Optics made of Borofloat
 
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BOROFLOAT® 33

Thermally and chemically resistant

borosilicate glass from SCHOTT

Special Properties

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

Typical Applications

  • Optics for increased operating temperatures
  • Medical and biotechnology applications
  • Glass wafer for anodic bonding processes
  • Flat glass substrate for dielectric coating systems
  • Components for lighting systems
  • Front glass for high power floodlights
  • Substrate for optical filters
  • Photo-voltaic applications
  • Sight glass window
  • Fiber optic applications
  • Glass cover for sensors
  • Base glass for industrial optics
  • Laboratory glass equipment
  • Glass components for environmental technology
  • Microscope slide for chemical analyses or medical use
  • Glass for harsh environments
  • Neutron absorbers
  • Glass packaging for 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 heat-resistant borosilicate glass which can be used permanently at temperatures up to 450 °C. In the short term (< 10 h) the glass withstands temperatures of up to 500 °C. It has a low coefficient of expansion close to that of silicon. This allows to use glass-wafers made of SCHOTT BOROFLOAT® for anodic bonding applications. The glass has an almost identical thermal expansion and density as PYREX® borosilicate glass. It is therefore often used today as a replacement material for PYREX® glass which was discontinued 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, it is characterized by excellent evenness and surface quality, a low micro roughness, as well as a high homogeneity. For a flat glass, BOROFLOAT® 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. In many cases it can be used as a substrate material for coated filters, mirrors or other optics, without the requirement of expensive additional mechanical polishing processes. BOROFLOAT® glass 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, the glass 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. BOROFLOAT® exceeds the chemical strength of many other glass materials and even of most metals. Acids and alkalis can only dissolve small amounts of ions from BOROFLOAT® glass. Therefore, the measurement results are not falsified, as is often the case when conventional soda-lime float glass is used. In many cases these special properties enable the use of BOROFLOAT® in medical technology and analytics applications.

But also the mechanical properties of this borosilicate glass exceed those of soda-lime glass and even most other borosilicate glass materials. For example, the abrasion resistance of BOROFLOAT® significantly surpasses the one of simple soda-lime float glass.

BOROFLOAT® flat glass is an ideal substrate material for coated optics like front surface coated mirrors, optical filters, anti-reflection coatings, or laser optics etc., and an excellent choice for the production of window optics, substrates, glass wafers, and other plane optics. It has proven to be a perfect economical choice for many glass applications particularly at increased operating temperatures. It is also well suited for lighting technology and for numerous applications in electronics. In case you have any additional queries about BOROFLOAT® please do not hesitate to contact us.

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 are marked in the thickness table on this website.)

 

Note: Further SCHOTT glass products like the brand glasses MEMpax®, ultrathin 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 glass delivery range. Please follow the links or contact us for further information about these SCHOTT glass products.

 

Specifications

  

UV-VIS-IR range

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

UV-VIS-IR transparency of BOROFLOAT® borosilicate glass

UV-range at 0,70 mm glass thickness

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

Ultraviolet transparency of BOROFLOAT® at 0,70 mm thickness

UV-range at 3,30 mm glass thickness

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

Ultraviolet transparency 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

 

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

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)

Thickness
(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 glass thicknesses () are available within our 48h–Express Service.

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

 

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

 

BOROFLOAT® 33 is a registered trademark of SCHOTT.