Dependence Of Piezoelectric Coefficients Research Articles

Loading rate independence of the evolutions of remnant state variables and linear material properties in ferroelectric ceramics during ferroelastic switching

Two series of compressive stress cycles are applied to a commercial poled ferroelectric cube specimen at room temperature $$\,20\,{^\circ }{\text{C}}$$ : one is big stress cycles of increasing magnitude and the other small stress cycles of constant magnitude. The former is applied at five different rates to induce domain switching, and the latter at the fastest loading rate possible to estimate the evolutions of linear material properties during switching. From measured data, we find that the relationships among remnant polarization, longitudinal remnant strain, and transverse remnant strain are equal and the same independent of loading rates. The dependence of piezoelectric coefficient, elastic compliance coefficients, and Poisson’s ratio on remnant state variables is also the same independent of loading rate. These observations lead to conclude that switching processes by compressive stress are loading rate independent, which would be useful in developing constitutive equations for nonlinear behavior of ferroelectric ceramics.

A new higher-order Landau–Ginzburg–Devonshire theory for KNbO3 crystal

ABSTRACTA Landau-Ginzburg-Devonshire(LGD) theory based on a structurally stable 8th-order potential with three varying expansion coefficients (a1, a11 and a2) was proposed for phenomenological description for KNbO3. The phase diagrams in the space of phenomenological parameters of the LGD potential model with co-dimension (Codim) of 2 and 3, invariant under the cubic point group m3m, were constructed. The values of the phenomenological coefficients of the potential model were determined by fitting experimental data. The theoretical pressure-temperature phase diagram which can explain the experimentally observed cubic-tetragonal-orthorhombic triple point and cubic-orthorhombic phase transition was constructed. Temperature dependences of spontaneous strain, lattice constants, dielectric constants and spontaneous polarization calculated with this potential model were in good agreement with the experimental data. Furthermore, the influence of the hydrostatic pressure on the dielectric constant (ε33) in the vicinity of the triple point and the dependence of piezoelectric coefficients on the applied electric field were predicted.

Y-doped ZnO nanosheets: Gigantic piezoelectric response for an ultra-sensitive flexible piezoelectric nanogenerator

Zinc oxide nanoparticles (NPs) with two different morphologies namely one-dimensional (1D) pure ‘pencil-like’ ZnO nanorods (NRs) and two-dimensional (2D) yttrium(Y)-doped ZnO nanosheets (NSs) were synthesized by wet chemical co-precipitation method. The morphological features and crystalline phase of as grown pure and Y-doped ZnO NPs were studied by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) techniques. A possible growth mechanism was proposed to understand the drastic change observed in the morphology of ZnO NPs from 1D NRs to 2D NSs as a result of Y3+ doping. The charge compensation of dopant YO2- anions at the Zn2+ terminated polar surface of ZnO played a crucial role in the formation of 2D NSs network. A gigantic piezoelectric coefficient (d33 ~ 420 pm/V) was achieved for Y-ZnO NSs, which is largely enhanced as compared to pure ZnO (d33 ~ 12.4 pm/V). The dependence of piezoelectric coefficient (d33) of ZnO on ionicchargecrystalradius ratio of dopant ion is reported. Finally, both pure and Y-doped ZnO nanocrystals have been used as the building blocks for fabricating flexible piezoelectric nanogenerators (NGs). The Y-doped ZnO based NG showed an ultra-sensitive characteristics by generating an output voltage around 20 V under gentle finger tapping (~0.01 kgf) and thus can be used in near future for powering various self-powered devices.

Piezoelectric Size Effects in a Zinc Oxide Micropillar.

In this work, the dependence of piezoelectric coefficients (PE) on the size of artificial fabricated ZnO micropillars on Si substrate is investigated. ZnO full film is grown with c-axis orientation and an average grain size of 20 nm at a substrate temperature of 500 °C by pulsed laser ablation. The micropillars with the size range of 1.5 to 7 μm are formed by top-down semiconductor device processing. The PE, characterized by piezoelectric force microscopy (PFM), is found to increase from 18.2 to 46.9 pm/V, when the ZnO pillar size is reduced from 7 to 1.5 μm. The strong PE dependence on ZnO pillar size can be explained by local changes in polarization and reduction of unit cell volume with respect to bulk values. These results have strong implications in the field of energy harvesting, as piezoelectric voltage output scales with the piezoelectric coefficient.

Finite element modeling of smart piezo structure: considering dependence of piezoelectric coefficients on electric field

ABSTRACTIn this work, variation of piezoelectric strain coefficient and permittivity with change in electric field is included in constitutive equations of piezoelectricity and used for developing finite element model of a plate instrumented with piezoelectric patches. Simulation results show that nodal displacement response and sensor voltage is less controlled if variation of piezoelectric strain coefficient and permittivity with change in electric field is not included in finite element modelling as compared to the case in which these variations are included in finite element modeling. An experiment is performed so as to validate simulation results.

Piezoelectric response of single-crystal PbZr1−xTixO3 near morphotropic phase boundary predicted by phase-field simulation

The piezoelectric property of hypothetic single-crystal PbZr1−xTixO3 (PZT) is studied using phase-field simulations. The dependence of piezoelectric coefficient (d33) on PbTiO3 compositions (x) near the morphotropic phase boundary of PZT was obtained. Using the existing thermodynamic description of PZT, it is shown that d33 reaches a peak value of 720 pC/N at x=0.47 which is more than three times of that for the ceramic counterpart. The relation between the domain structure of the poled PZT single crystals and the enhancement of d33 near the MPB composition is discussed.

Large displacement vertical translational actuator based on piezoelectric thin films

A novel vertical translational microactuator based on thin-film piezoelectric actuation is presented, using a set of four compound bend-up/bend-down unimorphs to produce translational motion of a moving platform or stage. The actuation material is a chemical-solution deposited lead–zirconate–titanate (PZT) thin film. Prototype designs have shown as much as 120 µm of static displacement, with 80–90 µm displacements being typical, using four 920 µm long by 70 µm legs. Analytical models are presented that accurately describe nonlinear behavior in both static and dynamic operation of prototype stages when the dependence of piezoelectric coefficients on voltage is known. Resonance of the system is observed at a frequency of 200 Hz. The large displacement and high bandwidth of the actuators at low-voltage and low-power levels should make them useful to a variety of optical applications, including endoscopic microscopy.

Phase transitions in Pb[(Ni1/3Sb2/3)xTiyZrz]O3 solid solution ceramics studied by piezoelectric measurements

The piezoelectric properties of Pb[(Ni1/3Sb2/3)xTiyZrz]O3 solid solution, where x+y+z = 1, x = 0.08 and y = 0.44–0.49 have been investigated in a wide temperature region using a resonance technique. The physical properties of PZT near the morphotropic phase boundary modified with the relaxor Pb(Ni1/3Sb2/3)O3 have been studied. The coefficients s11, k31 and d31 have been calculated basing on the damped harmonic oscillator model of piezoelectricly vibrating sample. Several anomalies in the temperature dependence of piezoelectric coefficients within the temperature range from 300 to 600 K have been found. For y > 0.46 the coexistence of rhombohedral and tetragonal phases occurs. The observed low piezoelectric activity confirms the existence of polar regions above Tm in Pb[(Ni1/3Sb2/3)xTiyZrz]O3.