N-SK18 by Schott

Obsolete Unknown Environmentally Friendly

N-SK18 by Schott is an obsolete optical glass. It transmits from 0.32 to 2.50 µm with an nd of 1.63854 and a Vd of 55.423596. It has low thermal expansion (CTE of 6.4×10⁻⁶/K), below average chemical resistance, and low relative cost.

Refractive Index vs Wavelength
Refractive Index Calculator
Valid range: 0.334–2.235 µm
dn/dλ vs Wavelength
dn/dλ Calculator
Valid range: 0.334–2.235 µm
Abbe Number Calculator
Transmission vs Wavelength
Transmission Calculator
Valid wavelength range: 0.320–2.500 µm
Optical Properties
Refractive Index (nd) 1.63854
Abbe Number (Vd) 55.423596
Dispersion Formula Sellmeier
Wavelength Range 0.334 — 2.235 µm
$$n(\lambda) = \sqrt{1 + \frac{1.53857\,\lambda^2}{\lambda^2 - 0.00863201} + \frac{0.0985934\,\lambda^2}{\lambda^2 - 0.0367156} + \frac{1.0231\,\lambda^2}{\lambda^2 - 100.118}}$$
Thermal Properties
TCE -30/70°C (10-6/K) 6.4
TCE 100/300°C (10-6/K) 7.6
Thermal Conductivity (W/mK) —
Heat Capacity (J/gK) —
$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.83 \times 10^{-7} + 2(1.31 \times 10^{-8})\,\Delta T + 3(-1.22 \times 10^{-11})\,\Delta T^2 + \frac{5.56 \times 10^{-7} + 2(5.92 \times 10^{-10})\,\Delta T}{\lambda - 0.146}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$
Physical Properties
Density (g/cm³) 3.64
Relative Cost 2.42
Mechanical Properties
Young's Modulus (GPa) —
Poisson's Ratio —
Knoop Hardness (kgf/mm²) —
Chemical Resistance
Climatic Resistance 3
Stain Resistance 4
Acid Resistance 52
Alkali Resistance 2
Phosphate Resistance 3
Notes

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Similar Glasses (Other Manufacturers)
Glass Manufacturer nd Vd Compare
H-ZK11 CDGM 1.63854 55.446553
BACD18 Hoya 1.63854 55.45
BSM18 Ohara 1.638539 55.384768
S-BSM18 Ohara 1.638539 55.380028
K-SK18 Sumita 1.63854 55.5
SK18RH Sumita 1.63854 55.5
SK18 Sumita 1.63854 55.5
K-SK18RH Sumita 1.63854 55.5
C39-56 Corning 1.638505 55.504447
MP-PCD55AR Hoya 1.63858 55.18
Similar Glasses (Schott)
Glass Manufacturer nd Vd Compare
SK18A Schott 1.63854 55.423596
N-LAK22 Schott 1.65113 55.89
LAKN22 Schott 1.65113 55.891754
LAKN6 Schott 1.642499 57.962061
SK10 Schott 1.622801 56.903777
N-SK10 Schott 1.62278 56.98
SSK4A Schott 1.61765 55.141867
N-SSK2 Schott 1.62229 53.27
SSK2 Schott 1.622301 53.154887
LAK11 Schott 1.658302 57.261599
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