Sunteți pe pagina 1din 35



A dissertation submitted in partial fulfillment


Under the Academic Autonomy



Under the supervision of

Prof.Simanchal Panigrahi

May 2012


This is to certify that the thesis entitled , “Synthesis and Characterization of Polymer-

Ferroelectric composite” submitted by Miss Rosalin Beura in the part of fulfillment for the

requirement for the award of Master of Science Degree in Physics department at National

Institute of Technology , Rourkela is an authentic work carried out by her under my supervision

and guidance .

To the best of my knowledge the matter embodied in this project has not been submitted by any

other university /Institute for the degree.

Rourkela Prof .Simanchal Panigrahi

Date: Department of Physics

National Institute of Technology

Rourkela -769008
Declaration of the candidate

I hereby declare that the project work entitled “Synthesis and characterization of Polymer-

Ferromagnetic composite” is an authentic work carried by me, during the one year project at

NIT, Rourkela, form July 2011-May2012 under the supervision of Prof.Simanchal Panigrahi and

is being submitted by for the partial fulfillment of the requirement for award of degree of Master

of Science in physics to NIT, Rourkela .This has not been submitted anywhere else for the award

of any other degree.

Date: Rosalin Beura


Before presenting my work I would first like to thank all those people who have been very kind
enough to extend their helping hand in completing this project work.

First of all I would thank the institute for giving me an opportunity to be a part of it where I
could gain knowledge and a lot of experience in the field of physics.

I extend my sincere thanks to my guide Prof. Simanchal Panigrahi for initiating me to this field
of work. It was a great opportunity to work under his guidance throughout this 1 yr. His vast
knowledge source helped me in enriching my knowledge power.

I thank Dr.Siddharth Jena , Professor and Head of the department for his help at various
necessary steps.

I thank Dr.Tanmaya Badapanda for guiding me to do this project and helping me at certain steps
while doing my project .

I owe my heartfelt gratitude to PhD. Scholar V.Senthil for his all-time support and guidance at
each and every step of my project work. Without his help it would have been very difficult to
complete the work. His deep and clear knowledge in this filed proved to be very fruitful. Thank
You sir for the support and help.

I extend my sincere thanks to research scholar Rakesh sir, Priyambada Didi, Jashashree didi and
other Ph.D scholars for their unhesitating help.

I thank the Department of ceramic engineering & Department of Metallurgical and Material
science for providing all facilities to carry out XRD and SEM.

I thank all my dear classmates for their help and support at various steps.

Last but not the least I express my gratefulness to my parents without whose blessings and moral
support the journey would have become very difficult.

Rosalin Beura

Materials existing in nature can be generally classified into four basic categories i.e.
metals, plastics, ceramics, composites. Composites are generally materials made by the
combination of two or more materials each having different physical and chemical properties.
Polymer ferroelectric composite is a composite of polymer and added ferroelectric ceramic.
Ferroelectric materials have a wide range of application because of its high dielectric
permittivity. But it has poor mechanical strength and lower break down strength, which can be
compensated by the polymer which is the matrix. In addition their properties can be tuned for the
requirement by changing the properties of the constituents. Because this is an upcoming field
much work is needed to understand the behavior thoroughly so that can be effectively used for
various applications.

Here we prepare the composite of the polymer polyvinyl alcohol (PVA) with the
ferroelectric ceramic BaZr0.1Ti0.9O3. BZT powder were prepared by solid state reaction route and
preliminary X-ray analysis for BaZr0.1Ti0.9O3 was done which resulted the formation of single
phase compound in cubic crystal system .Then the polymer composite of ferroelectric compound
was prepared using polyvinyl alcohol as the polymer matrix. The SEM micrograph shows that
the BZT particle distribution is homogenous with no porous matrix .The detailed study of
dielectric and impedance properties of the material in a wide range of temperature (50-1500C)
and frequency (102-106Hz) showed that these properties are highly temperature and frequency
List of Figures

Chapter Page No

Chapter 1-Introduction
1.1 Dielectric & Insulator 1
1.2 Piezoelectricity 1-2
1.3 Pyroelectricity 2-3
1.4 Ferroelectricity 4-5
1.5 Basics of ferroelectric in crystal 5-6
1.6 Perovskite structure 6-7
1.7 Poly Vinyl Alcohol (PVA) 7
1.8 Polymer- Ferroelectric composite 7-8
1.9 Motivation 8-9
1.10 Objective 9

Chapter 2-Experimental Techniques and Synthesis Process

2.1 Different experimental Techniques 10-11

2.2 Synthesis of Ferroelectric ceramic 11-12

2.3 Synthesis of Polymer composite 12-13

2.4 Characterization techniques 13-15

Chapter 3 –Result and Disscussion

3.1 XRD analysis 16

3.2 SEM analysis 16-17

3.3 Dielectric study 18-25

Chapter 4 – Conclusion 26

References 27-28
List of Figures
Fig.1-Ferroelectric Hysteresis loop

Fig-2 -Various polarizations

Fig.3- A cubic ABO3, perovskite type unit cell

Fig.4- XRD of BaZr0.1Ti0.9O3 ceramic

Fig.5- SEM Micrograph of hot pressed polymer composite (BaZr0.1Ti0.9O3) at

magnification x1500

Fig. 6- Frequency dependence of εr of polymer ceramic composite at various


Fig. 7- Frequency dependence of tanδ of polymer ceramic composite at various


Fig. 8 - Cole-Cole plot

Fig. 9 - Imaginary part of impedance vs frequency

Fig. 10- AC conductivity vs angular frequency

1.1. Dielectric & Insulators
The word dielectric is derived from the prefix dia, originally means through or across. Thus
dielectric is referred to as material that permits the passage of the electric field. Unlike
semiconductors, the energy gap is little higher so that thermally generated charge carriers are
generally absent. So at room temperature this material behaves as an insulator. In the presence
of electric field charge does not flow through the dielectric material as in a conductor but only
slightly shift from their average equilibrium positions causes polarization. The charge centre
shifts according to the fields causes various type of polarization such as 1-electronic
polarization, 2- ionic polarization, 3- orientational/dipolar polarization, and 4- space charge
polarization. This polarization gives a very attractive property which is characterized by
dielectric constant. When subjected to external mechanical stress, thermal variation various
dielectric phenomena such as piezoelectricity, pyroelectricity and ferroelectricity appeared
which are exploited for various applications in capacitors, actuators, transducers, sensors
memory applications etc.

An insulator also called as dielectric is a material that resists the flow of electric
charge. Here valence electron are tightly bonded to their atoms .Dielectric materials with high
dielectric constants are considered insulator.

The study of dielectric properties is concerned with the storage and dissipation of
electric and magnetic energy in materials .This explains various phenomena in electronics,
optics & solid state physics. Dielectric are used to store the electric charges while insulators
are used to block the flow of electric charges .All dielectric are insulators but all insulators are
not dielectric because they can‟t store charges like dielectric .

1.2. Piezoelectricity
Piezoelectricity is the property of charge separation in certain material in
response to the applied mechanical stress. As a result a voltage developed across the surface
of the material. This effect is understood as the linear electrochemical interaction between

mechanical and electrical state in crystal material with no inversion of symmetry. This is
termed as direct piezoelectric effect. The piezoelectric effect is a reversible process in i.e.
when the material is subjected to any external voltage, the material get strained. This is known
as reverse piezoelectric effect. The materials possessing non-centro symmetric structure are
come under the class of piezoelectric materials.

P=dF (direct effect)



d =piezoelectric coefficient

For converse effect



E=Electric field

Piezoelectric properties are dependent on the orientation direction, so they must be described
in terms of tensor

Pi=Σ dij Fj (direct effect)

Sj=Σ dji Ei (i=1,2,3 j=1,2,3,4,5,6)

(indirect piezoelectric effect)

Piezoelectric effect have so many application like they can be used as transducer, actuator,

1.3. Pyroelectricity

Some crystals with non centro-symmetric structure having unique polar axis are
characterized by spontaneous polarization. When such types of material are subjected to
thermal treatment, the dipoles align accordingly. This property is referred as pyroelectricity.

There are 10 pyroelectric crystal classes among 21 non–centro symmetric crystal groups.

Pyroelectricity is the ability of certain materials to generate a temporary voltage when they
are cooled or heated. The change in the temperature modifies the position of atoms slightly
within the crystal structure such that the polarization of the material changes.


∆Ps=spontaneous polarization

П=Pyroelectric coeffectient

∆T=change in temperature

This shows that spontaneous polarization depends upon temperature.

1.4. Ferro electricity

It is the property of certain materials characterized by a spontaneous electric
polarization which can be reversed with the application of external electric field. The non
centro symmetric nature of structural unit is the basic necessity for creating spontaneous
polarization. The reversibility of spontaneous polarization with applied field gives a
hysteresis loop which is analogous to ferromagnetism and is responsible for such naming.
Ferrroelectricity[6] was discovered in 1920 in Rochelle salt (Potassium sodium tartaret,
KNaC4H4O6.H2O) by Valasek. Thus the prefix ferro meaning iron was used to describe the
property despite the fact that ferroelectric materials do not contain iron .The crystal exhibiting
ferroelectricity are called ferroelectric crystal.

The most distinctive characteristic of ferroelectricity is the hysteresis loop i.e.
polarization versus electric field curve. A net spontaneous polarization exists even at zero
electric field and the loop disappears at the Curie temp Tc where the material undergoes phase
transition from high temperature par electric state to low temperature ferroelectric state. All
ferroelectric materials have a transition temperature called Curie point (Tc) above which the
crystal does not exhibits ferroelectricity and below it is ferroelectric .For more than one
ferroelectric phase the temperature at which the crystal transforms from one ferroelectric
phase to another is called the transition temperature.

This temperature dependence of dielectric above curie point in ferroelectric crystal is

governed by the Curie –Weiss law =
(T  TC )

Fig-2 Various types of polarization

1.5. Basics of ferroelectric in Crystal

Solid material can be described as:

1. Amorphous-The atoms are arranged in random way similar to the disorder we find in –glass

2. Crystalline –The atoms are arrange in a regular pattern with a smallest volume element
called unit cell that is repeated in 3D to describe the crystal.

32 crystal classes

11 centro symmetry 21 non centro symmetry

20 piezoelectric 1 non- piezoelectric

10 pyroelectric

if Ps is reversed -Ferroelectric

Ferroelectric structures are of four types:

1. Perovskite structure

2. Bismuth layer structure

3. Tungsten Bronze structure

4. Pyrochlore structure

1.6. Pervoskite Structure

Any material with the same crystal structure as calcium titanium oxide (CaTiO3)
known as perovskite structure. Perovskite take their name from this compound which was
first discovered in Ural mountain of Russia & is named after the mineralogist L.A.Perovskite .

The general Perovskite formula is ABX3 , where „A‟ & ‟B‟ are two cations of different sizes
and „X‟ is an anion that bonds with the both .The „A‟ atom is larger in size than the „B‟
atoms. Pervokite structure is adopted by many oxides that have the chemical formula

(ABO3). In ideal cubic unit cell of such a compound type „A‟atoms sits at cube corner
positions (0, 0, 0) type „B‟ atoms sits at center position (1/2,1/2,1/2) and oxygen atom sits at
face centered position ,(1/2,1/2,0).

B atoms have higher charge than A atom (B:Ti4+,Zr4+,Sn4+,Nd5+,Ta5+,W6+ etc,

A:Na+,K+,Ca2+,Ba2+,Pb2+ etc).

Fig.3 A cubic ABO3, perovskite type unit cell

Barium Titanate (BaTiO3)

Barium Titanate is one of the most used ferroelectric in the electronic industry
finding extensive applications as dielectric material in multilayer ceramic capacitors
(MLCCs), piezoelectric actuator, embedded capacitance in printed circuit boards, positive
temperature coefficient of resistivity sensors. BaTiO3 is an inorganic compound and a
ferroelectric ceramic.

One of theBaTiO3 solid solution, BaZxTi1-xO3 [8] is one of the most important
composition used as dielectric in MLCCs. The presence of Zr in BaTiO3 unit cell results in a
strong increase in permittivity.

At the same time the temperature characteristic is smoothened due to the

broadening of the permittivity temperature dependence .The dielectric data of
BaZrxTi1-xO3 (BZT) ceramic suggest that

a normal ferroelectric behaviour for 0<x<0.1

diffused phase transition 0.1<x<0.2

relaxor characteristic 0.2<x<0.5

The degree of diffuses of the ferro –para phase transition increases with Zr addition .For
x>0.5 it is no more ferroelectric.

Recently discovered piezoelectric system based BZT is an addition to the potential for lead
free materials .The composition lying near the morphotropic phase boundary offers
comparable piezoelectric properties to other high performance lead based system.

1.7. PVA (Polyvinyl alcohol)

PVA [1,4,5] is water soluble non toxic & odorless synthetic polymer. It is made
using vinyl acetate monomer by subjecting it to polymerization and partial hydrolysis.
Usually prepared by dissolving it in water & letting the water evaporate to form transparent
film with exceptional strength and resistance to tearing. Its solubility depends upon its degree
of hydrolysis molecular wt. and tendency to hydrogen bond. It dissolves only in hot water. It
has excellent adhesive property, inheritantly resistant to organic solvent, oil and grease .Its
density ranges from 1.19to 1.31g/cm3.In large amount it can be dangerous to environment
,especially if its mixed with H2O & comes in contact with fish .It is non toxic as long as it is
not burned or melted with fire. The advantages of PVA such as high mechanical strength, and
water soluble has played as a main role for this selection as compared to other polymer

1.8. Polymer-Ferroelectric Composite

Materials are broadly classified into four main categories i.e. metals, plastics,
ceramics and composites. Composites are generally artificial or naturally occurring materials
that are made from the combination of two or more constituents having different physical and
chemical properties. The composite materials are heterogeneous in nature.

None of materials existing in nature have all the properties that are required for
various purposes. So in order to meet the demand for the required material the composite of

materials is prepared. Fabrication of composite material is nothing but the combination of two
or more different material properties that often cannot be in single phase material.

Polymer composite [2] is composite made from polymer along with other kinds of material.

Polymer + ceramic = Polymer composite

Polymer has some merits like good mechanical property, easy to synthesize, low
acoustic impedance and high dielectric breakdown strength and demerit is low dielectric
constant. Similarly ceramic have poor mechanical properties, highly brittle, acoustic
impedance and high dielectric constant and lower breakdown strength.

In order to achieve such an objective high dielectric constant ferroelectric ceramic

such as BT, PZT, BZT, etc have been used as filler in polymer. These materials possess
superior physical properties such as enhanced mechanical strength & improved electric

1.9. Motivation
Dielectric materials with high dielectric constants are required for the reduction in
the dimension of electric devices and in particular in wireless communication product such as
cellular telephone & most important application is used for stress relief in high voltage
electrical supply .Dielectric materials have employed throughout the electrical industry as
insulators and capacitors .The properties of packaging materials significantly influence the
performance of high speed microelectronic devices. Electrical characteristic such as signal
attenuation, propagation velocity etc are influenced by dielectric properties of the package
substrate. Materials having low dielectric constant minimize capacitance coupling and reduce
signal delay. Materials with low dielectric loss reduces signal attenuation .Optimization of
both properties is critical to provide superior high frequency device performance.[23]

In the recent years the need for efficient transient energy storage has motivated
research for better material capable of accumulating large amount of charge per unit volume
when compared to state of the art technology .The energy density is governed by its dielectric
strength and permittivity. So either a new high permittivity polymer chemistry has to be
developed or composite approach has to be better understand or adopted. Recent investigation

indicates these polymer ceramic material may improve only permittivity at the expense of the
breakdown strength.[15-19]

Polymer[11] based microelectronic encapsulation materials are generally

comprised of micron scale inorganic particulate mixed with thermosetting polymer matrix.
Claussius & Mossotti performed some of the earliest work in the dielectric properties of
composite materials .They have derived individually a mean field theory for the disorder
system of polarizing sphere .Vo and Shi described the theoretical model to describe the effect
of this interphase region on the bulk dielectric constant of polymer composite material.

Polymer composite with high dielectric constant have attracted much attention
because of their flexibility and their ability to be easily fabricated into various shapes.
Polythene has high dielectric very less electrical conductivity and is a kind of outstanding
insulation for wires and cable application .But however its use is restricted for electrical stress
control in cable termination .PVA is a water soluble nontoxic polymer. The advantages of
PVA such as high mechanical strength ,and water soluble has played as a main role for this
selection as compared to other polymer matrices .the polymer phase lower the density and
permittivity and increase the elastic compliance of the composite .

The rapid advancement in electronic device need for a ceramic with tunable
dielectric constant & low loss at microwave frequency .Ferroelectric material possess
significant texability i.e change of dielectric constant on application of electric field. One of
theBaTiO3 solid solution, BaZxTi1-xO3 is one of the most important compositions used as
dielectric in MLCCs. The presence of Zr in BaTiO3 unit cell results in a strong increase in
permittivity. Hence we make a composite of BZT and PVA and study its characteristic.

 To synthesis the ferroelectric material BaZr0.1Ti0.9O3 by solid state method
 To synthesis the polymer composite of the synthesized ferroelectric material with Poly
Vinyl Alcohol
 To characterize the polymer composite by SEM for surface morphology, dielectric
study for electrical properties.


2. Experimental technique
In this chapter detailed study of synthesis of the ceramic ferroelectric (BaZr0.1Ti0.9O3) powder,
polymer composite ferroelectric materials and the experimental techniques employed to
characterize the specimen are briefly discussed.

2.1. Different experimental Techniques

1. Ball mill

A ball mill[7] , a type of grinder is a cylindrical device used to grind

materials into extremely fine powders for the use in mineral dressing processes, paints
,pyrotechnics& ceramics .It rotates around a horizontal axis partially filled with the material
to be ground plus grinding medium (here acetone).Different materials are used as media like
ceramic balls ,filth pebbles & stainless steel balls(here zirconium balls ).An internal cascading
effect reduces the material to fine powder .One more type of ball milling is planetary ball mill
which are smaller ones and are generally used for grinding sample to smaller size in
laboratories. It consists of one jar arranged eccentrically at the center of the so called sun
wheel. The difference in speed between the balls and grinding jars produce an interaction
between frictional and impact force with release of high dynamic energies. The interaction
between these forces produces the high & very effective degree of size reduction of planetary
ball mill.

2. Calcination

Calcination is a thermal process applied to ores and other solid materials in order
.Calcination normally takes place at temperature below m.p of the product material
.Calcination is to be distinguished from roasting in which more complex gas –solid reaction
takes place between furnace atmosphere & the solid. During calcinations intra diffusion of
ions of the constituents takes place .Greater is the calcinations temperature greater is the
homogeneity of the final product.

3. Hot press

Most of the times it is not possible to obtain a low porosity body by pressure less
sintering sintering in atmospheric pressure .It may prove difficult to combine the
complete elimination of porosity with the maintenance of small crystal size .These problems
are usually overcome by hot pressing i.e. by sintering under pressure between punches in a die
. The pressure provides the major part of driving force eliminating porosity & temperature can
be kept at a level at which crystal growth is minimized.

Synthesis of ferroelectric ceramic RAW MATERIAL

BaCO3 ZrO2 TiO2








The BZT ceramic was prepared by solid state reaction method by taking high purity raw
materials such as i)Barium Carbonate (BaCO3)

ii)Zirconium dioxide (ZrO2)

iii)Titanium dioxide (TiO2)

The constituents of the required specimen were taken in stoichiometric ratio .Mixing is
accomplished by using agate mortar & pestle .Then the ceramic were ball milled for 10 hrs for
proper mixing of powder in acetone medium with zirconium balls .After drying the mixed
powder were kept in programmable furnace for 6 hrs followed by grinding for phase
formation & removal of volatile fraction.

2.2. Synthesis of polymer composite (PVA-BaZr0.1Ti0.9O3)

Density of PVA is 1.31g/cm3 and density of BaTiO3 – 6.01g/cm3.Ceramic i.e.
BZT was added to the polymer (PVA) by volume percentage i.e. 10%, 20%, 30%, 40%, 50%.
Calculation was done for 1% BaTiO3.Since the Zirconium percentage was very less so the
composite was prepared with barium titanate.

1% BaTiO3=6.01/100=0.0601g

Hence accordingly for 10%, 20%, 30%, 40%, 50% it was calculated to be 0.601g, 1.201g,
1.803g, 2.404g, and 3.005g respectively.

For preparation of polymer composite (PVA-BZT) in ratio 90/10, 1.31g of PVA

& 0.601g of ceramic were taken .Then 1.3g of PVA was added to 40ml distilled water and
stirred constantly at 60°C for 3 hrs by using magnetic stirrer .Then 0.601g of BZT was added
to PVA suspension and mixed by agate mortar for 1 hr .After drying off the sample ,for
fabrication the composite was hot pressed at 120 °C for 10 mints with a pressure of 6 tons.
Then prepared PVA – BaZr0.1Ti0.9O3composite was kept for SEM & electrical study .For
electrical study silver paste was used for the electrode on both side of the samples. Similar
procedure was repeated for 20%, 30%, 40%, 50% ceramic composite.

PVA +40 ml distilled water 10%, 20%, 30%, 40%, 50%
ceramic (BaZr0.1Ti0.9O3)
(Heated at 60°C for 3 hrs )

Mixed for 2 hr until it becomes


Dried hard

Hot press (120°C for 10 mints )

Cut into small pellets

SEM, Dielectric study


2.3. Characterization Techniques

The following techniques were characterization used to study the structural, morphological
and electric study of the ceramic.

1. X-Ray diffraction

X Rays[9,25] are electromagnetic radiation of exactly the same nature of the

visible light but having wavelength 10 -80cm .The X Rays used for diffraction have the
wavelength lying between 0.5 -2.5 A0 .We know that the physical properties of solid i.e.
optical , electrical , magnetic ferroelectric etc. depends on atomic arrangement of materials .
So X ray powder diffraction is a rapid analytical technique used for phase identification of a
crystalline material & can provide information on a unit cell dimension.

Max van Laue in 1912 discovered that crystalline substances act 3-dimensional
diffraction grating for x-ray wavelength similar to the spacing of planes in a crystal lattice
.Hence was used determination of material & the finger print characterization of materials.

XRD is based on constructive interference of the monochromatic x-ray &

crystalline sample when the condition satisfies Bragg‟s law

n  =2d sin θ

Where, d= spacing between atomic planes,  = x ray wavelength, θ = angle of diffraction

n = 1, 2, 3, ……..

The diffracted x-rays are then detected, processed & counted .By scanning the
sample through a range of 2θ angle all possible diffraction direction of the lattice should be
attained due to random orientation of powder crystal. Conversion of diffraction peak to d-
spacing allows identification of a mineral because mineral has a set of unique d – spacing.

2. Scanning electron microscopy (SEM)


sample by scanning it with a beam of electron in a raster scan pattern .In SEM when a beam
of highly energetic electron strikes the sample the secondary electron, back scattered, are
ejected from the sample .The electron interact with the atoms that make up the sample
producing signals that are collected at the detector. These signals contain information about
the samples surface topography, composition & other properties such as electrical

3. Dielectric Measurement
To measure the relative permittivity (dielectric constant) and dielectric loss,
LCR meter can be used to measure the dielectric constant and dielectric loss. The electrode
samples were used to make the measurements. The LCR meter, was connected with the
computer and the data was collected as a function of temperature at different frequencies. The
following formula was used to calculate the dielectric constant
 r A

C= Capacitance in faraday (F), ε = Permittivity of free space in farad per meter (8.85 x
10-12F/m),  r = Dielectric constant or relative permittivity of the sample, A= Area of
each plane electrode in square meters (m2) ,d = Separation between the electrodes in
meters (m)

4. Impedance spectroscopy

Dielectric spectroscopy also known as electrochemical impedance

spectroscopy measures the dielectric properties of a medium as function of frequency .It is
based on the interaction of the external field with the electric dipole moment of the sample
.Impedance is the opposite to the flow of system comprises both energy dissipate & energy
storage element . Impedance is the opposition to the flow of AC in a complex system .A
passive complex electrical system comprises both of energy dissipated & storage element. It
is a powerful tool to investigate the electrical properties of the complex perovskite oxides.
The main advantages of the techniques, i) it involves relatively simple electrical
measurements that can readily be automated ii) the measurements can be implemented by
using arbitrary electrodes iii) the results can be often correlated with the properties such as
composition, microstructure, defects, dielectric properties, chemical reaction etc. of the


Result and Discussion

1. XRD




400 (111) (211)
200 (210)

20 30 40 50 60


Fig.4 XRD of BaZr0.1Ti0.9O3 ceramic

Fig4. shows the XRD pattern of BZT ceramic powder calcined at 12000 C for 6 hrs .The
pattern shows the clear single perovskite phase without any secondary phase.

2. SEM

The figure above shows the surface morphology of the hot pressed 100% PVA
and the polymer composite .The lighter region in the fig represents the ferroelectric ceramic
and the darker region the polymer matrix. With the increase in the ceramic concentration the
distribution becomes uniform.

100% PVA PVA +10 % BZT

PVA +20 % BZT PVA +30 % BZT

PVA +40 % BZT PVA +50 % BZT

Fig.5 SEM Micrograph of hot pressed polymer composite

3. Dielectric study

Dielectric spectroscopy also known as electrochemical impedance spectroscopy

measures the dielectric properties of medium as a function of frequency .It is based on the
interaction of an external field with the electric dipole moment of the sample.

3.1. Frequency dependence dielectric study

PVA+BZT10vol% 7000 PVA+BZT20vol%
1000 6000
50 C 5000 0
50 C
800 0
75 C 0
75 C
100 C 4000 0
100 C

600 0
125 C 0
0 125 C
150 C 3000 0
150 C

200 1000

2 3 4 5 6 2 3 4 5 6
10 10 10 10 10 10 10 10 10 10
log frequency log frequency

(a) (b)


7000 PVA+40vol %

6000 0
50 C
5000 75 C
100 C

4000 0
125 C
150 C



2 3 4 5 6
10 10 10 10 10
log frequency


Fig.6 Frequency dependence of εr of polymer ceramic composite at various temperatures

For polymer ceramic composites, the perovskite-type ceramics is in the powder
form instead of the sintered form. The removal of grain boundaries, elimination of constrained
forces from neighboring grains and a drop in domain density due to decrease in the particle
size will change the relaxation mechanisms of ceramic powders. Hence, sintered and
unsintered ceramic powders show a different dielectric behavior. Our work deals with a
composite medium composed of dispersed unsintered modified ceramic within the polymer
matrix. Figure 6 shows the frequency dependence of dielectric constant at temperatures
between 50 and 150 °C of the samples PVA+BZT10vol% (a) PVA+BZT20vol% (b), and
PVA+BZT40vol% (c). A relatively high dielectric constant at low frequencies is a
characteristic of polymer as well as oxide ceramic. So, the nature of the dielectric constant ε
can be expressed as follows, dielectric constant ε can be expressed as follows,

s 
r    (1)
1   2 2

Where εs and ε∞ are the static and infinite dielectric constant values respectively, ω is the
angular frequency and τ is the relaxation time. At very low frequencies (ω«1/τ, τ=relaxation
time), dipoles follow the field and we have εr= εs (value of the dielectric constant at
quasistatic fields). As the frequency increases (with ω<1/τ), dipoles begin to lag behind the
field and ε slightly decreases. When frequency reaches the characteristic frequency (ω=1/τ),
the dielectric constant drops (relaxation process). At very high frequencies (ω » 1/τ), dipoles
can no longer follow the field and εr ≈ ε∞ (high-frequency value of εr). Qualitatively, the same
behavior has been observed in Fig.6. At low temperatures, the ε value decreases
monotonically with increasing frequency and attains a constant value at high frequencies. This
behavior is typical of polar dielectrics/polymers because dipole orientation is facilitated by
increasing the temperature, thus increasing the permittivity. The same nature is observed in all
the composites, but the shift reduces with incorporating ceramics in polymer-ceramic

3.2. Frequency dependence tangent loss

PVA+10vol % 4
PVA+20vol %
3 0
50 C 0
75 C 50 C
3 0
0 75 C
100 C 0
0 100 C
2 125 C 0

0 125 C
150 C

2 0
150 C


0 0
2 3 4 5 6 2 3 4 5 6
10 10 10 10 10 10 10 10 10 10
log frequency log frequency

(a) (b)

PVA+40vol %

50 C
2 0
75 C
100 C

125 C
150 C

2 3 4 5 6
10 10 10 10 10
log frequency


Fig. 7 Frequency dependence of tanδ of polymer ceramic composite at various temperatures

Figure 7 illustrates the variation of tangent loss for all composites at different temperatures as
a function of frequency. In the amorphous phase, dipolar molecules can be able to orient from
one equilibrium position to another relatively easily, and contribute to absorption over a wide
frequency or temperature range [12,14]. In the present study, the high dielectric loss occurs at
the lower frequency is due to accumulation of free charges at the interface between the
electrolyte and the electrode (space charge polarization). At higher frequencies, the periodic

reversal of the electric field occurs so fast that there is no excess charge diffusion in the
direction of the field. So, the charge accumulation decreases, leading to a decrease in the
value of the dielectric loss. Then, the clear peak position appears above 150oC in
PVA+BZT10wt% (position increases with addition of ceramics) and shifts towards higher
frequency side with increase in temperature. The loss peaks and their shifts with temperature
suggest a thermally activated dielectric relaxation process [13].

3.3. Impedance spectroscopy

In the heterogeneous system (i.e., mixed state of polymer + ceramic), it is necessary to

explain the impedance spectroscopy to understand the complete relaxation and conduction
mechanism presence in the samples. In the polymer, segmental chains are involved in the
relaxation process whereas in ceramic, dipoles are involved and the conductivity of two
systems is different in nature. The complex impedance spectrum of the polymer composites at
100oC is shown in Fig. 8. It can be clearly seen that the different kind of behavior is present in
the spectrum; which confirms that the additional behavior added while increasing ceramic
concentration in the polymer composites. At PVA+BZT10vol% shows the single relaxation
behavior, as it contain small amount of ceramic (10vol%) (PVA dominates the ceramic-
polymer interface effect), but in the PVA+BZT20vol% and PVA+BZT40vol% shows the
additional effects. It may be due to the adding of ceramic powder into the polymer which
creates the interface effect and the higher concentration (40vol%) space charge polarization
added to the other effects. These kinds of nature can be explained in simple common model
contains a serial arrangement of one, two and three units that represent the contribution from
the bulk composite interface region and the space charge polarization of the ceramic–polymer
composite respectively. Each unit is depicted by a parallel combination of two possible
electrical current components, i.e., resistor and capacitor . The impedance datas are analyzed
to an equivalent circuit consisting of different RC combination as mentioned above. The
constant phase element (CPE) is introduced as the material obeys non-Debye type behavior
which replaced the capacitance from the electrical equivalent circuit . The impedance of CPE

𝛼 −1
𝑍𝐶𝑃𝐸 = 𝑄 𝑗𝜔 (2)

where Q indicates the value of the capacitance of the CPE element and α the degree of
deviation with respect to the value of the pure capacitor.

Fig. 8 Cole-Cole plot

3.4. Frequency dependence imaginary impedance

Figure 9 shows the variation of the imaginary part of impedance (Z‟‟) with frequency at
different temperature. The curves show that the Z” values reach a maxima peak (Z” max) and
the value of Z” max shifts to higher frequencies with increasing temperature. A typical peak
broadening, slightly asymmetrical in nature can be observed with the rise in temperature. The
broadening of peaks in frequency explicit plots of Z” suggests that there is a spread of
relaxation times, i.e. the existence of a temperature dependent electrical relaxation
phenomenon in the material. The merger of Z” values in the high frequency region may
possibly be an indication of the accumulation of space charge in the material. The relaxation
process may be due to the presence of immobile species at low temperature and defects at
higher temperature. In such a situation, one can determine the activation energy by the linear

fit of the temperature dependence of relaxation frequency, which satisfies the Arrhenius law
as shown in the Fig.9 inset. The law is as follows;

𝑓𝑚𝑎𝑥 = 𝑓𝑜 𝑒𝑥𝑝 (3)

where, fmax is the maximum peak frequency, fo is the characteristic frequency, K is the
boltzmann constant, Ea is the activation energy for the migration of free charges and T is the
absolute temperature. Activation energy increases with increasing the ceramic concentration
in polymer composite, which indicates the hardening of polymer chain when the more
ceramic particles incorporating into the polymer matrix.

-1.4 -0.6
PVA+BZT10vol% PVA+BZT20vol%
-1.0 50 C
50 C -0.4 0
75 C
75 C 0
100 C
Z" (M)
Z" (M)

100 C 0
125 C
-0.6 125 C 0
150 C
150 C


0.0 0.0
100 1000 10000 100000 1000000 100 1000 10000 100000 1000000
log frequency (Hz) log frequency (Hz)

-0.5 4.8
PVA+BZT40vol% 10vol%
-0.4 4.4
linear fit
50 C
75 C
Z" (M)

log 

100 C
0 3.6
125 C
-0.2 0
150 C
Ea = 0.172eV
2.8 Ea = 0.230eV
Ea = 0.255eV
100 1000 10000 100000 1000000 2.3 2.4 2.5 2.6 2.7 2.8 2.9
log frequency (Hz) 1000/T (K )

Fig. 9 Imaginary part of impedance vs frequency

1.1. AC conductivity study

PVA+BZT10vol% 10
-4 PVA+BZT20vol%
AC conductivity (ac)

AC conductivity (ac)

-5 10

10 0
50 C
0 50 C
75 C 75 C
10 10
100 C 100 C
125 C 125 C
-6 0
0 10 150 C
150 C
log  log 

(a) (b)

10 PVA+BZT40vol%
AC conductivity (ac)



-4 0
10 50 C
75 C
-5 0
10 100 C
125 C
-6 150 C

1 2 3 4 5 6 7
10 10 10 10 10 10 10

log 


Fig. 10 AC conductivity vs angular frequency

AC conductivity has been studied as a function of frequency in the temperature range 50-150
°C for all the compositions and the typical plot of logσac vs logω is shown in Fig. 10. The
characteristic features of conductivity spectra can be explained using Jonscher's power
law[24]; σac = σdc + Aωn (0 < n < 1) where A is a temperature dependent pre-exponential
factor and n is the power law exponent. The exponent n represents the degree of interaction
between mobile ions and lattices. The factor A determines the strength of the polarizability of
the sample. The conductivity of all the samples apparently enhanced with increasing

temperature. This can be easily understood based on the segmental chain motion of polymer
composites. When the temperature is increased, mobility of polymer chains is enhanced, and
the fraction of free volume in polymer composite increases accordingly, which leads to an
increase in the conductivity of the pure polymer. Furthermore, the number of charge carrier
increases with increasing temperature especially in modified ceramics due to the oxygen
vacancies. This is favorable to a high conductivity at higher temperatures. The frequency
independent behavior of the conductivity in the low frequency region is observed but that
become sensitive at high frequency region, which generally known as hopping frequency,
shifted towards the higher frequency side with an increase of temperature. The high-frequency
conductivity dispersion may be attributed to AC conductivity whereas the frequency
independent plateau region of the conductivity pattern corresponds to the dc conductivity (σdc)
of the sample.


The ferroelectric ceramic BaZr0.1Ti0.9O3 was prepared by solid state method.

XRD pattern of the powder calcined at 1250 0C for 6 hr and the pattern shows clear single
perovskite phase. SEM micrograph shows the homogeneous distribution of the ceramic in the
polymer. With increasing ceramic composition the distribution becomes uniform. From the
dielectric measurement various electrical properties were studied. We found that dielectric
constant increased with the rise in frequency & rise in temp for a particular composition .It is
also found that dielectric constant increased with the increase in the ceramic concentration.
Dielectric loss also increased with increase in temp at lower frequency. As well it increased
with increase in the ceramic composition. From impedance spectroscopy additional behavior
is introduced with the increase in the ceramic composition. For a particular composition the
Z‟‟ decreases with increasing frequency and the peak shift towards higher frequency.
Activation energy increased with the increase in the ceramic concentration implying the
hardening of polymer chain. AC conductivity increased with the increase in the temp and also
ceramic concentration.


1. A.W.M. de Last*, W.P.T. Derks, “Colloidal stabilization of BaTiO, with poly(viny1

alcohol) in water”, C&ids and Surfaces A: Physicochemical and Engineering Aspects, 71
(1993) 147-I 53
2. C.MURALIDHAR,P.K.C.PILLAI “XRD studies on barium titanate (BaTiO3)/Poly
vinlyidine fluoride(PVDF) composite” Indian Institute of Technology ,Delhi-110106

3. Mohd Hamzah Harun, Elias Saion, Anuar Kassim, Ekramul Mahmud, Muhd
Yousuf Hussain, and Iskandar Shahrim Mustafa “Dielectric Properties of Poly (vinyl
alcohol)/Polypyrrole Composite Polymer Films” vol-1

4. Organic Properties of Poly Vinyl Alcohol Day 4 Activity





MITOSERIUa,b,A. STANCUa, P. NANNIb “Relaxor properties of Ba(Zr,Ti)O3 ceramics
9. B.D.Cullity ,“Elements of X-Ray diffraction”

10. Mohan VM, Qiu W, Shen J, Chen W (2010) “Electrical properties of poly(vinyl alcohol)
(PVA) based on LiFePO4 complex polymer electrolyte films”. J Polym Res 17:143–150

11. Kota R, Ali AF, Lee BI, Sychov MM (2007) “Dielectric constant of barium
titanate/cyanoethyl ester of polyvinyl alcohol composite in comparison with the existing
theoretical models”. Microelectron Eng 84:2853–2858

12. Rastogi AC, Chopra KL (1975) “Dielectric loss behavior of solution grown thin
polyvinyl chloride films”. Thin Solid Films 27:311–318

13. Fan L, Dang Z, Wei G, Nan CW, Li M (2003) “Effect of nanosized ZnO on the
electrical properties of (PEO)16LiClO4 electrolytes”. Mater Sci Eng B 99:340–343

14. Sengwa RJ, Choudhary S, Sankhla S (2008) “Low frequency dielectric relaxation
processes and ionic conductivity of montmorillonite clay nanoparticles colloidal suspension
in poly(vinyl pyrrolidone)-ethylene glycol blends”. eXPRESS, Polym Lett 2:800–809

15. X. Y. Huang and P. K. Jiang, C. U. Kim “Electrical properties of polyethylene/

aluminum nanocomposites” JOURNAL OF APPLIED PHYSICS 102, 124103 _2007_
16. V. Tomera_ and C. A. Randall “High field dielectric properties of anisotropic polymer-
ceramic composites” JOURNAL OF APPLIED PHYSICS 104, 074106 _2008_

17. Michael G. Todda) and Frank G. Shi “Characterizing the interphase dielectric constant
of polymer composite materials: Effect of chemical coupling agents” JOURNAL OF APPLIED

18. Hyeung-Gyu Lee and Ho-Gi Kim “Ceramic particle size dependence of dielectric and
piezoelectric properties of piezoelectric ceramic-polymer composites”
Technology, Advanced Institute of Science and Technology
19. H.C. Pant, M.K. Patra, Aditya Verma, S.R. Vadera, N. Kumar “Study of the
dielectric properties of barium titanate–polymer composites” Acta Materialia 54 (2006) 3163–3169
R&D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace,
Jodhpur 342011, Rajasthan, India


21. V. Senthil & T. Badapanda & S. N. Kumar & P. Kumar &S. Panigrahi “Relaxation and
conduction mechanism of PVA:BYZT polymer composites by impedance spectroscopy”
NIT ,Rourkela
22. Senthil Venkatesan“Dielectric relaxation behavior and Electrical conduction
mechanism in Polymer-Ceramic composites based on Sr modified BZT ceramic” National
Institute of Technology, Rourkela
Ravi Kiran Kota to the Graduate School of Clemson University December 2006
24. Jonsher AK, The ‘universal’ dielectric response.Nature