviolet spectrum, so it is often used to make lenses and optics for the ultraviolet spectrum. Its low coefficient of thermal expansion makes it a great candidate for precision mirror substrates, and it is commonly used in semiconductor fabrication and laboratory equipment.

Other common applications are:

  • Windows for manned spacecraft, debris shields, etc.
  • Vacuum windows for high energy lasers
  • Precision instrumentation for medical and metrology
  • Projection mask for photolithography
  • First surface mirrors, such as those in telescopes
  • Laser windows
  • Glass wafers for photonic chips

Chemical Properties

Silica glass is one of the more chemically stable glass types. It has excellent chemical resistance; it is often used as the distillation container for various solvents and acid solutions or as the dissolution and washing container for various kinds of substances. Water, salt solutions, acids, and metals free from oxide (with the exception of alkalis and alkaline-earths) do not react with silica glass.

Etching and/or surface devitrification may occur in the presence of hydrofluoric acid, phosphoric acid, alkali, and alkali metal compounds. Silica glass is sensitive to all alkali and alkaline-earth compounds, so it is advisable to remove fingerprints, which contain trace amounts of alkalis, from silica glass with alcohol before heating.

Mechanical Properties

Fused silica has excellent elastic properties, making it a superb option for finished products that need to flex or otherwise move, but only when manufactured with the ultra-low stress femtoEtch process, which prevents microcracks in the glass.

Thermal Properties

Fused silica is known for having a deformation temperature as high as 1700 C degrees, and is suitable for environments that reach up to 1000 C degrees. It also has a small coefficient of thermal expansion (CTE), making it durable against rapid temperature changes. The average CTE value for quartz glass at about 5.0 × 10 -7/ °C, making silica and quartz glass one of the lowest options available.

It is possible to rapidly cool fused silica glass from over 100 degrees C by submerging it into ice-cold water without any breakage, but this property could be compromised by other variables of the glass, such as surface condition and geometry.

Optical Properties

Fused silica is transparent in the ultraviolet, visible, and near-infrared spectrums.

Each glass within this category will perform better in different wavelengths, and some materials won’t perform at all in certain wavelengths. Before you purchase a material, check with your optical supplier on which material is best suited for your application’s wavelength.

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