HUE UNIVERSITY
COLLEGE OF SCIENCES
-------------------
LE DAI VUONG
RESEARCH ON FABRICATION AND THE PHYSICAL PROPERTIES
OF THE MULTI-COMPONENT CERAMICS BASED ON PZT AND THE
RELAXOR FERROELECTRIC MATERIALS
Major: Solid State Physics
Code: 62.44.01.04
ABSTRACT OF THE THESIS
Hue, 2014
The thesis had implemented at College of Sciences, Hue University
Academic Supervisor: Assoc. Prof. Dr. Phan Dinh Gio
Reviewer 1:.....................................................................................................
Reviewer 2:.....................................................................................................
Reviewer 3:.....................................................................................................
This thesis will be reported at Hue University
Date & Time …../ …./…./….
1
INTRODUCTION
For more than 50 years, the ferroelectric materials are one of the most the
important materials and have been intensively investigated in both
fundamental research and applications. The reason is that they exist in many
important physical effects such as ferroelectric, piezoelectric, photovoltaic,
non-linear optical, pyroelectric effects, etc. These materials have the ability
for application in manufacturing of capacitors, high capacity memory, power
ultrasonic transducers used in biology, chemistry, pharmacology, and
piezoelectric transducers [3], [5], [35], [36], [81].
The important and main materials of applications often have the
perovskite structures, ABO3. That is the Pb(Zr,Ti)O3 (PZT) ceramics, and
PZT doped ‘‘soft’’and ‘‘hard’’ such as La, Ce, Nd, Nb, Ta, ... and Mn, Fe,
Cr, Sb, In. In addition to these families, there is a wide variety of complex
perovskite forms resulting from multiple ionic substitutions. Many of the
materials in the complex perovskite family are known to be relaxor
ferroelectrics. The general formula for the complex perovskite is:
(A’A’’…An’)BO3 or A(B’B’’..Bn’)O3, and their dielectric, piezoelectric and
ferroelectric properties of ceramics may be improved for high power
applications [3], [5], [16], [18], [30], [31], [37], [56], [57], [76], [81]. The
characteristics of relaxor ferroelectric materials are a high dielectric constant,
a broad ferroelectric- paraelectric transition (the diffuse phase transition) and
a strong frequency dependency of the dielectric properties. In addition, above
the Curie temperature of several tens of degrees still have spontaneous
polarization and hysteresis loops [5], [5], [58], [81].
Recently, the materials scientists have been intensively investigating the
application of multi-component ceramic systems combining the normal
ferroelectric PZT and relaxor ferroelectric materials such as: Pb(Zr,Ti)O3–
Pb(Zn1/3Nb2/3)O3 (PZT–PZN) [23], [24], [30], [31], [35], [42], [90];
Pb(Zr,Ti)O3–(Mn1/3Nb2/3)O3 (PZT-PMnN) [4], [15], [52]; Pb(Zr,Ti)O3–
Pb(Mn1/3Sb2/3)O3 (PZT-PMS) [5], [60], [80], [83]; Pb(Zr,Ti)O3–
Pb(Zn1/3Nb2/3)O3–Pb(Mg1/3Nb2/3)O3 (PZT–PZN–PMN) [13]; Pb(Zr,Ti)O3 –
Pb(Zn1/3Nb2/3)O3 – Pb(Mn1/3Nb2/3)O3 (PZT–PZN–PMnN) [29], [34], [64],
2
[84], [87]. These ceramics often have low dielectric loss (tanδ), large
dielectric constant ε, high mechanical quality factor (Qm), high
electromechanical coupling factor (kp) [3], [5], [29], [34], [64], [84], [87].
Recent research has demonstrated that the PZT–PZN–PMnN quaternary
ceramics (by combining PZT-PZN and PZT-PMnN ceramics) have excellent
piezoelectric properties: the high Qm, the low tanδ and the large kp, the high
remanent polarization, and the large dielectric constant [29], [34], [64], [75],
[84], [87] satisfy the requirements for practical application in piezoelectric
transformers, ultrasonic motors.
However, the sintering temperature of the ceramics is quite high (> 1150 oC)
[29], [34], [64], which leads to evaporation of PbO during the sintering
process, resulting in reduced properties of ceramic compositions and
environmental pollution. Therefore, lowering sintering temperature of PZT
based ceramics is very necessary. In order to reduce the sintering temperature
at which satisfactory densification could be obtained, various material
processing methods such as the 2-stage calcination method [5]; hot-pressed
method [3], [5], [32]; high energy mill [5]; liquid phase sintering [13], [15],
[26], [23], [33], [35], [41], [53]; using nano power [2], [17], [22] have been
performed. Among these methods, liquid phase sintering is basically an
effective method for aiding densification of specimens at low sintering
temperature. Many researchers have successfully decreased the sintering
temperature of PZT-based ceramics by using various additives such as
Li2CO3 (735 °C), Bi2O3 (820 °C), B2O3 (450 °C), CuO-PbO (790 °C), etc.
In some cases, these additives can facilitate a lower sintering temperature,
but decrease simultaneously the piezoelectric properties of ceramics due to
the formation of piezoelectrically inactive phases in the grain boundary
regions. Therefore, the research and fabrication ceramics sintered at low
temperature, while improving or not reducing the piezoelectric properties of
ceramics system is very important [16], [23], [44], [75], [80].
Thus, the PZT - PZN - PMnN ceramics is very attractive for both
fundamental research and applications. From the above fact, we have chosen
dissertation topic is “Research on fabrication and the physical properties
3
of the multi-component ceramics based on PZT and the relaxor
ferroelectric materials”.
The objective of the thesis is: (i) Fabrication and research the effects of
Pb(Zr0,47Ti0,53)O3 on the structure, microstructure and the physiscal properties of
xPb(Zr0,47Ti0,53)O3 - (0,925-x)Pb(Zn1/3Nb2/3)O3 - 0,075Pb(Mn1/3Nb2/3)O3 ceramic
systems. (ii) To study the effect of Zr/Ti ratio in PZT on the structure, and the
properties of the PZT - PZN - PMnN ceramics, determine PZT content which
ceramics have good electrical properties and the relaxor ferroelectric
characteristics. (iii) To study the characteristic properties of the Fe2O3 doped
PZT - PZN - PMnN ceramics. (iv) To study the effect of CuO on the sintering
behavior and electrical properties of PZT–PZN–PMnN ceramics.
Research objects: The main research objects of the dessertation were the
PZT - PZN - PMnN multi-component ceramic systems and the PZT - PZN PMnN doped CuO, Fe2O3 ceramics. The ceramic samples have been
prepared in our laboratory by ourself.
Experimental methods: To obtain the above objectives, we have used the
conventional ceramic technology and the B-site oxide mixing technique
(BO) for preparing the ceramic samples.
Scientific significance and practical: The thesis is a fundamental
research have oriented applications. The systematic research of the dielectric,
piezoelectric and ferroelectric properties contribute further understanding of
the physical properties of the multi-component ceramics based on PZT and
the relaxor ferroelectric materials, Pb(Zn1/3Nb2/3)O3 and Pb(Mn1/3Nb2/3)O3.
The results of the thesis will open up prospects for the fabrication of
electronic ceramic materials in our country, particularly the feasibility of
application of ceramic materials for fabricating ultrasonic sensors, ultrasonic
cleaners.
The layout of the thesis: The thesis is presented in four chapters including
118 pages.
Chapter 1. LITERATURE REVIEWS
4
Chapter 1 presents literature reviews in dissertation research, as a basis
for research and explains the survey results of physical properties of
materials such as: ferroelectric phase transition, hysteresis loops, domain
ferroelectric. Some characteristics of the PZT based ferroelectric ceramics
and the relaxor ferroelectric materials (PZN, PMnN). In addition, Raman
spectroscopy has also been introduced to explain the experimental results for
the next section.
Chapter 2. FABRICATION, STRUCTURE AND MICROSTRUCTURE
OF PZT –PZN – PMnN CERAMICS
2.1. Fabrication of PZT – PZN– PMnN ceramics
The PZT – PZN – PMnN ceramcis has been fabricated by the
conventional method and the B-site Oxide mixing technique (BO) includes
the following the sample groups:
Group 1: xPb(Zr0,47Ti0,53)O3 – (0,925-x)Pb(Zn1/3Nb2/3)O3 – 0,075Pb(Mn1/3Nb2/3)O3 +
0,7 % kl Li2CO3 (0,65 ≤ x ≤ 0,9); (MP: MP65, MP70, MP75, MP80, MP85
và MP90).
(2.1)
Group 2: 0,8Pb(ZryTi1-y)O3 – 0,125Pb(Zn1/3Nb2/3)O3 – 0,075Pb(Mn1/3Nb2/3)O3 +
0,7 % kl Li2CO3 (0,46 ≤ y ≤ 0,51); (MZ: MZ46, MZ47, MZ48, MZ49,
MZ50 và MZ51).
(2.2)
Group 3: 0,8Pb(Zr0,48Ti0,52)O3 – 0,125Pb(Zn1/3Nb2/3)O3 – 0,075Pb(Mn1/3Nb2/3)O3 +
0,7 % kl Li2CO3 + z % kl Fe2O3 (0,0 ≤ z ≤ 0,35); (MF: MF0, MF1, MF2,
MF3, MF4, MF5 và MF6).
(2.3)
Group 4: 0,8Pb(Zr0,48Ti0,52)O3 – 0,125Pb(Zn1/3Nb2/3)O3 – 0,075Pb(Mn1/3Nb2/3)O3 +
w % kl CuO (0,0 ≤ w ≤ 0,175); (MC: MC0, MC1, MC2, MC3, MC4, MC5
và MC6).
(2.4)
Firstly, the mixture of (Zn,Mn)Nb2(Zr,Ti)O6 (BO) [33], [51] was prepared by
reactions of ZnO, MnO2, Nb2O5, ZrO2 and TiO2 at temperature of 1100oC for 2h.
According to the results thermal analysis (DTA) and thermogravimetric analysis
(TGA) of (Zn,Mn)Nb2(Zr,Ti)O6 power (Figure 2.1) can see that the formation
reaction occurs when the temperature exceeds 978oC. However, experimental
results showed that (Zn,Mn)Nb2(Zr,Ti)O6 power was calcined at temperature
5
of 1100oC, the PZT-PZN-PMnN ceramics had the good electrical properties,
similarly to reports of methods [33].
Secondly, (Zn,Mn)Nb2(Zr,Ti)O6 and PbO were weighed and milled for
20 h. The powders were calcined at temperature 850 oC for 2 h, producing
the PZT–PZN–PMnN compound. Then, 0,7wt% Li2CO3 was mixed with the
calcined PZT–PZN–PMnN powder and then, powders milled for 20h. The
ground materials were pressed into disk 12mm in diameter and 1.5mm in
thick under 2 ton/cm2. The samples were sintered in a sealed alumina
crucible with PbZrO3 + 10 % kl ZrO2 coated powder at temperature 950 oC
for 2 h. Where, the purity of reagent grade oxide powders are above 99 %.
Δm (mg) -2.552
Δm (%) -6.208
TG |c (mg)
1
0
-1
-2
0.05
0
-0.05
HeatFlow (mW)
T: 239.63 (°C)
0
-10
T: 341.73 (°C)
T: 544.04 (°C)
-0.1
dTG |c (mg/min)
-3
T: 978.83 (°C)
Exo
T: 964.15 (°C)
-20
T: 240.19 (°C)
-30
-40
0
200
T: 342.15 (°C)
400
600
Sample Temperature (°C)
800
1000
Figure 2.1. TG and DTA curve of (Zn,Mn)Nb2(Zr,Ti)O6
2.2. Structure and microstructure of PZT – PZN – PMnN ceramics
2.2.1. Structure and microstructure of MP sample group
The X-ray diffraction analysis results (Figure 2.6) showed that all
samples have pure perovskite phase with tetragonal structure. When
increasing PZT content, the tetragonality c/a ratio increases (insert picture in
Figure 2.6). According to the PbZrO3–PbTiO3 phase diagram, at room
temperature Pb(Zr0.47Ti0.53)O3 is of the tetragonal phase (space group P4mm)
[24], [25], while Pb(Mn1/3Nb2/3)O3 is cubic structure [34], [60] and the PZN
composition was determined to be the rhombohedral (space group R3m) [3],
[24]. Therefore, with increasing molar fraction of PZT, the crystal symmetry
of ceramics should change due to the tetragonal distortions of PZT.
6
SEM image analysis results show that the sample group of the MP have
particle density of ceramic is quite dense and are closely-packed (Figure 2.8).
The average grain size and the density of samples are increased with an
increasing amount of PZT and reach maximum (∼ 1,04 µm, 7.81 g/cm3,
respectivety) at the PZT content of 0.8 mol and then rapidly decrease. The
grain size and the density of ceramics have a strong effect on dielectric,
piezoelectric and ferroelectric properties of ceramic materials. The
relationships between the grain size and the density of ceramics and electrical
properties are discussed in the next section.
1 .0 3 0
500
1 .0 2 5
T h e c/a ratio
600
Intensity (a.u)
400
1 .0 2 0
300
1 .0 1 5
200
1 .0 1 0
0 .6
0 .7
0 .8
P Z T c o n te n t (m o l)
0 .9
100
0
M P90
M P85
M P80
M P75
M P70
M P65
20
25
30
35
40
45
50
55
60
65
70
2 θ (D e g re e )
Figure 2.6. X-ray diffraction patterns
of MP sample group
Figure 2.8. SEM image of MP80
sample
20
30
40
50
(2 0 0 ) T
(0 0 2 ) T
112
211
44
45
2 θ (D e g re e )
102
201
002
200
111
110
43
60
46
300
1
2
3
4
5
6
202
220
-
Intensity (a.u)
M Z46
M Z47
M Z48
M Z49
M Z50
M Z51
001
100
Intensity (a.u)
101
2.2.2. Structure and microstructure of MZ sample group
6
5
4
3
2
1
70
2 θ (D e g re e )
Figure 2.10. X-ray diffraction patterns
of MZ sample group
Figure 2.12. Microstructures of
MZ48 sample
Figure 2.10 shows X-ray diffraction patterns (XRD) of the PZT–PZN–
PMnN ceramics with the variation of Zr/Ti ratio content. All the samples
showed a tetragonal perovskite phase. The tetragonal structures can be
determined from the double (002)T and (200)T peaks at 2θ ≈ 44.5o (insert
7
picture in Figure 2.10). The c/a ratio decreases with increasing Zr/Ti ratio,
indicating that the tetragonality of PZT-PZN-PMnN ceramics decreased
when Zr increased. With increasing Zr content (decreasing of Ti content),
the average grain size and the density of samples increases and reaches the
maximum value at Zr/Ti ratio of 48/52, then decreases.
In order to determine chemical composition of the PZT-PZN-PMnN
ceramics, the EDS spectrum is analyzed and shown in Figure 4.14. As shown
in Figure 2.14, the EDS spectrum clearly identifies that the Pb, Zr, Ti, Nb,
Zn and Mn elements are composed in PZT-PZN-PMnN ceramics. Based on
the EDS analysis, it can be confirmed that the qualitative and quantitative
chemical composition of the PZT-PZN-PMnN ceramic are quite good.
Nb
Pb
O
Ti
Zr
Nb
Ti
Mn
Zn
Pb
Pb
Figure 2.14. EDS spectrum of PZT-PZN-PMnN ceramics
Chapter 3. STUDY DIELECTRIC, FERROELECTRIC AND
PIEZOELECTRIC PROPERTIES OF PZT–PZN–PMnN CERAMICS
3.1. Dielectric properties of PZT–PZN–PMnN ceramics
3.1.1. The dielectric constant of MP, MZ sample groups at room temperature
In order to study the dielectric properties of PZT–PZN–PMnN ceramics,
the dielectric constant (ε) and dielectric loss (tanδ) of the ceramics at room
temperature was calculated from the capacitance (Cs) of the MP, MZ sample
groups measured at frequency of 1kHz shown in Table 3.1.
When the content of PZT increases from 0.65 to 0.8 mol, values of
dielectric constant ε increase and reach maximum (ε = 1230) at 0.8 mol PZT,
8
and then rapidly decreased. At this contant, the dielectric loss tanδ of 0.007
(Table 3.1). Table 3.1 shows the dielectric constant ε of MZ samples in the
range from 758 to 1319 and dependence of Zr/Ti ratio. When the ratio of
Zr/Ti increases the values of ε increase and reaches a maximum (ε = 1319)
at Zr/Ti = 48/52, and then decreases. While the dielectric loss tanδ desreases
with increasing Zr/Ti ratio. The minimum values of tanδ of 0.005 was
obtained at Zr/Ti = 48/52 and then increased. The increasing of dielectric
constant can be explained by increasing grain size effect [81].
Table 3.1. The average values of dielectric constant and dielectric loss
tan of the sample groups MP, MZ at room temperature and at 1kHz
Samples
tanδ
Samples
tanδ
MP65
1130 ± 3
0,007
MZ46
1109 ± 4
0,007
MP70
1134 ± 2
0,008
MZ47
1227 ± 2
0,007
MP75
1152 ± 2
0,008
MZ48
1319 ± 2
0,005
MP80
1226 ± 2
0,007
MZ49
1162 ± 2
0,006
MP85
1154 ± 2
0,09
MZ50
1146 ± 3
0,006
MP90
1143 ± 3
0,01
MZ51
758 ± 4
0,007
0.32
0.28
0.24
0.20
8000
0.16
4000
0.12
0.08
0
0.04
0
50
100
150
200
250
0
Temperature ( C)
300
0.00
350
Dielectric constant, ε
12000
20000
0.36
16000
12000
1
2
3
4
5
6
0.20
3
M Z46
M Z47
M Z48
M Z49
M Z50
M Z51
4
5
6
(b)
2
1
0.16
0.12
8000
0.08
4000
0.04
Dielectric loss, tanδ
0.40
(a)
M P65
M P70
M P75
M P80
M P85
M P90
16000
Dielectric loss, tanδ
Dielectric constant, ε
20000
0
0.00
50
100
150
200
250
300
350
0
Temperature ( C)
Figure 3.1 Temperature dependence of the dielectric constant and
dielectric loss at 1 kHz of MP (a), MZ (b) sample groups
Figure 3.1 shows the dependence of the dielectric constant ε and dielectric
loss tanδ on the temperature of MP (Figure 3.1 (a)), MZ (Figure 3.1 (b)) the
sample groups measured at frequency of 1kHz. As seen in Figure 3.1, the
dielectric properties exhibited characteristics of the relaxor ferroelectric
material in which the phase transition temperature occurs within a broad
temperature range. This is one of the characteristics of ferroelectrics with
9
disordered perovskite structure. It is different compare with the PbTiO3
ferroelectric materials [1], [3], [81].
The plot of ln(1/ε – 1/εmax) versus ln(T – Tm) of PZT-PZN-PMnN
ceramics at 1 kHz is shown in figure 3.2. The slopes of the fitting curves are
used to determine the γ value. For MP sample groups, the values of γ decrease
from 1.88 to 1.70 (Figure 3.2(a)) and the MZ sample groups, the values of γ
increase from 1.74 to 1.94 (Figure 3.2(b)). The temperature Tm of the MP
ceramic samples increases with increasing PZT content and in the range of
206 oC to 275 oC and εmax increased to a maximum value of 18371 when the
PZT is 0.8 mol and then decreased. Because of the different phase
transformation temperatures of PZN (Tm ≈ 140oC) [25], [74] and PZT (TC ≈
390oC) [74], so the phase transition temperature of the PZT–PZN–PMnN
ceramics should exhibit a significant dependence on PZT content [74]. For
MZ sample groups, with the increasing Zr content, the maximum of εmax
increase and reach biggest (εmax = 19473) at the Zr/Ti ratio is 48/52. The
Curie temperature decreases with the increasing Zr content because the
Curie temperature of PbZrO3 is about 232oC [71] and it is lower than that of
PbTiO3, 490oC [3], [74].
(a)
M P90 → γ6 = 1.70
M P85→ γ5 = 1.77
M P80 → γ4 = 1.83
M P75→ γ3 = 1.85
Ln(1/ε−1/εmax )
Ln(1/ε−1/εmax)
(b)
MZ46 → γ1 = 1.74
MZ47 → γ1 = 1.83
MZ48 → γ1 = 1.85
MZ49 → γ1 = 1.93
MZ50 → γ1 = 1.94
M P70→ γ2 = 1.86
MZ51 → γ1 = 1.90
M P65→ γ1 = 1.88
Fit
Fit
-1
0
1
2
3
Ln(T-T m )
4
5
-1
0
1
2
3
4
5
Ln(T-T m )
Figure 3.2 Plot of ln (1/ε – 1/εm) versus ln(T - Tm) of MP (a), MZ (b)
sample groups
3.1.3. The dependence of the dielectric properties versus the frequency
Figure 3.3, 3.4 show the temperature dependence of the dielectric
constant ε and dielectric loss tanδ of the MP80 and M48 samples measured
at frequency of 1kHz, 10kHz, 100kHz and 1MHz, respectively. We can see
that the shape of the ε peaks was broad, which is typical of a case diffuse
transition with frequency dispersion. When the measured frequency
10
increased, the maximum of εmax was decreased and shifted to higher
temperature while dielectric loss increased near the Curie point, which is
typical of a relaxor material [81].
20000
1kH z
10kH z
100kH z
1000kH z
14000
12000
0 .5
0 .4
10000
0 .3
8000
6000
0 .2
4000
2000
0 .1
0.40
18000
MZ48
16000
1kHz
10kHz
100kHz
1000kHz
14000
12000
0.35
0.30
0.25
10000
0.20
8000
6000
0.15
4000
0.10
2000
0.05
0
0
Dielectric loss, tanδ
M P80
16000
Dielectric constant, ε
0 .6
18000
Dielectric loss, tanδ
D ielectric constant, ε
20000
0.00
0
50
100
150
200
250
50
0 .0
350
300
100
150
200
250
300
350
0
Temperature ( C)
0
T em perature ( C )
Figure 3.3. Temperature dependence of
dielectric constant ε and dielectric loss
tanδ of MP sample group at different
frequencies
Figure 3.4. Temperature dependence of
dielectric constant ε and dielectric loss
tanδ of MZ sample group at different
frequencies
MP80
MP75
50
MP85
2
30
20
10
MP70
MP90
MP65
0
-25
-20
-15
-10
-5
Polarization, P (µC/cm )
40
MP65
MP70
MP75
MP80
MP85
MP90
2
Polarization, P (µC/cm )
3.2. Ferroelectric properties of PZT – PZN – PMnN ceramics
3.2.1 The effect of PZT content and Zr/Ti ratio on ferroelectric properties
of PZT – PZN – PMnN ceramics at room temperature
Figure 3.7, 3.8 show the forms of ferroelectric hysteresis loops of the
sample groups measured at room temperature. From ferroelectric hysteresis
loops of the sample groups, the remanent polarization Pr and the coercive
field Ec were determined, as shown in figure 3.9. The Pr reaches the highest
value (34.5 µC/cm2) at PZT content of 0.8 mol and Zr/Ti ratio of 48/52. At
contents, the coercive field Ec reaches value 9.0 kV/cm. This result is in good
agreement with the studied dielectric properties of the samples.
0
5
10
15
20
25
-10
-20
-30
-40
Field, E (kV/cm)
Figure 3.7 Hysteresis loops of MP
sample group
M Z 46
M Z 47
M Z 48
M Z 49
M Z 50
M Z 51
40
30
20
10
0
-30 -25 -20 -15 -10 -5 0
-10
5
10
15
20
25
30
-20
-30
-40
-50
Field, E (kV/cm )
Figure 3.8 Hysteresis loops of MZ
sample group
25
12
20
11
10
15
9
10
0.60
8
0.65
0.70
0.75
0.80
0.85
0.90
0.95
40
(b)
35
30
25
20
15
10
0.45
0.46
0.47
PZT content (mol)
0.48
0.49
0.50
0.51
18
17
16
15
14
13
12
11
10
9
8
7
6
0.52
Coercive field, E c(kV/cm)
13
2
14
(a)
Remanent polarization, P r (µC/cm )
30
Coercive field, E c(kV/cm)
2
Remanent polarization, P r (µC/cm )
11
Zr content (mol)
Figure 3.9. The Pr and the Ec as a function of PZT contents (a) and Zr/Ti
ratios (b)
3.2.2 The temperature dependence of ferroelectric properties of PZT –
PZN – PMnN ceramics
The effect of temperature on ferroelectric properties of ceramics is studied
by hysteresis loops of the MZ48 sample (Figure 3.10) measured at different
temperatures from 30 oC to 280 oC. When the temperature increased from
room temperature to 120 °C, the remanent polarization Pr increased. When the
temperature rises above 120 °C, the remanent polarization Pr and the coercive
field Ec decreased (Figure 3.11). The reason is when the temperature increases,
the oxygen vacancies in the perovskite structure will move and significantly
increase the conductivity of the material which should increase the dielectric
loss. The size of the hysteresis loops depend on dielectric loss of the material.
Therefore, the dielectric loss increases, the size of the hysteresis loops
increases, the remanent polarization Pr and the coercive field Ec increases[81].
When the temperature increases (above 120 oC), large thermal motion energy,
bipolar disorder increased, the hysteresis loops narrowed, the remanent
polarization Pr and the coercive field Ec decreases.
2
20
-2 0
-1 0
0
10
-2 0
-4 0
-6 0
20
140
160
180
200
220
240
260
280
o
C
C
C
o
C
o
C
o
C
o
C
o
C
30
o
o
F ie ld , E (k V /c m )
Figure 3.10 Hysteresis loops of MZ48
45
18
40
Pr
16
35
EC
14
30
12
25
20
10
15
8
10
6
5
4
0
0
50
100
150
200
250
300
Coercive field, E c (kV/cm )
2
P olarization, P (µC /cm )
40
0
-3 0
R em anent polarization, P r (µC/cm )
60
o
30 C
o
40 C
o
50 C
o
60 C
o
80 C
o
100 C
o
120 C
2
o
T e m p e ra tu re ( C )
Figure 3.11. Temperature dependence of
12
3.3. Piezoelectric properties PZT- PZN-PMnN ceramics
To determine piezoelectric properties of ceramics, resonant vibration
spectrum of sample groups were measured at room temperature. From these
resonant spectra, electromechanical coefficients kp, kt, k31, piezoelectric
coefficients d31, mechanical quality factor Qm were determined (Figure 3.16). As
seen in Figure 3.16 (a), piezoelectric properties were strongly influenced by
the composition of the ceramics. As the increase in PZT content not only
enhanced the electrical properties, but also increased the mechanical
properties of ceramics. The values of kp, kt, k31, d31 and Qm reach maximum
(kp = 0.58, kt = 0.48, k31 = 0.34, d31 = 130 and Qm = 1034) at 0.8 mol PZT,
and then rapidly decreased with increasing x content. These results are
consistent with the literature [74].
1000
0.4
900
0.3
kp
kt
k31
800
d31
700
Qm
600
0.7
0.8
PZT content (mol)
0.9
140
120
100
80
60
1600
(b)
0.6
1400
0.5
1200
0.4
0.3
kp
kt
0.2
0.45
1000
d31
Qm
k31
800
0.46
0.47
0.48
0.49
0.50
0.51
160
140
120
100
80
60
0.52
Zr content (mol)
Figure 3.16 The values of kp, kt, k31, d31, Qm and tanδ of the PZT-PZN-PMnN
ceramic as a function of PZT contents (a) and Zr/Ti ratios (b)
Piezoelectric coefficients, d 31 (pC/N)
1100
0.7
Mechanical quality factor, Q m
1200
Electromechanical coefficients, kp, kt, k31
1300
0.5
0.2
0.6
160
(a)
Piezoelectric coefficients, d 31 (pC/N)
1400
0.6
Mechanical quality factor, Q m
Electromechanical coefficients, kp, kt, k31
For MZ sample group (Figure 3.16 (b)), when the amount of Zr/Ti ratio
is lower than 48/52, the kp, kt, k31, d31 are rapidly increased with increasing
Zr/Ti ratio, while the mechanical quality factor Qm and the dielectric loss
tanδ are lightly decreased. This is probably related to characteristics of the
increasing grain size. As is well known, the increased grain size makes
domain reorientation easier and severely promotes domain wall motion,
which could increase the piezoelectric properties [81].
13
Chapter 4. STUDY THE EFFECTS OF CuO, Fe2O3 ON
PROPERTIES OF PZT–PZN–PMnN CERAMICS
4.1. Effect of Fe2O3 on properties of PZT-PZN-PMnN ceramics
To improve the mechanical quality factor Qm and dielectric loss tanδ of
PZT-PZN-PMnN ceramics, Fe2O3 doping were mixed into the PZT-PZNPMnN ceramics.
4.1.1. Effect of Fe2O3 on structure, microstructure of PZT-PZN-PMnN ceramics
4 .1 2
4 .0 4
a
c
40
1 .0 1 0
202
220
112
211
102
201
111
30
1 .0 1 5
6
(0 0 2 ) T
(2 0 0 ) T
(2 0 0 ) R
M6
M5
M4
M3
M2
5
4
3
2
1
0
R 111
002
200
0 .0
0 .1
0 .2
0 .3
0 .4
F e 2 O 3 c o n te n t (% w t)
1 .0 2 0
Intensity (a.u.)
c /a
c/a ratio
o
a,c ( A )
4 .0 6
4 .0 0
(b )
1 .0 2 5
4 .0 8
4 .0 2
001
100
20
1 .0 3 0
4 .1 0
300
(a )
101
M F0
M F1
M F2
M F3
M F4
M F5
M F6
110
0
1
2
3
4
5
6
R 100
Intensity (a.u.)
Figure 4.1 shows X-ray diffraction patterns (XRD) of the PZT–PZN–
PMnN ceramics at the different contents of Fe2O3. All samples have
perovskite phase with tetragonal structure. When increasing of Fe2O3
content, the tetragonality c/a ratio increases as shown in insert figure 4.1(a).
It can be determined from the (002)T and (200)T double peaks at 2θ ≈ 44.5o
(figure 4.1(b)).
50
2 θ (D e g re e )
60
70
M1
M0
4 3 .0
4 3 .5
4 4 .0 4 4 .5 4 5 .0
2 θ (D e g re e )
4 5 .5
4 6 .0
4.1 The
patterns
of PZT–PZN–PMnN
ceramics
Figure Figure
4.3 shows
theXRD
SEM
micrographs
of the fracture
surface of the
samples as Fe2O3 addition. It is seen from the micrographs that the grain size
grows with the increase of Fe2O3 addition. Below the 0.25 wt% Fe2O3, the
grain sizes increase and the grain boundaries present regular shapes.
However, when the addition of Fe2O3 is higher than 0.25 wt%, a few cavities
appeared between the grains (MF5, MF6 samples).
14
MF0
MF2
MF3
MF4
MF5
MF6
Figure 4.3 Microstructures of samples with the different Fe2O3 contents
4.1.2. Effect of Fe2O3 on dielectric properties of PZT-PZN-PMnN ceramics
0.35
0.30
0.25
10000
0.20
5000
0.15
4
0.10
3
0
0.05
o
Curie temperature, T m ( C )
15000
260
0.40
MF0
MF1
MF2
MF3
MF4
MF5
MF6
20000
Dielectric loss, tanδ
Dielectric constant, ε
25000
250
240
230
220
50
100
150
200
250
Temperature (oC)
300
350
0.0
0.1
0.2
0.3
0.4
Fe 2 O 3 content (%wt)
Figure 4.4 Temperature dependence of
the dielectric constant and dielectric
loss at 1 kHz of samples
Figure 4.5 The temperature Tm of
Fe2O3-doped PZT–PZN–PMnN
ceramic samples
Figure 4.4 shows the dependence of dielectric constant and dielectric
loss tan of the ceramics versus temperature at frequency of 1 kHz. With
increasing Fe2O3 doping, the εmax increased to a maximum value of (24500)
when the Fe2O3 content is 0.25wt% and then decreased. This can be
explained by increasing grain size effect [81]. Corresponding Fe2O3 content
increases, Tm temperature of ceramics lightly decreased from 244 to 234 oC
(Figure 4.5).
274
700
274
272
680
700
145
200
140
190
A1(1TO)
A1(1TO)
268
266
266
264
264
262
660
680
640
660
-1
1
150
210 E(2TO )
1
145
200
270
268
-1
-1
E(2TO1) (cm-1)
E(2TO1) (cm-1)
A1(2TO) (cm )
M6
-1
M6
(b) 272270
E + B1 (cm ) -1
E + B1 (cm )
Silent E +B1
155
220 Silent E +B1
150
210 E(2TO )
A1(2TO) (cm )
Rh
R
A 1 (3 L O ) h
A 1 (3L O )
R1
E (4 L O )
E (4L O )
R1
A 1 (2T O )
E (2L O )
E (2 L O )
(a )
E(4LO), R1 (cm ) -1
E(4LO), R1 (cm )
230
R1
A 1 (2 T O ) E + B 1
E + BE1 (2T O )
E (2A T1 (1T
O)O)
A 1 (1(a.u
T O ))
In ten sity
In te n s ity (a .u )
160
160
230
155
220R1
620
640
600
620
580
600
15
0
54
51
48
45
-4
-1
FW H M (cm )
Ln(1/ε-1/ε m )
-8
-1 2
M 0 → γ 0 = 1.88
-1 6
M 1 → γ 0 = 1.90
-2 0
M 3 → γ 0 = 1.93
M 2 → γ 0 = 1.91
M 4 → γ 0 = 1.94
M 5 → γ 0 = 1.79
-2 4
M 6 → γ 0 = 1.67
E(4LO )
104
102
100
98
R1
55
54
53
52
51
(E+B 1 )
72
71
70
69
E(2TO 1 )
3 1 .4
3 1 .2
3 1 .0
3 0 .8
3 0 .6
A 1 (1TO )
0 .0
F it
0 .1
0 .2
0 .3
0 .4
Fe 2 O 3 content (% w t)
-2 8
0
1
2
3
4
5
Ln(T -T m )
Figure 4.9 Ln(1/ −1/max) as a function of ln(T−T max) of samples FWHM
of the PZT-PZN-PMnN samples as a function of Fe2O3
Figure 4.8(a) shows the Raman scattering spectra of Fe2O3-doped PZT–
PZN-PMnN ceramics measured at room temperature. Compared with
PbTiO3 [1] and Pb(Zr,Ti)O3 [64], the vibration bands in the Raman scattering
spectra of Fe2O3-doped PZT–PZN–PMnN samples seem wider and more
dispersive. It can be seen from this figure that the silent mode at about 268
cm-1 shifts to a low frequency as the Fe2O3 doping increases. Dilsom [18]
assumed that the decrease in frequency with increasing Fe2O3 contents is due
to the difference in the atomic mass of Zr (91.22 g), Ti (47.87 g), Nb (92.90
g), Zn (65.39 g), and Mn (54.94 g) when they are replaced by Fe (56 g) in
the B site. The shift of the silent mode to a low frequency due to Fe2O3
content increases the average energy of the B–O bonding hence Tm of the
ceramics are decreased [91].
The value of γ gives information on the phase transition diffuse
characterized. The values of γ increases with increase of Fe2O3 contents
16
(Figure 4.9(a)). It is found that the full width at half maximum (FWHM) of
the B–O vibrations exhibit an obvious increase, leading to a strong
composition disorder (Figure 4.9(b)). However, when the Fe2O3 content is
higher than 0.25 wt%, the value of γ and FWHM decreases. This can be
explained by the solubility limit of Fe ion in the PZT-PZN-PMnN ceramics.
4.1.3. Effect of Fe2O3 on piezoelectric properties of PZT-PZN-PMnN ceramics
To determine piezoelectric properties of ceramics, resonant vibration
spectra of samples were measured at room temperature (Figure 4.11). From
these resonant spectra, piezoelectric parameters of samples were determined
(Figure 4.12).
6
5
10
4
10
3
10
2
10
1
10
0
80
7000
60
6000
40
0
-2 0
-4 0
-6 0
-8 0
-1 0 0
200
210
220
230
240
F re q u e n cy, f (kH z)
250
(b )
5000
20
Z (Ω)
Z (Ω)
10
8000
100
(a )
θ (D egree)
10
4000
3000
2000
1000
0
1
2
3
4
5
6
7
8
F re q u e n c y, f (M H z)
Figure 4.11. Spectrum of radial resonance (a) and thick resonance (b) of MF4
sample
Figure 4.12 shows the electromechanical coupling factor (kp, kt), the
piezoelectric constant (d31), the mechanical quality factor Qm and dielectric
loss tanδ change as a function of the amount of Fe2O3. The mechanical
quality factor (Qm) and the dielectric loss (tanδ) of the Fe2O3-doped PZT–
PZN–PMnN ceramics markedly improved, as shown in Fig. 4.12. As the
Fe2O3 content in the PZT–PZN–PMnN ceramics was increased up to 0.25
wt%, the Qm value increased steadily up to 1450 while dielectric loss tanδ
decreased steadily down to the lowest value (tanδ =0.003) because the Fe
ions at the (Ti, Zr, Nb) sites in the lattice acted as acceptors. As can be seen
in Figure. 4.12, the kp, kt and the d31 show a similar variation with increasing
Fe2O3 content. When the content of Fe2O3 is lower than 0.25 wt%, the kp, kt
and the d31 were increased with increasing Fe2O3 content. The optimized
values for kp of 0.64, kt of 0.51 and d31 of 155 pC/N were obtained at content
Fe2O3 = 0.25 wt%. This is probably related to characteristics of the increasing
grain size.
0.010
0.008
0.006
0.004
0.002
0.64
1800
kp
1600
Qm
1400
0.60
0.56
1200
0.52
0.48
kt
0.44
Tanδ
1000
800
0.40
600
0.0
0.1
0.2
0.3
160
140
120
100
80
60
60
50
MF
40
30
2
2000
d31
0.68
P (µC/cm )
0.012
0.72
The piezoelectric constant d31 (pC/N)
Dielectric loss tanδ
0.014
The mechanical quality factor, Qm
0.016
Electromechanical coupling factor, kp, kt
17
20
10
0
-30 -25 -20 -15 -10 -5
-10 0
5
10
15
-30
-40
-50
0.4
20
25
30
MF1
MF2
MF3
MF4
MF5
MF6
-20
-60
E (kV/cm )
Fe2O3 content (%wt)
Figure 4.12. The kp, kt, d31, Qm, and tanδ Figure 4.13 Hysteresis loops of Fe2O3doped PZT-PZN-PMnN ceramics
as a function of Fe2O3 contents
4.1.4. Effect of Fe2O3 on ferroelectric properties of PZT-PZN-PMnN ceramics
From the form of feroelectric hysteresis loops of the Fe2O3 doped PZTPZN-PMnN samples measured at room temperature, the remanent
polarization Pr and the coercive field Ec were determined, as shown in Table
4.5.
Table 4.5. The characterize parameters of ferroelectric properties (Pr, Ec) of Fe2O3
doped PZT-PZN-PMnN
Samples
MF0
MF1
MF2
MF3
MF4
MF5
MF6
EC (kV/cm)
9,8
9,8
8,4
9,0
8,6
8,7
10,5
34,5
34,1
35,6
36,0
37,0
35,0
26,0
2
Pr (µC/cm )
A sharp increase in Pr was observed for MF0-MF4 samples, reaches the
highest value (37 µC/cm2) with MF4 sample, and then decreases. This result
is in good agreement with the studied dielectric and piezoelectric properties
of the samples. While, the coercive field Ec decreases with increasing of
Fe2O3 content. The minimum value of the Ec is 8.6 kV/cm were obtained at
content of Fe2O3 = 0.25 wt%.
4.2. Effect of CuO on the sintering behavior and electrical properties of
PZT–PZN–PMnN ceramics
4.2.1. Effect of CuO on the sintering behavior of PZT–PZN–PMnN ceramics
Many material scientists are interested in research [29], [34], [64], [87] in
PZT−PZN−PMnN ceramics due to their large dielectric constant ε, large
electromechanical coefficient kp, large polarization Pr, high mechanical quality
18
factor Qm, and suitability for the application of ultrasound transducers. However,
the sintering temperature of this ceramic system is quite high (1150 °C), [29],
[64]. The most common and effective method to reduce the sintering
temperature of PZT based ceramics is using various additives such as
BiFeO3, CuO, CuO-ZnO, Li2CO3, Bi2O3, LiBiO2, B2O3, CuO-PbO, Cu2OPbO to create low-temperature liquid phases of ceramics [5], [13], [15], [16],
[20], [23], [33], [35], [41], [44], [53]. In this section, we have chosen the
CuO
doped
0,8Pb(Zr0,48Ti0,52)O3
0,125Pb(Zn1/3Nb2/3)O3
0,075Pb(Mn1/3Nb2/3)O3 ceramics sintered at 800 oC; 830 oC; 850 oC and 870 oC.
Table 4.7. The density, , tan, kp of
M0-1150 sample
Sample
D
ε
tanδ
kp
M0-1150 (g/cm3)
Figure 2.14. The density of PZT-PZNPMnN ceramics with diff erent amounts
of CuO additive sintered at 800 oC,
830 oC, 850 oC, 870 oC
M01
7,85
1217 0,007 0,57
M02
7,83
1108 0,007 0,56
M03
7,81
1209 0,006 0,55
M04
7,85
1168 0.007 0,55
TB
7,83
1219 0,007 0,56
Figure 2.14 shows the densities as a function of sintering temperature for
PZT-PZN-PMnN ceramics with various CuO additions. With increasing
sintering temperature and CuO content, the density increases and reaches the
maximum value (7.91 g/cm3) at 850oC and 0.125 wt % CuO content, before
the density starts to decrease. The sintering temperature of undoped PZTPZN-PMnN ceramics was higher 1150 °C (the density of 7.83 g/cm3). From
the phase diagram of Hitoshi Kitaguchi [17] has shown that CuO and PbO
form the liquid phase at point eutectic 789°C. So when CuO doped in PZTPZN-PMnN ceramics, CuO reacted with PbO and formed a liquid phase
during the sintering, which assisted the densification of the specimens. Thus,
the addition of CuO improved the sinterability, reduced the sintering
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