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Titre: Phase transition, ferroelectric and piezoelectric properties of Ba1-xCaxTi1-yZryO3 lead-free ceramics
Auteur: Wei Lin

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Current Applied Physics 13 (2013) 159e164

Contents lists available at SciVerse ScienceDirect

Current Applied Physics
journal homepage: www.elsevier.com/locate/cap

Phase transition, ferroelectric and piezoelectric properties of Ba1 xCaxTi1 yZryO3
lead-free ceramics
Wei Lin 1, Linli Fan 1, Dunmin Lin*, Qiaoji Zheng*, Ximing Fan, Hailing Sun
College of Chemistry and Materials Science, and Visual Computing and Virtual Reality Key Laboratory of Sichuan Province, Sichuan Normal University, Chengdu 610066, China

a r t i c l e i n f o

a b s t r a c t

Article history:
Received 14 April 2012
Received in revised form
30 April 2012
Accepted 5 July 2012
Available online 16 July 2012

Lead-free piezoelectric ceramics Ba1 xCaxTi1 yZryO3þ1mol%CuO were prepared by an ordinary sintering
technique and the effects of Ca2þ and Zr4þ on phase transition and electrical properties of the ceramics
were studied. The results of X-ray diffraction show that the ceramics exhibit a pure perovskite structure
at 0 x 0.175 and 0 y 0.175, suggesting that Ca2þ and Zr4þ diffuse into BaTiO3 lattices to form
a solid solution. The substitution of Zr4þ for the B-site Ti4þ ions of BaTiO3 decreases greatly Curie
temperature TC and strengthens the relaxor character of the ceramics, while the addition of Ca2þ has
a weak influence on TC and leads to an inhibition of grain growth. Owing to the more possible polarization states resulting from the coexistence of tetragonal and orthorhombic phases near room
temperature, the ceramics with x ¼ 0.075e0.125 and y ¼ 0.1 exhibit excellent piezoelectric properties:
d33 ¼ 254e345 pC/N and kp ¼ 38.0e45.2%, respectively.
Ó 2012 Elsevier B.V. All rights reserved.

Keywords:
Lead-free
Piezoelectric
Ferroelectric
Dielectric
BaTiO3

1. Introduction
Lead zirconate titanate (PZT) and PZT-based multi-component
materials have been studied extensively and widely used in electronic devices such as ceramic filters, transducers, actuators and
sensors because of their excellent properties. However, the use of
these lead-based materials has caused serious environmental
problems due to the high toxicity of lead oxide. Therefore, investigations have been extensively carried out to develop lead-free
ceramics with excellent piezoelectric properties for replacing the
lead-containing ceramics.
Barium titanate (BaTiO3) is a classical lead-free ferroelectric
with tetragonal symmetry of perovskite structure at room
temperature. For the past decades, BaTiO3-based lead-free materials are widely used as high dielectric materials but not piezoelectrics owing to their relatively poor piezoelectric properties
(d33 ¼ 191pC/N) [1] compared with PZT-based perovskite ceramics
(d33 ¼ 289e710pC/N) [2]. In recent years, for environmental
protection reasons, BaTiO3-based materials have attracted much
attention and been considered one of the possible alternatives to
the lead-based piezoelectric ceramics. Ang et al. reported that Zr4þ

* Corresponding authors. Tel.: þ86 28 84760802; fax: þ86 28 84767868.
E-mail addresses: ddmd222@yahoo.com.cn (D. Lin), joyce@sicnu.edu.cn
(Q. Zheng).
1
These authors contributed equally to the work.
1567-1739/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.cap.2012.07.006

can be incorporated into the B sites of BaTiO3 to form a solid
solution with improved piezoelectric properties (d33 ¼ 236pC/N)
[3]. Their study has also shown that Ce-modified BaTiO3 ceramics
possess weaker piezoelectricity compared with Zr4þ-doped
BaTiO3 ceramics [4]. Recently, Liu et al. designed a piezoelectric
system Ba(Zr0.2Ti0.8)-x(Ba0.7Ca0.3)TiO3 with a super high piezoelectric constant d33 (w 620pC/N) and reported that the high
piezoelectricity of Ba(Zr0.2Ti0.8)-x(Ba0.7Ca0.3)TiO3 originates from
a TCP (tricritical point)-type MPB (morphotropic phase boundary)
[5]. Since then, many modified BaTiO3-based ceramics, such as
(Ba1 xCax)(Ti0.98Zr0.02)O3 [6], (Ba0.95Ca0.05)(Ti1 xZrx)O3 [7], ZnOdoped Ba0.85Ca0.15Ti0.90Zr0.10O3 [8], (Ba0.93Ca0.07)(Ti0.95Zr0.05)O3
[9] and so on, have been prepared, and the effects of sintering
temperature [10], dwell time during sintering [11] and poling
conditions [12] on the piezoelectric properties of Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramics have been investigated. However, the
compositional effects of co-substitution of Ca2þ and Zr4þ for Aand B- site ions of BaTiO3 on the phase transition and electrical
properties of the ceramics are rarely reported. In the present work,
BaTiO3 ceramics co-modified with Ca2þ and Zr4þ in a wide doping
range were prepared by a conventional solid-state method, and
their microstructures, phase transition characteristics and electrical properties were studied systematically. It has been known
that BaTiO3-based ceramics can be sintered at high temperature
(>1500 C) [5]. Therefore, CuO is added as a sintering aid to
decrease the sintering temperature according to our previous
work [13].

160

W. Lin et al. / Current Applied Physics 13 (2013) 159e164

2. Experimental
Ba1 xCaxTi1 yZryO3þ1mol%CuO ceramics were prepared by
a conventional ceramic fabrication technique using metal oxide and
carbonate powders: BaCO3(99%, Sinopharm Chemical Reagent Co.,
Ltd, China), CaCO3(99%, Sinopharm Chemical Reagent Co., Ltd,
China), TiO2(98%, Sinopharm Chemical Reagent Co., Ltd, China),
ZrO2 (99%, Sinopharm Chemical Reagent Co., Ltd, China) and
CuO(99%, Sinopharm Chemical Reagent Co., Ltd, China). The
powders in the stoichiometric ratio of Ba1exCaxTi1eyZryO3 were
first mixed thoroughly in ethanol using zirconia balls for 10 h. After
the calcination at 1100 C for 4 h, CuO powder was added. The
mixture was ball-milled again for 8 h, mixed thoroughly with
a poly(vinyl alcohol) binder solution and then pressed into disk
samples. After the removal of the binder, the samples were sintered
at 1200e1325 C for 2 h. The sintered ceramics were coated with
silver paste to form electrodes on both sides and fired at 810 C. The
ceramics were poled at room temperature under a dc filed of
2e4 kV/mm in a silicone oil bath for 40 min.
The crystalline structure of the sintered samples was determined using x-ray diffraction (XRD) analysis with CuKa radiation
(DX1000, China). The microstructures were observed using scanning electron microscopy (JSM-5900LV, JEOL, Japan). The relative
permittivity εr and loss tangent tand at 1 kHz were measured as
a function of temperature using an LCR meter (Agilent E4980A,
Santa Clara, CA, USA). The polarization hysteresis (PeE) loops were
measured using a ferroelectric measuring system (Premier II,
Radiant Technologies, Inc. Albuquerque, NM, USA). The planar
electromechanical coupling factor kp was determined by the resonance method according to the IEEE Standards 176 using an
impedance analyzer (Agilent 4294A, Santa Clara, CA, USA). The
piezoelectric constant d33 was measured using a piezo-d33 meter
(ZJ-6A, Institute of Acoustics, Chinese Academy of Sciences, Beijing,
China).
3. Results and discussion
The XRD patterns of the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO and
Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics are shown in Figs. 1a and
b, respectively. As shown in Fig. 1, for the Ba1 xCaxTi0.90Zr0.10O3þ1mol
%CuO ceramics with x 0.175 and Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO
ceramics with y 0. 175, a pure perovskite structure can be observed,
indicating that Ca2þ and Zr4þ have diffused into the BaTiO3 lattices
to form a homogenous solid solution. As the substitution levels of
Ca2þ and Zr4þ increase above 0.175, a small amount of secondary
phase is formed. These results show that the solubility limits for both
Ca2þ and Zr4þ in the BaTiO3 lattices are 0.175. For the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics, an orthorhombic structure can
be observed at room temperature (20 C) (Fig. 1a). From Fig. 1b, the
Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics with low Zr4þ substitution levels possess a tetragonal symmetry. As y increases, (002)
and (200) diffraction peaks near 45 gradually merge into one peak,
suggesting that the ceramics undergo a structure transformation
from tetragonal to orthorhombic symmetry at room temperature
(20 C). Similar effect of Zr4þ on the crystal structure has been
observed in Zr-doped BaTiO3 ceramics [14].
Fig. 2 shows the SEM micrographs of the Ba1exCaxTi1ey
ZryO3þ1mol%CuO ceramics sintered at 1220 C for 2 h. It can be
seen that all the ceramics have a dense structure, giving a high
relative density (>95%) measured by Archimedes’ method. For the
Ba0.90Ca0.10Ti0.90Zr0.10O3þ1mol%CuO ceramic, there are distinct
grains of diameter about 11.5 mm uniformly distributed among the
grains which are of much smaller diameters, about 2.5 mm (Fig. 2a).
As x increases to 0.2, the grains become relatively uniform in size
and have an average size of 1.5 mm (Fig. 2b). This indicates that the

Fig. 1. (a) XRD patterns of the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics and (b) XRD
patterns of Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO.

introduction of Ca2þ leads to an inhibition of grain growth. Similar
phenomenon has been observed in Ca-modified PbTiO3 ceramics
[15]. Unlike Ca2þ, the substitution of Zr4þ for Ti4þ has a slight
influence on grain size and shape (Fig. 2c and d).
The P-E hysteresis loops of the Ba1 xCaxTi0.90Zr0.10O3þ1mol%
CuO ceramics with x ¼ 0, 0.05, 0.125, 0.175, and 0.25 and
Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics with y ¼ 0, 0.025, 0.1,
0.175, and 0.25 are shown in Figs. 3a and b, respectively. The variations of remanent polarization Pr and coercive field Ec with x and y
for the BCTZ-x/y-1ceramics are shown in Fig. 4. All the Ba1exCax
Ti1eyZryO3þ1mol%CuOceramics exhibit a typical P-E loop. The
Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics with x ¼ 0 exhibit
a well-saturated and squarelike P-E loop, giving a large Pr (14.2 mC/
cm2) and a relatively low Ec (0.15 kV/mm). As x increases from 0 to
0.25, the PeE loop becomes flattened and slanted gradually
(Fig. 3a). Similar compositional dependence of P-E loop is also
observed in the Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics
(Fig. 3b). For the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics with
x ¼ 0e0.10, the observed Pr has a weak dependence on x and
remains at the large values of 10.5e14.5 mC/cm2. However, the
observed Pr greatly decreases to 3.36 mC/cm2 with x increasing to
0.15 and then slightly decreases to 1.99 mC/cm2 with x further
increasing to 0.25. Different from Pr, the observed EC slightly
increases from 0.15 kV/mm to 0.34 kV/mm with x increasing from
0 to 0.25 (Fig. 4a). For the Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO

W. Lin et al. / Current Applied Physics 13 (2013) 159e164

161

Fig. 2. SEM micrographs of the Ba1exCaxTi1eyZryO3þ1mol%CuO ceramics sintered at 1220 C for 2 h: (a) x/y ¼ 0.1/0.1; (b) x/y ¼ 0.2/0.1; (c) x/y ¼ 0.15/0.175; (d) x/y ¼ 0.15/0.25.

ceramics, the observed Pr increases with y increasing and then
decreases, giving a maximum value of 8.70 mC/cm2 at y ¼ 0.025, and
the observed EC decreases monotonously from 0.68 kV/mm to
0.15 kV/mm with y increasing from 0 to 0.15. At y > 0.15, the
observed both Pr and EC are close to zero.

a

b

Fig. 3. PeE hysteresis loops of (a) the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics with
x ¼ 0, 0.05, 0.125, 0.175, and 0.25; (b) Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics with
y ¼ 0, 0.025, 0.1, 0.175 and 0.25.

Fig. 4. Variations of Pr and EC with (a) x for the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO
ceramics; and (b) y for the Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics.

162

W. Lin et al. / Current Applied Physics 13 (2013) 159e164

Fig. 5 shows the temperature dependences of εr for the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics with x ¼ 0, 0.05, 0.075, 0.1,
0.125, 0.15 and 0.225 and Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO
ceramics with y ¼ 0, 0.05, 0.075, 0.1, 0.125, 0.15 and 0.25 at 1 kHz.
For the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics with x ¼ 0, the
paraelectric cubic-ferroelectric tetragonal phase transition peak at
TC can be observed. As x increases from 0.025 to 0.175, two transition peaks are observed: one is associated with the paraelectric
cubiceferroelectric tetragonal phase transition near 90 C (TC), and
the other is the ferroelectric tetragonal-ferroelectric orthorhombic
phase transition near 40e60 C (TOeT). As x further increases, the
transition peak at TO T for the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO
ceramics with x ¼ 0.20, 0.225 and 0.25 becomes smeared (Fig. 5a).
For the Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics with y 0.075,
the paraelectric cubic-ferroelectric tetragonal phase transition peak
at TC can be observed. However, for the Ba0.85Ca0.15Ti1 y
ZryO3þ1mol%CuO ceramics with y ¼ 0.075e0.10, two transition
peaks (the paraelectric cubiceferroelectric tetragonal phase transition at 85 C (TC) and the ferroelectric tetragonal-ferroelectric
orthorhombic phase transition at 48 C (TO T)) can be observed.
As y further increases, the ferroelectric tetragonal-ferroelectric
orthorhombic phase transition at TO T can not be observed,
which may be ascribed to the pinched transition of ferroelectric to
ferroelectric phase. Similar pinched phase transition has been reported in Ba(Ti1 xZrx)O3 ceramics [14].
The variations of TC with x and y for the Ba1exCaxTi1ey
ZryO3þ1mol%CuO ceramics are shown in Fig. 6. For the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics, the observed TC exhibits a weak
dependence on x and has the values of about 80e94 C with
increasing x from 0 to 0.25 (Fig. 6a). Unlike x, the concentration of
Zr4þ in the Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics has an
important influence on TC. For the Ba0.85Ca0.15Ti1 yZryO3þ1mol%
CuO ceramic with x ¼ 0, the observed TC is 131 C. As y increases to

a

b

Fig. 5. Temperature dependences of εr at 1 kHz for (a) the Ba1 xCaxTi0.90Zr0.10O3þ1mol
%CuO ceramics with x ¼ 0, 0.05, 0.075, 0.1, 0.125, 0.15 and 0.225; (b) the Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics with y ¼ 0, 0.05, 0.075, 0.1, 0.125, 0.15 and 0.25.

a

b

Fig. 6. Variation of TC with x and y for the (a) Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO and (b)
Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics.

0.15, the observed TC greatly decreases to 40 C. The decrease in TC
may be attributed to the weakening of the bonding force between
the B-site ion and the oxygen ion and the distortion of the octahedron in the ABO3-type perovskites after the substitution of Zr4þ
for Ti4þ [14].
It is known that BaTiO3 is a normal ferroelectric and exhibits
a sharp dielectric peak at TC [1]. However, as shown in Fig. 5, the
Ba1exCaxTi1eyZryO3þ1mol%CuO ceramics possess the broadened
transition peak at TC. This suggests that a diffuse phase transition is
observed at TC. The diffuse phase transition has been observed in
many ABO3-type perovskite compounds such as Ba0.5Na0.5TiO3-based
ceramics [16], Pb(Mg1/3Nb2/3)O3 [17], Pb(Sc0.5Ta0.5)O3 [18,19], and Nbdoped (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 [20] and so on. The diffuseness in
the phase transition can be described by the equation (1)/εr 1/
εm ¼ C 1 (T T m)g [17], where εm is the maximum value of relative
permittivity at Tm (TC), g is the degree of diffuseness and C is the Curielike coefficient. The g can have a value ranging from 1 for a normal
ferroelectric to 2 for an ideal relaxor ferroelectric. Based on the
temperature plots of εr at 1 kHz, the graphs of ln(1/εr 1/εm) versus
ln(T Tm) for the Ba1exCaxTi1eyZryO3þ1mol%CuO ceramics were
plotted, giving the results shown in Fig. 7. All the samples exhibit
a linear relationship. By least-squared fitting the experimental data to
the equation, the g was determined. From Figs. 7aec, the observed g
of the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics decreases and
then increases with x increasing, giving the values of 1.92, 1.77 and
2.07 at x ¼ 0, 0.10 and 0.2, respectively. This is in agreement with the
temperature dependences of εr for the Ba1 xCaxTi0.90Zr0.10O3þ1mol%
CuO ceramics (Fig. 5a). Different from Ba1 xCaxTi0.90Zr0.10O3þ1mol%
CuO ceramics, the observed g of the Ba0.85Ca0.15Ti1 yZryO3þ1mol%
CuO ceramics increases from 1.50 to 1.90 with y increasing from 0 to
0.15 (Figs. 7def), indicating that the substitution of Zr4þ for Ti4þ
induces more relaxor phase transitions. Similar substitution effect of
Zr4þ has been observed in Zr-modified BaTiO3 ceramics [14,21]. It has
been known that for the A-site complex (A1A2)BO3 or B-site complex
A(B1B2)O3 ferroelectrics perovskite structure, a large difference in
ionic radii of the A- or B-site cations is favorable for the formation of
an ordered structure [16,18]. For the Ba1 xCaxTi0.90Zr0.10O3þ1mol%
CuO ceramics, as Ca2þ is much smaller than Ba2þ (0.134 nm vs.

W. Lin et al. / Current Applied Physics 13 (2013) 159e164

a

d

b

e

c

f

163

Fig. 7. Plots of ln(1/εre1/εm) versus ln(TeTm) for the Ba1exCaxTi1eyZryO3þ1mol%CuO ceramics. The symbols denote experimental data while the solid lines denote the least-squared
fitting line to the modified CurieeWeiss law.

0.161 nm, 12-fold coordination sites [22]), the substitution of Ca2þ for
the A-site Ba2þ should be favorable for forming an ordered structure;
hence, the disordered degree of the ceramics in the A site decrease
and thus the observed g decreases from 1.92 to 1.77 with x increasing
from 0 to 0.1. It has been also known that fine grain can induce more
diffuse phase transitions than large grain in K0.5Na0.5NbO3 [23],
BaTiO3 [24] and PbTiO3 [25] ceramics. Therefore, the increase in the g
from 1.77 to 2.07 with x increasing from 0.10 to 0.20 in the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO ceramics may be attributed to the
decrease in grain size (11.5 mm vs. 1.5 mm (Figs. 2aeb)). On the other

hand, due to the slightly small difference in the B-site ionic radii
between Ti4þ (0.061 nm) [22] and Zr4þ (0.072 nm) [22] in the 6-fold
coordination sites of the Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics,
the substitution of Zr4þ for Ti4þ increases the B-site disordered degree
and hence the local compositional fluctuation. As a result, the
Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics with high Zr4þ levels
exhibit a more diffuse phase transition and the large g was obtained.
The compositional dependences of the piezoelectric and
dielectric properties of the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO and
Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO ceramics are shown in Figs. 8

a

a

b

b

Fig. 8. Variation of d33, kp, εr and tand with x for the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO
ceramics.

Fig. 9. Variation of d33, kp, εr and tand with y for the Ba0.85Ca0.15Ti1 yZryO3þ1mol%CuO
ceramics.

164

W. Lin et al. / Current Applied Physics 13 (2013) 159e164

unchanged. Unlike Ca2þ, the substitution of Zr4þ has a weak
influence on the grain size of the ceramics and leads to the significant decrease in the TC. The relaxor character is observed in the
Ba1exCaxTi1eyZryO3þ1mol%CuO ceramics. The introduction of Ca2þ
weakens the diffuseness of phase transition at x < 0.10 and then
induces more relaxor diffuse phase transitions with x further
increasing because of small grain size, while the addition of Zr4þ
strengthens relaxor character of phase transition. Because of the
more possible polarization states resulting from the coexistence of
the orthorhombic and tetragonal phases near room temperature,
the ceramics with x ¼ 0.075e0.125 and y ¼ 0.1 exhibit excellent
ferroelectric and piezoelectric properties: d33 ¼ 254e345 pC/N and
kp ¼ 38.0e45.2%. A surprisingly large εr value of 10,370 is obtained
in the Ba1exCaxTi1eyZryO3þ1mol%CuO ceramics with x/y ¼ 0.15/
0.175.
Fig. 10. Variation of d33 with T for the Ba0.90Ca0.10Ti0.90Zr0.10O3þ1mol%CuO ceramic.

and 9, respectively. For the Ba1 xCaxTi0.90Zr0.10O3þ1mol%CuO
ceramics, the observed d33 increases with increasing x and then
decreases, giving a maximum value of 345 pC/N at x ¼ 0.1. Similarly,
the observed kp and εr reach the maximum values of 0.45 and 4009
at x ¼ 0.1 (Fig. 8a) and 0.125 (Fig. 8b), respectively. The observed
tand has a weak dependence on x and remains almost unchanged at
a value smaller than 3% (Fig. 8b). For the Ba0.85Ca0.15Ti1 y
ZryO3þ1mol%CuO ceramics, the maximum values of the observed
d33 and kp are obtained at y ¼ 0.075 (Fig. 9a). The observed εr
increases and then decreases, give a surprisingly high value of
10,370 at x ¼ 0.175 (Fig. 9b). The observed tand exhibit a weak
dependence on y and has a smaller value than 3.0%. It can be seen
from Figs. 8 and 9 that the Ba1exCaxTi1eyZryO3þ1mol%CuO
ceramics with x ¼ 0.05e0.15 and y ¼ 0.075e0.10 possess the
optimum piezoelectricity, which should be attributed to the
increase in the more possible polarization states resulting from the
coexistence of the orthorhombic and tetragonal phases near room
temperature as shown in Fig. 5. This is similar to the cases that PZT
and PZT-based ceramics near the morphotropic phase boundary
(MPB) between rhombohedral and tetragonal phases exhibit the
optimum piezoelectric properties [26].
Fig. 10 shows the temperature dependence of d33 for the
Ba0.90Ca0.10Ti0.90Zr0.10O3þ1mol%CuO ceramic which has the
optimum piezoelectric properties. The poled sample was annealed
at evaluated temperatures for 1 h, and then its d33 was measured.
As shown in Fig. 10, the observed d33 retain unchanged as the
annealing temperature increases from 30 to 70 C, and then
decreases rapidly with the annealing temperature further
increasing. The observed TC for the ceramic from the dielectric
measurement is about 84 C. It can be seen that as the annealing
temperature increase above TC, the piezoelectricity of the ceramic
does not disappear, which may be ascribed to relaxor character of
the ceramic.
4. Conclusions
Ba1exCaxTi1eyZryO3þ1mol%CuO lead-free ceramics were fabricated by a conventional solid-state reaction method and their
dielectric ferroelectric, and piezoelectric properties were studied.
The results of X-ray diffraction measurement show that Ca2þ and
Zr4þ diffuse into the BaTiO3 lattices to form a solid solution with
a perovskite structure at x/y < 0.175. After the addition of Ca, the
grain sizes decrease significantly and the TC retains almost

Acknowledgments
This work was supported by the projects of Education Department of Sichuan Province (11ZA104), Science and Technology
Bureau of Sichuan Province (2010JQ0046), and the Open Projects of
State Key Laboratory Cultivation Base for Nonmetal Composites and
Functional Materials of Southwest University of Science and Technology (10zxfk27) and State Key Laboratory of Electronic Thin Films
and Integrated Devices of University of Electronic Science and
Technology of China (KFJJ201108).

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