Modified Sawyer Tower Circuit Research Articles

In-plane characterization of PZT thin films for the creation of a general impedance model

The in-plane dielectric and ferroelectric properties of preferentially oriented lead zirconate titanate (PZT) thin films are characterized using interdigitated transducers (IDTs). By combining finite element method simulations and capacitance measurements, values of the dielectric constant of films with thicknesses between 150 nm and 800 nm are obtained. A modified Sawyer–Tower circuit is used to investigate the polarization loops measured in-plane using IDT electrodes. A well-defined hysteresis loop is obtained demonstrating the switching of the polarization of the ferroelectric domains. Leakage current measurements reveal high resistivity and are an indication of the high quality of the PZT film. The obtained characteristics are used to determine the total impedance of the IDT-PZT structure. Here, the structure is represented by an equivalent ladder circuit using the inductance and resistance of the IDT electrodes and the capacitance and conductance of the PZT film. The obtained total impedance matches low frequency measurements.

Effect of Nb, Ta and Sb Addition on Structure and Electrical Properties of PZT Ceramics

Abstract In this study, the effect of Nb, Ta and Sb addition on the structure, dielectric and ferroelectric properties of the Pb(Zr0.5Ti0.5)O3 ceramics in the morphotropic phase boundary (MPB) region were investigated. Powders of pure PZT, PZT + 0.1 mol% Nb, PZT + 0.1mol% Ta and PZT + 0.1mol% Sb were synthesized by conventional mixed oxide method via a vibro-milling technique. All compositions of powders were uniaxially pressed in pellets and sintered at the temperature of 1275°C for 2h. Phase formation, dielectric and ferroelectric properties of ceramics were characterized by XRD, LCR meter and modified Sawyer–Tower Circuit respectively.

Simulation and Experimental Data of P-E Hysteresis Loop in BNT and BKT

Hysteresis loop measurements performed both experimentally for Bismuth Sodium Titanate (BNT) and Bismuth Potassium Titanate (BKT) samples using modified Sawyer-Tower Circuit. The experiment showed that the P-E hysteresis had main parameters for BNT, remnant polarization (Pr = 27 μC/cm2), spontaneous polarization (Ps = 35 μC/cm2) and coercive electric field (Ec = 60 kV/cm) and for BKT the remnant polarization was (Pr = 5.2 μC/cm2), spontaneous polarization (Ps = 30 μC/cm2) and coercive electric field (Ec = 4.72 kV/cm). These three parameters (remnant polarization, spontaneous polarization, coercive electric field) were used in a simulated software depending on the mathematical model for the polarization in ferroelectric materials. The simulation software predicted the value of applied electric field required to perform the P-E hysteresis experiment varying with Pr, Ps, Ec. The results of the simulation exhibited agreement with the experimental data. The last prediction could help the researchers in studying the ferroelectric hysteresis loop, especially for those studying a fatigue behaviour or studying the effect of electric field cycle on the hysteresis loop.

Effect of uniaxial compressive pre-stress and temperature on the electromechanical behaviour of relaxor ferroelectric ceramics

The electromechanical behaviour of 0.98(0.9Pb(Mgl/3Nb2/3)O3–0.1PbTiO3)–0.02BaTiO3 (PMN–PT–2BT) relaxor ferroelectric ceramic under uniaxial compressive pre-stress is observed at stress up to 100 MPa using a homebuilt compress meter in conjunction with a modified Sawyer–Tower circuit. The results reveal that the maximum polarisation (Pm) and the longitudinal strain (x33) decrease with increasing pre-stress levels. It is owing to the restriction of the ferroelectric domains under both electric field and compressive pre-stress. Meanwhile, it is also found that temperature has significant effect on the electromechanical behaviour of this relaxor ferroelectric ceramic. The Pm and the x33 decrease with increasing temperature, and it is mainly because of the temperature-induced relaxor ferroelectric-paraelectric phase transition.

Effect of Sintering Condition on Electrical Properties of PLZT Ceramics

Feroelectric lead lanthanum zirconate titanate (PLZT) ceramics 9/70/30 were synthesized by conventional mixed-oxide method via a vibro-milling technique. The effect of sintering temperature and two-stage sintering method on electrical properties of PLZT ceramics was investigated. The ceramic powder was uniaxially pressed in pellets and sintered at the temperatures ranging from 1200 to 1275 °C for 4hrs and two-stage sintering temperature at 1200 °C for 4 hrs. Dielectric, ferroelectric and strain properties of ceramics were characterized by LCR meter, modified Sawyer–Tower Circuit and modified Michelson interferometric technique respectively.

Effect of Zr/Ti Ratio on Electrical Properties of Pb<sub>0.91</sub>La<sub>0.</sub><sub>0</sub><sub>9</sub>(Zr<sub>x</sub>Ti<sub>1-x</sub>)O<sub>3</sub> Ceramics

In this study, Pb0.91La0.09(ZrxTi1-x)O3 ceramics ( x = 0.75, 0.70, 0.65, 0.60, 0.55 and 0.50) have been synthesized by conventional mixed oxide method via a vibro-milling technique. The effect of composition on phase formation and electrical properties of PLZT ceramics was investigated. All compositions of powders were uniaxially pressed in pellets and sintered at the temperatures of 1275°C for 2h. Phase formation, dielectric, ferroelectric strain properties of ceramics were characterized by XRD, LCR meter, modified Sawyer–Tower Circuit and modified Michelson interferometric technique respectively. In this study new materials will be systematically developed based on the material engineering approach (processing vs electrical properties).

Polarization and Hysteresis in Tubular-Channel Fluoroethylenepropylene-Copolymer Ferroelectrets

Polarization-vs.-applied-voltage hysteresis curves are recorded on tubular-channel fluoroethylene-propylene (FEP) copolymer ferroelectrets by means of a modified Sawyer–Tower circuit. Dielectric barrier discharges (DBDs) inside the cavities are triggered when the applied voltage is sufficiently high. During the DBDs, the cavities become man-made macroscopic dipoles which build up an effective polarization in the ferroelectret. Therefore, a phenomenological hysteresis curve is observed. From the hysteresis loop, the remanent polarization and the coercive field can be determined. Furthermore, the polarization can be related to the respective piezoelectric coefficient of the ferroelectret. The proposed method is easy to implement and is useful for characterization, further development and optimization of ferro- or piezoelectrets.

Microstructure and relaxor ferroelectric properties of Bi2O3-doped strontium barium niobate ceramics

(1 − x) Sr0.4Ba0.6Nb2O6–xBi2O3 (0.00 ≤ x ≤ 0.20) ceramics were prepared by conventional solid-state reaction method. The microstructure, dielectric properties and P–E hysteresis loops of ceramics were investigated via X-ray diffraction, scanning electron microscope (SEM), Agilent E4980A and modified Sawyer–Tower circuit, respectively. XRD results showed the obtained ceramics were of tungsten bronze structure, and second phase Sr0.4Ba0.6Bi2Nb2O9 was detected at high doping concentration. SEM results showed suitable Bi2O3 addition could reduce the sintering temperature and assist the grain growth. The dielectric characteristics exhibited diffuse phase transition phenomena, which were verified by linear fitting of the modified Curie–Weiss law. Besides, the relaxor ferroelectric properties of ceramics followed the Vogel–Fulcher relationship well. The P–E hysteresis loops became slimmer with increasing the Bi2O3 addition, leading to a gradually decrease in both remnant polarization (Pr) and coercive field (Ec).

Direct hysteresis measurements on ferroelectret films by means of a modified Sawyer–Tower circuit

Ferro- and piezo-electrets are non-polar polymer foams or film systems with internally charged cavities. Since their invention more than two decades ago, ferroelectrets have become a welcome addition to the range of piezo-, pyro-, and ferro-electric materials available for device applications. A polarization-versus-electric-field hysteresis is an essential feature of a ferroelectric material and may also be used for determining some of its main properties. Here, a modified Sawyer-Tower circuit and a combination of unipolar and bipolar voltage waveforms are employed to record hysteresis curves on cellular-foam polypropylene ferroelectret films and on tubular-channel fluoroethylenepropylene copolymer ferroelectret film systems. Internal dielectric barrier discharges (DBDs) are required for depositing the internal charges in ferroelectrets. The true amount of charge transferred during the internal DBDs is obtained from voltage measurements on a standard capacitor connected in series with the sample, but with a much larger capacitance than the sample. Another standard capacitor with a much smaller capacitance—which is, however, still considerably larger than the sample capacitance—is also connected in series as a high-voltage divider protecting the electrometer against destructive breakdown. It is shown how the DBDs inside the polymer cavities lead to phenomenological hysteresis curves that cannot be distinguished from the hysteresis loops found on other ferroic materials. The physical mechanisms behind the hysteresis behavior are described and discussed.

Effect of La2O3 Addition on Electrical Properties of PZN-PZT Based Ceramics

In this study, compositions in the 0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr1/2Ti1/2)O3 based systems will be developed based on the material engineering approach (processing vs. electrical properties). This work involves the fabrication of high purity PZN-PZT based in ceramic forms, and a study of La2O3 addition on phase formation, microstructures and electrical properties was investigated which are especially important from the viewpoint of the development of practical piezoelectric materials. The effect of La2O3 addition was characterized on microstructure and electrical properties of PZN-PZT. Amounts of 0.05–1 wt% La2O3 were doped on 0.2PZN-0.8PZT. All compositions of powders were uniaxially pressed in pellets and sintered at the temperature 1250°C with dwell time 2 h. Phase and microstructure development, dielectric and ferroelectric properties of ceramics were characterized by XRD, SEM, LCR meter and Modified Sawyer–Tower Circuit respectively. In addition, the values of permittivity maximum and the temperature of permittivity maximum were substantially decreased by La-doping and these results show increased Pr, Ps and strain level but decreased Ec.

Effect of Uniaxial Compressive Prestress on the Electromechanical Behavior of Lanthanum Modified Lead Zirconate Titanate Stannate Ceramic

The antiferroelectric ceramics are often subjected to mechanical loading in transducer and high‐strain actuator applications. How the electromechanical behavior changes under different load conditions is therefore very crucial for design. The electromechanical behavior of La‐modified antiferroelectric ceramic lead zirconate titanate stannate (PLZST) under uniaxial compressive prestress is observed at stress up to 100 MPa using a homebuilt experimental setup in conjunction with a modified Sawyer–Tower circuit. The PLZST ceramic researched in this paper is near the ferroelectric—antiferroelectric phase boundary, and it has a lower forward phase transition electric field and slimmer electric hysteresis loop than conventional antiferroelectric ceramics. The results reveal that the area of the double hysteresis (P–E) loops, the saturation polarization (Psat), the longitudinal strain (S), and the remanent polarization (Pr) decrease with increasing compressive prestress, while the forward phase transition field increases as the compressive prestress increases. Meanwhile the applied prestress virtually does not affect the transition field hysteresis (ΔE) and the coercive field (Ec). These results are interpreted through the non‐180° domain switching processes and the stress induced decrease in the switchable part of ferroelectric and antiferroelectric domains under electric field.

Modeling and measurement of creep- and rate-dependent hysteresis in ferroelectric actuators

AbstractWe present a new model for the simulation of the hysteretic large-signal behavior in ferroelectric materials. The model is based on the Preisach operator and takes advantage of an analytic weight function for the underlying fundamental switching operators. The five independent parameters describing this weight function have been determined for a discoidal piezoceramic actuator by adapting the model output to measurements of the polarization. Since the classical Preisach model is only valid for creep- and rate-independent hysteresis loops, it is inappropriate to describe the entire ferroelectric material behavior. Therefore, we extended our model by an additional drift operator to consider creep phenomena. Furthermore, the rate-dependence of the hysteresis loops is described by a frequency-dependent parameter of the analytic weight function. For the identification and verification of the model, measurements have been performed using two different measurement principles: A modified Sawyer–Tower circuit as well as a method based on the integration of the electrical current. The agreement between measurements and simulations highlights the benefits of the enhanced hysteresis model.

Hysteresis Response of Lead Zirconate—Lead Nickel Niobate Ferroelectric Ceramic Under Compressive Stress

In this work, PZ–PNN ceramic was prepared by a columbite method and sintered at optimum temperature. The effect of uniaxial compressive stress on the hysteresis properties of PZ–PNN ceramics is investigated. The hysteresis loop and ferroelectric properties under the compressive stress of the ceramics are observed at stress up to 100 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. The results show that the applied stress has a significant influence on the hysteresis of PZ–PNN ceramics. The ferroelectric characteristics, i.e. the area of loops, P s and P r decrease with increasing compressive stress.

Polarization offset of homogeneous Bi3.15Nd0.85Ti3O12 ferroelectric thin films

In this report, the polarization offset usually observed in compositionally graded ferroelectric thin films was observed in homogeneous Bi3.15Nd0.85Ti3O12 thin films sandwiched in Pt electrodes. The observed polarization offset was studied as functions of temperature and of the driving voltage amplitude using a modified Sawyer–Tower circuit. The polarization offset is obvious only at temperatures above 150 °C and increases with increasing testing temperature and amplitude of driving voltage. The reported phenomena demonstrate that the composition gradient is not a necessity for such a polarization offset. The strong temperature and voltage dependence indicates that the polarization offsets may be related to thermionic charge injection, which is asymmetric to top and bottom electrodes.

Changes in ferroelectric properties of ceramics in lead magnesium niobate–lead titanate system with compressive stress

Effects of compressive stress on the ferroelectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) ceramics were investigated. The ceramics with the formula (1−x)Pb(Mg1/3Nb2/3)O3−(x)PbTiO3 or (1−x)PMN−(x)PT (x=0.1–0.5) were prepared by a conventional mixed-oxide method. Dense perovskite-phase PMN-PT ceramics with a uniform microstructure were obtained. The ferroelectric properties were measured under compressive stress (0–75 MPa) using a homebuilt compressometer in conjunction with a modified Sawyer–Tower circuit. The experimental results revealed that the superimposed compression stress significantly reduced both the dissipation energy and the polarizations of the near morphotropic phase boundary compositions, i.e., 0.8PMN-0.2PT, 0.7PMN-0.3PT, and 0.6PMN-0.4PT, while the stress influence was much less in other compositions. On the contrary, the applied compressive stress showed little or no influence on the coercive field. These results were interpreted through the non-180° ferroelastic domain switching processes and the stress induced decrease in the switchable part of domains.

Ferroelectric properties of Pb(Zr1/2Ti1/2)O3–Pb(Zn1/3Nb2/3)O3 ceramics under compressive stress

Effects of compressive stress on the ferroelectric properties of ceramics in PZT–PZN system were investigated. The ceramics with a formula (1− x )Pb(Zr 1/2 Ti 1/2 )O 3 – x Pb(Zn 1/3 Nb 2/3 )O 3 or (1− x )PZT–( x )PZN ( x = 0.1–0.5) were prepared by a conventional mixed-oxide method. The ferroelectric properties under the compressive stress of the PZT–PZN ceramics were observed at the stress levels up to 170 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis ( P – E ) loops, the saturation polarization ( P sat ), the remnant polarization ( P r ), and the coercive field ( E c ) decreased. These results were interpreted through the non-180° ferroelastic domain switching processes.

Stress-dependent ferroelectric properties of Pb(Zr1/2Ti1/2)O3–Pb(Zn1/3Nb2/3)O3 ceramic systems

Abstract Effects of compressive stress on the ferroelectric properties of ceramics in PZT–PZN systems were investigated. (1 − x )Pb(Zr 1/2 Ti 1/2 )O 3 ( x Pb(Zn 1/3 Nb 2/3 )O 3 or (1 − x )PZT–( x )PZN ( x = 0.1–0.5) ceramics were prepared by a conventional mixed-oxide method. The ferroelectric properties under compressive stress of the PZT–PZN ceramics were observed at stress levels up to 170 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization ( P sat ), the remanent polarization ( P r ), and the coercive field ( E c ) decreased. These results were interpreted through the non-180° ferroelectric domain switching processes.

Changes in ferroelectric properties of barium titanate ceramic with compressive stress

In this work, barium titanate (BT) ceramic was prepared using a conventional mixed oxide method. The effect of uniaxial compressive stress on the ferroelectric properties of BT ceramics were investigated. The changes in ferroelectric properties were observed at stress up to 60 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. The results showed that applied stress had a significant influence on the ferroelectric properties of BT ceramics. Ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis (P–E) loop, the saturation polarization (Psat), the remanent polarization (Pr) and the loop squareness (Rsq), decreased with increasing compressive stress, while the coercive field (Ec) remained constant. Stress-induced domain wall motion suppression and non-180° ferroelectric domain switching processes are responsible for the changes observed.

Effect of uniaxial compressive pre-stress on ferroelectric properties of soft PZT ceramics

The effect of uniaxial compressive pre-stress on the ferroelectric properties of commercial soft PZT ceramics is investigated. The ferroelectric properties under the uniaxial compressive pre-stress of the ceramics are observed at stress up to 24 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. The results show that the ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization (Psat), the remanent polarization (Pr), and the loop squareness (Rsq) decrease with increasing compressive pre-stress, while the coercive field (Ec) is virtually unaffected by the applied stress. The stress-induced domain wall motion suppression and non-180° ferroelectric domain switching processes are responsible for the changes observed. In addition, a significant decrease in these parameters after a full cycle of stress application has been observed and attributed to the stress-induced decrease in the switchable part of the spontaneous polarization at high stress. Furthermore, the permittivity calculated from the P–E loops is found to decrease with increasing applied pre-stress. This finding differs considerably from the results in the low-field experimental condition. Finally, this study clearly shows that the applied stress has a significant influence on the ferroelectric properties of soft PZT ceramics.

Uniaxial stress dependence of ferroelectric properties of xPMN-(1–x)PZT ceramic systems

Effects of uniaxial compressive pre-stress on the ferroelectric properties of ceramics in the PMN-PZT system are investigated. The ceramics with a formula xPb(Mg1/3Nb2/3)O3-(1-x)Pb(Zr0.52Ti0.48)O3 or xPMN-(1-x)PZT when x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0 are prepared by a conventional mixed-oxide method. The ferroelectric properties under the uniaxial compressive pre-stress of the PMN-PZT ceramics are observed at the stress levels up to 13 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It is found that with increasing compressive pre-stress levels the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization (Psat), the remanent polarization (Pr), and the coercive field (Ec) decrease. These results are interpreted through the non-180° ferroelastic domain-switching processes. Finally, the calculated differential permittivity for all the xPMN-(1-x)PZT ceramics, except for 0.5 PMN-0.5 PZT, decreases with increasing applied stress.