Optics made of Borofloat
 
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BOROFLOAT® 33

Temperature- and chemically resistant borosilicate glass

Special Properties

  • High temperature load capacity:
    - up to 450 °C permanent load
    - up to 500 °C temporarily (< 10 h)
  • Excellent chemical resistivity against strong acids,
    bases, and organic substances
  • Low thermal coefficient of expansion
    similar to the one of silicon wafers (anodic bonding)
  • High thermal shock resistivity
  • Clear, practically colorless appearance
  • Low self-fluorescence
  • High UV-transmission
  • Relatively low alkali content in the glass composition
  • Low specific weight
  • Good scratch and abrasion resistance
  • High elasticity and mechanical strength
  • Excellent glass flatness achieved by a micro-float process

Typical Applications

  • Window optics for high operating temperatures
  • Medical and biotechnology applications
  • Glass wafer for anodic bonding processes
  • Flat glass substrates for dielectric coating systems
  • Components for lighting systems
  • Front glass for high power floodlights
  • Substrates for optical filters
  • Photovoltaic devices
  • Sight glass windows
  • Fiber optic applications
  • Glass cover for sensors
  • Base glass for industrial optics
  • Laboratory glass equipment
  • Components for environment technology
  • Microscope slides for chemical analyses or medical use
  • Glass for harsh environments
  • Neutron absorbers
  • Packaging of optoelectronic components
  • Analytic systems
  • Measurement and sensor technology devices
Request for Quotation

48h-Express Service for custom optics Also available in 48 h Express-Service

BOROFLOAT® is a high-quality borosilicate glass which can be used permanently at temperatures up to 450 °C. In the short term (< 10 h) it can withstand temperatures up to 500 °C. The SCHOTT glass has a low coefficient of expansion close to that of silicon. This allows glass-wafers made of BOROFLOAT® to be used in anodic bonding applications. The glass has almost the same thermal expansion and density as PYREX® and is therefore often used today as a replacement for PYREX® borosilicate glass which was discontinued as a rolled sheet glass many years ago.

BOROFLOAT® is a clear-transparent glass that offers a very high and uniform optical light transmission. Thanks to a special micro-float manufacturing process developed by SCHOTT, BOROFLOAT® is characterized by excellent evenness and surface quality, a low micro roughness as well as a high homogeneity. For a flat glass it offers an exceptionally high optical quality which facilitates a wide scope of applications in the field of industrial optics, opto-electronics, photonics, analytics, and in lighting technology. BOROFLOAT® has low self-fluorescence over a wide light spectrum.

 

Borofloat borosilicate glass window
nullspacer CNC-manufactured, high temperature window for a micro reactor made of BOROFLOAT® borosilicate glass from SCHOTT.

 

BOROFLOAT® has practically the same glass composition as the laboratory glassware DURAN® also made by SCHOTT. Consequently, it is very resistant against water, neutral, saline, and acidic solutions as well as to iodine, chlorine, bromine, and organic substances even over long periods of time and at temperatures higher than 100 °C. It exceeds the chemical resistance of many other glass materials and even of most metals. Acids and alkalis can only dissolve small amounts of ions from the borosilicate glass so that the measurement results are not impaired as is often the case with conventional soda-lime glass. These properties allow the use of BOROFLOAT® in interesting applications of medical engineering and analytics.

But also the mechanical characteristics of BOROFLOAT® surpass the ones of soda-lime glass and even of most other borosilicate glass materials. For example, the abrasion resistance of BOROFLOAT® significantly exceeds the one of simple soda-lime glass.

BOROFLOAT® flat glass is an ideal substrate material for optical coatings like front surface coated mirrors, optical filters, anti-reflection coatings, etc., and an excellent material choice for the production of optical windows, optical substrates, glass wafers, and many other plane optics. It has proven to be a perfect economical choice for the design of many technical glass applications particularly at high operating temperatures and is well suited for lighting technology and numerous applications in electronics. In case you have any additional queries about BOROFLOAT® please don't hesitate to send an inquiry.

 

To request a window, substrate, or any other component made of original SCHOTT BOROFLOAT® 33 borosilicate glass with individual dimensions please use the button below:

 

Request for Quotation

 

48h-Express Service for custom optics (Glass thicknesses available as part of the express service were marked in the thickness table on this website.)

 

Note: Further SCHOTT glass brands like MEMpax®, ultra-thin D263 T glass, AF 45, AF 32® eco, ultra-thin AS 87 eco, N-BK7, SUPREMAX®, DURAN®, and ZERODUR® transparent glass ceramic are part of our company's extensive product range.

 

Specifications

  

Transmission in the UV-VIS-IR range

SCHOTT BOROFLOAT® Glass, transmission curve UV-VIS-IR

UV-VIS-IR transmission of BOROFLOAT® borosilicate glass

UV-Transmission at 0,70 mm glass thickness

SCHOTT BOROFLOAT® Glass UV-transmission curve at 0,7mm thickness

Ultraviolet transmission of BOROFLOAT® at 0,70 mm thickness

UV-Transmission at 3,30 mm glass thickness

SCHOTT BOROFLOAT® Glass, UV-transmission curve at 3,3mm thickness

Ultraviolet transmission of BOROFLOAT® at 3,30 mm thickness


Transmittance of other thicknesses available on request.

Optical Properties

  • Abbe constant ve: 65,41
  • Dispersion nF - nC : 71,4 x 10-4
  • Stress optical coefficient K: 4,0 x 10-6 mm2 N-1

Index of Refraction of BOROFLOAT® glass

 

Wavelength (nm)

Refractive Index

ng
435,8
1,48015
nF'
479,9
1,47676
ne
546,1
1,47311
nd
587,6
1,47140
nD
589,3
1,47133
nC'
643,8
1,46953
nC
656,3
1,46916

Mechanical Properties

  • Density: 2,2 g/cm3 (25 °C)
  • Young's modulus E: 64 kN/mm2
    (according to DIN 13 316)
  • Poisson's ratio μ: 0,2 (according to DIN 13 316)
  • Shear modulus σ: 25 Mpa
    (according to DIN 52 292 T 1)
  • Knoop hardness HK0,1/20: 480
    (according to ISO 9385)

Thermal Properties

  • Coefficient of thermal expansion:
    3,25 x 10-6/K (20-300 °C) (according to ISO 7991)
  • Specific heat capacity cP: 0,83 kJ (kg x K)-1
  • Specific heat conductivity:
    1,2 W (m x K)-1 (90 °C)
  • Transformation temperature Tg: 525 °C
  • Viscosities:
    • Working Point (104 dPa): 1270 °C
    • Softening Point (107,6 dPa): 820 °C
    • Annealing Point (1013 dPa): 560 °C
    • Strain Point (1014,5 dPa): 518 °C
  • Maximum operating temperatures σmax :
    (only valid considering the following RTG and RTS values)
    • for short term load 500 °C (< 10 h)
    • for long term load 450 °C (≥ 10 h)
  • Resistance to thermal gradients (RTG):
    • 110 K (< 1 h)
    • 90 K (1-100 h)
    • 80 K (> 100 h)
      (Testing method description on request)
  • Resistance to thermal shock (RTS):
    • 175 K (at thickness ≤ 3,8 mm)
    • 160 K (at thickness = 5,0-5,5 mm)
    • 150 K (at thickness = 6,5-15,0 mm)
    • 125 K (at thickness > 15,0 mm)
      (Testing method description on request)

Chemical Properties

  • Hydrolytic resistance:
    • Class HGB 1
      (according to ISO 719 / DIN 12 111)
    • Class HGA 1
      (according to ISO 720)
  • Acid resistance:
    • Class 1 (according to ISO 1776 / DIN 12 116)
  • Alkali resistance:
    • Class A2 (according to ISO 695 / DIN 52 322)

Chemical Glass Composition

  • 81% SiO2
  • 13% B2O3
  • 4% Na20 / K2O
  • 2% Al2O3

Chemical Durability of Borofloat

Solution

Reaction time/
Temperature

Weight loss
(mg/cm2)

5 Vol.-% HCl
24 h at 95 °C
<0,01
0,02 n H2SO4
24 h at 95 °C
<0,01
H20
24 h at 95 °C
<0,01
5% NaOH
6 h at 95 °C
1,1
0,02 n NaOH
6 h at 95 °C
0,16
0,02 n Na2CO3
6 h at 95 °C
0,16
10% HF
20 min at 23 °C
1,1
10% NH4F x HF
20 min at 23 °C
0,14

Electrical Properties

  • Dielectric constant εr: 4,6 (1 MHz ; 25 °C)
  • Loss tangent (tan δ):
    37 x 10-4 (1 MHz ; 25 °C)
  • Logarithm of the electrical volume resistivity lgρ:
    • 8,0 Ω x cm (250 °C)
    • 6,5 Ω x cm (350 °C)

Standard Glass Thicknesses

(To request a quotation click on the thickness)

Thicknes
(mm)

Tolerance

48h- Express Service icon
0,70 ±0,05
0,70 ±0,07
1,10 ±0,05
1,10 ±0,10
1,75 ±0,20
2,00 ±0,05
2,25 ±0,20
2,75 ±0,10
2,75 ±0,20
3,30 ±0,20
3,80 ±0,20
5,00 ±0,20
5,50 ±0,20 -
6,50 ±0,20
7,50 ±0,30 -
8,00 ±0,30 -
9,00 ±0,30 -
11,0 ±0,30 -
13,0 ±0,50 -
15,0 ±0,50 -
16,0 ±0,50 -
17,0 ±0,50 -
18,0 ±0,50 -
19,0 ±0,50 -
21,0 ±0,70 -
25,4 ±1,00 -

The marked thicknesses () are available within our 48h–Express Service.

Please do not hesitate to contact us if you need additional specifications about SCHOTT BOROFLOAT® 33.

 

All given details and specifications are mean reference values and are not guaranteed. In addition please consider our "Notes on technical specifications"

 

BOROFLOAT® 33 is a trademark of SCHOTT.