Papers by Keyword: Piezoelectric Constant

Abstract: Lead-free piezoelectric ceramics of (1-x)(K_0.5Na_0.5)NbO₃ - xCaZrO₃ (abbreviated as KNN-CZ, x = 0 ~ 0.04) were synthesized by the conventional solid state method. Their phase structures and piezoelectric properties were investigated with x-ray diffraction (XRD), Scanning Electron Microscope (SEM), d₃₃ meter and Impedance Analyzer. KNN-CZ samples exhibit only pure perovskite phases with a small monoclinic distortion. It was observed that the lattice parameter b has a maximum at x = 0.02 but the monoclinic distortion angle β shows a minimum at the same composition. From the dependence of the lattice parameters (a, b, c, β) and cell volume on the content of CZ, it is considered that the intermediate phase transition exists near at x = 0.02. Piezoelectric properties show the maximum value of d33 = 121 pC/N and kp = 0.35 for the sample with x = 0.02, which seems to be due to the co-existence of the two different phases.

Abstract: In this paper, the KNN powders with Li⁺ substituted (K_0.5Na_0.5)⁺ were prepared by the sol-gel method in order to make powders pure, (Na_0.50+xK_0.50-2xL_ix) -NbO₃ (x=0, 0.04, 0.06, 0.08) ceramics were prepared by pressureless sintering. The phase composition of powders was determined by XRD. The effects of the Li⁺ substitution on piezoelectric and ferroelectric properties of ceramics were systematically studied for determining optimal Li⁺ content. Li⁺ can significantly increase the piezoelectric constant of ceramic. When Li⁺ content was 0.04, piezoelectric properties of ceramics were the best, d₃₃=115 pC/N, P_r=6.35 μC/cm², E_c=14.24 kV/cm.

Abstract: The principles of measuring tiny deformation by scanning Fabry-Perot interferometer have been studied. The measuring method of piezoelectric constant testing based on laser scanning Fabry-Perot principle was proposed. This measuring method was verified through contrasting the measured values with the known ones of piezoelectric constant and the result showed the errors between them were less than 6%

Abstract: 0-3 cement based piezoelectric composites were fabricated using sulphoaluminate cement as matrix by compressing technique method. The effects of strontium ferrite content on the piezoelectric properties, dielectric properties and acoustic impedance of the composites were studied. The results show that the piezoelectric strain constant d33 and piezoelectric voltage constant g33 of the composites increase gradually with increaing strontium ferrite content. When the strontium ferrite mass fraction is 0.4%, both of the piezoelectric strain constant d33 and piezoelectric voltage constant g33 of the composite have the maximum value, and the values are 16.6pC•N-1 and 31.4mV•m•N-1, which are 35% and 19% larger than that of the composite without strontium ferrite doped, respectively. With the strontium ferrite content increase, both of the dielectric constant εr and the dielectric loss tanδ of the composites increase. With the addition of strontium ferrite the acoustic impedance Z increases, but there is no obvious relation between the strontium ferrite content and Z.

Abstract: (1-x)(Bi1/2Na1/2)TiO3-xBiAlO3 [BNTA100x (0 ≤ x ≤ 0.14)] ceramics were prepared by a conventional ceramic fabrication process. Single-phase perovskite structures were formed when x ≤ 0.08 for BNTA100x. The depolarization temperature, Td, at which piezoelectricity disappears, decreased with increasing x. The piezoelectric constant, d33, increased with increasing x because of the increase in free permittivity accompanied with decreasing Td. d33 and the electromechanical coupling factor, k33, of BNTA6 were 93 pC/N and 0.41, respectively. Normalized strain d33* (= Smax/Emax) at 60 kV/cm at the maximum field-induced strain was 122.2 pm/V for BNTA8. The value of d33* was higher than the calculated value of d33.

Abstract: (1-x)(Bi0.5Na0.5TiO3)-xBa(Ti0.95Zr0.05)O3 ceramics were prepared by the mixed oxide technique and their dielectric, piezoelectric and ferroelectric properties determined in detail in the range x = 0.06 to 0.09. At x = 0.07 the maximum relative permittivity of 1338 and piezoelectric constant of 167 pC/N were obtained. It was concluded that 0.93(Bi0.5Na0.5TiO3)-0.07Ba(Ti0.95Zr0.05)O3 is the morphotropic phase boundary region for this system.

Abstract: To induce fine engineered domain configurations into potassium niobate (KNbO3) single crystals, two kinds of methods were performed, i.e., (1) high DC electric field exposure along the opposite direction of polarization of KNbO3 single-domain crystals at room temperature, and (2) introduction of randomly oriented fine domain configuration by heat treatment at 700 °C and then high DC electric field exposure along [001]c direction of KNbO3 multidomain crystals at room temperature. When the method (1) was performed, finally, the poled KNbO3 crystals became to single-domain state again through the formation of multidomain state. On the other hand, the KNbO3 multidomain crystals were obtained by using the method (2), and an enhancement of piezoelectric-related properties was observed.

Abstract: We report an effective substitution of aluminum for gallium in langasite-type La3Ta0.5Ga5.5O14 (LTG) crystals for use in a pressure sensor at high temperature. Al-substituted LTG (La3Ta0.5Ga5.5-xAlxO14; LTGAx) single crystals up to the solubility limit of x=0.5 have been grown by the conventional Czochralski technique. The electric properties of the LTGAx crystals were investigated and compared with those of LTG. By Al substitution, the piezoelectric constant d11 and the electromechanical coupling factors (k12) became slightly larger. The LTGAx crystals showed a lower temperature dependence of d11 and a higher electric resistivity ρ than those of the LTG crystals.

Abstract: For potassium niobate (KNbO3) single crystal, the 31 resonators with the highest piezoelectric constant d31 were designed using transformation of axis. We confirmed that the engineered domain configurations with maximum d31 of –55.1 pC/N was caused by a combination between two polarization with polar directions along [101]c and [-101]c directions. Moreover, if there are larger piezoelectric constants from domain wall region, we can expect the much higher piezoelectric properties. To induce the above domain configuration, a new poling method using patterning electrode was investigated. In this study, the two methods on the basis of temperature-induced phase transition at 207 °C and electric-field-induced phase transition at room temperature were investigated.