|
Properties Schott Bk-7®:
For all
standard optical glass components, or when optical glass is generically
requested for custom elements, Glass Dynamics uses normal quality BK7, a
high quality optical glass that is used whenever the additional benefits of
fused silica are not required. Since BK7 performs well in all chemical
tests, no special handling is required, thus reducing manufacturing costs.
It is a relatively hard material with extremely low bubble and inclusion
content. BK7 provides excellent transmittance through-out the visible and
near infrared spectra and down to 350 nm in the ultraviolet.
|
Optimum
Transmission Range
350nm - 2.0 µm |
|
Index of
Refraction |
|
Wavelength,
nm |
Fused
Silica/ Quartz |
BK7 |
Sapphire |
|
213.86 |
1.53427 |
- |
- |
|
230.21 |
1.52005 |
- |
- |
|
239.94 |
1.51337 |
- |
- |
|
265.20 |
1.50000 |
- |
1.83360 |
|
280.35 |
1.49403 |
- |
1.82427 |
|
302.15 |
1.48719 |
- |
1.81351 |
|
334.15 |
1.47976 |
- |
1.80184 |
|
346.62 |
1.47746 |
- |
1.79815 |
|
365.02 |
1.47452 |
1.53626 |
1.79358 |
|
404.66 |
1.46962 |
1.53024 |
1.78582 |
|
435.84 |
1.46669 |
1.52669 |
1.78120 |
|
546.07 |
1.46008 |
1.51872 |
1.77078 |
|
706.52 |
1.45516 |
1.51289 |
1.76303 |
|
852.11 |
1.45247 |
1.50981 |
1.75885 |
|
1013.98 |
1.45025 |
1.50731 |
1.75547 |
|
1529.52 |
1.44427 |
1.50094 |
1.74660 |
|
1970.09 |
1.43853 |
1.49500 |
1.73833 |
|
2325.42 |
1.43293 |
1.48929 |
1.73055 |
|
3243.90 |
1.41315 |
- |
1.70437 |
|
3507.00 |
1.40566 |
- |
1.69504 |
|
4954.00 |
- |
- |
1.62665 |
|
5577.00 |
- |
- |
1.58638 |
|
Mechanical
Properties of Optical Materials |
|
Thermal
|
Units
|
Fused Quartz
|
Fused Silica
|
BK7
|
Pyrex®
|
Sapphire |
|
Softening Point |
°C |
1180 |
1120 |
550 |
565 |
|
|
Annealing Point
|
°C
|
1180 |
1120 |
550 |
565 |
|
|
Strain Point
|
°C
|
1075 |
1025 |
624 |
515 |
|
|
Maximum
Temperature (Continuous) |
°C
|
1000 |
950 |
350 |
230 |
1100 |
|
Maximum
Temperature (Momentary) |
°C
|
1300 |
1200 |
490 |
|
|
|
Thermal
Conductivity |
@ 20° C |
cal cm
cm2sec°C |
0.0033 |
0.0033 |
0.0026 |
0.0027 |
0.0065 |
|
@ 200°C |
0.0037 |
0.0037 |
|
|
|
|
@ 950° C |
0.0064 |
0.0064 |
|
|
|
|
Specific Heat |
0°–100° C |
cal
g °C |
0.18 |
0.18 |
0.21 |
0.2 |
|
|
0°–900° C |
0.25 |
0.25 |
|
|
|
|
Coefficient of
Thermal Expansion |
-50°–0° C |
cm
cm
°C |
2.7 × 10-7 |
2.7 × 10-7 |
|
|
|
|
0°–300° C |
5.9 × 10-7 |
5.9 × 10-7 |
86 × 10-7 |
33 × 10-7 |
|
|
0°–900° C |
4.8 × 10-7 |
4.8 × 10-7 |
|
|
90.3 × 10-7 |
|
Strength/Hardness |
|
Moh Hardness |
|
5.5–6.5 |
5.5–6.5 |
5 |
|
9 |
|
Microhardness |
kg/cm2 |
9.4 × 104 |
9.4 × 104 |
|
|
|
|
Knoop Hardness
(100g load) |
kg/mm2 |
605 |
615 |
520 |
481 |
1525–2000 |
|
Density |
g/cm3 |
2.203 |
2.203 |
|
|
|
|
Specific
Gravity |
|
2.203 |
2.201 |
2.53 |
2.23 |
3.98 |
|
Compressive
Strength |
kg/cm2 |
1.13 × 104 |
1.13 × 104 |
|
2.04 × 104 |
|
|
Tensile
Strength |
kg/cm2 |
500 |
500 |
|
282 |
7000 |
|
Torsional
Strength |
kg/cm2 |
300 |
300 |
|
|
1.5 × 106 |
|
Bending
Strength
|
kg/cm2 |
680 |
680 |
|
|
|
|
Young's Modulus |
kg/cm2 |
7.45 × 105 |
7.45 × 105 |
8.63 × 105 |
7 × 106 |
79 × 105 |
|
Shear Modulus |
kg/cm2 |
3.2 × 105 |
3.2 × 105 |
|
|
|
|
Bulk Modulus |
kg/cm2 |
3.76 × 105 |
3.76 × 105 |
|
|
|
|
Poisson's Ratio |
|
0.17 |
0.17 |
0.208 |
0.2 |
0.02 |
|
Electrical |
|
Dielectric
Strength |
@ 20° C |
kv/cm |
250–400 |
250–400 |
|
|
480 |
|
@ 500° C |
150–200 |
150–200 |
|
|
|
|
Dielectric
Constant |
(0–1Mhz) |
|
3.7 |
3.7 |
|
5.1 |
8.6–10.6 |
|
Dielectric Loss
Tangent |
1 MHz |
|
1 × 10-4 |
1 × 10-4 |
|
2.6 × 10-2 |
|
|
102
MHz |
|
1 × 10-4 |
1 × 10-4 |
|
|
|
|
3 × 104
MHz |
4 × 10-4 |
4 × 10-4 |
|
|
|
|
Resistivity |
@ 20° C |
Ω/cm |
1 × 1018 |
1 × 1018 |
|
|
|
|
@ 600° C |
8 × 107 |
8 × 107 |
|
|
1 × 1011 |
|
@ 1000°C |
1 × 106 |
1 × 106 |
|
|
1 × 106 |
|
All properties
measured at 20° C unless otherwise specified. |
|
Striae and
Homogeneity |
|
Material Code |
Type |
Striae/MIL-G-174A |
Index Variation
Δn(x10-6) |
|
S1-UVA |
Fused Silica |
A |
6 |
|
S1-UVB |
Fused Silica |
A |
10 |
|
A1 |
Fused Quartz
or Fused Silica |
B |
10 |
|
G1 |
Fused Quartz
or Fused Silica |
C-D |
20 |
|
I2-IR |
Fused Quartz |
A |
4 |
|
BK7 |
Optical Glass |
A |
10 |
|
Bubbles &
Inclusions |
|
|
up to 1.0" dia. |
from 1.0" to
2.0" dia. |
from 2.0" to
3.0" dia. |
|
Material
|
Max. Dia. |
Max. Qty. |
Max. Dia. |
Max. Qty. |
Max. Dia. |
Max. Qty. |
|
(inches) |
per pc. |
(inches) |
per pc. |
(inches) |
per pc. |
|
S1-UVA
|
0.006 |
0 |
0.008 |
1 |
0.01 |
1 |
|
S1-UVB
|
0.008 |
1 |
0.015 |
1 |
0.015 |
1 |
|
A1
|
0.01 |
1 |
0.015 |
1 |
0.02 |
2 |
|
G1
|
0.03 |
3 |
0.04 |
3 |
0.06 |
3 |
|
I2-IR
|
0.01 |
3 |
0.015 |
3 |
0.02 |
3 |
|
BK-7
|
0.006 |
0 |
0.006 |
0 |
0.01 |
1 |
|
* These
specifications are worst case conditions.
* Materials
can be selected and guaranteed to customer's requirements.
* Bubbles less
than the maximum diameter count as a fraction of the allowed limit.
* Bubbles less
than 0.004" are regarded as undetectable. |
|
|
