Creation of Charge Carriers in Nonpolar Liquids

We give a kinetic analysis of the mechanisms of charge carrier creation and of electrical conduction in liquids of low permittivity (er<5). Carriers are formed either in the bulk of the liquid or at the metal/liquid interface. We consider that creation of carriers in th6se liquids is a two-step process; the firs-t, ionic dipole-formation and the second, separation of these charges by the applied field. According to the kinetic rate constants involved in the steps, the number of free carriers is proportional either to kD, the kinetic constant of dissociation or to the kinetic constant of formation of the dipole. Only kD increases significantly with the field. Injection of charge carriers by a metallic electrode can be represented similarly by a two-step process, first creation of charge carriers at the metal/liquid interface, and then extraction of ions out of the image-force region. According to the values of the kinetic constants related to both steps, the injection current density increases quickly with the field or else saturates. This analysis of the charge carrier creation in a liquid is found to be in agreement with experimental investigations of both injection and bulk dissociation processes.