^{1}

^{*}

^{2}

^{1}

^{1}

In the paper, the results of investigations of temperature and frequency dependences of dielectric permeability and dielectric loss of compositions LDPE + xvol%Bi_{2}Te_{3} are stated. The investigations were carried out at frequency 10 – 10^{5} Hz and temperature 20°C - 150°C intervals, respectively. It was revealed that increase of percentage of the filler Bi_{2}Te_{3} in the matrix, reduces to increase of dielectric permeability and dielectric loss of composites LDPE + xvol%Bi_{2}Te_{3} in connection with the change reducing to Maxwell-Wagner’s volume polarization and emergence of comparative strong inner field in semiconductor clusters.

Creation of composite materials is one of the basic directions in development of new prospective materials. Filling of polymers reduces to changes in characteristics of supramolecular structuration and in density of packaging as solid high-dispersive fillers may serve as builders of nucleus of crystals or their imperfections [

Recently, in place of a filler semi-conductor compounds are frequently used, and the materials of scientific- practical interest have already been obtained [

In the present paper, we give the results of investigations of dielectric properties of composite materials based on lower density polyethylene (LDPE) filled with semiconductor compound Bi_{2}Te_{3}.

Composition samples were obtained by mechanical mixing of powder Bi_{2}Te_{3} with powder of LDPE in a porcelain motor. The mixing is continued up to receiving homogeneous mixture. The mixture some time is maintained at melting temperature of polymer under pressure 5 MPa. At the same temperature, by pressing the homogeneous mixture, the pressure slowly increases to 15 MPa. At this pressure, the sample is maintained within 5 minutes, and then is cooled in water. Herewith the sizes of the samples are: the thickness is about 80 - 120 mkm, diameter of the obtained samples 35 mm. In order to provide reliable electric contact between the samples and electrodes made of the stainless steel, the electrodes made of a thin aluminum foil of 7 mkm in thickness pressed on both working faces of the samples, are used.

Dielectric permeability and dielectric loss of LDPE + xvol%Bi_{2}Te_{3} were measured in the range of 296 - 520 K at linear growth of temperature with velocity 2.5 degree/min and in frequency range 1 by the technique described in the paper [

The reliable electric contact of electrodes made of stainless steel of diameter 15 mm was provided by using pressed electrodes made of aluminum foil of 7 mkm in thickness. The value of electric capacitance (C) and tangent of dielectric loss angle

where, C is the measured electrical capacitance of the sample, F; electrical constant ε_{0} = 8.85 ´ 10^{−12} F/m; d―thickness of the sample, m; S―area of the sample. In experiments, frequency of the given electric field changed from 10^{2} to 10^{6} Hz, and temperature range 20˚C - 140˚C. Measuring voltage amplitude is 1 B. The temperature was determined by means of a standard thermocouple copper-constantan.

Temperature dependences of dielectric permeability and dielectric losses of composite materials LDPE + xvol%Bi_{2}Te_{3} at temperature range 20˚C - 160˚C were studied. The results of investigations are given in Figures 1-4. As it follows from _{2}Te_{3} in the investigated temperature range in

For the composite 10 vol%Bi_{2}Te_{3} in all temperature range, the dielectric permeability remains constant. With increasing the content of Bi_{2}Te_{3} to 15 vol%, on temperature dependence of dielectric permeability weak maxima at 70˚C and 140˚C, minimum for 100˚C were revealed. Temperature dependences of dielectric loss of composites LDPE + xvol%Bi_{2}Te_{3} were also studied. The investigations were carried out in temperature interval 20˚C - 150˚C. The results are given in _{2}Te_{3} on the curve of _{2}Te_{3} the curve smoothies out and maxima disappear. However, also for this composite _{2}Te_{3} the

The results of investigation of frequency dependence of dielectric permeability of composites LDPE + xvol%Bi_{2}Te_{3} are given in ^{3} Hz, the dielectric permeability slightly decreases, and with further increase of frequency to 10^{6} Hz remains practically constant. With increasing volumetric content of the filled,

The results of investigations of frequency dependence of dielectric loss of composites LDPE + xvol%Bi_{2}Te_{3} are reduced in ^{3} - 10^{5} Hz the typical is that dielectric loss increases, while in the range 10^{5} - 10^{6} Hz decreases. Dispersions in

Thus, the analysis of the obtained results shows that with increasing the volumetric content of the filler Bi_{2}Te_{3} dielectric permeability and dielectric loss increase. Apparently this is connected with the fact that increase of the volumetric content of the Bi_{2}Te_{3} filler reduces to growth of the number of particles Bi_{2}Te_{3} per cross sections of the composite, and this is equivalent to the part of Bi_{2}Te_{3} in the general thickness of sample. The clusters closed with each other in the sample’s thickness may be considered as pure resistance included between electrodes. Since Bi_{2}Te_{3} has high conductivity compared with LDPE, we can assume that the composite’s resistance will be especially determined between the particles Bi_{2}Te_{3} on the boundaries of clusters (the clusters are surrounded with PE layers with small

By researches of temperature and frequency characteristics of dielectric permeability and dielectric loss of composites PELD + xvol%Bi_{2}Te_{3}, it was revealed that with a variation of the volume maintenance of a filler, temperature and frequency, it is possible to receive composites with the demanded dielectric parameters.

E. M.Gojayev,A. Y.Ismailova,S. I.Mammadova,G. S.Djafarova, (2016) Temperature-Frequency Characteristics of Dielectric Properties of Compositions LDPE + xvol%Bi_{2}Te_{3}. Open Journal of Organic Polymer Materials,06,25-29. doi: 10.4236/ojopm.2016.61003