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Crystal
quartz (SiO2) is a very useful material for fabrication of finished
optics: laser beamsplitters, AO elements, polarizing optics, prisms,
windows, lenses in the ultraviolet because of its high UV, VIS and NIR
transmittance, birefringence, ability to rotate plane polarized light,
high damage threshold and resistance to scratching. The optical grade
material is featured by highest possible transmittance throughout range
190 - 2900 nm, virtual freedom from bubbles and inclusions. Grown boules
are Z - crystals and about 100 mm in the direction down optic axis that
limits corresponding dimension in an optical part.
Silicon dioxide occurs naturally as sand or rock and when
melted, the resulting product is called Fused Quartz. If the
silicon dioxide is synthetically derived, the material is often called
Fused Silica. Fused Quartz is very pure, has a high chemical
resistance, good thermal shock resistance and is very strong in compression.
The low thermal expansion coefficient makes it ideal for mirrors and
optical flats. It is used for viewing windows, being transparent to
wavelengths from around 0.2 to 3.5 µm, insulators for electronic
applications and for semi-conductor manufacturing. |
Material
properties of the Crystal Quartz:
|
Quality
grade
|
Coefficient of absorption (αmax at 190 nm), cm-1
|
Coefficient
of absorption (αmax at 2800 nm), cm-1
|
|
1
|
0.010
|
0.030
|
|
2
|
0.025
|
0.045
|
|
3
|
0.050
|
0.070
|
Properties:
| Chemical
Formula |
SiO2 |
| Positive
uniaxial crystal |
ne
> no |
| Density,
g/cm3 |
2.65 |
| Mohs
Hardness |
7 |
| Heat
Capacity at 300 °K, J/kg·°K |
733 |
| Thermal
Expansion Coefficient at 300 °K, 10-6· °K-1 |
a||
= 7.64, a^= 14.00 |
| Thermal
conductivity at 300 °K, W/(m×k) |
æ||
= 9.5, æ^= 6.10 |
| |
æ||
= 9.5, æ^= 6.10 |
|
Refractive
indices at T = 291°K
|
Wavelength
|
no
|
ne
|
Wavelength
|
no
|
ne
|
|
193,6
|
1,65999
|
1,67343
|
706,5
|
1,540488
|
1,549472
|
|
250,3
|
1,60032
|
1,61139
|
766,5
|
1,539071
|
1,548005
|
|
303,4
|
1,576955
|
1,58720
|
844,7
|
1,537525
|
1,54640
|
|
340,4
|
1,56747
|
1,577385
|
1000,0
|
1,53503
|
1,54381
|
|
410,2
|
1,556502
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1,566031
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1300,0
|
1,53102
|
1,53962
|
|
467,8
|
1,551027
|
1,560368
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1529,6
|
1,52800
|
1,53646
|
|
508,6
|
1,548229
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1,557475
|
1600,0
|
1,52703
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1,53545
|
|
546,1
|
1,546174
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1,555350
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1800,0
|
1,52413
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1,53242
|
|
627,8
|
1,542819
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1,551880
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2058,2
|
1,51998
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1,52814
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Max. available size:
100 mm along axis <100> and <010> and <001> axis. Quartz elements which
we supply are manufactured as a rule according to customer's specifications.
Material
properties of the Fused Silica:
| Apparent
porosity ( % ) |
0 |
| Density
( g cm-3 ) |
2.2 |
| Refractive
index |
1.46 |
| Useful
optical transmission range |
180 - 2500
nm |
| Water
absorption - saturation ( % ) |
0 |
| Dielectric
constant |
3.8 |
| Dielectric
strength ( kV mm-1 ) |
25-40 |
| Volume
resistivity ( Ohmcm ) |
1018
@ 25°C |
| Compressive
strength ( MPa ) |
1100 |
| Hardness
- Knoop ( kgf mm-2 ) |
820 |
| Hardness
- Vickers ( kgf mm-2 ) |
1000 |
| Shear
strength ( MPa ) |
70 |
| Tensile
modulus ( GPa ) |
72-74 |
| Tensile
strength ( MPa ) |
48 |
| Coefficient
of thermal expansion ( x10-6 °K-1 ) |
0.54
@ 20-1000°C |
| Melting
point (°C ) |
1715 |
| Specific
heat ( J °K-1 kg-1 ) |
670-740
@ 25°C |
| Thermal
conductivity ( W m-1 °K-1 ) |
1.46
@ 20°C |
| Upper
continuous use temperature ( °C ) |
1100-1400 |
Fused Silica has
high homogenity and good transmission in the ultraviolet, visible and
infrared spectral regions. Depending on transmission range there are
UV and IR Fused Silica grades: the useful range of UV grade is 0.17
- 2 µm and of IR grade is 0.23 - 3.5 µm. Products manufactured:
Lenses, windows, wedges, optical beamsplitters, optical filters,
prisms, etc.
Cultured crystalline
quartz is mostly used The useful transmission range is represented
from 0.18 µm to 2.8 µm by three grades of optical quartz defined
by optical absorption.
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