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     Fused Silica
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Fused silica includes three types: JGS1 (Ultraviolet Grade Fused Silica),JGS2 (Optical Grade Fused Quartz), and JGS3 (Full Spectrum Fused Silica).

Fused Silica is the glassy form of quartz and is thus isotropic. It is tough and hard and has a very low expansion. Normal varieties contain water that gives strong absorption in the IR. Water-free varieties are available.

Today advances in raw material beneficiation permit transparent fusions from sand as well as from crystal. Consequently, if naturally occurring crystalline silica (sand or rock) is melted, the material is simply called Fused Quartz. If the silicon dioxide is synthetically derived, however, the material is referred to as synthetic Fused Silica.

These materials are ultra pure, single component glasses (SiO2) with a unique combination of thermal, optical and mechanical properties, which make them the preferred materials for use in a variety of processes and applications where other materials are not suitable. The very high purity (over 99.9%) ensures minimum contamination in process applications.

Fused Quartz is less expensive vitreous silica formed by fusing naturally occurring quartz crystal or lower grade synthetic stock material, The UV use is limited to 250nm and this material is usually used for windows covering visible wavelengths.

Fused Silica is vitreous silica formed by fusing high purity synthetic material. The UV use can be reached about 160nm.

Ultraviolet Grade Fused Silica: JGS1 (China), equivalent to Suprasil 1 and 2 (Heraeus), Spectrosil A and B (Saint-Gobain) and Corning 7940 (Corning), Dynasil 1100 and 4100 (Dynasil).

Optical Grade Fused Quartz: JGS2 (China), equivalent to Homosil 1, 2 & 3 (Heraeus), Dynasil 1000 & 4000 and 5000 & 6000 (Dynasil)

Full Spectrum Fused Silica: JGS3 (China), equivalent to Suprasil 300 (Heraeus).

Different Properties
Parameter Value JGS1 JGS2 JGS3
Maximum Size <200mm> <300mm> <200mm>
Transmission Range (Medium transmission ratio) 0.17~2.10um (Tavg>90%) 0.26~2.10um (Tavg>85%) 0.185~3.50um (Tavg>85%)
OH- Content 1200 ppm 150 ppm 5 ppm
Fluorescence (ex 254nm) Virtually Free Strong v-b Strong V-B
Impurity Content 5 ppm 20-40 ppm 40-50 ppm
Birefringence Constant 2-4 nm/cm 4-6 nm/cm 4-10 nm/cm
Melting Method Synthetic CVD Oxy-hydrogen melting Electrical melting
Applications Laser substrate: Window, lens, prism, mirror... Semiconductor and high temperature window IR & UV substrate
Same properties
Density 2.20g/cm3
Abbe Constant 67.6
Refractive Index (nd) at 588nm 1.4586
Wavelength (um) Refractive Index (n) Wavelength (um) Refractive Index (n)
0.200 1.55051 1.000 1.45042
0.220 1.52845 1.064 1.44962
0.250 1.50745 1.100 1.44920
0.300 1.48779 1.200 1.44805
0.320 1.48274 1.300 1.44692
0.360 1.47529 1.500 1.44462
0.400 1.47012 1.600 1.44342
0.450 1.46557 1.700 1.44217
0.488 1.46302 1.800 1.44087
0.500 1.46233 1.900 1.43951
0.550 1.46008 2.000 1.43809
0.588 1.45860 2.200 1.43501
0.600 1.45804 2.400 1.43163
0.633 1.45702 2.600 1.42789
0.650 1.45653 2.800 1.42377
0.700 1.45529 3.000 1.41925
0.750 1.45424 3.200 1.41427
0.800 1.45332 3.370 1.40990
0.850 1.45250 3.507 1.40566
0.900 1.45175 3.707 1.39936
Hardness 5.5 - 6.5 Mohs' Scale 570 KHN 100
Design Tensile Strength 4.8x107 Pa (N/mm2) (7000 psi)
Design Compressive Strength Greater than 1.1x109 Pa (160,000 psi)
Bulk Modulus 3.7x1010 Pa (5.3x106 psi)
Rigidity Modulus 3.1x1010 Pa (4.5x106 psi)
Young's Modulus 7.2x10-10 Pa (10.5x106 psi)
Poisson's Ratio 0.17
Coefficient of Thermal Expansion 5.5x10-7cm/cm.C (20C-320C)
Thermal Conductivity 1.4 W/m.C
Specific Heat 670 J/kg.C
Softening Point 1683C
Annealing Point 1215C
Strain Point 1120C
Electrical Receptivity 7x107 ohm.cm (350C)
Dielectric Properties (20C and 1 MHz) Constant Strength Loss Factor Dissipation Factor 3.75 5x107 V/m Less than 4x10-4 Less than 1x10-4
Velocity of Sound-Shear Wave 3.75x103 m/s
Velocity of Sound/Compression Wave 5.90x103 m/s
Sonic Attenuation Less than 11 db/m MHz
Permeability Constants (cm3mm/cm2 sec cm of Hg) Helium Hydrogen Deuterium Neon (700C) 210x10-10 21x10-10 17x10-10 9.5x10-17
Chemical Stability (except hydrofluoric) High resistance to water and acids