N-LAK21 by Schott

Preferred Unknown Environmentally Friendly

N-LAK21 by Schott is a preferred optical glass. It transmits from 0.32 to 2.50 µm with an nd of 1.64049 and a Vd of 60.1. It has medium thermal expansion (CTE of 6.8×10⁻⁶/K), below average chemical resistance, and low relative cost.

Refractive Index vs Wavelength
Refractive Index Calculator
Valid range: 0.32–2.5 µm
dn/dλ vs Wavelength
dn/dλ Calculator
Valid range: 0.32–2.5 µm
Abbe Number Calculator
Transmission vs Wavelength
Transmission Calculator
Valid wavelength range: 0.320–2.500 µm
Optical Properties
Refractive Index (nd) 1.64049
Abbe Number (Vd) 60.1
Dispersion Formula Sellmeier
Wavelength Range 0.32 — 2.5 µm
$$n(\lambda) = \sqrt{1 + \frac{1.22718\,\lambda^2}{\lambda^2 - 0.00602076} + \frac{0.420784\,\lambda^2}{\lambda^2 - 0.0196863} + \frac{1.01285\,\lambda^2}{\lambda^2 - 88.437}}$$
Thermal Properties
TCE -30/70°C (10-6/K) 6.8
TCE 100/300°C (10-6/K) 8.1
Thermal Conductivity (W/mK) 0.88
Heat Capacity (J/gK) 0.59
$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.36 \times 10^{-6} + 2(1.15 \times 10^{-8})\,\Delta T + 3(1.11 \times 10^{-11})\,\Delta T^2 + \frac{3.1 \times 10^{-7} + 2(2.78 \times 10^{-10})\,\Delta T}{\lambda - 0.234}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$
Physical Properties
Density (g/cm³) 3.74
Relative Cost 1.7
Mechanical Properties
Young's Modulus (GPa) 91.0
Poisson's Ratio 0.27
Knoop Hardness (kgf/mm²) 600.0
Chemical Resistance
Climatic Resistance 4
Stain Resistance 2
Acid Resistance 53
Alkali Resistance 4
Phosphate Resistance 4
Similar Glasses (Other Manufacturers)
Glass Manufacturer nd Vd Compare
LAKN2 Sumita 1.6405 60.1
K-LaKn2 Sumita 1.6405 60.1
C41-60 Corning 1.640495 60.130957
BSM81 Ohara 1.639999 60.091709
S-BSM81 Ohara 1.639999 60.078127
LACL6 Hoya 1.640003 60.153568
LACL60 Hoya 1.64 60.2
H-LAK4L CDGM 1.64 60.202769
S-BSM36 Ohara 1.642495 58.369399
BSM36 Ohara 1.642495 58.369399
Similar Glasses (Schott)
Glass Manufacturer nd Vd Compare
LAK21 Schott 1.640495 60.101885
LAKL21 Schott 1.64048 59.749915
LAKN6 Schott 1.642499 57.962061
N-LAK7 Schott 1.6516 58.52
LAKN7 Schott 1.6516 58.517773
SK51 Schott 1.6209 60.310926
SK55 Schott 1.620411 60.118763
N-SK16 Schott 1.62041 60.32
SK16 Schott 1.62041 60.323649
SK15 Schott 1.62299 58.059722
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