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, ABO 3 . That is the Pb(Zr,Ti)O 3 (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’’…A n’ )BO 3 or A(B’B’’ B n’ )O 3 , 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)O 3 – Pb(Zn 1/3 Nb 2/3 )O 3 (PZT–PZN) [23], [24], [30], [31], [35], [42], [90]; Pb(Zr,Ti)O 3 –(Mn 1/3 Nb 2/3 )O 3 (PZT-PMnN) [4], [15], [52]; Pb(Zr,Ti)O 3 – Pb(Mn 1/3 Sb 2/3 )O 3 (PZT-PMS) [5], [60], [80], [83]; Pb(Zr,Ti)O 3 – Pb(Zn 1/3 Nb 2/3 )O 3 –Pb(Mg 1/3 Nb 2/3 )O 3 (PZT–PZN–PMN) [13]; Pb(Zr,Ti)O 3 – Pb(Zn 1/3 Nb 2/3 )O 3 – Pb(Mn 1/3 Nb 2/3 )O 3 (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 (Q m ), high electromechanical coupling factor (k p ) [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 Q m , the low tanδ and the large k p , 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 o C) [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 Li 2 CO 3 (735 °C), Bi 2 O 3 (820 °C), B 2 O 3 (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(Zr 0,47 Ti 0,53 )O 3 on the structure, microstructure and the physiscal properties of xPb(Zr 0,47 Ti 0,53 )O 3 - (0,925-x)Pb(Zn 1/3 Nb 2/3 )O 3 - 0,075Pb(Mn 1/3 Nb 2/3 )O 3 ceramic systems. (ii) To study the effect of Zr/Ti ratio in PZT on the structure, and the propertiesof 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 Fe 2 O 3 doped PZT - PZN - PMnN ceramics. (iv) To study the effect ofCuOon 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, Fe 2 O 3 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(Zn 1/3 Nb 2/3 )O 3 and Pb(Mn 1/3 Nb 2/3 )O 3 . 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(Zr 0,47 Ti 0,53 )O 3 – (0,925-x)Pb(Zn 1/3 Nb 2/3 )O 3 – 0,075Pb(Mn 1/3 Nb 2/3 )O 3 + 0,7 % kl Li 2 CO 3 (0,65 ≤ x ≤ 0,9); (MP: MP65, MP70, MP75, MP80, MP85 và MP90). (2.1) Group 2:0,8Pb(Zr y Ti 1-y )O 3 – 0,125Pb(Zn 1/3 Nb 2/3 )O 3 – 0,075Pb(Mn 1/3 Nb 2/3 )O 3 + 0,7 % kl Li 2 CO 3 (0,46 ≤ y ≤ 0,51); (MZ: MZ46, MZ47, MZ48, MZ49, MZ50 và MZ51). (2.2) Group 3: 0,8Pb(Zr 0,48 Ti 0,52 )O 3 – 0,125Pb(Zn 1/3 Nb 2/3 )O 3 – 0,075Pb(Mn 1/3 Nb 2/3 )O 3 + 0,7 % kl Li 2 CO 3 + z % kl Fe 2 O 3 (0,0 ≤ z ≤ 0,35); (MF: MF0, MF1, MF2, MF3, MF4, MF5 và MF6). (2.3) Group 4: 0,8Pb(Zr 0,48 Ti 0,52 )O 3 – 0,125Pb(Zn 1/3 Nb 2/3 )O 3 – 0,075Pb(Mn 1/3 Nb 2/3 )O 3 + 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)Nb 2 (Zr,Ti)O 6 (BO) [33], [51] was prepared by reactions of ZnO, MnO 2 , Nb 2 O 5 , ZrO 2 and TiO 2 at temperature of 1100 o C for 2h. According to the results thermal analysis (DTA) and thermogravimetric analysis (TGA) of (Zn,Mn)Nb 2 (Zr,Ti)O 6 power (Figure 2.1) can see that the formation reaction occurs when the temperature exceeds 978 o C. However, experimental results showed that (Zn,Mn)Nb 2 (Zr,Ti)O 6 power was calcined at temperature 5 of 1100 o C, the PZT-PZN-PMnN ceramics had the good electrical properties, similarly to reports of methods [33]. Secondly, (Zn,Mn)Nb 2 (Zr,Ti)O 6 and PbO were weighed and milled for 20 h. The powders were calcined at temperature 850 o C for 2 h, producing the PZT–PZN–PMnN compound. Then, 0,7wt% Li 2 CO 3 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/cm 2 . The samples were sintered in a sealed alumina crucible with PbZrO 3 + 10 % kl ZrO 2 coated powder at temperature 950 o C for 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 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 PbZrO 3 –PbTiO 3 phase diagram, at room temperature Pb(Zr 0.47 Ti 0.53 )O 3 is of the tetragonal phase (space group P4mm) [24], [25], while Pb(Mn 1/3 Nb 2/3 )O 3 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. Sample Temperature (°C) 10008006004002000 TG |c (mg) 1 0 -1 -2 -3 HeatFlow (mW) 0 -10 -20 -30 -40 dTG |c (mg/min) 0.05 0 -0.05 -0.1 T: 239.63 (°C) Exo Δm (mg) -2.552 Δm (%) -6.208 T: 341.73 (°C) T: 544.04 (°C) T: 240.19 (°C) T: 342.15 (°C) T: 964.15 (°C) T: 978.83 (°C) 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/cm 3 , 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. 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 samples showed a tetragonal perovskite phase. The tetragonal structures can be determined from the double (002) T and (200) T peaks at 2θ ≈ 44.5 o (insert 20 30 40 50 60 7 0 43 44 45 46 (2 00 ) T In tensity (a .u) 2 θ (Degree) (0 02 ) T Intensity (a.u) 2 θ (Degree ) 30 0 20 2 22 0 21 1 11 2 20 1 10 2 11 1 11 0 10 1 10 0 00 1 20 0 1 2 3 4 5 6 M Z4 6 - 1 M Z4 7 - 2 M Z4 8 - 3 M Z4 9 - 4 M Z5 0 - 5 M Z5 1 - 6 00 2 Figure 2.10. X-ray diffraction patterns of MZ sample group Figure 2.12. Microstructures of MZ48 sample Figure 2.8. SEM image of MP80 sample Figure 2.6. X-ray diffraction patterns of MP sample group 0 10 0 20 0 30 0 40 0 50 0 60 0 2 0 2 5 30 3 5 4 0 45 5 0 5 5 60 6 5 70 0 .6 0.7 0.8 0.9 1.0 10 1.0 15 1.0 20 1.0 25 1.0 30 T h e c /a ra tio P Z T c o n te nt (m o l) M P9 0 M P8 5 M P8 0 M P7 5 M P7 0 M P6 5 2 θ (D e gre e) In te nsity (a.u ) 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. 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. Thedielectric constant of MP, MZsamplegroups 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 (C s ) 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, Figure 2.14. EDS spectrum of PZT-PZN-PMnN ceramics Nb Pb O Ti Zr Nb Ti Mn Zn Pb Pb 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 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 Figure 3.1 Temperature dependence of the dielectric constant and dielectric loss at 1 kHz of MP (a), MZ (b) sample groups 0 50 100 150 200 250 300 350 0 4000 8000 12000 16000 20000 0.00 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40 Dielectric constant, ε Temperature ( 0 C) Dielectric loss, tan δ (a) MP65 MP70 MP75 MP80 MP85 MP90 0 4000 8000 12000 16000 20000 50 100 150 200 250 300 350 0.00 0.04 0.08 0.12 0.16 0.20 1 MZ46 2 MZ47 3 MZ48 4 MZ49 5 MZ50 6 MZ51 1 2 5 6 4 3 (b) Dielectric constant, ε Temperature ( 0 C) Dielectric loss, tan δ [...]... 1112, tanδ = 0.005 and Pr = 34,5µC/cm2 - On the basis of the experimental results of the effects of temperature and frequency on the dielectric, ferroelectric, piezoelectric properties of ceramics has proven that the PZT - PZN - PMnN quaternary ceramics are relaxor ferroelectrics - The results of studies on the effects of Fe2O3 doping on the electrical properties of PZT – PZN – PMnN ceramics have proved... 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. .. 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... 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... /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... 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... 4.2.2 Effect of CuO on electrical properties of PZT PZN–PMnN ceramics 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 PZTPZN-PMnN ceramics, the EDS spectrum is analyzed and shown in Figure 4.20 From Figure 4.20 shows the presence of Pb, Zr, Ti, Nb, Zn, Mn and Cu elements of the CuO doped PZT- PZN-PMnN ceramics As... increasing content of CuO, while the dielectric loss tanδ are strong decreased The largest values for kp of 0.55, kt of 0.46, 21 d31 of 112 pC/N, Qm of 1174 and minimum value of the dielectric loss tanδ is 0.006 were obtained at content of CuO = 0.125 % wt These are probably related to characteristics of the density and the increasing grain size and the mechanism of the CuO hard doping in PZT - PZN - PMnN ceramics. .. 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,... 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 Li2CO3 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 . 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. 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. study the effect of Zr/Ti ratio in PZT on the structure, and the propertiesof the PZT - PZN - PMnN ceramics, determine PZT content which ceramics have good electrical properties and the relaxor ferroelectric characteristics.