Apr. 2008, Volume 2, No.4 (Serial No.5)
Journal of Materials Science and Engineering, ISSN1934-8959, USA
The fabrication and properties of 1-3 piezoelectric composite
QIU Yan-qin, LIU Jun, MENG Xian-feng, CHEN Cai-feng, YAN Ping, LUO Ying
(College of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China)
Abstract: PZT fibers were fabricated by extruding a mixture of
PZT powder and PZT sol. The microstructure, density and
shrinkage ratio of fibers were discussed theoretically. 1-3
piezoelectric composite which contained about 25 percent
ceramic phase was fabricated by arranging PZT fibers and
casting epoxy resin. Dielectric constant, electromechanical
coupling coefficient and mechanical quality factor were
calculated. The results indicated that Kp of 1-3 piezoelectric
composite was less than that of ceramic, but Kt and Kt/ Kp were
more than it; the εT,d33,, Kt and Kt/ Kp of composite ,whose fibers
were 400μm in diameter ,were all more than those of composite
made from fibers of 300μm.
Key words: 1-3 piezoelectric composite; ceramic fibers;
extruding a mixture; arrange-cast technique
1. Introduction
Piezoelectric ultrasonic transducer is used for
emitting while receiving waves[1]. In 1917 Langevin
P[2] developed piezoelectric single crystal quartz
transducer. Subsequently, piezoelectric ceramic
transducer, piezoelectric thin film transducer,
piezoelectric thick film transducer and piezoelectric
composite transducer were expanded. High frequency
transducer is almost from piezoelectric transducer. At
present, 1-3 piezoelectric composite is widely
researched and applied among the piezoelectric
composites[3-5]., which contains piezoelectric fibers
embedded in a polymer matrix and aligned through the
thickness of the device. It exhibits good characters such
as high piezoelectric constant, minor lateral

Acknowledgments: This research was supported by High
Technical Project of Jiangsu Province (No. BG2006026).
Additionally, the authors greatly acknowledge the helpful
assistance of Shandong University and Jiangsu Polytechnic
University.
Corresponding author: QIU Yan-qin, Master; research fields:
fabrication and analysis of piezoelectric composite. E-mail:
qiuyanqin0714@163.com.
electromechanical coupling, low acoustic impedance,
and broad bandwidth. Furthermore, it can be made into
many special shapes to meet kinds of applications for
the flexibility of polymer.
This paper describes the fabrication and property
analysis of fibers as well as 1-3 piezoelectric
composite. Importantly it expounds a method to
fabricate fibers by extruding from a mixture of PZT
powder and PZT sol.
2. Experimental
2.1 Fiber production
Firstly, extrusion from a mixture of PZT power
and an organic binder (PVA) was studied. There were
many pores and cracks in the fibers fabricated by this
way, because of volatilization of organic binder in
sintering[6]. Subsequently fibers were fabricated by
extrusion from a mixture where a sol instead of organic
binder. The process includes the fabrication of PZT
powder and PZT sol.
2.1.1 PZT powder preparation
To synthesize PZT powder, Pb3O4, TiO2, ZrO2,
and several additives were used. These raw materials
were mixed using a ball-mill for 48h with ethanol. The
mixed slurry was dried in an oven and precalcined in a
closed container at 900℃. Finally, PZT powder about 1
m was obtained.
2.1.2 PZT sol preparation
The PZT precursor solution was fabricated from
the precursor solution of lead acetate trihydrate,
zironium nitrate pentahydrate and titanium butoxide. In
order to control the hydrolysis reaction, acetic acid and
the mixed solution of barium and strontium were added
53
The fabrication and properties of 1-3 piezoelectric composite
to the precursor solution. This starting solution was
kept at 80℃ in a water-bath, and its concentration was
enhanced by the volatilization of solvent and additives.
The variables for controlling the hydrolysis reaction
were the curing temperature and the amount of water
and acetic acid. Till the spinnable concentration was
about 1.35-1.6 mmol/g, the sol had already fabricated.
2.1.3 Fiber production
The sol was adjusted by mixing it with the
fabricated PZT powder (powder: sol=5-8:1 in molar
ratio) in a breaker. The mixture was ground and pressed
into many cakes, which can remove the pore in the
mixture and increase its uniformity, density, and
plasticity. The mixture was put into the extrusion
apparatus and fibers were extruded through the
spinnerets with different diameters holes. Then the
extruded fibers were dried on an oblique glass panel for
48h and sintered at 1240℃ for 2h in a closed container
where fibers were covered by the mixture of Pb3O4 and
ZrO2. The procedure of fabrication of PZT fibers in this
study was summarized in Figure 1.
Lead acetate + MOE
Zirconium nitrate + MOE
Lead precursor
solution
Zirconium precursor
solution
Burium nitrate
and strontium
nitrate + water
Titanium butoxide + MOE
Titanium precursor
solution
PZT sol
PZT powder
Mixture (powder : sol=5~8:1)
Sintering(1240℃)
Fig. 1
drying
The procedures of fabrication of PZT fibers
The extruded fibers about several meters in length
were attainable, which were flexile all the same after
several hours. Figure 2 shows the SEM micrographs of
green fibers. The powder and sol were mixed
uniformly. Figure 3 shows the SEM micrographs of the
sintered fibers. The micrographs show that the sintered
fibers were polycrystalline, and had no defects such as
pores or cracks. It was considered that the added sol,
instead of organic binder which resulted in many pores
and cracks in sintering stage, promoted the
densification of fibers effectively. Table 1 shows the
shrinkage ration and density of fibers 400 m in
diameter extruded from the mixture of powder and
54
extruding
PVA(A), and fibers extruded from the mixture of
powder and sol (B and C), where the diameter of B and
C are 300 m and 400 m, respectively. It can be
concluded that density of the fibers fabricated by
extrusion from a mixture of PZT power and PZT sol
were promoted, because gel changed into oxide
ceramic with the desired composition during the
sintering stage.
Table 1
Shrinkage ratio and density of fibers A, B and C
Serial number
Shrinkage ratio
(%)
Density
(g/cm3)
A
24.80
5.82
B
14.04
7.23
The fabrication and properties of 1-3 piezoelectric composite
C
15.74
7.44
a
b
Fig. 2 Microstructure of the green fibers (a) diameter of 300μm (b) diameter of 400μm
a
b
Fig. 3 Microstructure of fibers after sintering (a) diameter of 300μm (b) diameter of 400μm
2.2 Composite fabrication
There are arrange-cast technique and dice-fill
technique to fabricate 1-3 type piezoelectric composite.
Dice-fill technique costs and wastes too much, and it’s
difficult to fabricate higher volume fraction of the
ceramic in composite. Arrange-cast technique is
aligning fibers in the matrix firstly, and then casting
epoxy resin to cover up the fibers. 1-3 type
piezoelectric composite was obtained after curing[7-8] in
an oven at 80℃ for 24h. The composite had a disk
shape, 16mm in diameter and 1.6mm in thickness,
where the ceramic volume fraction was about 25%.
discontinuousness of fibers, uniformity of silver and
intenerate of polymer, we determined the optimal
polarizing condition: processed on time of 20-30 min,
temperature of 100-120℃, and electric field of about
2.5-3 KV/mm.
2.3 Composite properties
Piezoelectric constant d33 was tested by
piezoelectric instrument. Low-frequency capacitance
The arranging density of fibers, in diameter 300m and
400m, were about 3.6/mm2 and 1.3/mm2.
After curing the composite needed to be polished
to the desired thickness, and its thickness was even.
The piezoelectric phase of specimen was visible. Then
the two sides of composite were sputtered with silver.
Here, the thickness of silver was about 0.01-0.02mm.
Specimen was curing at 100-140 ℃ . Consider
dielectric constant T, radial coupling coefficient Kp,
thickness coupling coefficient Kt and mechanical
quality factor were calculated, as shown in Table 2. In
order to contrast, the parameters of PZT were also
listed in Table 2.
Cp, dielectric loss tan, resonant frequency fs, parallel
resonant frequency fp and the minimum impedance ｜
Zmin ｜ of the composite were measured by precise
impedance analyzer (4294A, Agilent). Relative
55
The fabrication and properties of 1-3 piezoelectric composite
Table 2
Parameters of PZT ceramic and composite
Serial
number
d33
(pC/N)
T
tan (%)
Kp (%)
Kt (%)
Kt/Kp
Qm
A
469.0
3933.0
2.40
48.95
45.49
0.9293
65.80
B
168.2
275.1
3.76
35.79
51.49
1.4387
5.62
C
226.9
409.0
6.40
33.54
63.19
1.8840
1.48
2.3.1 Comparison in property between PZT
ceramic and composite
(1) Electromechanical coupling coefficient
Table 2 shows radial coupling coefficient kp of 1-3
composite less than PZT ceramic, thickness coupling
coefficient kt more than PZT ceramic, and its reachable
Kt/Kp 1.8840, more than 0.9293 of PZT. Therefore, it
made anisotropic property greater, the energy fastened
on thickness mold and resonance enhanced in
thickness. These were due to participation of polymer.
The sound wave was weakened when it transmit from
fibers of higher rigidity to flexile polymer. It
continuously reduced as transmitting to other fibers. So
resonance in radial was restrained and only wave in
thickness was left. As a result there was more energy in
thickness[9].
(2) Mechanical quality factor
Qm=2πfsL/Rmin= fp 2/2πfs ｜ Zmin ｜ C0( fp2 - fs2)
=fs/(f1/2 - f1/2)= fs/f1/2 Ex. (1)[10]
Where ｜Zmin｜ is the minimum impedance, fs is
resonant frequency and fp is parallel resonant
frequency. As a supplement, there are main resonances
in radial mold in PZT and in thickness in composite.
Therefore, Qm were calculated through resonance in
radial of PZT and in thickness of composite.
Table 2 also shows Qm of composites are (5.62
and 1.48) less than that of PZT. It is known that the
bandwidth (f1/2) of composite is extended.
2.3.2 Comparative of composites in property
between fibers of different diameter
Table 2 shows εT, d33, Kt and Kt/ Kp of composite
whose fibers are 400m in diameter more than those of
composite whose fibers are 300m in diameter.
56
However, Kp and Qm are contrary. The property of
composites depended on its fibers mainly, as the
ceramic volume fractions were in the same. It is known
that the density of 400m diameter fiber was more than
that of 300m diameter fiber as shown in Table 1. The
probable reason was that pores in the thinner fibers
were more than those in the fibers of 400m, because
the more of surface of fibers touched the air, the
heavier of volatilization of lead. Therefore, the
piezoelectric property of composite where fibers were
300m in diameter was inferior to that of composite
where fibers were 400m in diameter.
3. Conclusions
(1) The PZT fibers fabricated by extrusion from a
mixture of PZT power and PZT sol can meet
fabrication of 1-3 composite, whose shrinkage were
about 15%, density between 7.2 and 7.5.
(2) The radial coupling coefficient kp of 1-3
composite was less than that of PZT ceramic while its
thickness coupling coefficient kt and Kt/Kp were more
than that of PZT ceramic.
(3) The mechanical quality factor Qm of
composite was less than that of PZT, so the bandwidth
(f1/2) of composite was extended.
(4) εT, d33, Kt and Kt/ Kp of composite whose fibers
were 400m in diameter were more than those of
composite whose fibers were 300m. However, Kp and
Qm were contrary. Probably because volatilization of
lead was more heavier in 300m diameter fibers.
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