# Infrared (IR) Grade Fused Silica

IR grade fused silica is a grade of fused silica. The graph bars on the material properties cards below compare IR grade fused silica to other glass and glass-ceramics (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

## Mechanical Properties

Compressive (Crushing) Strength

1100 *MPa* 160 *x 10 ^{3} psi*

Elastic (Young's, Tensile) Modulus

73 *GPa* 11 *x 10 ^{6} psi*

Flexural Strength

67 *MPa* 9.7 *x 10 ^{3} psi*

Knoop Hardness

570

Poisson's Ratio

0.17

Shear Modulus

31 *GPa* 4.5 *x 10 ^{6} psi*

Tensile Strength: Ultimate (UTS)

50 *MPa* 7.2 *x 10 ^{3} psi*

## Thermal Properties

Maximum Temperature: Decomposition

1100 *°C* 2010 *°F*

Maximum Temperature: Mechanical

1080 *°C* 1980 *°F*

Melting Onset (Solidus)

1900 *°C* 3450 *°F*

Specific Heat Capacity

720 *J/kg-K* 0.17 *BTU/lb-°F*

Thermal Conductivity

1.4 *W/m-K* 0.79 *BTU/h-ft-°F*

Thermal Expansion

0.5 *µm/m-K*

## Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 MHz

3.8

Dielectric Strength (Breakdown Potential)

30 *kV/mm* 1.2 *V/mil*

Electrical Dissipation At 1 MHz

0.00011

Electrical Resistivity Order of Magnitude

14 *10 ^{x} Ω-m*

## Otherwise Unclassified Properties

Density

2.2 *g/cm ^{3}* 140

*lb/ft*

^{3}Light Transmission Range

0.25 to 3.5 *µm*

Refractive Index

1.5

## Common Calculations

Stiffness to Weight: Axial

18 *points*

Stiffness to Weight: Bending

63 *points*

Strength to Weight: Axial

6.3 *points*

Strength to Weight: Bending

14 *points*

Thermal Diffusivity

0.85 *mm ^{2}/s*

Thermal Shock Resistance

97 *points*

## Followup Questions

## Further Reading

Ceramic and Glass Materials: Structure, Properties and Processing, James F. Shackelford and Robert H. Doremus (editors), 2008

Glass: Mechanics and Technology, Eric Le Bourhis, 2007

Handbook of Optical Materials, Marvin J. Weber, 2003

Handbook of Optical Constants of Solids, Edward D. Palik (editor), 1998

Ceramics and Composites: Processing Methods, Narottam P. Bansal and Aldo R. Boccaccini (editors), 2012