research on fabrication and the physical properties of the multi-component ceramics based on pzt and the relaxor ferroelectric materials

ii To study the effect of Zr/Ti ratio in PZT on the structure, and theproperties of the PZT - PZN - PMnN ceramics, determine PZT content whichceramics have good electrical properties and

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

Academic Supervisor: Assoc Prof Dr Phan Dinh Gio

Reviewer 1:

Reviewer 2:

Reviewer 3:

This thesis will be reported at Hue University

Date & Time … / …./…./…

important materials and have been intensively investigated in bothfundamental research and applications The reason is that they exist in manyimportant physical effects such as ferroelectric, piezoelectric, photovoltaic,non-linear optical, pyroelectric effects, etc These materials have the abilityfor application in manufacturing of capacitors, high capacity memory, powerultrasonic transducers used in biology, chemistry, pharmacology, andpiezoelectric transducers [3], [5], [35], [36], [81].

The important and main materials of applications often have theperovskite structures, ABO3 That is the Pb(Zr,Ti)O3 (PZT) ceramics, andPZT 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 complexperovskite forms resulting from multiple ionic substitutions Many of thematerials in the complex perovskite family are known to be relaxorferroelectrics The general formula for the complex perovskite is:(A’A’’…An’)BO3or A(B’B’’ Bn’)O3, and their dielectric, piezoelectric andferroelectric properties of ceramics may be improved for high powerapplications [3], [5], [16], [18], [30], [31], [37], [56], [57], [76], [81] Thecharacteristics 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, abovethe Curie temperature of several tens of degrees still have spontaneouspolarization and hysteresis loops [5], [5], [58], [81]

Recently, the materials scientists have been intensively investigating theapplication of multi-component ceramic systems combining the normalferroelectric 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],

[84], [87] These ceramics often have low dielectric loss (tanδ), largedielectric constant ε, high mechanical quality factor (Qm), highelectromechanical coupling factor (kp) [3], [5], [29], [34], [64], [84], [87].Recent research has demonstrated that the PZT–PZN–PMnN quaternaryceramics (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 piezoelectrictransformers, ultrasonic motors

However, the sintering temperature of the ceramics is quite high (> 1150oC)[29], [34], [64], which leads to evaporation of PbO during the sinteringprocess, resulting in reduced properties of ceramic compositions andenvironmental pollution Therefore, lowering sintering temperature of PZTbased ceramics is very necessary In order to reduce the sintering temperature

at which satisfactory densification could be obtained, various materialprocessing methods such as the 2-stage calcination method [5]; hot-pressedmethod [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 beenperformed Among these methods, liquid phase sintering is basically aneffective method for aiding densification of specimens at low sinteringtemperature Many researchers have successfully decreased the sinteringtemperature 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 tothe formation of piezoelectrically inactive phases in the grain boundaryregions Therefore, the research and fabrication ceramics sintered at lowtemperature, while improving or not reducing the piezoelectric properties ofceramics system is very important [16], [23], [44], [75], [80]

Thus, the PZT - PZN - PMnN ceramics is very attractive for bothfundamental research and applications From the above fact, we have chosen

dissertation topic is “Research on fabrication and the physical properties

Pb(Zr0,47Ti0,53)O3on the structure, microstructure and the physiscal properties ofxPb(Zr0,47Ti0,53)O3- (0,925-x)Pb(Zn1/3Nb2/3)O3- 0,075Pb(Mn1/3Nb2/3)O3ceramicsystems (ii) To study the effect of Zr/Ti ratio in PZT on the structure, and theproperties of the PZT - PZN - PMnN ceramics, determine PZT content whichceramics have good electrical properties and the relaxor ferroelectriccharacteristics (iii) To study the characteristic properties of the Fe2O3dopedPZT - PZN - PMnN ceramics (iv) To study the effect of CuO on the sinteringbehavior and electrical properties of PZT–PZN–PMnN ceramics.

Research objects: The main research objects of the dessertation were the

PZT PZN PMnN multicomponent ceramic systems and the PZT PZN PMnN doped CuO, Fe2O3 ceramics The ceramic samples have beenprepared 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 ofthe physical properties of the multi-component ceramics based on PZT andthe 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 ofelectronic ceramic materials in our country, particularly the feasibility ofapplication of ceramic materials for fabricating ultrasonic sensors, ultrasoniccleaners

The layout of the thesis: The thesis is presented in four chapters including

118 pages

Chapter 1 LITERATURE REVIEWS

Chapter 1 presents literature reviews in dissertation research, as a basisfor research and explains the survey results of physical properties ofmaterials such as: ferroelectric phase transition, hysteresis loops, domainferroelectric Some characteristics of the PZT based ferroelectric ceramicsand the relaxor ferroelectric materials (PZN, PMnN) In addition, Ramanspectroscopy has also been introduced to explain the experimental results forthe 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 theconventional method and the B-site Oxide mixing technique (BO) includesthe following the sample groups:

20 h The powders were calcined at temperature 850oC for 2 h, producingthe PZT–PZN–PMnN compound Then, 0,7wt% Li2CO3was mixed with thecalcined PZT–PZN–PMnN powder and then, powders milled for 20h Theground materials were pressed into disk 12mm in diameter and 1.5mm inthick under 2 ton/cm2 The samples were sintered in a sealed aluminacrucible with PbZrO3+ 10 % kl ZrO2coated powder at temperature 950oCfor 2 h Where, the purity of reagent grade oxide powders are above 99 %.

Figure 2.1 TG and DTA curve of (Zn,Mn)Nb 2 (Zr,Ti)O 6

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 allsamples have pure perovskite phase with tetragonal structure Whenincreasing PZT content, the tetragonality c/a ratio increases (insert picture inFigure 2.6) According to the PbZrO3–PbTiO3 phase diagram, at roomtemperature Pb(Zr0.47Ti0.53)O3is of the tetragonal phase (space group P4mm)[24], [25], while Pb(Mn1/3Nb2/3)O3is cubic structure [34], [60] and the PZNcomposition 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

Sample Temperature (°C)

1000 800

600 400

200 0

T: 239.63 (°C) Exo

SEM image analysis results show that the sample group of the MP haveparticle 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 anincreasing 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 Thegrain size and the density of ceramics have a strong effect on dielectric,piezoelectric and ferroelectric properties of ceramic materials Therelationships between the grain size and the density of ceramics and electricalproperties are discussed in the next section.

2.2.2 Structure and microstructure of MZ sample group

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 samplesshowed a tetragonal perovskite phase The tetragonal structures can bedetermined from the double (002)T and (200)T peaks at 2θ ≈44.5o (insert

the average grain size and the density of samples increases and reaches themaximum value at Zr/Ti ratio of 48/52, then decreases.

In order to determine chemical composition of the PZT-PZN-PMnNceramics, 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 onthe EDS analysis, it can be confirmed that the qualitative and quantitativechemical composition of the PZT-PZN-PMnN ceramic are quite good

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 roomtemperature was calculated from the capacitance (Cs) of the MP, MZ samplegroups measured at frequency of 1kHz shown in Table 3.1

When the content of PZT increases from 0.65 to 0.8 mol, values ofdielectric constantεincrease and reach maximum (ε= 1230) at 0.8 mol PZT,

Figure 2.14 EDS spectrum of PZT-PZN-PMnN ceramics

Nb Pb

and then rapidly decreased At this contant, the dielectric loss tanδ of 0.007(Table 3.1) Table 3.1 shows the dielectric constantεof MZ samples in therange from 758 to 1319 and dependence of Zr/Ti ratio When the ratio ofZr/Ti increases the values ofεincrease and reaches a maximum (ε= 1319)

at Zr/Ti = 48/52, and then decreases While the dielectric loss tanδ desreaseswith increasing Zr/Ti ratio The minimum values of tanδ of 0.005 wasobtained at Zr/Ti = 48/52 and then increased The increasing of dielectricconstant 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

Figure 3.1 Temperature dependence of the dielectric constant and

dielectric loss at 1 kHz of MP (a), MZ (b) sample groups

0.04 0.08 0.12 0.16

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 MPceramic samples increases with increasing PZT content and in the range of

206oC to 275oC andεmaxincreased to a maximum value of 18371 when thePZT is 0.8 mol and then decreased Because of the different phasetransformation temperatures of PZN (Tm≈ 140oC) [25], [74] and PZT (TC≈

390oC) [74], so the phase transition temperature of the PZT–PZN–PMnNceramics 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 TheCurie temperature decreases with the increasing Zr content because theCurie temperature of PbZrO3is about 232oC [71] and it is lower than that ofPbTiO3, 490oC [3], [74]

3.1.3 The dependence of the dielectric properties versus the frequency

Figure 3.3, 3.4 show the temperature dependence of the dielectricconstantεand dielectric loss tanδof the MP80 and M48 samples measured

at frequency of 1kHz, 10kHz, 100kHz and 1MHz, respectively We can seethat the shape of the εpeaks was broad, which is typical of a case diffusetransition with frequency dispersion When the measured frequency

increased, the maximum of εmax was decreased and shifted to highertemperature while dielectric loss increased near the Curie point, which istypical of a relaxor material [81].

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 thesample groups measured at room temperature From ferroelectric hysteresisloops of the sample groups, the remanent polarization Pr and the coercivefield Ecwere determined, as shown in figure 3.9 The Prreaches the highestvalue (34.5µC/cm2) at PZT content of 0.8 mol and Zr/Ti ratio of 48/52 Atcontents, the coercive field Ecreaches value 9.0 kV/cm This result is in goodagreement with the studied dielectric properties of the samples

-40 -30 -20 -10 0 10 20 30

40 MP65

MP75

MP85

MP90 MP65 MP80 MP75

MP70 MP85

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

0 2000 6000 10000 14000 18000

50 100 150 200 250 300 350

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

MZ48

1kHz 10kHz 100kHz 1000kHz

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 differenttemperatures from 30 oC to 280 oC When the temperature increased fromroom temperature to 120 °C, the remanent polarization Princreased When thetemperature rises above 120 °C, the remanent polarization Prand the coercivefield Ecdecreased (Figure 3.11) The reason is when the temperature increases,the oxygen vacancies in the perovskite structure will move and significantlyincrease the conductivity of the material which should increase the dielectricloss The size of the hysteresis loops depend on dielectric loss of the material.Therefore, the dielectric loss increases, the size of the hysteresis loopsincreases, the remanent polarization Prand the coercive field Ecincreases[81].When the temperature increases (above 120oC), large thermal motion energy,bipolar disorder increased, the hysteresis loops narrowed, the remanentpolarization Prand the coercive field Ecdecreases

Figure 3.9 The P r and the E c as a function of PZT contents (a) and Zr/Ti

ratios (b)

8 10 12 14 16 18

10 15 20 25 30 35 40

3.3 Piezoelectric properties PZT- PZN-PMnN ceramics

To determine piezoelectric properties of ceramics, resonant vibrationspectrum of sample groups were measured at room temperature From theseresonant spectra, electromechanical coefficients kp, kt, k31, piezoelectriccoefficients d31, mechanical quality factor Qmwere determined (Figure 3.16) Asseen in Figure 3.16 (a), piezoelectric properties were strongly influenced bythe composition of the ceramics As the increase in PZT content not onlyenhanced the electrical properties, but also increased the mechanicalproperties of ceramics The values of kp, kt, k31, d31and Qmreach 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 areconsistent with the literature [74]

For MZ sample group (Figure 3.16 (b)), when the amount of Zr/Ti ratio

is lower than 48/52, the kp, kt, k31, d31are rapidly increased with increasingZr/Ti ratio, while the mechanical quality factor Qm and the dielectric losstanδ are lightly decreased This is probably related to characteristics of theincreasing grain size As is well known, the increased grain size makesdomain reorientation easier and severely promotes domain wall motion,which could increase the piezoelectric properties [81]

Hình 6 Sự phụ thuộc của trường kháng E c và độ

phân cực dư P r theo nhiệt độ của gốm PZT

-PZN-PMnN.

Figure 3.16 The values of k p , k t , k 31 , d 31 , Q m and tanδ of the PZT-PZN-PMnN ceramic as a function of PZT contents (a) and Zr/Ti ratios (b)

0.2 0.3 0.4 0.5 0.6

600 700 800 900 1000 1100 1200 1300 1400

60 80 100 120 140 160

800 1000 1200 1400 1600

60 80 100 120 140 160

Zr content (mol)

(b)

d31

Chapter 4 STUDY THE EFFECTS OF CuO, Fe 2 O 3 ON

PROPERTIES OF PZT–PZN–PMnN CERAMICS

4.1 Effect of Fe 2 O 3 on properties of PZT-PZN-PMnN ceramics

To improve the mechanical quality factor Qmand dielectric loss tanδ ofPZT-PZN-PMnN ceramics, Fe2O3 doping were mixed into the PZT-PZN-PMnN ceramics

4.1.1 Effect of Fe 2 O 3 on structure, microstructure of PZT-PZN-PMnN ceramics

Figure 4.1 shows X-ray diffraction patterns (XRD) of the PZT–PZN–PMnN ceramics at the different contents of Fe2O3 All samples haveperovskite 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)Tand (200)Tdouble peaks at 2θ≈44.5o

(figure 4.1(b))

Figure 4.3 shows the SEM micrographs of the fracture surface of thesamples as Fe2O3addition It is seen from the micrographs that the grain sizegrows with the increase of Fe2O3addition Below the 0.25 wt% Fe2O3, thegrain sizes increase and the grain boundaries present regular shapes.However, when the addition of Fe2O3is higher than 0.25 wt%, a few cavitiesappeared between the grains (MF5, MF6 samples)

Figure 4.3 Microstructures of samples with the different Fe 2 O 3 contents

4.1.2 Effect of Fe 2 O 3 on dielectric properties of PZT-PZN-PMnN ceramics

Figure 4.4 shows the dependence of dielectric constant  and dielectricloss tan of the ceramics versus temperature at frequency of 1 kHz Withincreasing Fe2O3doping, theεmaxincreased to a maximum value of (24500)when the Fe2O3 content is 0.25wt% and then decreased This can beexplained by increasing grain size effect [81] Corresponding Fe2O3content

increases, Tmtemperature of ceramics lightly decreased from 244 to 234 oC(Figure 4.5)

Figure 4.4 Temperature dependence of

the dielectric constant and dielectric

135 140 145 150 155 160

180 190 200 210 220 230

560 580 600 620 640 660 680 700

135 140 145 150 155 160

180 190 200 210 220 230

560 580 600 620 640 660 680 700

Figure 4.8(a) shows the Raman scattering spectra of Fe2O3-doped PZT–PZN-PMnN ceramics measured at room temperature Compared withPbTiO3[1] and Pb(Zr,Ti)O3[64], the vibration bands in the Raman scatteringspectra of Fe2O3-doped PZT–PZN–PMnN samples seem wider and moredispersive It can be seen from this figure that the silent mode at about 268

cm-1shifts to a low frequency as the Fe2O3 doping increases Dilsom [18]assumed that the decrease in frequency with increasing Fe2O3contents is due

to the difference in the atomic mass of Zr (91.22 g), Ti (47.87 g), Nb (92.90g), Zn (65.39 g), and Mn (54.94 g) when they are replaced by Fe (56 g) inthe 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 Tmof theceramics are decreased [91]

The value of γ gives information on the phase transition diffusecharacterized The values of γ increases with increase of Fe2O3 contents

Figure 4.9 Ln(1/ −1/max ) as a function of ln(T−T max ) of samples FWHM

(Figure 4.9(a)) It is found that the full width at half maximum (FWHM) ofthe B–O vibrations exhibit an obvious increase, leading to a strongcomposition disorder (Figure 4.9(b)) However, when the Fe2O3 content ishigher than 0.25 wt%, the value of γ and FWHM decreases This can beexplained by the solubility limit of Fe ion in the PZT-PZN-PMnN ceramics.

4.1.3 Effect of Fe 2 O 3 on piezoelectric properties of PZT-PZN-PMnN ceramics

To determine piezoelectric properties of ceramics, resonant vibrationspectra of samples were measured at room temperature (Figure 4.11) Fromthese resonant spectra, piezoelectric parameters of samples were determined(Figure 4.12)

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 Qmand 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

Fe2O3content in the PZT–PZN–PMnN ceramics was increased up to 0.25wt%, the Qmvalue 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 d31show a similar variation with increasing

Fe2O3content When the content of Fe2O3is lower than 0.25 wt%, the kp, kt and the d31 were increased with increasing Fe2O3content The optimized

values for kp of 0.64, kt of 0.51 and d31of 155 pC/N were obtained at content

Fe2O3= 0.25 wt% This is probably related to characteristics of the increasinggrain size

4.1.4 Effect of Fe 2 O 3 on ferroelectric properties of PZT-PZN-PMnN ceramics

From the form of feroelectric hysteresis loops of the Fe2O3doped PZN-PMnN samples measured at room temperature, the remanent

PZT-polarization Pr and the coercive field Ecwere determined, as shown in Table4.5

Table 4.5 The characterize parameters of ferroelectric properties (P r , E c ) of Fe 2 O 3

is in good agreement with the studied dielectric and piezoelectric properties

of the samples While, the coercive field Ec decreases with increasing of

Fe2O3content The minimum value of the Ecis 8.6 kV/cm were obtained atcontent 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] inPZT−PZN−PMnN ceramics due to their large dielectric constant ε, largeelectromechanical coefficient kp, large polarization Pr, high mechanical quality

-6 0 -4 0 -3 0 -2 0 -1 0 0

60 80 100 120

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 sinteringtemperature of PZT based ceramics is using various additives such asBiFeO3, CuO, CuO-ZnO, Li2CO3, Bi2O3, LiBiO2, B2O3, CuO-PbO, Cu2O-PbO 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 theCuO doped 0,8Pb(Zr0,48Ti0,52)O3 - 0,125Pb(Zn1/3Nb2/3)O3 -0,075Pb(Mn1/3Nb2/3)O3ceramics sintered at 800oC; 830oC; 850oC and 870oC.

Figure 2.14 shows the densities as a function of sintering temperature forPZT-PZN-PMnN ceramics with various CuO additions With increasingsintering temperature and CuO content, the density increases and reaches themaximum value (7.91 g/cm3) at 850oC and 0.125 wt % CuO content, beforethe density starts to decrease The sintering temperature of undoped PZT-PZN-PMnN ceramics was higher 1150 °C (the density of 7.83 g/cm3) Fromthe phase diagram of Hitoshi Kitaguchi [17] has shown that CuO and PbOform the liquid phase at point eutectic 789°C So when CuO doped in PZT-PZN-PMnN ceramics, CuO reacted with PbO and formed a liquid phaseduring the sintering, which assisted the densification of the specimens Thus,the addition of CuO improved the sinterability, reduced the sintering

Sample M0-1150

D (g/cm 3 )

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

Table 4.7 The density,, tan, k p of

M0-1150 sample

Figure 2.14 The density of

4.2.2.1 Effect of CuO on structure, microstructure of PZT–PZN–PMnN ceramics

In order to determine chemical composition of the CuO doped PZN-PMnN ceramics, the EDS spectrum is analyzed and shown in Figure4.20 From Figure 4.20 shows the presence of Pb, Zr, Ti, Nb, Zn, Mn and Cuelements of the CuO doped PZT-PZN-PMnN ceramics As seen in Figure4.21 that all the samples with the addition of CuO had a tetragonal structure

PZT-as indicated by the splitting of (002) and (200) peaks at 2θ ≈440 This resultsuggests that Cu2+ ions are substituted for B-site of perovskite structureABO3which lead to the distortion of crystal lattice

The microstructure of MC4 sample (0,125 wt % CuO) becomes dense andlarge grain size (1,2µm, Figure 4.22) It is sample large density of ceramic(7.91 g/cm3)

Figure 4.21 X-ray diffraction

patterns of the MC samples

4.2.2.2 Effect of CuO on dielectric properties of PZT-PZN-PMnN ceramics

Figure 4.23 shows temperature dependence of dielectric constant ε anddielectric loss tanδas a function of CuO content With increasing CuO doping,the Tmtemperature of PZT-PZN-PMnN ceramics become lower, the peak of thedielectric spectrum moves toward low temperature corresponding to Tm

temperature The composition with 0.125 wt % CuO content shows highest peakdielectric constants (12000), which appears at about 266oC

Figure 4.24 shows the values of γ at 1 kHz are found from 1.63 to 1.86

indicating transitions are of diffuse type The value of γ shows that thematerial is highly disordered

4.2.2.3 Effect of CuO on piezoelectric properties of PZT-PZN-PMnN ceramics

From these resonant spectra, piezoelectric parameters of samples weredetermined (Figure 4.26) Figure 4.26 shows the electromechanical couplingfactor (kp, kt), the piezoelectric constant (d31), the mechanical quality factor

Qmand dielectric loss tanδ change as a function of the amount of CuO Whenthe amount of CuO is lower than 0.125 wt %, the values of kp, kt, d31,εand

Qmare rapidly increased with increasing content of CuO, while the dielectricloss tanδ are strong decreased The largest values for kpof 0.55, ktof 0.46,

Figure 4.23 Temperature dependence

of dielectric constant ε and dielectric

loss of the MC sample group at 1 kHz.

Figure 4.24 Plot of ln(1/ε – 1/ε m )

groups

Figure 4.23 Temperature dependence

of dielectric constant ε and dielectric

loss of the MC sample group at 1 kHz.

mechanism of the CuO hard doping in PZT - PZN - PMnN ceramics.

4.3 Fabrication ultrasonic cleaner on PZT-PZN-PMnN based ceramics

The PZT - PZN - PMnN + 0,10 % kl CuO ceramic sintered at 850 °C havegood electrical properties for fabrication ultrasonic transducers Therefore,

we used of the PZT-PZN-PMnN doped CuO ceramics for fabricatingultrasonic cleaners On that basis, we successfully fabricated an ultrasoniccleaner (Figure 4.31) with working frequency of 40.26 kHz From the effects

of cavitacy (figure 4.32), the power of ultrasonic cleaner determined about

of PZT-based ceramics and the relaxor ferroelectric materials (PZN, PMnN)with perovskite structure The sample components were systematic and had

a high repeatability We used the method of X-ray diffraction analysis,scanning electron microscopy, Raman spectroscopy and EDS spectrum tocheck quality of the ceramic samples

- The characteristic parameters of dielectric, piezoelectric ferroelectricproperties of PZT - PZN - PMnN ceramics have been investigated.Experimental results showed that the electical properties of PZT - PZN -PMnN ceramics are optimal at PZT content of 0.8 mol and Zr/Ti ratio of48/52 At these contents the ceramics have good electrical properties: d31=

140 pC/N; kp= 0.62; kt= 0.51, Qm= 1112, tanδ= 0.005 and Pr= 34,5µC/cm2

- On the basis of the experimental results of the effects of temperature andfrequency on the dielectric, ferroelectric, piezoelectric properties of ceramicshas proven that the PZT - PZN - PMnN quaternary ceramics are relaxorferroelectrics

- The results of studies on the effects of Fe2O3doping on the electricalproperties of PZT – PZN – PMnN ceramics have proved that Fe2O3is harddoping in PZT - PZN – PMnN ceramics The hard characteristics of Fe2O3

doped PZT - PZN – PMnN ceramics have shown that the dielectric loss ofceramic decreased, the mechanical quality factor of ceramic increased.Moreover, Fe2O3 doping also increased the average particle size andsignificantly improve the dielectric, piezoelectric and ferroelectric properties

of ceramics

temperature of ceramics decreased 300oC compared to samples without CuO(density of 7.91g/cm3, ε = 1179, kp= 0.55, Qm= 1174 and tanδ = 0.006).

- Applications of the PZT-PZN-PMnN doped CuO ceramics forfabricating ultrasonic cleaners have been successful with working frequency

of 40.26 kHz and the power of ultrasonic cleaner about 40 W

LIST OF PUBLICATIONS

1) Phan Đình Giớ và Lê Đại Vương (2011), Tính chất điện môi, sắt điện của gốm

PZT-PZN-PMnN Tạp chí khoa học, Đại học Huế, Số 65, tr 53-61.

2) Phan Đình Giớ và Lê Đại Vương (2011), Ảnh hưởng của nồng độ PMnN đến cấu

trúc và các tính chất áp điện của gốm PZT-PZN-PMnN Tạp chí khoa học, Đại học

Huế, Số 65, tr 63-71.

3) Phan Đình Giớ, Nguyễn Thị Bích Hồng, Lê Đại Vương (2012), Ảnh hưởng của tỉ số

nồng độ Zr/Ti đến các tính chất vật lý của hệ gốm PZT-PZN-PMnN Tạp chí Khoa

học và Công nghệ 50 (1A),tr 112-118.

4) Phan Đình Giớ, Nguyễn Văn Quý, Lê Đại Vương (2012), Sự phụ thuộc nhiệt độ của

một số tính chất vật lý của hệ gốm PZT-PZN-PMnN Tạp chí Khoa học và Công nghệ

50 (1A), tr 235-240.

5) Phan Đình Giớ, Lê Đại Vương, Nguyễn Thị Trường Sa (2013), Ảnh hưởng của thời

gian thiêu kết đến một số tính chất của hệ gốm áp điện PZT-PZN-PMnN thiêu kết ở nhiệt độ thấp, Tạp chí khoa học, Đại học Huế, Tập 87, Số 9, (2013), tr 45-51.

6) Phan Đình Giớ, Lê Đại Vương và Nguyễn Quang Long (2013), Nghiên cứu, chế tạo

máy rửa siêu âm trên cơ sở hệ gốm PZT - PZN – PMnN, Hội nghị toàn quốc lần thứ

3 Vật lý kỹ thuật và ứng dụng (CAEF-2013), Huế, 8-12 tháng 10 năm 2013 7) Phan Đình Giớ, Lê Đại Vương, Hồ Thị Thanh Hoa, Ảnh hưởng của CuO đến nhiệt

độ thiêu kết của gốm áp điện PZT-PZN-PMnN, Hội nghị Vật lý chất rắn và Khoa học

vật liệu toàn quốc lần thứ 8 (SPMS-2013) – Thái Nguyên 4-6/11/2013 (đã được Tạp chí Khoa học và Công nghệ 50 nhận đăng 5/6/2014).

Tạp chí khoa học, Đại học Huế, Tập 87, Số 9, (2013), tr 225-231.

Ảnh hưởng của chế độ ủ đến một số tính chất vật lý của hệ gốm PZT-PZN-PMnN.

Tạp chí khoa học, Đại học Huế, Tập 73, số 4, tr 253-261.

10) Phan Dinh Gio, Le Dai Vuong and Nguyen Phan Nhu Y (2012), Effect of PZT

content on the structure and electrical properties of PZT-PZN-PMnN ceramics The

6th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2012) - October 30-November 02, 2012 - Ha Long City, Vietnam.

11) Le Dai Vuong, Phan Dinh Gio, Truong Van Chuong, Dung Thi Hoai Trang, Duong

Viet Hung, Nguyen Trung Duong (2013), Effect of Zr/Ti ratio content on some

physical properties of the low temperature sintering PZT-PZN-PMnN ceramics.

International Journal of Materials and Chemistry, Vol 3(2), pp: 39-43.

12) Le Dai Vuong, Phan Dinh Gio, Nguyen Thi Kieu Lien (2013), Physical properties

of PZT-PZN-PMnN ceramics were fabricated by B-site oxide mixing technique,

Journal of science, Hue University, Vol 84, No.6, pp: 93-99.

13) Le Dai Vuong, Phan Dinh Gio, Nguyen Truong Tho, and Truong Van Chuong

(2013), Relaxor Ferroelectric Properties of PZT-PZN-PMnN Ceramics Indian

Journal of Engineering & Materials Sciences, Vol 20, pp: 555-560.

14) Le Dai Vuong, Phan Dinh Gio (2013) Effect of Li 2 CO 3 addition on the sintering behavior and physical properties of PZT-PZN-PMnN ceramics, International Journal

of Materials Science and Applications, Vol 2(3), pp: 89-93.

15) Le Dai Vuong, Phan Dinh Gio (2014), Structure and electrical properties of Fe 2 O 3 Doped PZT–PZN–PMnN ceramics, Journal of Modern Physics,Vol 5, pp: 1258-

-1263.

16) Le Dai Vuong, Phan Dinh Gio, Vo Thi Thanh Kieu (2014), Raman scattering

spectra and dielectric relaxation behavior of PZT-PZN-PMnN ceramics,

International Journal of Chemistry and Materials Research, Vol 2(6), pp: 48-55.

17) Phan Dinh Gio, Le Dai Vuong, Ho Thi Thanh Hoa (2014), Electrical Properties of

CuO-Doped PZT-PZN-PMnN Piezoelectric Ceramics Sintered at Low Temperature,

Journal of Materials Science and Chemical Engineering, Vol 2, pp: 20-27.