Microstructure, ferroelectric and piezoelectric properties of PZT pmnsbn ceramics
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https://www.eduzhai.net International Journal of M aterials and Chemistry 2013, 3(3): 51-58 DOI: 10.5923/j.ijmc.20130303.02 Microstructure, Ferroelectric and Piezoelectric Properties of PZT-PMnSbN Ceramics Nguyen Dinh Tung Luan1, Le Dai Vuong2,*, Bui Cong Chanh1 1Departerment of Fundamental Science College of Industry Hue City, Viet Nam 2Department of Physics, College of Sciences, Hue University, 77 Nguyen Hue street, Hue city, Vietnam Abstract In this paper, in order to achieve a type of material with mixing “soft” and “hard” properties for piezoelectric transformer applications, polycrystalline ceramics of PbZrO3 – PbTiO3 – Pb[(Mn1/3Nb2/3)x(Sb1/2Nb1/2)1-x]O3 (PZT-PMnSbN), x = 0.4; 0.5; 0.6; 0.7; 0.8; 0.9; 1.0, having a rho mbohedral perovskite structure have been synthesized by the Co lu mbite precursor method. Scanning electron micrograph (SEM) shows the compactness of the sample and the average grain size was found about ~ 1.89 µm. The electro mechanical coupling factor (kp), p iezoelectric constant (d31), mechanical quality factor (Qm) of PZT-PMnSbN composition ceramics with x = 0.7 showed the optimal value of 0.6, 180 pC/ N, and 1895, respectively, and spontaneous polarization Pr ≈ 49.2µC/cm2 were observed at room temperature. These values indicated that the newly developed composition may be suitable for piezoelectric t ransformer applications. Keywords Dielectrics, Piezoelectrics, Piezoelectric Transformer, PZT-PMnSb N, Co lu mbite Precursor Method 1. Introduction Single and mult ilayer-type piezoelectric transformers (PTs) for LCD backlights have been intensively studied in order to increase the set-up ratio and output power. These PTs, however, were not applicable to fluorescent lamps. Namely, when conventional fluorescent lamps are lit, their equivalent resistance is smaller at a few hundreds and thousands ohms than that of co ld cathode fluorescent lamps (CCFL). In order to achieve a PT with high output current, its output capacitance must be high. Therefore, co mposition ceramics for h igh power PTs must have a h igh dielectric constant. Moreover, to achieve the piezoelectric transformer transferring high power, it is necessary to increase its strength by producing fine grains and to have a high mechanical quality factor (Qm) because the piezoelectric transformer operated at its resonant frequency under a high input voltage leads to the temperature rise and the deterioration of piezoelectric properties with the increase of its vibration velocity[1,2,3,4,5]. The properties of these materials should combine a high mechanical quality factor (Qm) with high electro mechanical coupling factor (kp) and low dielectric loss (tan δ) simultaneously because the piezoelectric t ransformer operated at its resonant frequency in transformat ion between electrical and mechanical energy. * Corresponding author: firstname.lastname@example.org (Le Dai Vuong) Published online at https://www.eduzhai.net Copyright © 2013 Scientific & Academic Publishing. All Rights Reserved Satoh et al. investigated Pb(Zr,Ti)O3 – Pb(Sb1/2Nb1/2)O3 ceramics with compositions close to the morphotropic phase boundary (MPB) and pointed out that these ceramics have large electromechanical coupling factors kp and dielectric constant. However, the small mechanical quality factor Qm constrained their use to high power p iezoelectric devices such as multilayer p iezoelectric transformers and piezoelectric motors. It is necessary to optimize the piezoelectric properties of the ceramics for high power device applications. Pb(Zr,Ti)O3 – Pb(Mn1/3Nb2/3)O3 ceramics are a type of hard piezoelectric ceramic with very h igh mechanical quality factor Qm, but dielectric constant and radial coupling coefficient kp, are relative low[7,8]. With purposing to establish a material suitable for the production of piezoelectric transformers and other high power devices, in this paper, PMnN and PSbN were added to the PZT-PMnSbN co mpositions near morphotropic phase boundary to form a piezoelectric ceramic with the optimal values of Qm and kp. 2. Experimental Procedure 2.1. Sample Preparation The general formu la of the material studied was: 0. 9Pb(Z r0.53Ti0.47)O3-0. 1Pb[ (Mn1/3Nb2/3)x(Sb1/2Nb1/2)1-x]3 where x is 0.4; 0.5; 0.6; 0.7; 0.8; 0.9; 1.0. and are denoted by M1; M2; M3; M 4; M5; M6; M 7, respesively. Step 1: Synthezise MnNb2O6 and Sb2Nb2O8 MnCO3 and Nb2O5; Sb2O3 and Nb2O5 were mixed and 52 Nguyen Dinh Tung Luan et al.: M icrostructure, Ferroelectric and Piezoelectric Properties of PZT-PM nSbN Ceramics acetone- milled for 20hr in a zirconia ball mill (the PM 400/2 milling machine) and then calcined at 1200℃ fo r 2hr to form MnNb2O6 and Sb2Nb2O8. The material was acetone-ground for 10hr in the mill and dried again. Step 2: Synthezise PZT – PMnSb N Reagent grades PbO, ZrO2, TiO2 were mixed with MnNb2O6 and Sb2Nb2O8 powders by ball mill for 20hr in acetone. Powders were calcined at 850℃ for 2 h, then milled again for 20h. The ground materials were p ressed into disk 12mm in d iameter and 1.5mm in thick under 100 MPa. The samp les were sintered in a sealed alu mina crucible with PbZrO3 coated powder at temperature 1150℃ for 2h. The sintered samples were ground and cut to 1mm in thick. A silver electrode was fired at 680℃ fo r 10 minutes on the major surfaces of samples. Poling was done in the direction of thickness in a silicon oil bath under 30kV/cm for 15 minutes at 120℃. microstructures of ceramic samp les. When the amount of PMnN increased, the ceramic samp les became mo re dense, and at x = 0.7, the ceramic sample was almost fully dense (fig. 4). When the further increasing the PMnN content to 0.8 and above, a large number of pores were present, giving rise to density decreased. 2.2. Measurements The bulk densities of sintered specimens were measured by Archimedes technique. The crystalline phase was analyzed using an X-ray d iffactometer (XRD). The microstructure of the sintered bodies was examined using a scanning electron microscope (SEM). The grain size was measured by using the line intercept method. The dielectric permittiv ity and dielectric d issipation of samp les were measured by the highly automatized RLC HIOKI 3532 at 1 kHz. The electromechanical coupling factor, kp, mechanical quality factor, Qm, and several other piezoelectric constants were calculated by a resonant – anti resonant frequency method measured using an automatized impedance analyzer (HP-4193A). The polarizat ion – electric field (P – E) hysteresis loops were measured by a Sawyer – Tower circu it at 50Hz. Figure 1. Bulk density dependence on amount of PMnN in PMnSbN compo sit io n 3.2. Struture and Microstructure Fig. 2 shows the XRD pattern of all samples at room temperature. The subdivision in intensities of the (200) and (002) peaks demonstrated exist of tetragonal phase in the base of rhombohedral phase of the perovskite structure. No pyrochlore and any second phase were found in all compositions. The changes of lattice parameters of the samples we re shown in the table 2 and figure 3. It is indicated that c/a ratio increase significant with increasing of amount of PMnN in PMnSbN co mposition. The largest strain of cell unit is at x = 0.7(c/a = 2.4865). Table 2. Calculated lattice parameters samples 3. Results and Discussion 3.1. Density of Ceramic Table 1 shows the density of PZT – PMnSbN ceramics and the change of density shows in Fig.1. Table 1. Ceramic densities of samples Sample M1 M2 M3 M4 M5 M6 M7 ρ (g/cm3) 7.40 7.47 7.58 7.64 7.56 7.50 7.44 It is clear that the densities of all samples were strongly changed with amount of PMn N and PSbN in PMnSb N. The maximu m density was obtained at x = 0.7 (7.64g/cm3). The density increased with increasing amount of PMnN up to x = 0.7 and then decrease. This can be exp lained fro m M2 M3 M4 M5 M6 M7 a 5.7651 5.7554 5.7506 5.7544 5.7548 5.7546 b 5.7651 5.7554 5.7506 5.7544 5.7548 5.7546 c 14.2989 14.3000 14.2989 14.3001 14.2996 14.2989 SEM micrographs of M1, M2, M 3, M4, M5, M6, M7 samples are presented in figure 4. As shown in the figures, the grain structures of all samples were very fine, grain growth rise to decreasing of amount of PMn N in PMnSbN compositions. Most of all samples had clearly grain boundaries except M1 and M 2 samples appeared grain boundaries and grain size of M 1, M 2, M 3 samples were limited to 2.33µm shown in fig.5, it is explained that excess PSbN and PMn N in beyond the solubility limit to segregate at grain boundaries and inhibits grain growth[9,10]. International Journal of M aterials and Chemistry 2013, 3(3): 51-58 53 Figure 2. XRD pattern of M2-a; M3-b; M4-c; M5-d; M6-e; M7-f samples Figure 3. Dependence of c/a ratios on amount of PMnN in PMnSbN compositions In addition to, such variation in grain size can be also interpreted in terms of the solubility limited of PSbN and PMn N in the PZT – PMnSbN co mposition matrix[10,11]. 54 Nguyen Dinh Tung Luan et al.: M icrostructure, Ferroelectric and Piezoelectric Properties of PZT-PM nSbN Ceramics Fi gure 4. SEM images of samples International Journal of M aterials and Chemistry 2013, 3(3): 51-58 55 Figure 5. Grain size dependence on amount of PMnN in PMnSbN composition Figure 6. Dielectric constant ε/ε0 and dielectric dissipation tanδ dependence on amount of PMnN in PMnSbN compositions 3.3. Dielectric, Ferroelectric and Piezoelectric Properties Dielectric properties of samples are presented in table 3 and in figure 6. It is cleared that, dielectric constant and dielectric dissipation of the samp les strongly decrease with increasing of amount PMnN in PMnSbN co mpositions. Especially, with M4(x = 0.7) d ielectric constant is very high while dielectric d issipation very low. It is indicated that the mixing amount of PMnN and PSbN into PMnSbN composition to form a material with the existence of both of the soft and hard properties is perfect at x = 0.7. Figure 7 shows P – E hysteresis loops of all samples. The well-saturated hysteresis loops were observed and the values of remanent polarization (Pr) and coercive field (EC) were presented in table 4 and figure 8. It’s demonstrated that the hysteresis loops of all samples are of typical forms characterizing ferroe lectric materia ls. EC strongly increased with increasing of amount PMn N in PMnSbN co mposition. Meanwhile, Pr increased up to 49.2µC/cm2 at x = 0.7 and then decreased. This result is in good agreement with the studied dielectric and piezoelectric properties of the samples. Table 3. Dielect ric constant s and dielect ric dissipation of samples Sample M1 M2 M3 M4 M5 M6 M7 ε/ε0 1533 1592 1477 1434 1041 820 690 tanδ 0.033 0.021 0.018 0.010 0.014 0.012 0.01 56 Nguyen Dinh Tung Luan et al.: M icrostructure, Ferroelectric and Piezoelectric Properties of PZT-PM nSbN Ceramics 80 60 40 20 0 -50 -40 -30 -20 -10 0 -20 -40 -60 -80 P(µC/cm2) M1 10 20 30 40 50 E(kV/cm) P(µC/cm2) P(µC/cm2) 80 60 40 20 0 -50 -40 -30 -20 -10 0 -20 -40 -60 -80 M2 10 20 30 40 50 E(kV/cm) 80 60 40 20 0 -50 -40 -30 -20 -10 0 -20 -40 -60 -80 M3 10 20 30 40 50 E(kV/cm) 80 60 40 20 0 -50 -40 -30 -20 -10 0 -20 -40 -60 -80 P(µC/cm2) M4 10 20 30 40 50 E(kV/cm) 80 60 40 20 0 -50 -40 -30 -20 -10 0 -20 -40 -60 -80 P(µC/cm2) 10 20 30 40 50 E(kV/cm) 80 60 40 20 0 -50 -40 -30 -20 -10 0 -20 -40 -60 -80 P(µC/cm2) M6 10 20 30 40 50 E(kV/cm) 80 60 40 20 0 -50 -40 -30 -20 -10 0 -20 -40 -60 -80 P(µC/cm2) M7 10 20 30 40 50 E(kV/cm) Fi gure 7. P -E hyst eresis loops of samples International Journal of M aterials and Chemistry 2013, 3(3): 51-58 57 Table 4. Calculated Pr and EC values of samples Sample Ec(kV/cm) P r(µC/cm2 ) M1 7.69 33.0 M2 7.79 37.0 M3 9.36 42.0 M4 10.28 49.2 M5 10.00 46.0 M6 11.85 28.0 M7 15.40 25.0 Figure 9. The Qm, kp dependence on amount of PMnN in PMnSbN Figure 8. Pr and EC dependence on amount of PMnN in PMnSbN compo sit io n s The values of the piezoelectric constants are shown in table 5. Figure 9 and figure 10 show the effect of amount of PMnN in PMnSb N co mposition on the piezoelectric properties, that is, rad ial coupling coefficient (kp), piezoelectric constant (d31) and mechanical quality factor (Qm) for the base composition PZT – PMnSb N. It is cleared that, kp and d31 increased with increasing amount of PMnN up to x = 0.7 and then strongly decreased. On other hand, increasing of amount of PMnN lead to decreasing the resonant resistance (R) and increasing Qm. The specimen at x = 0.7 exh ibited the most excellent dielectric, ferroelectric and piezoelectric properties of ε/ ε0 = 1447, Pr = 49.2µC/cm2, kp = 0.60, d31 = 180p C/N and Qm = 1895 is the best one for high-power piezoelectric transformer applications[1,2,11,12 ,13,14,15,16,17]. Table 5. Calculated kp, d31 and Qm values of samples Sample kp d31(pC/N) Qm M1 0.45 108.23 456 M2 0.50 119.3 487 M3 0.56 121.18 900 M4 0.60 180 1895 M5 0.52 102.6 1844 M6 0.50 86.22 1886 M7 0.44 72.57 2044 Figure 10. The d31 dependence on amount of PMnN in PMnSbN 4. Conclusions Piezoelectric propert ies of 0.9Pb(Zr0.53Ti0.47)O3-0.1Pb[(M n1/3Nb2/3)x(Sb1/2Nb1/2)1-x]O3 ceramics were investigated with the variation of x = 0.4 – 1.0 for high power p iezoelectric transformer application. The results obtained from the experiment are as follows: 1. The structures of PZT – PMnSb N co mpositions were changed not much with amount of PMnN and PSbN. The splitting of (200) and (002) peaks demonstrated the presence of tetragonal phase in the base of rhombohedral phase of perovskite. No pyrochlore were found in all co mpositions.. 2. With the increase of amount of PMnN in PMnSbN composition, grain size decreased, EC increased, Pr increased up to x = 0.7 and then decreased. At x = 0.7, the values of grain size, EC, Pr were 1.89µm, 10.28kV/cm and 49.2µC/cm2, res p ectiv ely . 3. Dielectric constant ε/ε0 and dielectric loss tanδ were decreased with increasing of amount PMnN. While Qm was strongly increased with increasing of amount of PMnN in PMnSbN co mposition, kp and d31 increased of maximu m at x = 0.7 and then decreased. The optimal values of Qm, kp, d31 were 1895, 0.6 and 180pC/N, respectively. It can be concluded that the specimen 0.9Pb(Zr0.53Ti0.47)O3-0.1Pb[(M n1/3Nb2/3)0.7(Sb1/2Nb1/2)0.3]O3 with the solubility suitably of soft and hard compositions is best for piezoelectric 58 Nguyen Dinh Tung Luan et al.: M icrostructure, Ferroelectric and Piezoelectric Properties of PZT-PM nSbN Ceramics transformer applications.  J. Yoo, Y. Lee, K. Yoon, S. Hwang, S. Suh, J. Kim and C. Yoo, Jpn. J. Appl. Phys 40, 2001, 3256–3259. REFERENCES  J.H.Yoo, Y.W.Lee, K.H.Yoon, H.S.Jung, Y.H.Jeong and C.Y.Park: J.Kor.Inst. Electr.& Electron. M ater. Eng. (KIEEM E) 11, 1998, 849.  G. H. Haertling, J. Am. Ceram. Soc. 82, 1999, 797.  Yuhuan Xu, Ferroelctric Materials and Their Applications (North-Holland, Amsterdam- London- Newyork-Tokyo), 1991.  F. Gao., L. Cheng, Hong R., J. Liu, C. Wang and C. Tian, Ceramics International 35, 2009, 1719–1723.  R. M uanghlua, S. Niemchareon, W. C. Vittayakorn and N. Vittayakorn, Advanced M aterials Research 55-57, 2008, 125-128.  C. W. Ahn, H. C. Song, S. 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