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Borosilicate Crown Glass BK7
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Glass BK7 - the colourless optical glass, it differs high degree of uniformity, is steady in relation to carbonic acid action, well keeps the form and is easily processed. Glass BK7 is one of the basic materials for manufacturing of optical details for the lasers of visible and near IR spectrum range. The spectral transmittance of glasses BK7 is shown.
Elektrosteklo Ltd. manufactures different kinds of optics from the glass BK7, namely, the plane-parallel plates (window), lens, prisms, spherical lenses, cylindrical lenses, the mirrors both under the catalog and the customer’s specification.
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BASE PROPERTIES
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PARAMETER |
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VALUE |
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| OPTICAL |
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Refractive Index of the glass BK7 |
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nd=1.51680; nå=1.51872 |
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Abbe Constant |
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Àd = 64.17; Àe = 63.96 |
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Principal Dispersion |
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nF – nC = 0.008054
nF' - nC' = 0.008110 |
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Bubble class |
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0 |
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| PHSYCAL |
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Density |
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2.51 g/cm3 |
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Transformation Temperature, Tg |
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557° C |
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Temperature of glass in at a viscosity of 107.6 dPa s |
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719° C |
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Thermal Conductivity |
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1.114 W/(m*K) |
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Coefficient of Expansion |
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7.1 õ 10-6/K -30° ... +70° C
8.3 õ 10-6/K 20° ... 300° C |
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Knoop hardness (0.1/20) |
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610 |
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Specific Heat Capacity |
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0.858 J/(g*K) |
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Young's Modulus (E) |
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82 õ 103 Í/ìì2 |
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Stress optical coefficient |
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2.77 x 10-6 mm2/Í |
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Poisson's Ratio |
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0.206 |
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| CHEMICAL |
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Climatic resistance |
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2 |
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Stain resistance |
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0 |
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Acid resistance |
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1 |
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Phosphate resistance |
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2.3 |
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Alkali resistance |
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2.0 |
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REFRACTIVE INDEX of the glass BK7
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Wavelength, nm |
2325.4 |
1970.1 |
1529.6 |
1060.0 |
1014.0 |
852.1 |
706.5 |
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Refractive Index |
1.489 |
1.495 |
1.501 |
1.507 |
1.507 |
1.510 |
1.513 |
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Wavelength, nm |
656.3 |
643.8 |
632.8 |
589.3 |
587.6 |
546.1 |
486.1 |
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Refractive Index |
1.514 |
1.515 |
1.515 |
1.517 |
1.517 |
1.519 |
1.522 |
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Wavelength, nm |
480.0 |
4358 |
404.7 |
365.0 |
334.1 |
312.6 |
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Refractive Index |
1.523 |
1.527 |
1.530 |
1.536 |
1.543 |
1.549 |
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Relative partial dispersion of glass BK7
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P(s,t) |
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0.3098 |
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P(C,s) |
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0.5612 |
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P(d,C) |
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0.3076 |
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P(e,d) |
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0.2386 |
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P(g,f) |
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0.5349 |
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P(i,h) |
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0.7483 |
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P(s,t) |
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0.3076 |
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P(C',s) |
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0.6062 |
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P(d,C') |
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0.2566 |
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P(e,d) |
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0.2370 |
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P(g,F') |
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0.4754 |
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P(i,h) |
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0.7432 |
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