Showing papers on "Lead zirconate titanate published in 2012"

Lone-Pair-Induced Covalency as the Cause of Temperature- and Field-Induced Instabilities in Bismuth Sodium Titanate

Abstract: Bismuth sodium titanate (BNT)-derived materials have seen a flurry of research interest in recent years because of the existence of extended strain under applied electric fields, surpassing that of lead zirconate titanate (PZT), the most commonly used piezoelectric. The underlying physical and chemical mechanisms responsible for such extraordinary strain levels in BNT are still poorly understood, as is the nature of the successive phase transitions. A comprehensive explanation is proposed here, combining the short-range chemical and structural sensitivity of in situ Raman spectroscopy (under an applied electric field and temperature) with macroscopic electrical measurements. The results presented clarify the causes for the extended strain, as well as the peculiar temperature-dependent properties encountered in this system. The underlying cause is determined to be mediated by the complex-like bonding of the octahedra at the center of the perovskite: a loss of hybridization of the 6s2 bismuth lone pair interacting with the oxygen p-orbitals occurs, which triggers both the field-induced phase transition and the loss of macroscopic ferroelectric order at the depolarization temperature.

Lead zirconate titanate nanowire textile nanogenerator for wearable energy-harvesting and self-powered devices.

Abstract: Wearable nanogenerators are of vital importance to portable energy-harvesting and personal electronics. Here we report a method to synthesize a lead zirconate titanate textile in which nanowires are parallel with each other and a procedure to make it into flexible and wearable nanogenerators. The nanogenerator can generate 6 V output voltage and 45 nA output current, which are large enough to power a liquid crystal display and a UV sensor.

Pyroelectric Nanogenerators for Driving Wireless Sensors

Abstract: We demonstrate a pyroelectric nanogenerator (PENG) based on a lead zirconate titanate (PZT) film, which has a pyroelectric coefficient of about −80 nC/cm 2 K. For a temperature change of 45 K at a rate of 0.2 K/s, the output open-circuit voltage and short-circuit current density of the PENG reached 22 V and 171 nA/cm 2 , respectively, corresponding to a maximum power density of 0.215 mW/ cm 3 . A detailed theory was developed for understanding the high output voltage of PENG. A single electrical output pulse can directly drive a liquid crystal display (LCD) for longer than 60 s. A Li-ion battery was charged by the PENG at different working frequencies, which was used to drive a green light- emitting diode (LED). The demonstrated PENG shows potential applications in wireless sensors.

PZT-Based Piezoelectric MEMS Technology

Abstract: This review article presents recent advancements in the design and fabrication of thin-film (<3 μm) lead zirconate titanate (PZT) microelectromechanical system (MEMS) devices. The article covers techniques for optimizing highly (001)/(100) oriented chemical solution deposited PZT films to achieve improved piezoelectric coefficients. These PZT films combined with surface and bulk micromachining techniques are fabricated into actuators and transducers for radio frequency (RF) switches, nanomechanical logic, resonators, and power transformers for use in communication systems and phased-array radar. In addition, the large relative displacements generated by PZT thin films have been used to demonstrate mechanical mobility in MEMS devices, including insect-inspired flight actuators and ultrasonic traveling wave motors. In conjunction with actuation, PZT films are being developed for feedback sensors for the integrated control of insect-inspired robots.

Substrate clamping effects on irreversible domain wall dynamics in lead zirconate titanate thin films.

Abstract: The role of long-range strain interactions on domain wall dynamics is explored through macroscopic and local measurements of nonlinear behavior in mechanically clamped and released polycrystalline lead zirconate-titanate (PZT) films. Released films show a dramatic change in the global dielectric nonlinearity and its frequency dependence as a function of mechanical clamping. Furthermore, we observe a transition from strong clustering of the nonlinear response for the clamped case to almost uniform nonlinearity for the released film. This behavior is ascribed to increased mobility of domain walls. These results suggest the dominant role of collective strain interactions mediated by the local and global mechanical boundary conditions on the domain wall dynamics. The work presented in this Letter demonstrates that measurements on clamped films may considerably underestimate the piezoelectric coefficients and coupling constants of released structures used in microelectromechanical systems, energy harvesting systems, and microrobots.

Enhancement of Photocurrent in Ferroelectric Films Via the Incorporation of Narrow Bandgap Nanoparticles

Abstract: A novel nanostructured ferroelectric photovoltaic material, consisting of the ferroelectric lead zirconate titanate (PZT) film and Ag(2) O semiconductor nanoparticles of comparatively narrow bandgap, has demonstrated a remarkable enhancement in the photovoltaic effects and the highest light-electricity conversion efficiency among those PZT-based photodiodes previously reported. This work sheds light on the design and enhanced performance of new optoelectronic and solar energy devices.

Pyroelectric waste heat energy harvesting using relaxor ferroelectric 8/65/35 PLZT and the Olsen cycle

Abstract: Waste heat can be directly converted into electrical energy by performing the Olsen cycle on pyroelectric materials. The Olsen cycle consists of two isothermal and two isoelectric field processes in the electric displacement versus electric field diagram. This paper reports on the electrical energy generated by lanthanum-doped lead zirconate titanate (8/65/35 PLZT) subjected to the Olsen cycle. The material was alternately dipped into a cold and a hot silicone oil bath under specified electric fields. A maximum energy density of 888 J l−1/cycle was obtained with a 290 µm thick 8/65/35 PLZT sample for temperatures between 25 and 160 °C and electric fields cycled between 0.2 and 7.5 MV m−1. To the best of our knowledge, this is the largest pyroelectric energy density experimentally measured with multiple cycles. It corresponded to a power density of 15.8 W l−1. The electrical breakdown strength and therefore the energy and power densities of the material increased as the sample thickness was reduced from 720 to 290 µm. Furthermore, a physical model for estimating the energy harvested by ferroelectric relaxors was further validated against experimental data for a wide range of electric fields and temperatures.

Resonant PZT MEMS Scanner for High-Resolution Displays

Abstract: A resonant piezoelectric scanner is developed for high-resolution laser-scanning displays. A novel actuation scheme combines the principle of mechanical amplification with lead zirconate titanate (PZT) thin-film actuation. Sinusoidal actuation with 24 V at the mechanical resonance frequency of 40 kHz provides an optical scan angle of 38.5° for the 1.4-mm-wide mirror. This scanner is a significant step toward achieving full-high-definition resolution (1920 × 1080 pixels) in mobile laser projectors without the use of vacuum packaging. The reported piezoscanner requires no bulky components and consumes <; 30-mW power at maximum deflection, thus providing significant power and size advantages, compared with reported electromagnetic and electrostatic scanners. Interferometry measurements show that the dynamic deformation is at acceptable levels for a large fraction of the mirror and can be improved further for diffraction-limited performance at full resolution. A design variation with a segmented electrode pair illustrated that reliable angle sensing can be achieved with PZT for closed-loop control of the scanner.

Three-dimensional micro electromechanical system piezoelectric ultrasound transducer

Abstract: Here we present the design and experimental acoustic test data for an ultrasound transducer technology based on a combination of micromachined dome-shaped piezoelectric resonators arranged in a flexible architecture. Our high performance niobium-doped lead zirconate titanate film is implemented in three-dimensional dome-shaped structures, which form the basic resonating cells. Adjustable frequency response is realized by mixing these basic cells and modifying their dimensions by lithography. Improved characteristics such as high sensitivity, adjustable wide-bandwidth frequency response, low transmit voltage compatible with ordinary integrated circuitry, low electrical impedance well matched to coaxial cabling, and intrinsic acoustic impedance match to water are demonstrated.

Direct strain energy harvesting in automobile tires using piezoelectric PZT-polymer composites

Abstract: Direct piezoelectric strain energy harvesting can be used to power wireless autonomous sensors in environments where low frequency, high strains are present, such as in automobile tires during operation. However, these high strains place stringent demands on the materials with respect to mechanical failure or depolarization, especially at elevated temperatures. In this work, three kinds of ceramic–polymer composite piezoelectric materials were evaluated and compared against state-of-the-art piezoelectric materials. The new composites are unstructured and structured composites containing granular lead zirconate titanate (PZT) particles or PZT fibers in a polyurethane matrix. The composites were used to build energy harvesting patches which were attached to a tire and tested under simulated rolling conditions. The energy density of the piezoelectric ceramic–polymer composite materials is initially not as high as that of the reference materials (a macro-fiber composite and a polyvinylidene fluoride polymer). However, the area normalized power output of the composites after temperature and strain cycling is comparable to that of the reference devices because the piezoelectric ceramic–polymer composites did not degrade during operation.

Piezoelectric PZT MEMS technologies for small-scale robotics and RF applications

Abstract: Thin-film piezoelectric lead zirconate titanate (PZT) is one of the most efficient electromechanical coupling transducer materials currently available for microelectromechanical systems (MEMS). This article reviews piezoelectric MEMS (piezo MEMS) technologies using PZT thin films in radio frequency (RF) devices for communications and radar applications and in the emerging field of millimeter-scale robotics. The electromechanical material properties of thin-film PZT uniquely enable insect-inspired and insect-scale autonomous robots. Recent progress on large force and displacement actuators for robotic leg joints, compact and high torque ultrasonic motors, and bioinspired millimeter-scale flapping wing platforms will be presented. The use of thin-film PZT to achieve high performance and low-voltage RF MEMS switches, ultralow power consumption nanomechanical logic circuits, and high coupling and low loss resonators, filters, and transformers are also reviewed.

Piezoelectric single crystal langatate and ferromagnetic composites: Studies on low-frequency and resonance magnetoelectric effects

Abstract: Mechanical strain mediated magnetoelectric (ME) effects are studied in bilayers and trilayers of piezoelectric single-crystal lanthanum gallium tantalate (LGT) and magnetostrictive permendur (P). The ME voltage coefficient ranges from 2.3 V/cm Oe at 20 Hz to 720 V/cm Oe at bending resonance and is higher by an order of magnitude than in composites with ferroelectric lead zirconate titanate or lead magnesium niobate-lead titanate. The low-frequency magnetic noise for P-LGT-P is a factor of 2-10 smaller than for ferroelectrics based composites. Langatate is free of ferroelectric hysteresis, pyroelectric effects, and phase transitions up to 1450 °C and is of interest for ultrasensitive, high temperature magnetic sensors.

Voltage impulse induced bistable magnetization switching in multiferroic heterostructures

Abstract: We report on voltage impulse induced reversible bistable magnetization switching in FeGaB/lead zirconate titanate (PZT) multiferroic heterostructures at room temperature. This was realized through strain-mediated magnetoelectric coupling between ferroelectric PZT and ferromagnetic FeGaB layer. Two reversible and stable voltage-impulse induced mechanical strain states were obtained in the PZT by applying an electric field impulse with its amplitude smaller than the electric coercive field, which led to reversible voltage impulse induced bistable magnetization switching. These voltage impulse induced bistable magnetization switching in multiferroic heterostructures provides a promising approach to power efficient bistable magnetization switching that is crucial for information storage.

A PZT-based smart aggregate for compressive seismic stress monitoring

Abstract: A PZT-based smart aggregate (SA) for compressive seismic stress monitoring is proposed in this paper. The proposed SA consists of a piece of PZT (lead zirconate titanate) patch sandwiched between a pair of marble cubes through epoxy. A soft PZT is selected, rendering the SA as a potential actuator in active sensing. Finite element analysis (FEA) was conducted to investigate the stress distribution in the SA under compression, which is used for calculating its sensitivity to compressive stresses. With a commercially available charge amplifier, the frequency response of both the amplitude and the phase shift of the sensing system are investigated by applying the frequency sweep loading scheme on the proposed SA. The frequency ranges from 0.01 to 10 Hz, corresponding to the range of seismic frequency response of most building structures. The alternating load for evaluating SA sensitivity was applied by the servo-hydraulic machine. The lower limit of frequency response is determined to be 0.5 Hz. The depolarization process of the piezoelectric coefficient of the selected PZT material was investigated to decide the load-holding time in calibration tests. The degradation of the piezoelectric coefficient with a series of compressive pre-stresses from 4.8 to 24 MPa was evaluated, and the experimental results showed that the influence from the considered range of pre-stresses is negligible. Using a commercially available charge amplifier, the proposed SA-based sensing system can monitor the seismic stress of low- and middle-rise building structures under moderate earthquakes.

Dynamic Hysteresis and Scaling Behavior of Energy Density in Pb0.99Nb0.02[(Zr0.60Sn0.40)0.95Ti0.05]O3 Antiferroelectric Bulk Ceramics

Abstract: The evolution of dynamic hysteresis of lead zirconate titanate stannate antiferroelectric bulk ceramics at various frequencies (f) and field amplitudes (E0) has been investigated systematically. A series of asymmetrical minor loops were observed when the working fields were slightly lower than the forward switching field EAF. As E0 increased above EAF, symmetrical double loops appeared and their energy densities w against f and E0 were found to be fit the scaling behavior as w∝∝∝∝f−0.02(E0 − Ec)0.08, where Ec representing the threshold field is designated as EAF. The study is helpful to application of antiferroelectrics as energy-storage capacitors.

Integrated thin-film piezoelectric traveling wave ultrasonic motors

Abstract: An integrated approach to the fabrication of thin-film piezoelectric traveling wave ultrasonic motors at the mm-scale is being developed for low power, high torque motors for small scale robotics, biomedical, and sensing applications. This paper describes the realization of ultrasonic motor stators ranging in diameter from 1 to 3 mm using wafer scale MEMS fabrication techniques with lead zirconate titanate (PZT) thin films. Using laser Doppler vibrometry (LDV), controlled traveling waves were demonstrated in the bulk silicon elastic medium of the stator and the standing wave behavior was characterized for control purposes. Furthermore, the resonant modes of the fabricated stators were modeled using finite element models, and experimental results agree well with this analysis.

Electrode-shaping for the excitation and detection of permitted arbitrary modes in arbitrary geometries in piezoelectric resonators

Abstract: This paper reports theoretical analysis and experimental results on a numerical electrode shaping design technique that permits the excitation of arbitrary modes in arbitrary geometries for piezoelectric resonators, for those modes permitted to exist by the nonzero piezoelectric coefficients and electrode configuration. The technique directly determines optimal electrode shapes by assessing the local suitability of excitation and detection electrode placement on two-port resonators without the need for iterative numerical techniques. The technique is demonstrated in 61 different electrode designs in lead zirconate titanate (PZT) thin film on silicon RF micro electro-mechanical system (MEMS) plate, beam, ring, and disc resonators for out-of-plane flexural and various contour modes up to 200 MHz. The average squared effective electromechanical coupling factor for the designs was 0.54%, approximately equivalent to the theoretical maximum value of 0.53% for a fully electroded length-extensional mode beam resonator comprised of the same composite. The average improvement in S21 for the electrode-shaped designs was 14.6 dB with a maximum improvement of 44.3 dB. Through this piezoelectric electrodeshaping technique, 95% of the designs showed a reduction in insertion loss.

De-aging of Fe-doped lead-zirconate-titanate ceramics by electric field cycling: 180°- vs. non-180° domain wall processes

Abstract: Acceptor-doped ferroelectrics tend to show pronounced aging behavior. The microscopic effects of aging are commonly related to oxygen vacancies, however, there are still open questions with respect to their impact on domain wall movements. To elucidate the latter, the reverse process of de-aging by electric field cycling is investigated here on Pb(Zr0.54Ti0.46)O3 doped with iron in different concentrations. Measurements of the hysteretic behavior of large-signal parameters, i.e., polarization and strain, as well as small-signal parameters, i.e., electrical permittivity and piezoelectric coefficient, are used to distinguish between reversible and irreversible movement of 180°- and non-180° domain walls. The results indicate that for low doping concentrations, the de-aging behavior of 180° domain wall motion is governed by irreversible domain wall motion and a coarsening of the domain structure, while for non-180° domain walls the change in reversible domain wall mobility is the dominant de-aging mechanism. For high doping concentrations, an additional clamping effect related to the smaller grain size occurs.

The effects of embedded piezoelectric fiber composite sensors on the structural integrity of glass-fiber-epoxy composite laminate

Abstract: Piezoelectric fiber composite sensors (PFCSs) made from micro-sized lead zirconate titanate (PZT) fibers have many advantages over the traditional bulk PZT sensors for embedded sensor applications. PFCSs as embedded sensors will be an ideal choice to continuously monitor the stress/strain levels and health conditions of composite structures. PFCSs are highly flexible, easily embeddable, have high compatibility with composite structures, and also provides manufacturing flexibility. This research is focused on examining the effects of embedding PFCS sensors (macro-fiber composite (MFC) and piezoelectric fiber composite (PFC)) on the structural integrity of glass-fiber–epoxy composite laminates. The strengths of composite materials with embedded PFCSs and conventional PZT sensors were compared, and the advantages of PFCS sensors over PZTs were demonstrated.Initially a numerical simulation study is performed to understand the local stress/strain field near the embedded sensor region inside a composite specimen. High stress concentration regions were observed near the embedded sensor corner edge. Using PFCS leads to a reduction of 56% in longitudinal stress concentration and 38% in transverse stress concentration, when compared to using the conventional PZTs as embedded sensors. In-plane tensile, in-plane tension–tension fatigue, and short beam strength tests are performed to evaluate the strengths/behavior of the composite specimens containing embedded PFCS. From the tensile test it is observed that embedding PFCS and PZT sensors in the composite structures leads to a reduction in ultimate strength by 3 and 6% respectively. From the fatigue test results it is concluded that both embedded PFCS and PZT sensors do not have a significant effect on the fatigue behavior of the composite specimens. From the short beam strength test it is found that embedding PFCS and PZT sensors leads to a reduction in shear strength by 7 and 15% respectively. Overall the pure PZT sensors seem to have low compatibility with composites when compared to PFCSs.

Reduction of the piezoelectric performance in lead-free (1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 piezoceramics under uniaxial compressive stress

Abstract: The effect of a uniaxial compressive stress on the properties of BZT-BCT samples across the morphotropic phase boundary (MPB) is investigated using direct piezoelectric coefficient measurements. In contrast to many lead zirconate titanate compositions, the piezoelectric coefficient decreases monotonically with increasing stress and does not show an initial increase or plateau. Electrically softer rhombohedral and MPB compositions are found to be more susceptible to a decrease in piezoelectric coefficient under an increasing pre-stress than tetragonal compositions. Depoling due to ferroelastic domain switching alone, as observed by x-ray diffraction, does not explain this reduction, but instead a decreasing domain wall density is proposed to be responsible for reduced piezoelectric coefficients under increasing compressive stress. The relaxation of the piezoelectric response after complete unloading supports this proposed mechanism.

Measurement of effective piezoelectric coefficients of PZT thin films for energy harvesting application with interdigitated electrodes

Abstract: Interdigitated electrode (IDE) systems with lead zirconate titanate (PZT) thin films play an increasingly important role for two reasons: first, such a configuration generates higher voltages than parallel plate capacitor-type electrode (PPE) structures, and second, the application of an electric field leads to a compressive stress component in addition to the overall stress state, unlike a PPE structure, which results in tensile stress component. Because ceramics tend to crack at relatively moderate tensile stresses, this means that IDEs have a lower risk of cracking than PPEs. For these reasons, IDE systems are ideal for energy harvesting of vibration energy, and for actuators. Systematic investigations of PZT films with IDE systems have not yet been undertaken. In this work, we present results on the evaluation of the in-plane piezoelectric coefficients with IDE systems. Additionally, we also propose a simple and measurable figure of merit (FOM) to analyze and evaluate the relevant piezoelectric parameter for harvesting efficiency without the need to fabricate the energy harvesting device. Idealized effective coefficients e IDE and hIDE are derived, showing its composite nature with about one-third contribution of the transverse effect, and about two-thirds contribution of the longitudinal effect in the case of a PZT film deposited on a (100)-oriented silicon wafer with the in-plane electric field along one of the Si directions. Randomly oriented 1-μm-thick PZT 53/47 film deposited by a sol-gel technique, was evaluated and yielded an effective coefficient eIDE of 15 C���m���2. Our FOM is the product between effective e and h coefficient representing twice the electrical energy density stored in the piezoelectric film per unit strain deformation (both for IDE and PPE systems). Assuming homogeneous fields between the fingers, and neglecting the contribution from below the electrode fingers, the FOM for IDE structures with larger electrode gap is derived to be twice as large as for PPE structures, for PZT-5H properties. The experiments yielded an FOM of the IDE structures of 1.25 × 1010 J/m3 and 14 mV/μ strain.

Graphene-lead zirconate titanate optothermal field effect transistors

Abstract: We have developed a pyroelectric field effect transistor (FET) based on a graphene-lead zirconate titanate (PZT) system Under the incidence of a laser beam, the drain current can be increased or decreased depending on the direction of the polarization of the PZT substrate The drain current sensitivity of the optothermal FET can reach up to 360 nA/mW at a drain field of 67 kV/m more than 5 orders of magnitude higher than that of the photogating transistors based on carbon nanotube on SiO2/Si substrate Graphene is an excellent component for pyroelectric FET due to its high optical transparency and conductance

Temperature-dependent ferroelectric hysteresis properties of modified lead zirconate titanate ceramics

Abstract: Temperature-dependent ferroelectric hysteresis properties of modified lead zirconate titanate ceramics have been investigated in a wide temperature range from 300 to 433 K. It is observed that remnant polarization, saturation polarization, and coercive field are increasing with an increase of the temperature in a low-field region and decreasing in a high-field region. Such behavior is explained by the competition between switching and backswitching mechanisms. A three-stage dependence of the logarithm of the hysteresis loop area on the logarithm of the electric field is identified. The temperature dependence of backswitching properties has been studied. The obtained results indicate that the temperature dependence of the polarization backswitching can be well described by the Arrhenius law. The activation energy for the domain switching determined from the fitting results exhibits decreasing tendency with the increase of the electric field.

A permendur-piezoelectric multiferroic composite for low-noise ultrasensitive magnetic field sensors

Abstract: Low-frequency and resonance magnetoelectric (ME) effects have been studied for a trilayer of permendur (alloy of Fe-Co-V) and lead zirconate titanate (PZT). The high permeability and high magnetostriction for permendur, key ingredients for magnetic field confinement, and ME response result in ME voltage coefficient of 23 V/cm Oe at low-frequency and 250 V/cm Oe at electromechanical resonance (EMR) for a sample with PZT fibers and inter-digital-electrodes. Theoretical ME coefficients are in agreement with the data. Measured magnetic noise floor of 25 pT/√Hz at 1 Hz and 100 fT/√Hz at EMR are comparable to best values reported for Metglas-PZT fiber sensors.

Atomic‐Scale Imaging and Quantification of Electrical Polarisation in Incommensurate Antiferroelectric Lanthanum‐Doped Lead Zirconate Titanate

Abstract: Lanthanum doping of zirconium rich lead zirconate titanate gives rise to incommensurate, long-period antiferroelectric structures. The structure of two stacking sequences in this incommensurate phase is determined using quantitative analysis of high-resolution scanning transmission electron microscopy images, with the lead atom positions located with an exceptional precision of about 6 pm. This allows the estimation of local polarisation variations across the stacking units, and the polarisation varies in an approximately sinusoidal fashion along the stacking direction. The measured peak Pb atom displacements of about 28 pm and peak polarisation values of about 60 mu C cm-2 match extremely well to reported values for the commensurate antiferroelectric PbZrO3 phase.