Optical Glass picture, 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)
  • 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
  • High chemical resistivity against strong acids,
    bases and organic substances
  • Relatively low alkali content in the glass composition
  • Low specific weight
  • Good scratch and abrasion resistance
  • High elasticity and mechanical strength
  • Excellent flatness obtained by a special
    micro-float process

Typical Applications

  • Windows for high operating temperatures
  • Glass wafers for anodic bonding processes
  • Flat glass substrates for dielectric coatings
  • Components for lighting systems
  • Front windows for high power floodlights
  • Substrates for optical filters
  • Medical and biotechnology applications
  • Photovoltaic glass
  • Sight glass windows
  • Base glass for industrial optics
  • Laboratory glass
  • Components for environmental technology
  • Chemically resistant microscope slides
  • Glass for harsh environments
  • Neutron absorbers
  • Packaging for opto-electronics
  • Measurement and sensor technology

BOROFLOAT® is a high-quality temperature-resistant borosilicate glass, which can be used permanently at temperatures up to 450 °C. Short-term (< 10 h) it even resists temperatures up to 500 °C. The SCHOTT glass has a low thermal coefficient of expansion similar to the one of silicon. This often allows glass-wafers made of BOROFLOAT® to be used in anodic bonding applications. The glass has almost the same thermal expansion and nearly the same specific weight as PYREX® and it nowadays is often used to replace PYREX® borosilicate glass , which has been discontinued many years ago.

BOROFLOAT® is a clear-transparent, glass material that offers a very high and steady optical transmission. Resulting from a special micro-float manufacturing process, developed by SCHOTT, BOROFLOAT® features an excellent flatness, surface quality, low micro roughness and 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 optics, optoelectronics, photonics, analytics and in lighting technology. BOROFLOAT® has a low self-fluorescence over a broad light spectrum.

 

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

 

BOROFLOAT® has practically the same glass composition as the laboratory glass DURAN®, also made by SCHOTT. Hence 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 bases dissolve only small amounts of ions from the borosilicate glass, so that test results are not impaired, as it is often the case when ordinary soda-lime glass is used. These properties allows the use BOROFLOAT® in interesting applications of medical engineering and in analytics.

But also the mechanical characteristics of BOROFLOAT® surpass the ones of soda-lime glass and 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 raw material for optical coatings, front surface mirrors, optical filters, optical windows, optical substrates, glass wafers and many other plane optics. It has proven to be an excellent and economical choice for many technical glass applications, particularly at high operating temperatures and is as well perfectly suited for lighting applications.

 

To request windows, substrates or any other components made of original SCHOTT BOROFLOAT® 33 borosilicate glass with individual dimensions, please use the button below:

 

Request for Quotation

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48-h Express Service available

(Glass thicknesses available as part of the express service were marked in the thickness table on this website.)

 

Note: Further SCHOTT glass materials like MEMpax®, ultra-thin D263 T glass, AF 45, AF 32® eco, ultra-thin AS 87 eco, N-BK7, SUPREMAX, DURAN® and ZERODUR® glass ceramic are part of the extensive delivery program of our company.
BOROFLOAT® 33 is a trademark of SCHOTT.

 

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

UV-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

UV-transmission of BOROFLOAT® at 3,30 mm thickness

 

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

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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.

 

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