Technical Details of 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.

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®

Material properties of B 270® Thin

B 270® products

Material properties of B 270®

1. Optical properties

Optical Properties	Value
Refractive index* n_g	1.5341
Refractive index* n_F'	1.5297
Refractive index* n_F	1.5292
Refractive index* n_e	1.5251 ± 0.001
Refractive index* n_d	1.5230
Refractive index* n_D	1.5229
Refractive index* n_C'	1.5207
Refractive index* n_C	1.5203
Abbe value ν_e	58.3 ± 0.6
Photoelastic constant in (nm/cm)/Mpa	27.5

2. Thermal properties

General thermal properties	Unit	Value
Mean specific heat capacity c_p	in J/(g·K) (20 °C ; 100 °C)	0.8
Transformation temperature T_g	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	4
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

Spectral transmittance 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
λ_c (τ = 0.46)	310
λ_S ( τ = 0.05)	293
λ_P ( 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	τ_vD65 in %	τ_vA in %
2.0	91.7	91.7

UV - transmittance at thickness in mm	τ_UVA in %	τ_UVB in %
2.0	84	19

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

Solar direct transmittance at thickness	τ_e in %
2.0	91.6

7. Colorimetry

Chromaticity coordinates* at thickness 2.0 mm	Value
D₆₅	x = 0.313
D₆₅	y = 0.329
A	x = 0.448
A	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* n_g	1.5341
Refractive index* n_F'	1.5297
Refractive index* n_F	1.5292
Refractive index* n_e	1.5251 ± 0.001
Refractive index* n_d	1.5230
Refractive index* n_D	1.5229
Refractive index* n_C'	1.5207
Refractive index* n_C	1.5203
Abbe valueν_e	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 c_p	in J/(g·K) (20 °C ; 100 °C)	0.8
Transformation temperature T_g	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 ρ_D 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 t_{k 100} in °C	Value
at 108 Ω · cm	272

6. Transmittance values

Spectral transmittance 250 - 3050 nm

Spectral Transmittance: 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	τ_vD65in %	τ_vA 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.

Want to know more? Let’s talk

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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Technical Details of B 270®

Market-leading transmittance and thickness range

High transmittance from UV-A to NIR

Homogenous refractive index

Flexibility of thickness

High surface and geometrical quality

Material properties of B 270®

Material properties of B 270® Thin

B 270® products

Want to know more? Let’s talk

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