The compensation law revisited-Application to dielectric aging

The fundamental origin of the compensation law observed by P. K. David (1987, 1988) and G. C. Montanari (1988) in several aging mechanisms of dielectrics is discussed. It is shown that this is due to a linear relation between activation entropy and enthalpy of a given process. An aging model, partially based on the rate theory, is presented. One of its advantages is that it characterizes dielectric aging by a free energy change, rather than by an apparent activation energy. Some aging data are analyzed with the proposed model, and it is shown that under high stresses the failure time varies exponentially with stress. Some critical comments are made regarding the use of arbitrary end points as a method of selection for a failure criterion