Dielektrikot

Dielektrikot, also called dielectric materials, are insulating substances that can be polarized by an applied electric field. When placed in a field, their internal charges shift slightly, creating an opposing field and enabling the storage of electrical energy. Dielektrikot are essential in capacitors, as insulating layers in cables, and as substrates in electronic devices.

Key properties include high electrical resistivity and low dc conductivity, a relative permittivity (dielectric constant) ε_r greater than 1, and an absolute permittivity ε = ε_r ε0. They also have a dielectric strength, which is the maximum electric field they can withstand before breakdown, and a dielectric loss described by the loss tangent tan δ. The values of ε_r and tan δ depend on frequency, temperature, and the strength of the applied field.

Polarization mechanisms in dielektrikot include electronic polarization, ionic polarization, and orientation of permanent dipoles. At higher frequencies, some mechanisms cannot respond quickly enough, causing ε_r to decrease and tan δ to change. Material behavior is further influenced by temperature; some materials exhibit strong changes in permittivity near phase transitions, such as ferroelectric ceramics.

Categories and examples include air and vacuum (very high dielectric strength, low ε_r), liquids (e.g., transformer oil), polymers (polyethylene, PTFE, polyimides), and ceramics (silica, alumina, barium titanate). Ferroelectric ceramics and certain polymers offer high ε_r for compact capacitors, while others prioritize low loss and high breakdown strength.

Applications and design considerations involve selecting dielektrikot for insulators, dielectric layers in capacitors, and microwave substrates. Design must account for breakdown voltage, operating frequency, temperature, humidity, aging, and material impurities that can affect performance.