Mobile communications masts against a dark sky

Specialty Glass for High-Frequency Applications

The world is increasingly run using high-frequency applications. Whether it’s high speed data transfer or a pan-global conference call, the demand for telecoms equipment operating at maximum efficiency with consistent performance rises every day. An emerging material for the communications equipment is specialty glass, which offers low dielectric loss in combination with a broad range of dielectric constants for minimal scattering and high precision processing in µm range. In a rapidly developing industry, glass answers every challenge.

Game-changing properties

The requirements for materials in the high frequency market are very challenging and complex. Due to the shift towards higher and higher frequency bands, the dielectric properties and processing precision become extremely important. Consequently, the typically used materials like polymers and ceramics are subjected to a constant material development process. SCHOTT has a broad portfolio of glasses that are suitable for high-frequency applications, with the ideal combination of properties for this demanding area. 

The high purity/homogeneity of glass results in almost zero density fluctuations. In contrast, ceramics dielectrics have pores from sintering leading to density variations with local shifts in DK (dielectrical constant) value. The resulting natural frequency cannot be met precisely enough to reliable met the desired frequency from the device. Moreover, our glassportfolio offers a broad range of dielectrical properties (dielectric constant and loss tan values) which can be combined with certain CTE (coefficient of linear thermal expansion) levels for an individual product design. Unlike polymers, which have a high surface roughness, glass is supremely smooth with root mean square values (RMS) of 1 nm and below. This enables metallization and smooth metal coatings with ideal electrical performance of metal layers with low energy losses due to absence of scattering. Another important parameter at high frequencies is the processing precision. In contrast to polymers and ceramics, glass can be processed in the µm range what enables specified frequency characteristics. Various shapes like rods, discs and tubing are available on request. Low temperature coefficients together with exceptional heat resistance (0 - 950 Kelvin) also make them suitable for a range of environments – even space.

The ideal antenna material

One of the most exciting areas of telecoms is 5G. This new generation of mobile communication requires a global network of high-frequency antennas made of highly efficient and specialized materials. These materials require specific physical properties to withstand the harshest environments, including space.

Discover how specialty SCHOTT glass leads to low dielectric loss and improved communications performance.

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The shape of things to come

For efficient wavelength detection, the latest high-frequency antennas are made using components with accurate and complex shapes. For many materials, this can present a problem, but glass has the ability to be precisely processed in a vast range of forms to suit highly specific shapes. Taken with its superior physical properties, this gives the material a huge advantage in the communications industry.

Specialty Glass for High-Frequency Applications

The best glass for the job

We compared the relative permittivity and dielectric loss factor of SCHOTT 8252 glass to DURAN® glass tubing and found the following results. While DURAN® glass tubing shows a lower dielectric constant, SCHOTT 8252 shows a lower dielectric loss. Therefore, which glass you use depends on the requirements of your application.

High Precision Dielectric Characterisation (ɛ, tan(δ)) at 1.1, 1.9, 5, 10 and 15 GHz Microwave Frequency

f0 [GHz] Relative permittivity
ɛ (±0.1)
 Loss factor
tan(δ) (±0.0001)

DURAN® SCHOTT 8252 DURAN® SCHOTT 8252
 1.1  4.4  6.0  0.0042  0.0026
 1.9  4.5  6.1  0.0045  0.0029
 5  4.4  6.0  0.0054  0.0038
 10  4.4  6.1  0.0061  0.0046
 15  4.4  6.1  0.0068  0.0052


Testing method

  • Split Post Dielectric Resonator (SPDR) at 25° C

Wall thickness samples

  • 1.1 GHz, 1.9 GHz: ca. 1 mm
  • 5 GHz, 10 GHz, 15 GHz: ca. 0.5 mm

 

DURAN® is a registered trademark of DWK Life Sciences GmbH.

 

Additional material properties of suitable glass types*

 
Glass types Coefficient of mean linear thermal expansion α (20°C; 300°C) (ISO 7991) [10-6 K-1] Dielectric loss factor tan δ [10-4] at 1 MHz Dielectric constant ε Transformation temperature Tg   (ISO 7884-8)
8360 9.1 24 7.3 465
8245 5.1 80 5.7 505
8250 5.1 22 4.9 490
8253 4.7 15 6.6 790
8252 4.6 11 6.1 720
DURAN® 3.3  37 4.6 525

*Excerpt of our glass portfolio, more information on request

 

The ideal properties for high-frequency applications

Smooth surface
Smooth surface
Surface roughness with RMS of max. 1 nm resulting in minimal scattering on the interface between the glass and metallization, resulting in low loss of energy.
Dielectric properties
Dielectric properties
Low dielectric loss enables highly efficient designs with minimal energy loss in costly HF radiation, and a broad range of dielectric constants is accessible.
High homogeneity
High homogeneity
The accurate processing and material quality of our glass results in high homogeneity, which enables consistent dielectric properties compared to ceramics.
High precision processing
High precision processing
Various shapes can be processed, such as tubes, rods and discs. Due to µm precision tolerance levels, a significant reduction in frequency shifts is possible.

Browse the portfolio

by dielectric constant Ɛr and / or dielectric loss tan δ
Glass Tubing Explorer

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

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Dr. Christoph Bäumler
Dr. Christoph Bäumler

Product Manager Technical Tubing