Lead Zirconate Titanate Structure Research Articles

Magnetoelectric effects in a composite ferromagnet–piezoelectric heterostructure under pulsed excitation

Magnetoelectric (ME) effects in multiferroic ferromagnet–piezoelectric (PE) composite heterostructures result in a change in the electric polarization under the action of magnetic field or a change in the magnetization under the action of electric field and, therefore, are interesting from scientific point of view and for applications. In this work, the direct and converse ME effects are experimentally studied when a planar amorphous ferromagnet–PE lead zirconate–titanate structure is excited by magnetic and electrical field pulses with duration from microseconds to tens of milliseconds. Under the action of magnetic field pulses, the structure generates damped voltage oscillations with a frequency equal to the acoustic resonance frequency of the structure, as well as an exponentially decreasing dc voltage. By choosing the duration of magnetic pulses, it is possible selectively excite the linear ME effect in the structure or generate the second voltage harmonic at the resonance frequency. Electrical field pulses result in the excitation of damped magnetization oscillations at the resonance frequency of the heterostructure. The pulsed excitation method allows to estimate the ME conversion coefficients for both the direct and converse ME effects.

Magnetoelectric coil-free voltage transformer based on monolithic ferrite-piezoelectric heterostructure

Low-power voltage transformers using magnetoelectric (ME) effect in ferromagnetic-piezoelectric heterostructures occupy an intermediate position between electromagnetic and piezoelectric transformers. They have low input and high output impedance, their transformation ratio is controlled by magnetic field. The paper describes design and manufacturing technology of monolithic ME transformers based on the nickel-zinc ferrite - lead zirconate-titanate structure. A prototype of the transformer is fabricated, in which a bulk electromagnetic coil in the input circuit is replaced with a planar electrode, deposited directly on the ferrite layer. This results in simplification of the design and reduction in the size of the transformer. At operating frequency of 70 kHz, the input impedance of the transformer is 0.1 Ω, the output impedance depends on the direction of the piezoelectric polarization and is 6–300 kΩ, the transformation ratio is tuned in the range 0–43 by magnetic field up to 60 Oe. The coil-free magnetoelectric transformers are promising to match circuits with very different impedances.

Vibration control of a lead zirconate titanate structure considering controller–structure interactions

This study focuses on integrating an active vibration controller into the finite element model of a piezoelectric laminated plate with the controller–structure interactions considered. A finite element model of a piezoelectric laminated plate is formulated using the third-order shear deformation theory. A state-space model is set up by performing a system identification technique. The state-space model is then used to design an optimal vibration controller. Considering that the finite element model is more appropriate than state-space model for dynamic simulation, the state-space model-based controller is integrated into the finite element model to capture the controller–structure interactions. The results obtained by applying vibration controller in state-space model are also presented to make a comparison. It is numerically demonstrated that the controller–structure interactions occur and cause performance degradation in case that the state-space model-based controller works with the finite element model. There is no prior guarantee that a state-space model-based controller satisfying the control requirements still works well in closed loop with the finite element model. The results of this study can be used to evaluate the controller performance for the piezoelectric smart structures during the preliminary design stage.

A refined shear lag model for adhesively bonded piezo-impedance transducers

The performance (sensing/actuating) of a piezotransducer highly depends upon the ability of the bond layer to transfer the stress and strain (through shear lag mechanism) between the transducer and the structure. Therefore, the coupled electromechanical response of the piezotransducer should consider the effect of dynamic behaviour, geometry and composition of the adhesive layer used to bond the transducer patch on the structure. This article presents a new refined analytical model for inclusion of the shear lag effect in modelling of adhesively bonded piezoelectric ceramic (lead zirconate titanate) patches for consideration in the electromechanical impedance technique. The previous models neglected the inertial term in shear lag formulations for simplicity. The present refined model, on the other hand, considers the inertial and the shear lag effects simultaneously, and is therefore more rigorous and complete. In this article, the formulations are first derived for one-dimensional case, and then extended to two-dimensional lead zirconate titanate–structure interaction. The overall results are found to be in better proximity to experimental observations. The refined formulations are employed for a detailed stress analysis of the bond layer. The article concludes with a parametric study on the influence of various sensor parameters on the electromechanical impedance signatures.

Small-scale piezoelectric devices: Pyroelectric contributions to the piezoelectric response

The recent trend in miniaturization of piezoelectrically active devices is driving research on size effects of these functional materials under reduced length scales. In this paper, we measure and model the generation of charge in thin piezoelectric structures under sinusoidal hydrostatic pressure and show how the subsequent thermally induced pyroelectric effect dominates the response in the smallest samples. We calculate the temperature profiles through the lead zirconate titanate structures, and determine the pyroelectric coefficient in these materials to be p′=0.28±0.02 mC m−2 K−1. The analysis of the piezoelectric and pyroelectric charge response described in this paper has significant impact on the design and fundamental functional behavior of small-scale piezoelectric devices.

Effect of the Nature of Chemical Reagents on the Formation of Nano-Sized Piezoceramics of Lead Zirconate-Titanate

The effect of the initial chemical reagents on the synthesis and sintering of lead zirconate-titanate has been investigated. The initial components underwent preliminary mechanical activation in a ball planetary-centrifugal mill. The initial components were titanium oxides TiO2 as rutile and anatase and TiO as nanosized powder, monoclinic zirconium oxide ZrO2, lead oxides as orthorhombic PbO and tetragonal PbO, Pb3O4, PbO2 as well as pure metals, i.e., zirconium and titanium. The possibility to obtain lead zirconate-titanate as early as during mechanical activation of samples was demonstrated. In some systems, cubic lead oxide Pb2O is formed during mechanical activation; then it disappears completely at annealing at 400°C. Changes in the structure and chemical composition of samples during annealing were investigated. The final formation of the lead zirconate-titanate structure occurs at the annealing of samples in the temperature range 1000°C to 1100°C depending on the initial components. The formation of nanodispersed structure with the grain size 10 to 40 nm was demonstrated by X-ray diffraction and transmission electron microscope (TEM).

Dielectric nonlinearity in a compositionally graded lead zirconate titanate structure

The dielectric response of a compositionally graded lead zirconate titanate (PZT) structure was studied as a function of frequency and amplitude of measuring field. The nonlinear behavior was observed above “threshold” value Et of electric field strength giving rise to field-dependent dielectric properties. Just above Et the nonlinearity was well fitted by the empirical Rayleigh relations. The values of Rayleigh coefficients were observed to be different from those of homogenous PZT films. The analysis of the nonlinearity allows us to suggest higher density of domain walls and/or their better mobility in graded structure.

Novel forming of columnar lead zirconate titanate structures

The present study is focused on the processing of columnar lead zirconate titanate (PZT) structures on Ti/Pt-coated silicon substrates using electrohydrodynamic deposition. It was found that the as-deposited PZT structure is highly dependent on the concentration of the sprayed precursor, which is believed to be the characteristic of electrohydrodynamic deposition. 0.01, 0.03, 0.06, 0.12, 0.3 and 0.6 M PZT sols were used to prepare as-deposited structures. Columnar PZT structures, which are important for the processing of 1-3 composites, were obtained with the 0.6 M sol. As-deposited and heat-treated columnar PZT structures were investigated using scanning electron microscopy and X-ray diffraction. The development of the PZT columns was studied by observing the cross-section of the structures deposited over different time sprays, revealing a three-stage growth process for these structures. The affect of substrate temperature on the columnar structure was also analysed by studying the density of the columns. Finally, a 1-3 composite was produced by infiltrating photoresists into the columnar PZT structures and the relative permittivity and dissipation factor of such composite were measured as 105 and 0.021. Modelling the structures as a PZT and a polymer capacitor connected in parallel in the PZT/polymer composite suggests that the relative permittivity of PZT columnar material is approximately 154.

Impedance spectroscopy study of a compositionally graded lead zirconate titanate structure

The dielectric response of a compositionally graded lead zirconate titanate (PZT) structure prepared by pulsed laser deposition was studied as a function of frequency and temperature (from room temperature up to 419 °C) using impedance spectroscopy. The analysis of combined impedance and modulus spectroscopy, as well as complex plane plots, revealed that the bulk grain relaxation was the dominant relaxation process over the frequency and temperature range studied. The calculated bulk grain capacitance of the graded structure shows an anomalous behavior near temperatures related to the phase transition temperatures of the corresponding PZT compositions. The hopping conduction obeying the “universal power law” and an exponent equal to 0.88 was observed to dominate in alternating current conductivity over the entire frequency range from 10 Hz to 2 MHz at room temperature. At higher temperatures the relaxation spectrum was found to be much influenced by the increased direct current (dc) conductivity. The measured low frequency conductivity and the bulk grain dc conductance, calculated from impedance analysis indicate nearly the same Arrhenius-type thermally activated process with activation energies of 1.09 and 1.12 eV, respectively. These values were found to be in excellent agreement with those published in literature for perovskite ferroelectrics and may be attributed to motion of oxygen vacancies or field-enhanced emission of carriers from traps within the bulk.