Electrolytic capacitors

A brief survey is given of aluminium and tantalum electrolytic capacitors. The fundamental behaviour of the dielectrics are discussed particularly with reference to the temperature coefficient of capacitance. It is shown, however, that the fundamental properties are masked by the presence of electrolyte, used to heal the dielectric film during use and to connect to the dielectric when it is deposited in the etched channels that can be formed in both aluminium and tantalum foils. The practical preparation of both etched aluminium and tantalum foil and also sintered tantalum capacitors are discussed. Scanning electron micrographs are used to illustrate the structures obtained.