Mica Capacitors have the naturally occurring mineral mica as their dielectric. Mica is transparent and, due to its layered structure, can be split into thin mica flakes with thicknesses of a few micrometers. It is acid, alkali and temperature resistant up to several hundred degrees and has a permittivity of 7.
In mica capacitors, the mica platelets are about 20 µm thin, they are vaporized with silver and form an electrode. Thinner mica platelets with thicknesses of 1 m or 2 µm have lower dielectric strength, but can be stacked to form compact multilayer mica capacitors with relatively high capacitance values. Mica capacitors can be used at operating temperatures up to 150 °C and have a high dielectric strength of 1,000 V and more. Their service life at 100 °C is given as `10^7` hours, and their capacitance constancy is 0.3 % over 10,000 hours.
Mica capacitors are used because of their low dissipation factors and high stability in broadcasting technology, in measurement standards, in filters and oscillating circuits. Their capacitance values reach far into the micro- farad range.