The dielectric constant -or permittivity- of aluminium oxide is a very important property in electrolytic capacitors made from foil anodised with a thin and highly insulating barrier type oxide film.

In this section the features which determine this dielectric property are introduced.

Learning Outcomes for this Section

After completing this section, you should be able to:

• explain what a dielectric is
• formulate the capacitance of a dielectric film
• describe the parameters which determine the dielectric properties
• explain the phenomenon of dielectric loss
• calculate the capacitance of an aluminium oxide film of certain thickness
• describe electrolytic capacitors
• describe the aluminium pre-treatments used to produce capacitor foil