Materials Sciences and Applications, 2011, 2, 1199-1204
doi:10.4236/msa.2011.29162 Published Online September 2011 (
Copyright © 2011 SciRes. MSA
The Structure and the Electrical Properties of
Ferroelectric Ceramics
Malika Abba1, Ahmed Boutarfaia1,2*
1Laboratoire de Chimie Appliquée, Université de Biskra, RP-Biskra, Algérie; 2Département de Sciences de la Matière, Université de
Ouargla, RP-Ouargla, Algérie.
Email: *
Received January 30th, 2011; revised March 9th, 2011; accepted May 31st, 2011.
The structural, the dielectric, and the piezoelectric properties of new ferroelectric
Pb0.95La0.05[Zrx,Ti(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3 (0.46 x 0.55) ceramics have been investigated. All the samples were
being sintered at a temperature ranging from 1000 to 1180˚C after being compacted in circular discs. The detailed
structural and ferroelectric properties were carried out for sintered specimens. The results of X-ray diffraction showed
that all the ceramics specimens have a perovskite phase. The phase structure of
Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3, In2/3)0.05]0.9875O3 ceramics was transformed from the tetragonal to the rhombohedral, with
an increase in the ratio of Zr/Ti in system. In the present system the MPB that coexists with the tetragonal and rhombo-
hedral phases is a narrow composition region of x = 0.50 – 0.51. The scanning Electron Microscopy (SEM) showed an
increase of the mean grain size when the sintering temperature was increased. The dielectric constant
and the cou-
pling factor Kp reached the maximum values, while the mechanical quality factor Qm and the loss tangent reached the
lowest values when x = 0.50. For the composition where x = 0.50, these properties include
= 5414 (at the Curie tem-
perature), tang
= 0.039, Kp = 0.67, Qm = 20 and a Curie temperature of 335˚C.
Keywords: MPB, Sintering, Piezoelectric, Dielectric, Zr/Ti Ratio, Ceramic
1. Introduction
The lead zirconate titanate materials Pb(ZrxTi1x)O3 (PZT)
of a perovskite-type represented by the formula ABO3,
have been extensively used for the piezoelectric applica-
tions such as capacitors, sensors, actuators and other high
piezoelectric devices. In the PZT materials, the dielectric,
the ferroelectric, and the electromechanical characteris-
tics have been modified when several substitutions were
being done on the A- or/and B-sites, and also by varying
the ratio of Zr/Ti [1-6]. Since the discovery of the
behavior of the relaxor in Pb(Mg1/3,Nb2/3)O3 [7],
Pb(Zn1/3,Nb2/3)O3 [8], and Pb(Ni1/3,Nb2/3)O3 [9], the
studies of the ferroelectrics of the relaxor with Pb(B’1/3,
B”2/3)O3–type perovskites have attracted much attention
because of their excellent dielectric and electromechanical
properties. In a conventionally prepared PZT ceramics
with compositions near the morpho-tropic phase bound-
ary (MPB), the tetragonal, and the rhombohedral phases
always coexist [9]. The width and the properties of the
coexistence region are associated with the occurrence of
the compositional fluctuation of Ti4+ and Zr4+ ions in the
PZT materials [10]. The compositional fluctuation,
which is due to a non-uniform distribution of Titanium
and Zirconium ions, leads to a broad variation in the di-
electric constant accompanied with a Zirconium concen-
tration in the MPB region [11]. The width of this
coexistence region and the structure of the PZT ceramics
were greatly affected by the firing time and temperature
[12]. The selection of dopants or substitutions to tailor
some physical properties of PZT was based on many
factors which are the following: 1) charge neutrality, 2)
tolerance factors, 3) ionic radius, and 4) solubility/
miscibility. The substitution of lanthanides and the
different doped material at Pb-sites and Zirconium at the
Ti-sites with a different ratio of Zr/Ti have produced
many solid solutions with interesting properties for wide
industrial applications. The understanding of the relation-
ships between the variations in the physical properties
The Structure and the Electrical Properties of PbLa [Zr Ti (Mo ,In )]O Ferroelectric Ceramics
1200 0.95 0.05x(0.95–x)1/32/3 0.050.98753
and the phase coexistence with a composition is very
important because, first, they produce a great influence
on the characteristics of the PZT ceramics; and, second,
they stabilize the temperature and the time in the region
of the phase transition between the tetragonal and the
rhombohedral phases.
In this study,
Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3 piezoelec-
tric ceramics were investigated near the MPB by varying
the ratio of Zr/Ti. The purpose of this work was to study
the phase structure, the dielectric, and the piezoelectric
properties of these ceramics near the MPB in detail.
2. Experimental Procedure
The polycrystalline samples with a general composi-
tional formula Pb1–zLaz[ZrxTiy(Mo1/3,In2/3)1–(x+y)]1–z/4O3
with z = 0.05, (x + y)= 0.95 and 0.46 x 0.55 were
being prepared by a conventional dry ceramic method to
form the solid solution of a composition that follows:
Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3. The re-
agent grade oxide of PbO, ZrO2, TiO2, La2O3, MoO3 and
In2O3 were used as starting materials in a stoichiometric
ratio. The powders were, first, ball-milled for twelve
hours; and, then, calcined at 800˚C for two hours at the
following heating and cooling rates: 2˚C/min. After cal-
cination, the mixture was, first, ball-milled for twenty-
four hours; and then, dried and granulated with PVA as a
binder. After drying, the powders were pressed into discs
of a diameter of thirteen millimeters and of a thickness of
about one millimeter. The compacted discs were being
sintered at a temperature ranging from 1000˚C - 1180˚C
for two hours in air. To prevent PbO volatilization from
the pellets, a PbO atmosphere was controlled with a bed
of PbZrO3 powder placed in the vicinity of the pellets.
The X-ray diffraction (XRD, Simens D500) was used
to determine the crystalline phases present in the powder.
The compositions of PZT phases were identified by the
analysis of the peaks [(002)T, (200)R, (200)T] in the
twenty range 43˚ - 46˚. The Cu Kα radiation with a step
of 0.01˚ was used. The bulk densities of the sintered ce-
ramics were being measured by the Archimedes method.
The micrographs of the fractured samples were taken on
a JEOL scanning electron microscope. The average grain
size of the samples was determined from the micrographs
by the linear intercept technique. To investigate the elec-
trical properties, the electrodes were made by applying a
silver paste on the two major faces of the sintered disks
followed by a heat treatment at 750˚C for thirty minutes.
The dielectric constant was calculated from the capaci-
tance at a frequency of one kHz. It was measured at tem-
peratures ranging from 25˚C to 400˚C with a heating rate
of one ˚C/minute by using an impedance analyzer (HP
4192A, Hewlett-Packard). The piezoelectric samples were,
first, being poled in a silicone oil bath at 120˚C by apply-
ing a d.c. field of thirty kV/cm for thirty minutes; and,
then, were being cooled under the same electric field.
They were aged for twenty-four hours before testing.
The electromechanical coupling factor Kp, along with the
mechanical quality factor Qm were determined by the
resonance and anti-resonance technique from the equa-
tions [13]:
 
fa: anti-resonant frequency (Hz)
fr: resonant frequency (Hz)
R: resonant resistance (ohms)
C: capacity (faraday)
3. Results and Discussion
The analysis of the phase was performed from the XRD
(at a room temperature) patterns over a range of 2θ = 43˚
to 46˚, where the tetragonal phase displays two peaks,
(002)T and (200)T, and the rhombohedral phase displays
one peak, (200)R. There was a broad region where the
two phases, the rhombohedral and the tetragonal, coex-
isted. This indicated a typical morpho-tropic phase be-
havior (MPB). The typical patterns of the X-ray diffrac-
tion of Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3
compositions is shown in Figure 1. The samples ob-
tained in this study are summarized in Table 1. At
1150˚C, a typical tetragonal phase was observed at a
room temperature when xT 0.50. The (002)T and (200)T
peaks split into the (200)R peak as the ratio of Zr/Ti was
increased. The rhombohedral phase can be obtained
when xR 0.51. A transition from the tetragonal to the
rhombohedral phase was observed as the ratio of Zr/Ti
was increased. The Rhombohedral and the tetragonal
phases coexisted at x = 0.50 – 0.51, and demonstrated
that the ceramic resided at the morpho-tropic phase
boundary (MPB) [14]. The parameters of the lattice were,
then, determined from the triplets (200) by using a
non-linear least squares method [15]. The aR-parameter
of the rhombohedral phase and the aT-parameter, cT-pa-
rameter, and the tetragonality (cT/aT) of the tetragonal
phase of Pb0.95 La0.05[Zrx,Ti(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3
ceramics are plotted as a function of the ratio of Zr/Ti in
Figure 2. The results showed that the parameters of the
lattice of the tetragonal phase changed when the ratio of
Zr/Ti was modified. While the value of the aT parameter
increased, the one of cT parameter decreased, and the aR
parameter of the rhombohedral phase increased along
Copyright © 2011 SciRes. MSA
The Structure and the Electrical Properties of PbLa [Zr Ti (Mo ,In )]O Ferroelectric Ceramics 1201
0.95 0.05x(0.95–x)1/32/3 0.050.98753
Table 1. Series of compositions and crystal structure.
Crystal structure
Sample 1000˚C 1100˚C 1150˚C 1180˚C
Pb0.95 La0.05[Zr0.46Ti0.49(Mo1/3,In2/3)0.05]0.9875O3 T T - -
Pb0.95 La0.05[Zr0.47Ti0.48(Mo1/3,In2/3)0.05]0.9875O3 T + R T T -
Pb0.95 La0.05[Zr0.49Ti0.46(Mo1/3,In2/3)0.05]0.9875O3 T + R T + R T T
Pb0.95 La0.05[Zr0.50Ti0.45(Mo1/3,In2/3)0.05]0.9875O3 T + R T + R T + R T + R
Pb0.95 La0.05[Zr0.51Ti0.44(Mo1/3,In2/3)0.05] 0.9875O3 T + R T + R T + R T + R
Pb0.95 L0.05[Zr0.52Ti0.43(Mo1/3,In2/3)0.05]0.9875O3 T + R T + R R R
Pb0.95 L0.05[Zr0.54Ti0.41(Mo1/3,In2/3)0.05]0.9875O3 T + R T + R R -
Pb0.95 La0.05[Zr0.55Ti0.40(Mo1/3,In2/3)0.05]0.9875O3 R R - -
T = Tetragonal; R = Rhombohedral; T-R = Tetragonal-Rhombohedral.
(a) (b)
(c) (d)
Figrue 1. XRD patterns of Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3 ceramics sintered at 1150˚C for 2h: (a) x = 0.52, (b) x
= 0.46, (c) x = 0.50 and (d) x = 0.51.
with the sintering temperature in the coexistence region.
The resulting values of the parameters of the lattice of
the tetragonal phase showed that the c
T/aT axial ratio
decreased as aT increased and cT decreased. The values
of the parameters of the lattice were revealed to be
practically the same as those previously studied [16,
Figure 3 shows the SEM micrographs of
Pb0.95La0.05[Zr0.50Ti0.45(Mo1/3, In2/3)0.05]0.9875O3 ceramics
sintered at different temperatures. It can be observed
Copyright © 2011 SciRes. MSA
The Structure and the Electrical Properties of PbLa [Zr Ti (Mo ,In )]O Ferroelectric Ceramics
1202 0.95 0.05x(0.95–x)1/32/3 0.050.98753
Figure 2. The parameters of the lattice of Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3 ceramics as a function of composition
( for a sintering temperature about 1150˚C) .
Figure 3. SEM micrographs for Pb0.95La0.05[Zr0.50Ti0.45(Mo1/3,In2/3)0.05]0.9875O3 ceramics sintered at (a)1000˚C, (b) 1100˚C and
(c) 1150˚C.
that many distinct pores exist on the surface of the
Pb0.95La0.05[Zr0.50Ti0.45(Mo1/3,In2/3)0.05]0.9875O3 ceramics
sintered at 1000˚C and the average grain size is under 9
m. When the sintering temperature is increased, the
pores can hardly be observed and the grain size is about 9
m. This indicates that a high sintering temperature
promotes a grain growth process. The obtained images
show a slight difference in the particle size and also give
rise to the different phases, viz. the tetragonal, the rhom-
bohedral, and the tetragonal-rhombohedral. In addition to
the morphological modification of grains, different grain
sizes could be noticed for these samples. In this way, the
coexistence region of the tetragonal-rhombohedral phases
was demonstrated.
The values of the room temperature of the dielectric
constant (
) and the dissipation factor (tan δ) at 1 kHz for
all samples are given in Figure 4. It can be seen that the
curve appears to be parabolic, and the values of
crease sharply from 46/49 to 50/45; and, also, large di-
electric constants are obtained at the compositions of
50/45 (
= 430 at 1 kHz) and 51/44 (
= 390 at 1 kHz). It,
then, follows a decreasing trend when the ratio of Zr/Ti is
increased further. The present results verify the conclu-
sions about the dielectric constant peak in MPB. The
increase in Zr content induces the microstructure transi-
tion of Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3
from the rhombohedral to the tetragonal phase within the
MPB region, as indicated by the above XRD investiga-
tions. The tan shows an inverse trend and reaches the
minimum value of 3.9% when x = 0.50. Thus the compo-
sitions at 50/45 and 51/44 are at the center of the MPB.
Figure 5 reveals the dielectric constant
as a function
of temperature for the
Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3 ceramics (x
= 0.50 and x = 0.51) sintered at 1150˚C, which were
measured at a frequency of 1 kHz. As it might be known,
two peaks are observed on the dielectric constant versus
temperature curves in the measured temperature which
ranges between 265˚C and 330˚C for a sample of a ce-
ramic 50/45. The first dielectric peak corresponds to the
transition temperature TR–T, of the rhombohedral to the
tetragonal phase, but the second peak, which results at a
Copyright © 2011 SciRes. MSA
The Structure and the Electrical Properties of PbLa [Zr Ti (Mo ,In )]O Ferroelectric Ceramics1203
0.95 0.05x(0.95–x)1/32/3 0.050.98753
Figure 4.The dielectric constant ε and the loss tangent (at
room temperature, 1 KHz) for
Pb0.95La0.05[Zrx,Ti(0.95–x)(Mo1/3, In2/3)0.05]0.9875O3 ceramics as a
function of composition.
Figure 5. The dielectric constant ε (at 1 KHz) for
Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3 ceramics as a
function of temperature.
higher temperature, is the Curie temperature Tc. The
broadening in the transition phase is attributed to the
structural disorder and the compositional fluctuation
present in the arrangement of cation at A-site and B-site
with lattice vacancies. This results in a microscopic het-
erogeneity in the composition and the distribution of
different local Curie points [18].
Figure 6 shows the variation of the electromechanical
coupling factor Kp and the mechanical quality factor Qm
for Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3, In2/3)0.05]0.9875O3 ceramics.
It is observed in Figure 6 that as the ratio of Zr/Ti in-
creases, the value of kp increases; and, subsequently,
represents a peak of 0.67 at the ratio of Zr/Ti of 50/45;
but, when the ratio of Zr/Ti is further increased, the
value of Kp decreases. Qm continues to decrease; and,
finally, shows the minimum value when the ratio of
Figure 6. The Coupling factor Kp and Qm for
Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3 ceramics sin-
tered at 1150˚C as a function of composition (x).
Zr/Ti is 50/45 (Qm = 20). This is due to the fact that the
structure of the phase of
Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3 ceramics
changes, first, from the tetragonal phase to the coexis-
tence of both the tetragonal and the rhombohedral phases;
and, then, changes to a single rhombohedral phase when
the ratio of Zr/Ti is increased.
4. Conclusions
The aim of this study was to investigate the structure and
the behavior of the electrical properties in
Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3. The phases
of the sintered samples were examined by X-ray diffrac-
tometry. The structure of the phase of the system was
changed from the tetragonal to the rhombohedral as the
ratio of Zr/Ti was increased. The XRD results reveal that
an MPB with the co-existence of the rhombohedral and
the tetragonal for the ceramics lies in the range of x =
0.50 – 0.51. The parameters of the lattice: aT and cT of the
tetragonal structure and aR of the rhombohedral structure
were found to change when composition is modified. The
Pb0.95La0.05[Zr50Ti45(Mo1/3,In2/3)0.05]0.9875O3 ceramics sin-
tered at 1150˚C exhibit good piezoelectric properties: Kp
= 0.67, Qm = 20 and TC = 335˚C. This means that this
system is a promising candidate for the lead-free piezo-
electric applications.
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The Structure and the Electrical Properties of Pb0.95La0.05[ZrxTi(0.95–x)(Mo1/3,In2/3)0.05]0.9875O3 Ferroelectric Ceramics
Copyright © 2011 SciRes. MSA
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