Electrochemical impedance in ac diagnosticsof weakly conducting media
LIONS, NIMBE, CEA, CNRS, Université Paris-Saclay, CEA Saclay, Gif-sur-Yvette 91191, France
N. F. Gamaleya Federal Research Centre of Epidemiology and Microbiology, Moscow 123098, Russia
Institute of Solid State Physics, Chernogolovka, Moscow District 142432, Russia
Received March 1, 2021, published online May 26, 2021
Impedance ac diagnostics is regularly used to study the transport phenomena in conducting systems of differrent dimensionalities. A common reason for using ac methods that are more complex than dc methods is the pos-sibility to exclude the influence on the current-voltage (I–V) characteristic of contact phenomena accompanying dc measurements. In some cases (2d electron systems over helium) dc transport measurements are impossible. In weakly doped semiconductors (diluted electrolytes), the situation is less critical, but problems with the ohmic properties of the conducting contacts remain. The analysis of the details of the formalism that determines the reaction of a conducting medium to an external disturbance depends largely on the form of Ohm’s law for a conductor introduced into the impedance circuit. If there is a reason to define this law by the formula j=σE, where j, σ, E correspond to local values of current density, conductivity, and transport electric field, the structure of complex resistance ẐF(ω) is considered as a force one. If there is a diffusion component in Ohm’s law then the structure of complex resistance Ẑμ(ω) is considered as an electrochemical one. We describe a standard electrolytic capacitor in series RC with a step load in terms of force or complex electrochemical impedance. Comparison with experiment shows the electrochemical structure of the complex resistance.
Key words:  transport phenomena, current density, conductivity, electrochemical impedance, Ohm’s law.