Technical ceramics
Versatile electrical properties
Technical ceramics play a crucial role in many industrial applications, including those that require electrical performance and insulation with corresponding reliability. In this section, we provide an overview of the diverse electrical properties of this high-performance material, which plays an important role in areas such as electronics, power generation and other key industries.
Electrical insulation
Ceramic materials are primarily known in electrical engineering as insulating materials, i.e. materials that do not conduct electrical current. Some examples of products that utilise the insulating properties of high-performance ceramics are X-ray anodes and cathodes, as well as tubes for magnetic-inductive flow meters. Ceramic insulators are also used in mobile phones, printed circuit boards and other electronic components. Ceramic housings provide advanced hermetic sealing and electrical insulation between the electrical conductors to ensure the high reliability of these electronic components.
Conductivity
Although technical ceramics are generally insulating materials, certain ceramics can also be used as conductors or semiconductors due to their electrical functionality. Semiconductor ceramics can conduct electricity depending on the temperature and voltage applied.
A thermistor is an electronic component that utilises the property that electrical resistance decreases with increasing temperature, allowing current to flow more easily when the material becomes hot. These components are used in sensors that monitor temperature changes and in devices that are designed to prevent electronics from overheating.
A varistor has the property that the resistance decreases as the electrical voltage increases. Varistors are often made of zirconia and installed in parallel with other sensitive components to protect them from voltage peaks.
Dielectricity
The permittivity (dielectric constant) describes the polarisation capacity of a material due to electric fields. It is a measure of how strongly a material "allows" electric fields.
Dielectricity is measured using the relative dielectric constant. The relative dielectric constant is the ratio between the dielectric constant of the material in question in a vacuum . The dielectric constant of quartz is 3.8, while that of sapphire (main component: oxidised aluminium) is 9.4. The dielectric constant of barium titanate, a ferroelectric material, is 4,000 to 5,000.
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Piezoelectricity
As already mentioned, not all ceramics are pure insulators. Some ceramics are piezoelectric. Probably the best-known piezoelectric material is lead zirconate titanate (PZT). Lead (Pb), zirconium (Zr) and titanium (Ti) are combined with additives to achieve the desired performance. The piezoelectric effect describes the dependence of mechanical pressure and electrical voltage in a solid. In the piezo effect, charges appear on the surface when the material is mechanically deformed (for example in lighters). In the inverse piezo effect, the materials deform when an electric field is applied (tip in atomic force microscopes). These effects can be used to register and generate the smallest changes in length or electrical voltages.