الفهرس 
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Abstract
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Summary ud Condusions
The present thesis includes, the preparation of composite materials for
F~03, Ah03 and polyesterurethane using 10 % LiF and 20 % uo
(mole %). Also, it deals with the study of the thermal stability and the
electrical properties: I-V characteristics, DC-, AC-conductivity, dielectric
constant and dielectric loss for the parent compounds and their composites.
The work carried out in this thesis has been presented in five main
chapters:
The first chapter, is the general introduction, which contains literature
survey about the investigated samples and the aim of work.
The second chapter, describes and explains the theoretical review and
the different .methods of calculation used for analyzing the results
(DC-, AC-conductivity, dielectric constant 6’ and dielectric loss 6”).
The third chapter, shows the experimental work which consists of:
(i)- The preparation methods of the investigated compounds including the
three parents (ferric oxide, aluminum oxide, and polyesterurethane ) and
their composites prepared by mixing with 10% LiF and 20% LiCl,
(mole %), separately.
(ii)- The techniques used in the investigation of the samples (pT-IR, TG and
DTA, as well as two probes DC- and AC-electrical measurements).
The fourth chapter deals with the characterization of the samples by
the instruments used and investigating their thermal stability and
I-V characteristics.
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In the fifth chapter, the results of DC and AC-conductivity, relative
permittivity e’ , and dielectric loss e” for the investigated samples at a wide
temperature range of 303-723 K for inorganic samples and 78-420 K for
organic samples and at a frequency range of 102_106 Hz were reported and
discussed.
The main conclusions ar.e the foUowing:
(1). All investigated substances did not show switching phenomenon at room
temperature using electric field up to 5000 Vtern, and the organic
samples obey Ohm’s law at a voltage up to 1000 V, while the values of
n in the 1- V- relation is higher than unity for the inorganic samples due
to the formation of space-charge limiting current.
(2). The DC-conductivity values obtained at -400 K and AC-conductivity at
300 K for inorganic samples were found to increase in the order:
Fe.zOJ<( Fe LiF 10) < ( Fe LiCI 20 )
And AI20J < (AI LiF 10 ) < ( AI LiCI 20 )
While for organic samples the order of increase is:
(po LiCI 20) <Polymer <(po LiF 10)
(3). The change in conductivity values was explained on the basis of the
change in the concentration of additive compounds, molecular
rearrangement, type of phases formed in the materials, as well as the
ionic radii of F- and cf ions.
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(4). UAC are higher than UDC for all samples, at any temperature, referring to
the presence of polarization effect. At the same time the AC-conductivity
increases with increasing the frequency due to the decrease in the barrier
effect with increasing frequency (i.e. hopping mechanism predominates in
the investigated samples). Although some other conduction mechanisms
were employed to explain the obtained results.
(5). The AC-conductivity showed a semimetallic behaviour at lower
temperatures for ferric oxide, polyesterurethane, and their composites.
Also the DC- and AC-conductivities showed a metallic behaviour at lower
temperatures for alumina and its composites.
(6). The DC- and AC-conductivities for all samples showed also
semiconducting and insulating behaviour at certain temperature ranges,
especially at higher temperatures, depending on their composition.
(7). There are many types of polarization in the investigated samples, the
most important of them is the ionic polarization.
(8). The values .of e’ are less ~40 for the pure ferric oxide, aluminum
oxide, and polyesterurethane at the whole temperature range
investigated, which refers to that these compounds behave as simple
dielectric materials especially at lower temperatures.
(9). While some compounds such as ( AI LiF 10 ), ( Po LiF 10 ), and
( Po LiCI 20 ) are simple dielectrics, other composites such as
( Fe LiF 10), and( AI LiCI 20 ) behave as ferroelectric materials and
have a relative permittivity values higher than 10000.
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(10). The breaks occurring in the electrical properties data with temperature,
for all samples, suggested the presence of some phase transitions in
the investigated samples.
(11). The investigated composites can be used in many electric applications,
especially in the form of ceramics, depending on the wide range of their
conductivity values, and encouraged by their economic prices.