Modification of Dielectric Properties, after Barium

Titanate Nanoparticles Sintering, from a

Thermoplastic Polymer Matrix

Vlad – Andrei Scarlatache, Andrei Niagu, Daniel Brunetto Martorana

Matasaru, Romeo Cristian Ciobanu Centro Ricerche Fiat
Department of Electrical Measurements and Materials Torino, Italy
The “Gheorghe Asachi” Technical University of Iasi brunetto.martorana@crf.it
Iasi, Romania
vscarlatache@ee.tuiasi.ro

Abstract—This paper illustrate the effects of BaTiO3 (barium adhesive are inserted ferromagnetic particles, in idea that this
titanate) particles sintering on dielectric properties at a ferroelectric ceramics will help the melting process.
poliolefinic adhesive who have inserted this particles. The
dielectric characteristics analyzed are the real and imaginary Recently was developed some invention in terms of
part of permittivity and dielectric losses of the poliolefinic thermoplastic adhesive with high dielectric constant. For
adhesives with sintered particles (PO-S) and the poliolefinic example a high dielectric constant polyimide film, composite
adhesives with non-sintered particles (PO-NS). The and high dielectric constant polyimide liquid for use in
measurements are done in a range of frequency between 0.1 Hz electronic circuitry and electronic components including
to 10 MHz and for a variation of temperature from 30 ºC to 150 multilayer printed circuits, flexible circuits, semiconductor
ºC, with a step of 10 ºC. We also analyzed the effect of Curie packaging and buried film capacitors. The invention provides a
temperature of samples, to understand the structure effect on high dielectric constant, flexible polyimide film composed of a
dielectric properties. Samples structure was analyzed with a X- single layer of an adhesive thermoplastic polyimide having
ray difractometer. dispersed therein from 4 to 85 weight %, based on the weight
of the film, of a ferroelectric ceramic filler, wherein the
Keywords - permittivity; dielectric losses; Curie temperature; polyimide film has a dielectric constant of from 4 to 60
sinterization; characterized in that said polyimide film further comprises a
conductive core/shell particulate filler [4].
I. INTRODUCTION
There is an increasing interest in multi-constitute II. DESCRIPTION OF MATERIALS AND MEASUREMENT
composites because the combination of two or more materials SYSTEM
can lead to enhanced performance [1].
The samples was made by inserting barium titanate
In general this type of particles are more inserted in nanoparticles in a thermoplastic polyolefin polymer in order to
thermosetting polymers for development of new high dielectric observe their dielectric behavior of the insertion of barium
permittivity materials (known as high-K materials), which titanate nanoparticles without sintered compared with those
combine at the same time, suitable dielectric properties, sintered.
mechanical strength and ease processing [2].
This kind of thermoplastic poliolefinic adhesives in TABLE I PRESENTATION OF POLYOLEFIN NANOCOMPOSITE SAMPLES WITH
INSERTION OF BARIUM TITANATE NANOPARTICLES
combination with some ferromagnetic particles have a wide
variety of existing and potential applications in electronics and Polyolefins with insertion of Polyolefins with insertion of
especially in transportation (rail, automotive, aerospace) where non-sintered BaTiO3 sintered BaTiO3
low-cost, lightweight and high strength materials are required nanoparticles (PO-NS) nanoparticles (PO-S)
more and more for energy saving purposes [3].
Sample
In the present paper will analyzed the dielectric losses Type
effect on polyolefin samples after insertion of barium titanate
particles sintered and non-sintered.
Melting temperature of this kind of thermoplastic adhesives
is around of 150 ºC, sow if this kind of material is supposed to
electromagnetic field for melting when inside of thermoplastic Diameter/ 20 mm / 1.25 mm 20 mm / 1.8 mm
Thickness

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 Figure 1. The measurement system of dielectric characteristics at low
frequencies.

The production method of samples is based on a thermal

mixing on the teflon films, therefore major differences appear
in thickness, shown in Table 1, and for leveling was used a
thermal press.
The measurement system used to analyze the dielectric Figure 2. The Lenton furnace with argon flame used for particle sintering up
properties in the frequency and temperature variation is to 1000 °C.
composed of an impedance analyzer from Alpha - A
Novocontrol, a ZGS cell and a temperature control system Due to the particular importance of molecular structure of
Quatro Cryosistem, Fig. 1. barium titanate is obviously an analysis. Molecular structure
analysis was performed using an X-ray diffractometer supplied
The Alpha – A impedance analyzer have a band of by PANalytical model X'Pert Powder, Fig. 3, analysis being
frequency from 0.001 Hz to 10 MHz, high phase accuracy performed as well as particle sintering on the National
(2.10-3 °) and loss factor tan(δ) absolute accuracy (3.10-5) for Research Institute of Metrology (INRIM), Italy.
low loss dielectric materials and isolators broadband
characterization. Quatro Cryosystem have a range of The crystalline powder method is based on obtaining
temperature between -160 ºC to + 400 ºC, with a ramps from diffraction pattern by passing a fascicle of X-rays through a
0.01 °C / min to 20 °C / min and a stability of 0.01 °C. polycrystalline sample. The powder method can give
information on the symmetry of the crystal structure. This can
The results are analyzed with WinDeta software from determine the size of parameters that defining the elementary
Novocontrol and saved in ascii form. Diagrams are developed cell.
in Origin program.

III. SINTERING AND STRUCTURE ANALYSIS OF BARIUM

TITANATE PARTICLES
The barium titanate powders that will be inserted into the
polymer matrix are branded Sigma-Aldrich, with a purity of
99%, less than 3 micrometer diameter and a density of 6.08 g /
mL at 25 °C. In the literature many researchers have made
many arguments that these powders by sintering become to
have high dielectric properties.
Fig. 2 presents the Lenton furnace with argon flame that
was used in sintering of barium titanate particles.
The maximum temperature was about 1000 °C, which was
reached in about 2 hours after start of combustion.
The main gains of sintering consist in removing impurities
arising from doping substances used in the manufacture of
barium titanate and densification particles. At the crystalline
materials the sintering is achieved by diffusion, thus
eliminating the porosity and interfacial area solid - porous
decreases. In the same time by removing impurities and
increasing the particle density will result a substantial increase Figure 3. The X-ray diffractometer XPERT-PRO XRD.
of dielectric properties.
 The distribution diffraction lines in the image obtained TABLE II THE PLANES INVOLVED IN THE REFLECTION, [5]
allows the identification crystalline system to which it belongs Peak 1 2 3 4 5 6 7 8 9 10 11
sample studied. On the other hand, this method enable the Nr.
internal tensions in the sample and represent a process for hkl 100 110 111 200 210 211 220 300 310 311 222
determining and identifying the number of defects in the
crystalline structure. From studying the diffraction pattern can
identify substances present in the sample, each substance where the points are regularly arranged in three directions
having a crystalline structure, so a distinct diffraction image. In x, y, z at distances a1, a2, a3.
the case of the crystalline powder method, the integrated Fig. 4 presents the results from the analysis of X-ray
intensity of a maximum diffraction is given by: diffractometer for barium titanate particles.
Measurements were made with step-scan model of rank 20
2
A λ3 to 120 ° 2θ with a step size of 0.02º in 5001 points. XRD data
I hkl = (1) evaluation was made using Highscore Plus software.
V 2
4 sin θ
For tetragonal crystalline structure the numbers of
where: hkl is the coordinate system, A amplitude, V the interference lines in roentgenogram are usually as in Table 2.
volume of the elementary cell, λ the wavelength, θ the angle
between the fascicle and the atomic planes. From roentgenogram, Fig. 4, is clearly observed a splitting
of the reflection lines which clearly shows the presence of
The reflected rays by the crowd planes from crystal that tetragonal structure for sintered barium titanate particles, [6 ÷
satisfy the Bragg condition are distributed on a cone whose 8]. This phenomenon is evident for the fourth line reflection
semi-aperture is 2θ and whose axis coincides with the direction corresponding to the plane (200) being preceded by reflection
of propagation of the incident fascicle. The general Bragg (002) at an angle smaller, shown in Fig. 5.
condition is specified as follows: if on the crystal falls an
narrow incident fascicle of X-rays, with a determined In cubic phase the interference lines remain cleaved, but in
wavelength λ, under angle θ to the atomic planes, parallel to the case of sintered particles, two peaks are evident and
the crystal surface, the distance between planes is d, then Wulf automatic the structure is tetragonal.
and Bragg relation is valid: If goes from crystal with cube network to crystal with
tetragonal network, the number of interference lines for flat
type (hhl) (two indices) will be at two times higher, and the
2 d sin θ = n λ (2) planes (hkl) at three times.
where n is an integer number. In the transition from the tetragonal to cubic network, each
interference line splits in two or three lines and by switching to
Expressing in the Bragg relation the inter-planar distance d a more complicated, rhombic system, the number of planes of
by constants network and indices system plane given by (hkl), type (hkl) increases to six. Thus, the number of the interference
obtaining the relation for tetragonal crystallographic systems: lines in roentgenogram and their position are determined
primarily from the shape and size of the elementary cell.
λ2 ⎛ h 2 + k 2
l2 ⎞
sin 2
θ = ⎜ + ⎟ (3)
4 ⎜⎝ a 1
2
a 32 ⎟
⎠
Intensitate S
Intensity (cps)

Intensitate NS

900
1000
Intensity (cps)

400

100

100

50 51 52 53 54 55
2Theta
0
20 30 40 50 60 70 80 90 100 110 120
2Theta (°)
Figure 5. The enlarged Roentenogram around 53 ° 2θ angle, to make it clear
Figure 4. X-ray difraction Roentgenogram of barium titanate particles before division in (002) and (200) of the interference lines.
(green) and after (red) sintering.
 IV. EXPERIMENTAL RESULTS In terms of conductivity, Fig. 9, is observed that it rises
The measurements were realized at the ambient with frequency increasing and for lower frequency the PO-NS
environment and at temperature variance. The strip frequency sample has this characteristic a little higher due to higher
was between 0.1 Hz ÷ 106 Hz, with a logarithmic scale and a dielectric losses. The evolution of dielectric constant at
number of 43 measurement points. In the temperature variation temperature variation is shown in Fig. 10, from where it
was used a range between 30 ºC and 150 ºC with a step of 10 observe an increase at its value with temperature, lower to 120
ºC. °C slowly and above that temperature increases suddenly to
140 ºC.
In the ambient environment were characterized real and
10
imaginary permittivities with dielectric losses derived from two
characteristics to frequency variation.
1 T an(D elta) PO-N S
Fig. 6 presents the dielectric constant for the two samples T an(D elta) PO-S

PO-NS and PO-S, where is clearly observed a noticeable

Tan(Delta)
increase for the sample with sintered particles. 0.1

Making an analogy with Fig. 7, it is evident the appearance

of a slight orientational polarization, polarization that will be 0.01

analyzed more to the variation of temperature.

Both real and imaginary permittivity decrease with the 0.1 1 10 100 1000 10000 100000 1000000

increasing frequency, at the sample PO-NS more suddenly Frequency (H z)

whiles for the PO-S slower.

Figure 8. The dielectric losses of the polymer nanocomposite samples with
The dielectric losses for the two samples analyzed are insertion of barium titanate particles without sintering (green) and with
represented by Tan (Delta), Fig. 8, and represent the imaginary sintering (red).
and real permittivity ratio, from where resulting losses a little
higher for PO-NS sample and the PO-S sample tend to have a
1E-6

peak at frequencies around kHz. 1E-7 Sig (S/cm) PO-NS

Sig (S/cm) PO-S

1E-8
Sig (S/cm)

4 1E-9
Eps' PO-NS
Eps' PO-S 1E-10

1E-11
Eps'

1E-12

3
0.1 1 10 100 1000 10000 100000 1000000
Frequency (Hz)

0.1 1 10 100 1000 10000 100000 1000000

Figure 9. The electrical conductivity of the polymer nanocomposite samples
Frequency (Hz)
with insertion of barium titanate particles without sintering (green) and with
sintering (red).

Figure 6. The real permittivity of the polymer nanocomposite samples with

insertion of barium titanate particles without sintering (green) and with
5.5
sintering (red).
5

4.5
10

4
Eps'

Eps'' PO-NS
1 Eps'' PO-S

3.5
Eps"

0.1
3 160
140
120
0.1 100
1 80
0.01 Fre 10 60 )
que (°C
100
ncy 1000 40 e
0.1 1 10 100 1000 10000 100000 1000000 (Hz 10000 t ur
) 100000 ra
Frequency (Hz)
20 pe
1000000 m
Te
Figure 7. The imaginary permittivity of the polymer nanocomposite samples
with insertion of barium titanate particles without sintering (green) and with Figure 10. The 3D diagram of real permittivity for sample PO-S in the
sintering (red). frequency band 0.1 Hz ÷ 1 MHz, at the variation from 30 ºC to 150 ºC with a
step of 10 ºC.
 10
1
1

lta)
0.1

Tan(De
0.1
Eps"

0.01 0.01

1E-3
1E -3
0.01 0.01
0.1 160 0.1 160
Fr 140 140
eq 1 120 Fr 1 120
ue 10 100 eq 10 100
80 80
nc 100 C) u e 100 )
y 1000 60 e(
°
n c 1000 60 (°C
(H tu r y tu
r e
z) 10000 40 era ( H 10000 40 ra
mp z ) 100000 pe
100000 Te m
1000000 20 1000000 20 Te

Figure 11. The 3D diagram of imaginary permittivity for sample PO-S in the Figure 13. The 3D diagram of dielectric losses for sample PO-S in the
frequency band 0.1 Hz ÷ 1 MHz, at the variation from 30 ºC to 150 ºC with a frequency band 0.1 Hz ÷ 1 MHz, at the variation from 30 ºC to 150 ºC with a
step of 10 ºC. step of 10 ºC.

5
Eps' 30 (°C)
8 Eps' 40 (°C)
Eps' 50 (°C)
7 Eps' 60 (°C)
Eps' 70 (°C)
Eps' 120 (°C) Eps' 80 (°C)
6
Eps' 130 (°C) Eps' 90 (°C)
4 Eps' 100 (°C)
Eps'

5 Eps' 110 (°C)

Eps'
Eps' 120 (°C)
Eps' 130 (°C)
Eps' 140 (°C)
4 Eps' 150 (°C)

3
0.1 1 10 100 1000 10000 100000 1000000 1E7
Frequency (Hz)
0.1 1 10 100 1000 10000 100000 1000000 1E7
Frequency (Hz)
10

10 0 Eps" 3 0 (°C )
1 Eps" 4 0 (°C )
Eps" 120 (°C) Eps" 5 0 (°C )
Eps" 6 0 (°C )
Eps" 130 (°C) 10 Eps" 7 0 (°C )
Eps" 8 0 (°C )
Eps" 9 0 (°C )
Eps" 1 0 0 (°C )
Eps"

0.1 1 Eps" 1 1 0 (°C )

Eps" 1 2 0 (°C )
Eps" 1 3 0 (°C )
Eps"

Eps" 1 4 0 (°C )
0.1 Eps" 1 5 0 (°C )

0.01
0 .0 1

1 E -3

0.1 1 10 100 1000 10000 100000 1000000 1E7 0.1 1 10 1 00 1 0 00 10 0 00 1 00 0 00 10 0 00 00 1E 7

Frequency (Hz) F re q u e n c y (H z )

Figure 12. Real and imaginary permittivity of the polymeric nanocomposite Figure 14. Real and imaginary permittivity of the polymeric nanocomposite
sample PO-S for temperatures of 120 ºC and 130 ºC. sample PO-NS in the frequency band 0.1 Hz ÷ 1 MHz, at the variation from
30 ºC to 150 ºC with a step of 10 ºC.
If analyze the variation of imaginary permittivity in Fig. 11,
it can see a slight polarization at low temperatures and at This spontaneous polarization is not present at higher
temperatures of 120 ºC and 130 ºC there is a sudden temperature than 130 ºC and can say that it passed from
polarization around the value of 20 kHz. This is shown more ferroelectric tetragonal phase to paraelectrical cubic phase.
clearly in Fig. 12 which presents the real and imaginary Also, with temperature increasing is observed a evident
permittivity at temperatures of 120 ºC and 130 ºC. This increase in the permittivity due to interfacial polarization. As
polarization is attributed to the Curie temperature of barium an analogy at these frequencies if temperatures grows and the
titanate particles, which is usually around this value of dielectric losses increase. From Fig. 13 is also observed the
temperature.
peak of losses caused by the Curie temperature of barium level” project, financed by the European Social Found and
titanate particles. Romanian Government.
To make a comparison on matrix with non-sintered Also a contribution for development of this paper it have
particles and sintered particles, at temperature variation, in Fig. the Polimag project as a source of the polymer samples:
14 is presented the real versus imaginary permittivity of PO-
NS. • Regione Piemonte POR-FESR Asse I Innovazione e
transizione produttiva I.1.3 Innovazione e P.M.I.
It is observed that around the Curie temperature is a
instability in evolution of dielectric characteristics at • Partners POLIMAG: Coord MECT, CRF, INRIM,
frequencies of kHz order, but the molecules are non-oriented VABER, KGR, UPO.
along the applied field and not appear an obvious peaks of
losses. REFERENCES
Thus, by sintering the barium titanate particles from the [1] Z. M. Dang, L. Z. Fan, Y. Shen, C. W. Nan, “Study on dielectric
behavior of a three-phase CF/(PVDF + BaTiO3) composite,” Elsevier
nanocomposite polymer matrices are obtained much clearer Science, Chemical Physics Letters 369, pp. 95–100, 2003.
peaks of dielectric losses, around the Curie temperature at [2] A. Patsidis, G. C. Psarras, “Dielectric behaviour and functionality of
frequencies of kHz order. polymer matrix – ceramic BaTiO3 composites,” eXPRESS Polymer
Letters Vol.2, No.10, pp. 718–726, 2008.
V. CONCLUSIONS [3] A. Caprile, M. Coïsson, F. Fiorillo, P. Kabos, O. M. Manu, E. S.
Olivetti, M. A. Olariu, M. Pasquale, V. A. Scarlatache, “Microwave
Is very clear that after sinterization, the barium titanate behaviour of polymer bonded Iron oxide nanoparticles,” International
particles have a tetragonal structure. Magnetics Conference, INTERMAG, 2012.
[4] Lee, Yueh-ling, Min, Gary, “High dielectric constant flexible polyimide
At Curie temperature (120 ºC ÷ 130 ºC), the PO-S sample film and process of preparation,” European Patent EP0902048, 2005.
have a peak of dielectric losses at frequency around 10 kHz. [5] A. Habib, N. Stelzer, P. Angerer and R. Haubner, “Effect of temperature
and time on solvothermal synthesis of tetragonal BaTiO3,” Bull. Mater.
At the same temperature and frequency the dielectric losses Sci., Vol. 34, No. 1, 2011.
of sample PO-NS start to have a nonlinear evolution, but the [6] P. K. Dutta, R. Asiaie, S. A. Akbar and W. Zhug, Chem. Mater. 6, 1994.
cubic structure of barium titanate particles not offer the [7] M. Wu, R. Xu, S. H. Feng, L. Li, D. Chen and Y. Luo, J. Mater. Sci. 36,
possibility to appear a spontaneous polarization. 1996
[8] S. W. Lu, B. I. Lee, Z. L. Wang and W. D. Samuels, J. Cryst. Growth
VI. AKNOWLEDGMENT 219, 2000.

This paper was realised with the support of EURODOC

“Doctoral Scholarships for research performance at European