N-BK7

N-BK7 - Borosilicate glass with high purity

Outstanding expertise

State-of-the-art production technology

Many variants available

Material: N-BK7 / S-BSL7

Borosilicate crown glass is used for the production of mirrors, lenses, windows, prisms and flat plates with low dispersion. These can be made from the following materials:

N-BK7 (Schott)
S-BSL7 (Ohara)

Mechanical properties

Density g/cm³ 2,51

Knoop hardness HK0,1/20: 610

Poisson's ratio 0,206

Speed of sound m/s 5720

Thermal data

Softening temperature °C 724

Upper relaxation temperature °C 1120 (Suprasil) / ~ 1180 (Infrasil)

Lower relaxation temperature °C 1025 (Suprasil) / ~ 1075 (Infrasil)

Max. Max. service temp. continuous °C 950 (Suprasil) / ~ 1150 (Infrasil)

Physical Data

Average spec. heat J/kg · K (100 °C) 772

Thermal conductivity 1,38 W/m · K (20°C)

Mean coefficient of expansion 5,1 10-7 K-1 (20°C)

Applications

Borosilicate crown glasses are manufactured for applications that require a low coefficient of expansion and good temperature resistance.

Mirror for broadband applications
Optical windows

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Material properties

Density:

2.51

Young‘s modulus:

82.0

Knopp Hardness:

610

Poisson Ratio:

0.21

Heat capacity:

858

Thermal conductivity:

1.11

Transmission range:

0.4 - 2.5

Other optical components

Fused Silica / Quarz

Zerodur

Suprasil / Infrasil

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