Constant phase element

In electronics, a constant phase element is an equivalent [electrical circuit] component that models the behaviour of a double layer, that is, an imperfect capacitor.
Constant phase elements are also used in equivalent circuit modeling and data fitting of electrochemical impedance spectroscopy data.
A constant phase element also currently appears in modeling the imperfect dielectrics' behavior. The generalization in the fields of imperfect electrical resistances, capacitances, and inductances leads to the general "phasance" concept: http://fr.scribd.com/doc/71923015/The-Phasance-Concept

General equation

The electrical impedance can be calculated:
where the CPE admittance is: and Q₀ and n are frequency independent.
Q₀ = 1/|Z| at ω = 1 rad/s
The constant phase is always −°, with n from 0 to 1. The case n = 1 describes an ideal capacitor while the case n = 0 describes a pure resistor.