Journal of Babylon University/Pure and Applied Sciences/ No.(2)/ Vol.(21): 2013
Effect Of Addition Ferric Chloride (FeCl3 ) On
Electrical Conductivity Of Polystyrene
Raheem Al- Marshedy , Zaynab Al- Ramadhan
Babylon University, Faculty of Science
Hussein Al- khagani
University of Mstnasrah, College of Education
Abstract
In the present work , effect of addition ferric chloride (FeCl3) on some electrical properties of
polystyrene has been studied . for that purpose , many samples have been prepared by adding (FeCl3)
on the polystyrene by different weight percentages from (FeCl3) with polymer and with different
thickness . The experimental results showed that the D.C electrical conductivity increased with
increasing concentration of additional (FeCl3) and increasing of temperature . Also the activation
energy decreased with increasing of additional (FeCl3).
‫الخالصة‬
‫ ولرضذا الرضر‬. ‫الهررااييضة لللضولي سضتايري‬
‫الخضوا‬
‫) على بعض‬FeCl3( ‫في هذا البحث تم دراسة تأثير إضافة كلوريد الحديديك‬
‫أظرضضر‬.‫(ذضضا اللضضوليذر وبأسضضذاك ذختلفضه‬FeCl3) ‫وزايضضة ذختلفضضة ذض‬
‫ كذضا أ يضيم قايضة التا ضي تقض‬. ‫وزيضاد در ضة الحضرار‬
‫( إلضضى اللضضولي سضضتايري وااسض‬FeCl3( ‫لإضضضافة‬
‫تضضم تحضضضير اذضضاذ‬
‫ ( الذضضا‬FeCl3) ‫الاتضاي أ التويضيلية الهررااييضة الذسضتذر تضزداد لزيضاد تركيضز‬
. ‫(الذضا‬FeCl3 ( ‫لزياد تركيز‬
Introduction
Electrical conduction is the process of the transfer of electric charges through a
medium from one place to another under the influence of electric field. Electrical
conduction is based on two factors [F. Jon, 1980 ]:First: The type of charge carrier (n)
Charge carriers can be electrons, gaps, or ions automatically generated due to the
addition of impurities.Second: Mobility (µ) Mobility depends on temperature (T) and
the potential exerted (V).Polymers of special structure (alternating) have the
properties of semiconductors, whereas most commercial polymers are insulator.
Given that polymers are easily formed . Chemists and physician started mid the
twentieth century to conduct studies designed to develop conductor polymers
characterized by alternating double bonds [A.wegner, 1981].
In its stable state,
alternating polymers are insulators or semiconductors because it is easy for electrons
to transfer from one chain to another. These insulator polymers can be transformed
into conductors by adding small molecules that have certain properties among
polymer chains; these molecules are called Dopants, and the process of adding
impurities is called Doping. Dopants can operate as oxidizing or reducing agents.
Charge transfer complexes can be created between dopants and polymers that make
these polymers conductors[R.siegmar,1989]. Studies have focused on synthesizing
alternating polymers such as polyaniline and polyacetylene, etc. Shirakwa, a Japanese
scientist, was the first in this field. He synthesized polyacetylene as a thin film by
blowing acetylene on concentrated solution surface of Ziegler-Nata motivators
dissolved in inert solvents. Shirawkwa was the first chemist who synthesized
polyacetylene in this method. This method was the starting point to study many
important properties of polymers such as conductivity, molecular structure and other
physical properties[K.G.Neoh etal,1989]. Heeger was the first scientist who
approached the process of Doping in 1977. He synthesized polyacetylene in the same
previous method to obtain a film of polymer. Heeger observed that the conductivity of
polyacetylene was significantly increased when the polymer was treated with a strong
oxidizing or reducing agent such as Iodine, Bromine, Sodium Naphthalate and AsF5.
577
For instance, the conductivity of polyacetylene doped with Iodine was 2*10-2
(Ohm.cm) -1, whereas its conductivity without doping was 10-9 (Ohm.cm)-1
[J.A.Heeger,2001].
Experimental part
The materials which used in this paper is polystyrene as matrix and ferric chloride
(FeCl3) as a filler. The electronic balanced of accuracy 10-4 have been used to obtain a
weight amount of (FeCl3) powder and polymer powder .The weight percentages of
(FeCl3) are ( 0 , 5 , 10 ,15,20,25) wt% . Thickness ranged between (.031-.01) mm .
The Casting Method has been used for prepared of thin film.The resistivity was
measured over range of temperature from (20 to 90)oC using Keithly electrometer
type (616C) . The volume electrical conductivity
defined by [E. Al-Rabthi


,2006].



1


v
L
……………………(1)
RA
Where :
A = guard electrode effective area.
R = volume resistance (Ohm) .
L = average thickness of sample (cm) .
In this model the electrodes have circular area A= D2π/4 where D= 2.5 cm2.
Results and Discussion
Figure (1) shows electrical volume conductivity as a function of the concentration
of (FeCl3) at a temperature of (20oC) .From the figure we note that the electrical
conductivity is slightly increasing with increase the concentration of (FeCl3) . When
increasing the focus more than that, the electrical conductivity to a large increase to
the value 5.6×10-12 (Ohm.cm) -1 at the concentration of (FeCl3) (20 wt%) and an
increase in the concentration of (FeCl3), the conductivity reach to(5×10-10) (Ohm.cm)
-1
at the concentration (25wt%).The increase of conductivity with increasing of
concentration of (FeCl3) caused by the increase of the charge carriers ions in which
thy increased with increasing filler contact when the (FeCl3)
ions at low
concentrations are represented by small darker regions and become large when the
ferric chloride (FeCl3)content increases but when the concentration of (FeCl3)
reaches to (20wt%), the network will be connected to each other containing the
overlapping paths to allow the charge carriers to pass through, where the charge
carriers with routes through which the electrical resistance be less [ R. M. Mehra,2003
, X. J. He et.al,2005, N. K. Srivastava and S. Bhattacharya et.al,2008].
1.E-08
1.E-09
σ(Ω.cm)-1
1.E-10
1.E-11
1.E-12
1.E-13
1.E-14
1.E-15
1.E-16
0
5
10
15
20
25
30
con.FeCl3.wt%
Figure (1) variation of D.C electrical conductivity with(FeCl 3) wt%
concentration for (PS-FeCl3) composite at T=20 oC .
578
Journal of Babylon University/Pure and Applied Sciences/ No.(2)/ Vol.(21): 2013
Figure (2) shows the behavior of electrical volume conductivity of the composite
with the temperature. Note that the electrical conductivity increase with increasing
temperature that any of this material has positive thermal coefficient .The
interpretation of this is that the polymeric chains and (FeCl3) particles act as traps the
charge carriers which transited by hopping process. On increasing the temperature,
segments of the polymer being to move , releasing the trapped charges. The released
of trapped charges is intimately associated with molecular motion. The increase of
current with temperature is attributed to two main parameters , charge carriers and
mobility of these charges. The increase of temperature will increase the number of
charge carriers exponentially. The mobility depends on the structure and the
temperature [K.S. Majdi and H .J. Fadhal,1997 and Z.Al-Ramadhan,2008].
1.00E-08
pure
1.00E-09
5wt.%
10wt.%
σ(Ω.cm)-1
1.00E-10
15wt%
1.00E-11
20wt%
25wt%
1.00E-12
1.00E-13
1.00E-14
1.00E-15
20
30
40
50
60
70
80
90
100
T(C)
Figure(2) variation of D.C electrical conductivity with
temperature for (PS-FeCl3) composite
Figure (3) shows the relationship between the conductivity and inverted absolute
temperature of the (PS- FeCl3) composites . From the calculations the values to the
activation energy ranges between (0.589 - 0.939)eV for (PS- FeCl3) composites these
values are due to the presence of free ions in the commercial polymers and the
addition of low concentration of (FeCl3) reduced the activation energy values of all
samples of (PS- FeCl3) composites the result of the space charge effect in the
contact regions where the shipment in addition to the concentration of low-power
levels localized in the forbidden energy gap act as traps to charge carriers and charge
carriers were moving by hopping[M. Hamzah et.al ,2008] .
pure
-20
5wt%
-22
10wt%
lnσ(Ω.cm)-1
-24
15wt%
-26
20wt%
-28
25wt%
-30
-32
-34
-36
2.7
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
1000/T(k)-1
Figure(3) the relationship between ln(σ) and inverted absolute temperature
of the (PS- FeCl3) composites .
579
The concentration increasing of( FeCl3) leads to the lowering the activation
energy values , as shown in the figure (4) , it is clear that the mechanism of
conductivity in the samples at low filler concentration is hopping.
Eact(eV)
1.4
1.2
1
0.8
0.6
0.4
0
5
10
15
20
25
30
con .FeCl3.wt%
Figure (4)Variation of activation energy for D.C electrical conductivity with
FeCl3 wt.% concentration for (PS- FeCl3 ) composite
The low values of activation energy extends from (0.589-0.705) eV at higher
(FeCl3) concentration . The amount of interconnecting network is increased , this
enhance the conduction between FeCl3 particles and lead to decrease of the activation
energy[ M. S. Ahmed and A. M. Zihilif,1992].
Conclusions
1. The D.C electrical conductivity of the Ps increases with increasing of FeCl3
concentrations and temperature .
2. The activation energy of D.C electrical conductivity is decreases with increasing
the FeCl3 concentrations .
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