E. Tuncer et al., Dielectric relaxation in dielectric mixtures: Application of the finite element method and its comparison with dielectric mixture formulas, J APPL PHYS, 89(12), 2001, pp. 8092-8100
In this article, the frequency dependent dielectric properties, epsilon(ome
ga), of an "ideal" binary composite structure were investigated by using th
e finite element method in the frequency domain. The material properties of
the phases, i.e., dielectric permittivity, epsilon, and direct-current con
ductivity, sigma, were assumed to be frequency independent. Moreover, the i
nclusion phase was more conductive than the matrix phase. The inclusions we
re infinitely long unidirectional cylinders which could be assumed to be ha
rd disks in two dimensions in the direction perpendicular to the cylinder d
irection. Three different inclusion concentration levels were considered, e
.g., low, intermediate, and high. The calculated dielectric relaxations wer
e compared with those of the dielectric mixture formulas in the literature
and it was found that there were no significant differences between the for
mulas and the numerical solutions at low inclusion concentration. Furthermo
re, the obtained responses were curve fitted by the addition of the Cole-Co
le empirical expression and the ohmic losses by using a complex nonlinear l
east squares algorithm in order to explain the plausible physical origin of
the Cole-Cole type dielectric relaxation. The dielectric relaxations were
Debye-like when the concentration of the inclusions were low. For intermedi
ate and high concentrations, the responses obtained from the numerical simu
lations deviated from that of the Debye one, whose curve fittings with the
Cole-Cole empirical expression were inadequate. (C) 2001 American Institute
of Physics.