Diffusion and Electrolytic Conduction in Crystals (Ionic Semiconductors)

In the present paper a mechanism of diffusion and electrolytic conduction in solids is discussed, which is based on a formal treatment given by Frenkel. It is assumed that in a crystal in thermal equilibrium some of the atoms or ions are removed from their normal positions in the lattice to irregular ones in the interlattice space. Then diffusion and electrolytic conduction is possible by two processes; first by migration of the ions in the interlattice space, second by migration of the vacant places. The number of ions in the interlattice space can be calculated. If one considers the influence of polarization the result agrees in the order of magnitude with the observed data. It is also shown that the activation energy connected with the processes of movement is of the correct order of magnitude. Thus a satisfactory explanation of the exponential factor occuring in the empirical conductivity (or diffusion) formula is obtained. The constant factor multiplying the exponential can be explained at once for one group of cases; for the other group, where the constants apparently are too high, a tentative explanation is proposed.