, and [epsilon]' = dielectric permittivity.
The complex capacitance (C in Farads) is composed of a real capacitance (C in Farads) and an imaginary capacitance or dissipation (Din Farads) and related to the real and imaginary components of the complex permittivity
Figure 5a and b shows the real and imaginary pans of relative complex permittivity
measured at 303 K (Fig.
ASTM Standard D 5568-95, Standard test method for measuring relative complex permittivity
and magnetic permeability for solid materials at microwave frequencies, in Annual Book of ASTM Standards, Vol.
where go is the complex permittivity
of the free space.
Therefore, the complex permittivity
parameters of real ([epsilon]') and imaginary ([epsilon]") parts of the PCN thin films were studied.
The complex permittivity
was converted to the complex dielectric modulus M*(f) according to an equation described in the literature (30).
Dielectric characteristics involving the frequency dependence of the real part (dielectric constant,[epsilon]') and imaginary part of the complex permittivity
(dielectric loss, [epsilon]") in the frequency range of 1 MHz-3 GHz were determined with an Radio Frequency (RF) Impedance Analyzer (Agilent E4991A, USA) using capacitive method (on a dielectric material test fixture which comes furnished with the device).
Figure 8 presents the dependence of real and imaginary parts of complex permittivity
on frequency, for samples PI-0, PI-10, PI-20, and PI-30, at three chosen temperatures, in the second scan of measurements.
The increase of the real part of complex permittivity
can thus chiefly be attributed to dielectric relaxation and the space charge polarization effect, whereas the increase of the imaginary part of complex permittivity
can be assigned to the improved electrical conductivity of the composites.
For a two-phase, concentrated suspension system with spherical particles dispersed in a continuous medium, the complex permittivity
can be expressed using the Bruggeman-Hanai equation (14):
Lee investigated the complex permittivity
spectra and conductivity of graphite nanosheet/epoxy composites at the microwave range (41).