Papers by Keyword: Lead-Free Piezoelectric Ceramic

Abstract: To obtain lead-free 0.5Ba (Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ ceramics with excellent microstructure and electrical properties, BZT-BCT ceramics doping Mn⁴⁺ and Nb⁵⁺ was synthesized follow a conventional solid state reaction route. By means of SEM, XRD, quasi-static d₃₃ meter, the influence of sintering temperature on microstructure, piezoelectric and dielectric properties of BZT-BCT-Mn-Nb ceramics was discussed. The results show that grain size and the dielectric loss of BZT-BCT-Mn-Nb ceramics increase as raising the sintering temperature. When BZT-BCT-Mn-Nb ceramics is sintered at 1380°C, the optimum piezoelectric coefficient and dielectric constant are 264pC/N and 4142, respectively.

Abstract: (1- x) K_0.5Na_0.5NbO₃ – x BiFeO₃ lead-free piezoelectric ceramics were prepared by the conventional ceramic processing. The compositional dependence of the phase structure and the electrical properties of the ceramics were studied. A morphotropic phase boundary (MPB) between the orthorhombic and tetragonal phases was identified in the composition range of x = 0.01. The ceramics exhibit a strong compositional dependence and enhanced piezoelectric properties. The ceramics with 0.6 mol.% BF exhibit good electrical properties (d₃₃ ～146 pC/N, kp ～51%, Tc ～405°C, To-t ～185 °C, εr ～432, and tan θ～ 4.60 %. The related mechanism of the enhanced electrical properties of the ceramics was also discussed. These results show that the air-sintered (1−x) KNN− x BF (0.006 < x < 0.01) ceramic is a promising lead-free piezoelectric material.

Abstract: Plated-like Bi₄Ti₃O₁₂ particles with anisotropic properties were prepared by the NaCl-KCl molten salt method. The effect on microstructure and patterns of Bi₄Ti₃O₁₂ particles was investigated by adjusting salt quantities, calcined temperature and excessive Bi₂O₃ content. The results show that the size of Bi₄Ti₃O₁₂ particle and the degree of anisotropy of pure perovskite structure of Bi₄Ti₃O₁₂ particles prepared at 750°C simultaneously increased with the quantities of molten salt and the temperature of the calciner. Excessive Bi₂O₃ content also shows a positive effect to obtain the anisotropic Bi₄Ti₃O₁₂ particles whose preparation process was optimized.

Abstract: The high-power piezoelectric characteristics of lead-free piezoelectric ceramics, based on a bismuth layer-structured ferroelectric, MnCO₃-doped (Sr_0.7Ca_0.3)₂Bi₄Ti₅O₁₈ (abbreviated as SCBT0.3 + Mn x wt%), were studied. SCBT0.3 + Mn x wt% lead-free ceramics showed an extremely high mechanical quality factor (Q_m) of more than 3000 in the (33) vibration mode under small-amplitude vibration. The high-power piezoelectric characteristics of SCBT0.3 + Mn x wt% were measured using the high-power measurement method based on frequency sweep driving under a constant voltage condition. It was found that the vibration velocity v_0-p of SCBT0.3 + Mn 0.2 wt% linearly increased up to approximately 3.0 m/s. Therefore, the Mn-doped SCBT0.3-based ceramics are a promising candidate for lead-free high-power applications.

Abstract: High-power piezoelectric characteristics of (Bi_1/2Na_1/2)TiO₃ (BNT)- and KNbO₃ (KN)-based ceramics at continuous driving were investigated. The selected compositions of BNT- and KN-based ceramics were 0.88(Bi_1/2Na_1/2)TiO₃-0.04(Bi_1/2Li_1/2)TiO₃-0.08(Bi_1/2K_1/2)TiO₃ doped with 0.6 wt% MnCO₃ [BNLKT4-8Mn0.6] and KNbO₃-MnCO₃ 0.8 wt% [KN-Mn0.8] ceramics. It was found that the vibration velocity v_0-P of BNLKT4-8Mn0.6 and KN-Mn0.8 ceramics linearly increased up to approximately 0.8 and 0.6 m/s, respectively. The temperature increases of BNLKT4-8Mn0.6 and KN-Mn0.8 ceramics were approximately 5°C under continuous driving at the vibration velocity of 0.6 m/s.

Abstract: In this study, the relationships between the electrical properties and polarization switching of lead-free (Li_0.06Na_0.94)NbO₃ (LNN6) ceramics were investigated. The electrical properties of stoichiometric LNN6 did not change with polarization switching. On the other hand, the frequency dependence of the impedance of Na-deficient LNN decreased with polarization switching, and the coupling factor k_p, the piezoelecric constant d₃₃ and the dielectric constant ε33T/ε0 decreased with polarization switching. Moreover, the dielectric curve of Na-deficient LNN6 after 10 switchings showed peaks at approximately 330, 400 and 500 °C

Abstract: The ZnO based glass was added to calcined K_0.5Na_0.5NbO₃ by ball milling for 20h. The addition of 1wt.% ZnO- based glass exhibited the following piezoelectric properties (kp=36%, Qm=236, e₃₃^T/e₀=464). By increasing the amount of glass powder ~5wt.%, kp was decreased to 24%. However, Qm and e₃₃^T/e₀ were observed slightly decreasing. Besides, the moisture-resistance of ZnO-based glass added K_0.5Na_0.5NbO₃ was enhanced considerably as compared to that of K_0.5Na_0.5NbO₃.

Abstract: Lead-free K_0.5Na_0.5NbO₃-xwt% (0.4ZnO-0.6B₂O₃) ceramics were synthesized by conventional ceramics process. The co-doping of ZnO and B₂O₃ can decrease the sintering temperature of K_0.5Na_0.5NbO₃ ceramics to 1000°C, and the samples show high relative density around 96%. X-ray diffraction (XRD) reveals that Co-doping of ZnO and B₂O₃ induces lattice distortion. Liquid phase is observed by scanning electron microscopy (SEM), which is resulted from the addition of ZnO and B₂O₃. The ceramics show better piezoelectric and dielectric properties with planar electromechanical coupling factor k_p= 40.7%, piezoelectric constant d₃₃=117pC/N, dielectric constant ε^T₃₃/ε₀=318.6, and loss tangent tanδ=0.034.

Abstract: In this paper, Plated-like Bi₄Ti₃O₁₂ particles with anisotropic properties were prepared by the NaCl-KCl molten salt method. The effect on microstructure and patterns of Bi₄Ti₃O₁₂ particles was investigated by adjusting salt quantities, calcined temperature and excessive Bi₂O₃ content. The results show that the size of Bi₄Ti₃O₁₂ particle and the degree of anisotropy of pure perovskite structure of Bi₄Ti₃O₁₂ particles prepared at 750°C simultaneously increased with the quantities of molten salt and the temperature of the calciner. Excessive Bi₂O₃ content also shows a positive effect to obtain the anisotropic Bi₄Ti₃O₁₂ particles whose preparation process was optimized.

Abstract: 0.85(Na_0.5Bi_0.5)TiO₃-0.144(K_0.5Bi_0.5)TiO₃-0.006BaTiO₃(0.85NBT-0.144KBT-0.006BT) lead-free piezoelectric ceramics was prepared by conventional ceramic technique. The influence of La₂O₃ doping amount and CeO₂ doping amount on properties , crystal structure and surface topography of 0.85NBT-0.144KBT-0.006BT ceramics were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and other analytic methods. It shows that all compositions show the characteristics of pure perovskite structure solid states, La₂O₃ and CeO₂ doping only changes crystal cell dimension rather than crystal structure. The piezoelectric strain constant (d₃₃) starts increasing and then decreasing, the dielectric constant (ε^T₃₃/ε₀) increases, the dielectric loss (tanδ) starts increasing and then decreasing and then increasing while La₂O₃ doping amount increasing. d₃₃ and ε^T₃₃/ε₀ of ceramics starts increasing and then decreasing, tanδ decreases while CeO₂ doping amount increasing . When the La₂O₃ doping amount is up to 0.4 wt.%, the doped samples show good performances with d₃₃=151 pC/N, ε^T₃₃/ε₀=1543 and tanδ=4.3%. When the CeO₂ doping amount is 0.1 wt.%, the doped samples show good performances with d₃₃=156 pC/N, ε^T₃₃/ε₀=1364 and tanδ=3.8%. La₂O₃ doping promotes crystal grain growth, CeO₂ doping makes grain crystal size uniform, changes tetragonal into granular structure and restrains crystal grain growth.