B 270®

B 270® is an enduringly popular material thanks to strong technical credentials such as excellent optical performance and high quality geometrical and surface properties. SCHOTT customers also benefit from a unique flexibility in terms of design and thickness, covering a wide variety of requirements.

Market-leading transmittance and thickness range

High transmittance from UV-A to NIR

The consistently strong level of transmittance achieved by B 270® ranges all the way from UV-A up to NIR regardless of glass thickness, with no characteristic loss in the VIS range. Under standardized light D65, the luminous transmittance of B 270® can reach an outstanding 91.9 %.

Homogenous refractive index

Combined by SCHOTT’s state-of-the-art manufacturing process, the top-quality raw materials that make up B 270® enable tightly controlled tolerance levels for the refractive index (with an accuracy of ± 0.001), regardless of glass thickness.

Flexibility of thickness

B 270® and B 270® Thin are available in a wide range of stock thicknesses to suit a customer’s individual need, from 10 mm down to 0.3 mm. If you require a different thickness, many other sizes can be manufactured on request.

High surface and geometrical quality

SCHOTT’s industry-leading manufacturing techniques ensure that B 270® offers highly impressive geometrical properties. All available thicknesses are produced with a fire-polished surface and homogenous geometry, ensuring consistent performance regardless of application.

Material properties of B 270®

1. Optical properties

Optical Properties Value
Refractive index* ng 1.5341
Refractive index* nF' 1.5297
Refractive index* nF 1.5292
Refractive index* ne 1.5251 ± 0.001
Refractive index* nd 1.5230
Refractive index* nD 1.5229
Refractive index* nC'  1.5207
Refractive index* nC 1.5203
Abbe value νe 58.3 ± 0.6
Photoelastic constant in (nm/cm)/Mpa 27.5

 

2. Thermal properties

General thermal properties Unit Value
Mean specific heat capacity cp  in J/(g·K) (20 °C ; 100 °C) 0.8
Transformation temperature Tg   in °C 542


"Coefficient of thermal Expansion (CTE) α in 10-6·K-1 (static measurement)"

Degree Value
(20 °C; 300 °C) 9.4
(20 °C; 200 °C)  9.0 
(20 °C; 100 °C)  8.6
 

"Coefficient of thermal Expansion (CTE) α in 10-6·K-1 (dynamic measurement)"

Degree Value
(20 °C; 100 °C) 8.6
(20 °C; 150 °C)  8.8 
(20 °C; 200 °C) 9.0 
(20 °C; 250 °C)  9.2 
(20 °C; 300 °C)  9.4 
(20 °C; 350 °C)  9.6 
(20 °C; 400 °C)  9.7 
(20 °C; 450 °C)  9.9 

 

Viscosities Viscosity lg ŋ in dPas  Temperature in °C
Strain point 14.5  507 
Annealing point  13.0  535 
Softening point  7.6  711 

Fuseability:
Fusing with SCHOTT ARTISTA® glasstypes using an adapted temperature / time programme results in a technically stressfree compound with a maximum stress birefringence of 70 nm/cm.

 

3. Mechanical properties

 
Mechanical Properties
Unit  Value 
Density ρ in g/cm³ 2.56
Young's modulus E  in kN/mm²  71.1 
Poisson's ratio µ    0.22 
Torsion modulus G  in kN/mm²  29 
Knoop hardness  HK 0.1/20  500 
Vickers hardness  HV 0.2/25  510 

 

Chemical toughening (for thickness = 2.0 mm)

Unit
Value 
Temperature ϑ in °C  410 
Time t in h 
Compressive stress (CS) in MPa  441 
Depth of layer (DoL) in µm  11 

 

Thermal Toughening
Thermal toughening of B 270® is possible

 

4. Chemical properties

Hydrolytic resistance (acc. to DIN ISO 719) Value
Class  HGB 3 
Equivalent of alkali per gram glass grains in µg/g 136

 

Acid resistance (acc. to DIN 12116) Value
Class S 2
Half surface weight loss after 6 hours in mg/dm² 0.7

 

Alkali resistance (acc. to DIN ISO 695) Value
Class A 1
Surface weight loss after 3 hours in mg/dm² 71

 

5. Electrical properties

Dielectric constant εr (at ϑ =  25 °C) Value 
at 1 MHz  7.5
at 1 GHz  6.7 
at 2 GHz   6.8 
at 5 GHz  6.7 
at 24 GHz  6.6 

 

Dissipation factor tan δ  (at ϑ =  25 °C)
Value
at 1 MHz 32 · 10-4
at 1 GHz 59 · 10-4
at 2 GHz 66 · 10-4
at 5 GHz 84 · 10-4
at 24 GHz 150 · 10-4

 

Electric volume resistivity ρD  in Ω·cm (at 50 Hz)
6.1 · 107  ( ϑ = 250 °C)
1.6 · 106  (ϑ = 350 °C)  

6. Transmittance values

 

Spectral transmittance 250 - 3200 nm

Graph showing the spectral transmittance of SCHOTT B 270® (250-3200 nm)

 

Spectral transmittance 250 - 450 nm

Graph showing the spectral transmittance of SCHOTT B 270® (250 -450 nm)

Wavelength in nm at thickness 2.0 mm: τ (λ) in % 
254  < 0.1 
380  90.8 
632.8  91.9 
1064  91.8 

 

Edge wavelength at 2 mm thickness Wavelength in nm
λc  (τ = 0.46) 310
λS ( τ = 0.05)  293
λP ( τ = 0.85)  338 

 

Solarization* after UV-radiation at 2 mm thickness Δ λc in nm 
Shifting of the UV edge wavelength λc (τ = 0.46) in the direction of longer wavelength < 2

 

*Measuring and Test Procedures

The sample will be irradiated with a UV - F 400 flood lamp.
The irradiation time amounts to 7h; the distance between flood lamp and sample fastening is 14 cm.

 

Luminous transmittance at thickness in mm τvD65 in % τvA in %
2.0 91.7 91.7

 

UV - transmittance at thickness in mm τUVA in % τUVB in % 
2.0 84 19 

 

IR – transmittance  at thickness in mm τA in %
2.0 91.9

 

Solar direct transmittance at thickness τe in %
2.0 91.6

 

7. Colorimetry

Chromaticity coordinates* at thickness 2.0 mm Value
D65 x = 0.313
D65  y = 0.329 
x = 0.448 
y = 0.408 

 

General color rendering index Ra at thickness in mm Value
2.0 100

* Chromaticity coordinates (color locus) are referred to the named Standard Illuminant according to CIE (2°-Observer)

 

Material properties of B 270® Thin

1. Optical 

Optical properties Value
Refractive index* ng 1.5341
Refractive index* nF' 1.5297
Refractive index* nF 1.5292
Refractive index* ne 1.5251 ± 0.001
Refractive index* nd 1.5230
Refractive index* nD 1.5229
Refractive index* nC' 1.5207
Refractive index* nC 1.5203
Abbe valueνe 58.3 ± 0.6
Photoelastic constant in (nm/cm)/Mpa 28.6

* Refractive indices:
  Pretreatment of samples. Condition as supplied ["as drawn"] 

 

2. Thermal

General thermal properties Unit Value
CTE (Coefficient of thermal expansion) α    10-6·K-1 (20 °C; 300 °C)  9.4
Mean specific heat capacity cp in J/(g·K) (20 °C ; 100 °C) 0.8
Transformation temperature Tg in °C 536

 

Viscosities Viscosity lg ŋ in dPas Temperature in °C
Strain point 14.5 505
Annealing point 13.0 535
Softening point 7.6 723

3. Mechanical

Mechanical properties
Unit Value
Densityρ in g/cm³ 2.56
Young's modulus E in kN/mm² 69.8
Poisson's ratio µ 0.25
Torsion modulus G in kN/mm² 28
Knoop hardness HK 0.1/20 480
Vickers hardness HV 0.2/25 520

 

Chemical toughening (for thickness = 0.3 mm)

Unit Value
Temperatureϑin °C 410
Time t in h 4
Compressive stress (CS) in MPa 331
Depth of layer (DoL) in µm 16

  

4. Chemical

Hydrolytic resistance (acc. to DIN ISO 719) Value
Class HGB 3
Equivalent of alkali per gram glass grains in µg/g 170

 

Acid resistance (acc. to DIN 12116) Value
Class S 2
Half surface weight loss after 6 hours in mg/dm² 1.0

 

Alkali resistance (acc. to DIN ISO 695) Value
Class A 2
Surface weight loss after 3 hours in mg/dm² 80

 

5. Electrical 

Dielectric constant εr (at ϑ= 25 °C) Value
at 1 MHz 7.2
at 1 GHz 6.8
at 2 GHz
6.8
at 5 GHz 6.7
at 24 GHz
6.8
at 77 GHz  6.5

 

Dissipation factor tanδ (atϑ= 25 °C)
Value
at 1 MHz 32 · 10-4
at 1 GHz 59 · 10-4
at 2 GHz

66 · 10-4

at 5 GHz 84 · 10-4
at 24 GHz 150 · 10-4
at 77 GHz 230 · 10-4

 

Conductivity σ in S/cm for direct current  Value
at 25 °C  5 · 10-16
at 250 °C  4 · 10-9
at 350 °C   2 · 10-7

 

Electric volume resistivity ρD in Ω·cm for alternating current 50 Hz Value 
at 25 °C  8.6 · 1011
at 250 °C  2.4 · 108
at 350 °C   5.8 · 106

 

Temperature tk 100 in °C  Value
at 108 Ω · cm  272

 

6. Transmittance values

 

Spectral transmittance 250 - 3050 nm

Graph showing the spectral transmittance of SCHOTT B 270® Thin (250 - 3050 nm)

Spectral Transmittance: 250 - 450 nm

Graph showing the spectral transmittance of SCHOTT B 270® Thin (250 - 450 nm)

 

Wavelength in nm at thickness 0.3 mm: τ(λ) in %
254 < 0.1
380 91.3
632.8 92.0
1064 92.2

 

Edge wavelength λc (τ  = 0.46) at thickness in mm Wavelength in nm
0.3 287
0.9 299

 

Luminous transmittance at thickness in mm τvD65 in % τvA in %
0.3 91.9 91.9
0.9  91.6 91.7 

B 270® products

SCHOTT B 270® is available as:

  • Sheets
  • Cut-to-size substrates
  • Polished substrates and wafers

SCHOTT B 270® Thin is available as:

  • Cut-to-size substrates
  • Unpolished substrates and wafers

 

To find out more, please see the related products on the overview page.

 

 

 

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Whether you need more information, samples, a quote, or advice for a project, we would be delighted to talk to you.

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