Quantized relaxation of polarization

Whitehead1 reviewing early work quotes that Kohlraush as early as 1845 suggested the decay current formula i = a.t−n and surprisingly the physical reasons for this relationship still remain the subject of discussion. For electronic conductors, Walden2 and Wintle3 have provided extensive evidence that the discharge currents are mainly due to trapped space charge in the region around the electrodes. There are however many others who prefer the theory of Debye and its extension by Cole that for polar dielectrics the decay of current with time is caused by the relaxation of polarization mechanisms having a wide range of distributed activation energies. Jonscher4 suggests that the discharge can be usually explained by a small number of processes of different and specific activation energies. Das Gupta and Joyner,5 in a recent review which also included decay current measurements on polypropylene films, suggested that the relaxation of charge formed during the charging period is responsible for the effects observed at room temperature and that the contribution of the dipole relaxation is small. However Adamec and Calderwood6 concluded from extensive studies of non-polar polymers that at room temperature and at low fields the depolarization current is due to the relaxation of polarization within the bulk of the dielectric.