BAK4 by Schott

Obsolete Unknown Environmentally Dangerous

BAK4 by Schott is an obsolete optical glass. It transmits from 0.31 to 2.50 µm with an nd of 1.56883 and a Vd of 56.130661. It has medium thermal expansion (CTE of 7.0×10⁻⁶/K), good chemical resistance, low relative cost, and dangerous environmental properties.

Refractive Index vs Wavelength
Refractive Index Calculator
Valid range: 0.31–2.5 µm
dn/dλ vs Wavelength
dn/dλ Calculator
Valid range: 0.31–2.5 µm
Abbe Number Calculator
Transmission vs Wavelength
Transmission Calculator
Valid wavelength range: 0.310–2.500 µm
Optical Properties
Refractive Index (nd) 1.56883
Abbe Number (Vd) 56.130661
Dispersion Formula Sellmeier
Wavelength Range 0.31 — 2.5 µm
$$n(\lambda) = \sqrt{1 + \frac{1.22966\,\lambda^2}{\lambda^2 - 0.00723553} + \frac{0.191513\,\lambda^2}{\lambda^2 - 0.0277771} + \frac{0.95689\,\lambda^2}{\lambda^2 - 109.687}}$$
Thermal Properties
TCE -30/70°C (10-6/K) 7.0
TCE 100/300°C (10-6/K) 8.2
Thermal Conductivity (W/mK) —
Heat Capacity (J/gK) —
$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.85 \times 10^{-6} + 2(1.29 \times 10^{-8})\,\Delta T + 3(-1.93 \times 10^{-11})\,\Delta T^2 + \frac{4.92 \times 10^{-7} + 2(7.7 \times 10^{-10})\,\Delta T}{\lambda - 0.218}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$
Physical Properties
Density (g/cm³) 3.1
Relative Cost 1.35
Mechanical Properties
Young's Modulus (GPa) —
Poisson's Ratio —
Knoop Hardness (kgf/mm²) —
Chemical Resistance
Climatic Resistance 2
Stain Resistance 0
Acid Resistance 2
Alkali Resistance 1
Phosphate Resistance 2
Notes

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Similar Glasses (Other Manufacturers)
Glass Manufacturer nd Vd Compare
H-BAK7A CDGM 1.568828 56.127804
B69-56 Corning 1.568797 56.044859
H-BAK7 CDGM 1.56883 56.041308
H-BAK7GT CDGM 1.56883 56.041308
BAC4 Hoya 1.56883 56.04
BAK4 Sumita 1.56883 56.0
BAL14 Ohara 1.568832 56.339266
S-BAL14 Ohara 1.568832 56.363897
BAC6 Hoya 1.574441 56.357089
H-BAK8 CDGM 1.5725 57.486797
Similar Glasses (Schott)
Glass Manufacturer nd Vd Compare
N-BAK4 Schott 1.56883 55.98
N-BAK4HT Schott 1.56883 55.98
BAK1 Schott 1.5725 57.54931
N-BAK1 Schott 1.5725 57.55
BAK50 Schott 1.567736 57.990411
KZFSN2 Schott 1.558361 54.157173
N-KZFS2 Schott 1.55836 54.01
N-BALF4 Schott 1.57956 53.87
BALF4 Schott 1.579569 53.708241
BAK5 Schott 1.556709 58.649202
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