The effect of inhomogeneities in particle distribution on the dielectric properties of composite films

Abstract

A practical approach for the modelling of the dielectric constants of thin composite films is presented. A general distribution function for composition fluctuations in the thin composite films is introduced to describe the transition from a non-percolative to a percolative morphology using physically meaningful parameters and is applied to model a wide range of experimental and simulated polymer–ceramic composite film behaviour from the literature, up to ceramic particle filler volume fractions of 75%. The parameters describing the morphologies of the various composites are used to predict effective dielectric properties with good accuracy. The model is applied further to composites that show early percolation behaviour, and the deviation of their effective dielectric behaviour from the standard effective medium theory at high filler volume fractions is discussed.

Dielectric relaxation studies of low thermal expansion polymer composites

“…Such decreasing trend has been reported in few other systems consisting of polymer : ferroelectric filler composites. 14,43 But, satisfactory explanation for this observation remains elusive. It is also important to mention that there are a few other mixing rules/models for studying binary systems which have been recently proposed by Yamada et al and Jayasundere and Smith.…”

Predicting effective permittivity of composites containing conductive inclusions at microwave frequencies

“…2 As we observed, this approach can be challenging for large electrical contrasts, leading us to investigate semi-empirical techniques. [3][4][5][6][7][8] The most common such technique is the generalized EMT (GEMT) developed by McLachlan. [5][6][7] The GEMT modifies the MG relationship by introducing two fitting parameters, s and t, to obtain…”

Manufacture of electrical and magnetic graded and anisotropic materials for novel manipulations of microwaves

“…A range of expressions—or ‘mixing laws’—are available to predict composite effective permittivity and permeability of films and bulk materials from the individual component properties and their fractions, as described in [ 23 ], with the logarithmic Lichtenecker mixing law the most widely applied for composite permittivity ε ′ c : where V m and V f are the matrix and filler volume fraction, and ε ′ m and ε ′ f are the real permittivity of matrix and filler. Comparison with experimental data shows mixing laws such as Lichtenecker or Bruggeman [ 5 ] generally approximate well to composite properties for minority filler additions, but significant deviations can occur where there is significant agglomeration [ 25 ] or where the filler has a high aspect ratio [ 24 ].…”