Optical Glass picture, Borofloat
 
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BOROFLOAT® 33
Borosilicate Glass

Special Properties

  • High temperature load capacity:
    - up to 450°C permanent load
    - up to 500°C temporarily (< 10h)
  • Low thermal coefficient of expansion
  • Thermal coefficient matches silicon
    (anodic bonding)
  • High thermal shock resistance
  • Clear practically colorless appearance
  • Low fluorescence
  • High UV-Transmission
  • High chemical resistance against acids,
    bases and organic substances
  • Low alkali content in the glass composition
  • Low specific weight

Typical Applications

  • Substrates for dielectric coatings
  • Lighting applications
  • Optical filter coating substrates
  • Wafer substrates
  • Biotechnology
  • Photovoltaics
  • Environmental Technology
  • Harsh Environments
  • Neutron absorbers
  • Measurement and Sensor-Technology
Borofloat window
Fig.: CNC-manufactured, temperature resistant window made of BOROFLOAT glass. Parts like this optical window for a micro reactor are economically made of borosilicate glass.

BOROFLOAT® glass has an excellent optical quality. Resulting from a special micro-float manufacturing process, BOROFLOAT offers a good flatness and surface quality. BOROFLOAT 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 resistance of most metals and many other materials. The borosilicate glass is an ideal substrate for dielectric coatings and has shown to be a good choice for many different technical glass applications, particularly at high operating temperatures. BOROFLOAT® 33 is a registered trademark of SCHOTT.


To request windows or substrates made of BOROFLOAT® glass with your individual dimensions, please click the button below:


Specifications of BOROFLOAT®

 

Optical Properties

Index of Refraction of Borofloat

Title

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
    (acc. to DIN 13 316)
  • Poisson's ratio μ: 0,2 (acc. to. DIN 13 316)
  • Shear modulus σ: 25 Mpa (acc. to. DIN 52 292 T 1)
  • Knoop hardness HK0,1/20: 480 (acc. to. ISO 9385)

Thermal Properties

  • Coefficient of thermal expansion:
    3,25 x 10-6/K (20-300°C) (acc. 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 of Borofloat borosilicate glass:
    • 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 if the following RTG and RTS values
    are considered)
    • for short term load 500°C (< 10 h)
    • for long term load 450°C (≥ 10 h)
  • Resistance to thermal gradients (RTG):
    • 110K (< 1h)
    • 90K (1-100h)
    • 80K (> 100h)
      (Testing method description on request)
  • Resistance to thermal shock (RTS):
    • 175K (at thickness ≤ 3,8mm)
    • 160K (at thickness = 5,0-5,5mm)
    • 150K (at thickness = 6,5-15,0mm)
    • 125K (at thickness > 15,0mm)
      (Testing method description on request)

Chemical Properties

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

Chemical Durability of Borofloat

Solution

Reaction time/
Temperature

Weight loss
(mg/cm2)
5 Vol.% HCl
24h at 95°C
<0,01
0,02 n H2SO4
24h at 95°C
<0,01
H20
24h at 95°C
<0,01
5% NaOH
6h at 95°C
1,1
0,02 n NaOH
6h at 95°C
0,16
0,02 n Na2CO3
6h at 95°C
0,16
10% HF
20min at 23°C
1,1
10% NH4F x HF
20min 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 Thicknesses

Thickness

Tolerance

Thickness

Tolerance
0,70mm ±0,1 7,5mm ±0,3
1,10mm ±0,1 8,0mm ±0,3
1,75mm ±0,2 9,0mm ±0,3
2,00mm ±0,2 13,0mm ±0,3
2,25mm ±0,2 15,0mm ±0,3
2,75mm ±0,2 16,0mm ±0,5
3,30mm ±0,2 17,0mm ±0,5
5,00mm ±0,2 18,0mm ±0,5
5,50mm ±0,2 19,0mm ±0,5
6,50mm ±0,2 21,0mm ±0,7

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