On the Theory of Mixed Conduction with Special Reference to Conduction in Silver Sulfide Group Semiconductors

A macroscopic theory of mixed conduction–partly electronic and partly ionic conduction–is developed with special reference to the conduction in silver sulfide group semiconductors. Current equations combined with continuity equation give an equation which can be reduced to a diffusion equation under simplifying assumptions. It can be integrated with ease under boundary conditions which are prescribed by the nature of electrodes employed. General expressions for potential distributions arc derived. Two kinds of potentials are distinguished. One is the potential as measured by the use of probes consisting of electronic conductor, and the other as measured by the use of probes consisting of ionic conductor such as silver iodide for silver sulfide. The former reveals the relative electrochemical potential of electrons and the latter that of ions. Calculated time variations of potential distributions for formation and decay processes of stationary polarizations are compared with experiments for Ag 1.93 Te at 161°C showing satisfactory agreements.