BK7G18 by Schott

Preferred Unknown Radiation Resistant Environmentally Dangerous

BK7G18 by Schott is a preferred optical glass. It transmits from 0.38 to 2.50 µm with an nd of 1.51975 and a Vd of 63.58. It has medium thermal expansion (CTE of 7.0×10⁻⁶/K), excellent chemical resistance, low relative cost, radiation resistance, and dangerous environmental properties.

Refractive Index vs Wavelength
Refractive Index Calculator
Valid range: 0.38–2.5 µm
dn/dλ vs Wavelength
dn/dλ Calculator
Valid range: 0.38–2.5 µm
Abbe Number Calculator
Transmission vs Wavelength
Transmission Calculator
Valid wavelength range: 0.380–2.500 µm
Optical Properties
Refractive Index (nd) 1.51975
Abbe Number (Vd) 63.58
Dispersion Formula Sellmeier
Wavelength Range 0.38 — 2.5 µm
$$n(\lambda) = \sqrt{1 + \frac{1.26539\,\lambda^2}{\lambda^2 - 0.00813104} + \frac{0.0144191\,\lambda^2}{\lambda^2 - 0.0543303} + \frac{1.00323\,\lambda^2}{\lambda^2 - 102.821}}$$
Thermal Properties
TCE -30/70°C (10-6/K) 7.0
TCE 100/300°C (10-6/K) 8.22
Thermal Conductivity (W/mK) 1.19
Heat Capacity (J/gK) 0.82
$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.52 \times 10^{-6} + 2(1.37 \times 10^{-8})\,\Delta T + 3(-1.26 \times 10^{-11})\,\Delta T^2 + \frac{4.36 \times 10^{-7} + 2(4.17 \times 10^{-10})\,\Delta T}{\lambda - 0.194}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$
Physical Properties
Density (g/cm³) 2.52
Relative Cost 1.8
Mechanical Properties
Young's Modulus (GPa) 82.0
Poisson's Ratio 0.21
Knoop Hardness (kgf/mm²) 580.0
Chemical Resistance
Climatic Resistance —
Stain Resistance 0
Acid Resistance 1
Alkali Resistance 2
Phosphate Resistance —
Notes

radiation resistant glass

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Glass Manufacturer nd Vd Compare
H-K90GTI CDGM 1.51948 63.291634
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Similar Glasses (Schott)
Glass Manufacturer nd Vd Compare
BK8 Schott 1.520152 63.685744
P-BK7 Schott 1.5164 64.06
BK7 Schott 1.5168 64.167336
N-BK7 Schott 1.5168 64.17
N-BK7HTSultra Schott 1.5168 64.17
N-BK7HT Schott 1.5168 64.17
N-BK7HTi Schott 1.5168 64.17
BK7HT Schott 1.51633 64.14348
UBK7 Schott 1.516801 64.289727
BK1 Schott 1.510091 63.464788
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