Fused Silica

ULC stocks materials from the major manufacturers in all grades and specifications. All fused silica offered by United Lens is certified by the manufacturers.


PDF HPFS 7980 (PDF – 104KB)
PDF KrF (PDF – 104KB)
PDF ArF (PDF – 106KB)


PDF Suprasil (PDF – 83KB)
PDF Infrasil (PDF – 90KB)
PDF Homosil (PDF – 104KB)
PDF Herasil (PDF – 75KB)


PDF NIFS Series (PDF – 3MB)

Fused Silica, SiO2

Fused silica is a noncrystalline (glass) form of silicon dioxide (quartz, sand). It lacks long range order in its atomic structure. Its highly cross linked three dimensional structure gives rise to it’s high use temperature and low thermal expansion coefficient.

Key Properties

  • Near zero thermal expansion
  • Exceptionally good thermal shock resistance
  • Very good chemical inertness
  • Can be lapped and polished to fine finishes
  • Low dielectric loss
  • Good UV transparency

Typical Uses

  • High temperature lamp envelopes
  • Temperature insensitive optical component supports
  • Lenses, mirrors in highly variable temperature regimes
  • Microwave and millimeter wave components
  • Aeronautical radar windows

General Information

High purity sand deposits provide the raw material for bulk refractory grade, which is electric arc melted at extremely high temperatures. Optical and general purpose fused silica rods and tubing are drawn from a melt made from high purity chemicals. Fiber optic purity is made by thermal decomposition of high purity gaseous silica containing chemicals. The glass may be clear or translucent, in which case it is often referred to as fused quartz. The glass has very high viscosity, and this property allows the glass to be formed, cooled and annealed without crystallizing. Fused silica glass is a very low thermal expansion material, and so is extremely thermal shock resistant. The material is also chemically inert up to moderate temperatures except to hydrofluoric acid, which dissolves silica. It will devitrify above about 1100°C in the presence of contaminants such as sodium, phosphorus and vanadium, with the formation of cristobalite crystals which destroy the properties of the glass. The dielectric properties are stable up through gigahertz frequencies.

Engineering Properties*

Fused Silica
Mechanical Units of Measure SI/Metric (Imperial)
Density gm/cc (lb/ft3) 2.2 (137.4)
Porosity % (%) 0 0
Color - clear -
Flexural Strength MPa (lb/in2x103) - -
Elastic Modulus GPa (lb/in2x106) 73 (10.6)
Shear Modulus GPa (lb/in2x106) 31 (4.5)
Bulk Modulus GPa (lb/in2x106) 41 (6)
Poisson's Ratio - 0.17 (0.17)
Compressive Strength MPa (lb/in2x103) 1108 (160.7)
Hardness Kg/mm2 600 -
Fracture Toughness KIC MPa•m1/2 - -
Maximum Use Temperature (no load) °C (°F) 1100 (2000)
Thermal Conductivity W/m•°K (BTU•in/ft2•hr•°F) 1.38 (9.6)
Coefficient of Thermal Expansion 10-6/°C (10-6/°F) 0.55 (.31)
Specific Heat J/Kg•°K (Btu/lb•°F) 740 (0.18)
Dielectric Strength ac-kv/mm (volts/mil) 30 (750)
Dielectric Constant @ 1 MHz 3.82 (3.82)
Dissipation Factor @ 1 MHz 0.00002 (0.00002)
Loss Tangent @ 1 MHz - -
Volume Resistivity ohm•cm >1010 -

*All properties are room temperature values except as noted.
The data presented is typical of commercially available material and is offered for comparative purposes only. The information is not to be interpreted as absolute material properties nor does it constitute a representation or warranty for which we assume legal liability. User shall determine suitability of the material for the intended use and assumes all risk and liability whatsoever in connection therewith.