Effects of gradient of polarization on dielectric relaxation

We present a non-equilibrium thermodynamic model to describe diffusion effe cts in dielectric materials with spatial inhomogeneities in the polarizatio n vector and with local viscoelastic effects. The model presented here is a generalization of the Debye relaxation equation including inertial effect, and contributions from the spatial inhomogeneities of the polarization vec tor, together with a contribution from the antisymmetric stress tensor via the divergence operator. At the same time, a Maxwell viscoelastic-relaxatio n type equation for the antisymmetric stress tensor is proposed to describe the time evolution of this tensor. On the other hand, a generalized hydrod ynamics model for the dielectric memory for short wave length and high freq uencies is obtained, by considering the linearized complete set of differen tial equations of the model. By working in the Fourier-Laplace space, the d ielectric susceptibility is obtained and their main features are described and compared with pi and alpha dielectric relaxation. (C) 1999 Elsevier Sci ence B.V. All rights reserved.