PZT Layer Research Articles

The free-standing multilayer thick films of 0.7Pb(Zr0.46Ti0.54)O3–0.1Pb(Zn1/3Nb2/3)O3–0.2Pb(Ni1/3Nb2/3)O3 with low co-fired temperature

High performance free-standing multilayer PNN–PZN–PZT thick films have been successfully fabricated by tape-casting and one step co-fired method. Optimal formulation of slurries has been found. Free-standing multilayer thick films with Ag electrodes were obtained after co-fired at 900 °C. With proper pretreatment, compact structure and well combined PZT layers can be obtained, which indicates the tightly integrated structure of multilayer thick films. Diffusion and permeation between Ag electrodes and PZT layers was not observed in specimens sintered at 900 °C. The influences of organic content and sintering temperature on density and crystallinity were discussed. Nine layered specimens showed great electrical properties: d33, tanδ, e33 T /e0, g33 and Pr of 1880 pC N−1, 2.3%, 1067, 199.00 mV m/N, 82.77 µC cm−2. The displacement of nine layers specimens under same applied voltage was increased from 901 to 8489 nm compared with bulk ceramics. Those outstanding properties indicate that co-fired free-standing PNN–PZN–PZT multilayer thick films are suitable for application in MEMS system, energy harvesting device and piezoelectric power generation.

Enhanced Piezoelectric Response in Hybrid Lead Halide Perovskite Thin Films via Interfacing with Ferroelectric PbZr0.2Ti0.8O3.

We report a more than 10-fold enhancement of the piezoelectric coefficient d33 of polycrystalline CH3NH3PbI3 (MAPbI3) films when interfacing them with ferroelectric PbZr0.2Ti0.8O3 (PZT). Piezoresponse force microscopy (PFM) studies reveal [Formula: see text] values of 0.3-0.4 pm/V for MAPbI3 deposited on Au, indium tin oxide, and SrTiO3 surfaces, with small phase angle fluctuating at length scales smaller than the grain size. In sharp contrast, on samples prepared on epitaxial PZT films, we observe large-scale polar domains exhibiting clear, close to 180° PFM phase contrasts, pointing to polar axes along the film normal. By separating the piezoresponse contributions from the MAPbI3 and PZT layers, we extract a significantly higher [Formula: see text] of ∼4 pm/V, which is attributed to the enhanced alignment of the MA molecular dipoles promoted by the unbalanced surface potential of PZT. We also discuss the effect of the interfacial screening layer on the preferred polar direction.

Thickness dependence of magnetoelectric properties for Pb(Zr0.52Ti0.48)O3/La0.67Sr0.33MnO3 heterostructures

In this work, magnetoelectric thin film heterostructures of Pb(Zr0.52Ti0.48)O3/La0.67Sr0.33MnO3(PZT/LSMO) were epitaxially grown on SrTiO3(STO) substrates. aa-phase and r-phase in PZT layer could be observed simultaneously. Thickness dependent magnetoelectric effect of these heterostructures is investigated in detail. The results show that the r-phase in PZT layer will significantly improve the magnetoelectric voltage coefficient (αE31), and the amount of r-phase will decrease with increasing thickness of PZT layer. The maximum αE31 can reach 1153 mV/cm Oe for the sample with PZT thickness of 32 nm. This work will be of significance for tuning magnetoelectric effect via thickness ratio between ferroelectric and ferromagnetic layers.

Direct-Write Laser Greyscale Lithography for Multi-Layer Lead Zirconate Titanate Thin Films.

Direct-write laser greyscale lithography has been used to facilitate a single step patterning technique for multi-layer lead zirconate titanate (PZT) thin films. A 2.55 μm thick photoresist was patterned with a direct-write laser. The intensity of the laser was varied to create both tiered and sloped structures that are subsequently transferred into multi-layer PZT(52/48) stacks using a single Ar ion mill etch. Traditional processing requires a separate photolithography step and an ion mill etch for each layer of the substrate, which can be costly and time consuming. The novel process allows access to buried electrode layers in the multi-layer stack in a single photolithography step. The greyscale process was demonstrated on three 150 mm diameter Si substrates configured with a 0.5 μm thick SiO2 elastic layer, a base electrode of Pt/TiO2, and a stack of four PZT(52/48) thin films of either 0.25 μm thickness per layer or 0.50 μm thickness per layer, and using either Pt or IrO2 electrodes above and below each layer. Stacked capacitor structures were patterned and results will be reported on the ferroelectric and electromechanical properties using various wiring configurations and compared to comparable single layer PZT configurations.

A low-working-field (2 kV/mm), large-strain (>0.5%) piezoelectric multilayer actuator based on periodically orthogonal poled PZT ceramics

In this work, we proposed a special designed multilayer actuator based on the periodically orthogonal poled (POP) PZT ceramics. Only the in-plane poled regions of the neighboring PZT layers were bonded together thus the large reversible switching strain in these regions can always be employed. A six-layer actuator was fabricated and testing results show that it can output actuation strains over 0.5% under a low field of 2 kV/mm at 0.1 Hz, about 3.5 times of that in conventional PZT actuators which is less than 0.15% under the same field. Furthermore, the output large strain is fairly uniform, which varies from 0.50% to 0.53% along the period direction, in comparison with that varying from 0.35% to 0.59% in a single-layer POP PZT. The large actuation strain drops quickly with the increasing frequency, and stabilized at about 0.2% under 2 kV/mm at or above 1 Hz. The low-frequency large strain is very stable and keeps unchanged after 20 k cycles of operation. To solve the charge accumulation problem during successive unipolar loading/unloading, an asymmetric bipolar field from −300 V/mm to 2 kV/mm is applied and meanwhile the actuation strain turns to be more uniform, only varying from 0.51% to 0.52% at 2 kV/mm. The low driving field, large strain of the proposed actuator makes it very promising in low-frequency, large strain/displacement actuation areas.

Multiple broadband magnetoelectric response in Terfenol-D/PZT structure**Project supported by the National Natural Science Foundation of China (Grant Nos. 11702120, 11372120, 11421062, and 11572143) and the Fundamental Research Funds for the Central Universities, China (Grant No. lzujbky-2016-106).

In this paper, a novel magnetoelectric (ME) composite structure is proposed, and the ME response in the structure is measured at the bias magnetic field up to 2000 Oe (1 Oe = 79.5775 A·m−1) and the excitation frequency of alternating magnetic field ranging from 1 kHz to 200 kHz. The ME voltage of each PZT layer is detected. According to the measurement results, the phase differences are observed among three channels and the multi-peak phenomenon appears in each channel. Meanwhile, the results show that the ME structure can stay a relatively high ME response within a wide bandwidth. Besides, the hysteretic loops of three PZT layers are observed. When the frequency of alternating current (AC) magnetic field changes, the maximum value of ME coefficient appears in different layers due to the multiple vibration modes of the structure. Moreover, a finite element analysis is performed to evaluate the resonant frequency of the structure, and the theoretical calculating results accord well with the experimental results. The experiment results suggest that the proposed structure may be a good candidate for designing broadband magnetic field sensors.

Nonlinear Physics-based Modeling of a Piezoelectric Energy Harvester

Piezoelectric vibration-based energy harvesting has received great attention over the past decade. Because of the significant influence on the amount of generated power, several research efforts recently focused on capturing nonlinear hysteretic behavior exhibited by piezoceramic materials.In this paper, effects of PZT nonlinearities on the dynamic response of a vibrating harvester device are investigated. A physics-based Gibbs energy model is employed to assess the response of a piezoelectric unimorph under the simplified assumption that the constitutive behavior of the active layer can be approximated using a piezoceramic single crystal model. Numerical simulations have been carried out in near-resonance conditions and comparisons with results obtained adopting linear constitutive equations for the PZT layer are reported. Numerical results confirm that nonlinear hysteretic effects can significantly increase the amount of harvested energy. Furthermore, they are relevant also when the device is operating in geometric linear conditions.

Smart Piezo-ceramic Coating for Multifunctional Applications

Piezo-ceramic PZT coating was developed with unique combination of the high electro-active properties of ceramics and the mechanical conformability of polymers. The other advantages of the PZT coating is improved electro-mechanical coupling properties, large area coverage, ease of coating on intricate shapes, etc. The developed PZT coating is efficiently used for both sensors and actuators by electrically isolating them from each other or using them in an array for cumulative effects by linking the distributed electrodes. Because of the improved electro-mechanical coupling of insitu PZT layer, the vibration responses of host structures is monitored very effectively by measuring the output voltage from the piezoelectric coating. The developed coating is used for multifunctional applications towards ultrasonic transmitter and receivers for structural health monitoring, strain gauge sensors for natural frequency estimation, actuators for insect scale flapping wing and energy harvesting.

Development of a unimorph deformable mirror with water cooling.

Deformable mirror (DM) used for intracavity compensation in high-power lasers should be able to withstand very high laser intensity. This paper proposes a water-cooled unimorph DM which can withstand the laser power up to 10 kW in thermal simulation. The proposed DM consists of an annular PZT layer and a circular Si layer which are glued together with edge clamped. All the 32 piezoelectric actuators are distributed around the correction area and on the front side of the DM. The cooling water flows through the back side of the DM and cools the mirror directly. This design realizes the physical separation of the actuators and the coolant. The experimental results of a fabricated DM prototype show that the DM can reproduce typical low-order aberrations accurately with relatively large amplitude. The wavefront PV amplitudes of the reproduced tip/tilt, astigmatism, defocus, trefoil and coma shapes for 15 mm aperture are about 40 μm, 24 μm, 18.7 μm, 10 μm and 6 μm, respectively.

Non-linear deflection of a circular diaphragm-type piezoactuator under loads of voltage and pressure

Analytical non-linear equations are formulated to predict the deflection of a circular diaphragm-type piezoactuator, which consists of a passive layer, a bonding layer and a PZT layer. Previous similar analytical solutions presented in the literature are based on thin plates with small deflections (linear problem), however the linear solutions fail to predict the deflection of the piezoactuator when the driven loads, such as voltage and pressure loads, are large. In this research, a non-linear analytical solution for the piezoactuator deflection under loads of voltage and pressure is derived using the principal of minimum energy and the Rayleigh-Ritz method. Each of the three layers in the piezoactuator is considered as an individual layer. The energy associated with the solution includes elastic potential energy of the deformed piezoactuator, electric potential energy in the piezodisc, and the work done by the uniform pressure force. The proposed non-liner solution is validated via static deflection measurements, and it approves that the non-linear analytical results are found to be in a good agreement with the measurements while the linear solution is invalid when the loads are large. Based on the non-linear equations, the effects of the piezoactuator dimensions and the imposed loads on the actuator performance (stroke volume) are also investigated.

Enhancement of the Magnetoelectric Effect in Multiferroic CoFe2O4/PZT Bilayer by Induced Uniaxial Magnetic Anisotropy

In this study we have compared magnetic, magnetostrictive and piezomagnetic properties of isotropic and anisotropic cobalt ferrite pellets. The isotropic sample was prepared by the ceramic method while the sample exhibiting uniaxial anisotropy was made by reactive sintering using Spark Plasma Sintering (SPS). This technique permits to induce a magnetic anisotropy in cobalt ferrite in the direction of the applied pressure during SPS process. Sample with uniaxial anisotropy revealed a higher longitudinal magnetostriction and piezomagnetism compared to the isotropic sample, but the transversal magnetostriction and piezomagnetism were dramatically reduced. In the case of magnetoelectric layered composite, the magnetoelectric coefficient is directly related to the sum of the longitudinal and transversal piezomagnetic coefficients. These two coefficients being opposite in sign, the use of material exhibiting high longitudinal and low transversal piezomagnetic coefficient (or vice versa) in ME devices is expected to improve the ME effect. Hence, ME bilayer devices were made using isotropic and anisotropic cobalt ferrite stuck with a PZT layer. ME measurements at low frequencies revealed that bilayer with anisotropic cobalt ferrite exhibits a ME coefficient three times higher than a bilayer with isotropic cobalt ferrite. We also investigated the behavior of such composites when excited at resonant frequency.

Multiferroic and magnetoelectric properties of Pb0.99[Zr0.45Ti0.47(Ni1/3Sb2/3)0.08]O3–CoFe2O4 multilayer composites fabricated by tape casting

A 2-2 type multiferroic composite device encompassing three CoFe2O4 (CFO) layers confined between four Pb0.99[Zr0.45Ti0.47(Ni1/3Sb2/3)0.08]O3 (PZT) layers was fabricated by tape casting. X-ray diffraction data showed good chemical compatibility between the two phases, whereas Scanning Electron Microscopy imaging also revealed an intimate contact between CFO and PZT layers. Under an applied electric field of 65kV/cm, this multilayer device shows a saturated polarisation of 7.5μC/cm2 and a strain of 0.12%, whereas under a magnetic field of 10kOe it exhibits a typical ferromagnetic response and a magnetic moment of 33 emu/g. This device can be electrically poled, after which it exhibits magnetoelectric coupling.

Experimental and mathematical analysis of a piezoelectrically actuated multilayered imperfect microbeam subjected to applied electric potential

In this paper we propose to fabricate a microcantilever beam actuator using thin layer PZT material. The multilayered microbeam is initially curved due to fabrication process. The device is also modeled using a the Euler-Bernoulli beam theory and takes into account the multilayer structure of the device. The inclusion of these imperfection into the theoretical model generates geometric nonlinearities. Static and dynamic experimental analysis is conducted to examine the physiomechanical behavior of the considered microstructure. To this end, The model is first compared and validated with experimental findings for an applied constant voltage. Very good agreement depicts the accuracy of the proposed mathematical model. When time varying voltage is applied, the nonlinear differential equation is solved using a perturbation technique. Again good agreement with experiments are found. Finally, a parametric study is carried out to explore the influences of different parameters on the frequency response of the piezoelectrically actuated imperfect microbeams.

Buckling delamination of a PZT/Metal/PZT sandwich rectangular thick plate containing interface inner band cracks

This work studies the 3D buckling delamination problem around the interface band cracks which are in the PZT/Metal/PZT sandwich rectangular thick plate within the scope of the piecewise homogeneous body model by utilizing the so-called 3D linearized theory of stability loss for piezoelectric materials. It is assumed that the plate is simply supported with respect to mechanical quantities and short-circuit conditions with respect to the electric potential along all its lateral edge-surfaces. On the face planes of the PZT layers, the open-circuit condition with respect to the electrical displacement is satisfied. It is also assumed that on the opposite two ends of the plate which are parallel to the band cracks’ front, uniformly distributed normal compressive mechanical forces act. The critical values of these forces under are determined by employing an initial imperfection criterion. For solution of the corresponding boundary value problems the 3D FEM is utilized and numerical results on the critical forces and on the influence of the problem parameters on these forces are presented and discussed. In particular, it is established that the piezoelectricity of the face layers and the three dimensionality of the problem cause to increase the values of the critical forces.

Morphology-dependent photo-induced polarization recovery in ferroelectric thin films

We investigate photo-induced ferroelectric domain switching in a series of Pb(Zr0.2Ti0.8)O3/La0.7Sr0.3MnO3 (PZT/LSMO) bilayer thin films with varying surface morphologies by piezoresponse force microscopy under light illumination. We demonstrate that reverse poled ferroelectric regions can be almost fully recovered under laser irradiation of the PZT layer and that the recovery process is dependent on the surface morphology on the nanometer scale. The recovery process is well described by the Kolmogorov-Avrami-Ishibashi model, and the evolution speed is controlled by light intensity, sample thickness, and initial write voltage. Our findings shed light on optical control of the domain structure in ferroelectric thin films with different surface morphologies.

Nonvolatile MoS2 field effect transistors directly gated by single crystalline epitaxial ferroelectric

We demonstrate non-volatile, n-type, back-gated, MoS2 transistors, placed directly on an epitaxial grown, single crystalline, PbZr0.2Ti0.8O3 (PZT) ferroelectric. The transistors show decent ON current (19 μA/μm), high on-off ratio (107), and a subthreshold swing of (SS ∼ 92 mV/dec) with a 100 nm thick PZT layer as the back gate oxide. Importantly, the ferroelectric polarization can directly control the channel charge, showing a clear anti-clockwise hysteresis. We have self-consistently confirmed the switching of the ferroelectric and corresponding change in channel current from a direct time-dependent measurement. Our results demonstrate that it is possible to obtain transistor operation directly on polar surfaces, and therefore, it should be possible to integrate 2D electronics with single crystalline functional oxides.

High performance bimorph piezoelectric MEMS harvester via bulk PZT thick films on thin beryllium-bronze substrate

This letter presents a high performance bimorph piezoelectric MEMS harvester with bulk PZT thick films on both sides of a flexible thin beryllium-bronze substrate via bonding and thinning technologies. The upper and lower PZT layers are thinned down to about 53 μm and 76 μm, respectively, and a commercial beryllium bronze with the thickness of about 50 μm is used as the substrate. The effective volume of this device is 30.6 mm3. The harvester with a tungsten proof mass generated the close-circuit peak-to-peak voltage of 53.1 V, the output power of 0.979 mW, and the power density of 31.99 mW/cm3 with the matching load resistance of 360 kΩ at the applied acceleration amplitude of 3.5 g and the applied frequency of 77.2 Hz. Meanwhile, in order to evaluate the stability, the device was measured continuously under applied acceleration amplitudes of 1.0 g and 3.5 g for one hour and demonstrated a good stability. Then, the harvester was utilized to light up LEDs and about twenty-one serial LEDs were lighted up at resonance under an applied acceleration amplitude of 3.0 g.

Characteristic analysis of diaphragm-type transducer that is thick relative to its size

In recent years, high-performance piezoelectric micromachined ultrasonic transducers (PMUTs) have been fabricated by micro electro mechanical systems (MEMS) technology. For high-resolution imaging, it is important to broaden the frequency bandwidth. By reducing the diaphragm size to increase the resonance frequency, the film thickness becomes relatively larger and hence the transmitting and receiving characteristics may different from those of a usual thin diaphragm. In this study, we examine the performance of a square-diaphragm-type lead zirconate titanate (PZT) transducer through simulations. To realize the desired resonance frequency of 20 MHz, firstly, the diaphragm size and the thickness of the layers of PZT and Si constituting a PMUT are examined, and then, three PZT/Si models with different thicknesses are selected. Subsequently, using the models, we analyze the transmitting efficiency, transmitting bandwidth, receiving sensitivity (piezoelectric voltage/electric charge), and receiving bandwidth using an FEM simulator. It is found that the proposed models can transmit ultrasound independently of the diaphragm vibration and have wide bandwidth of the receiving frequency as compared with that of a typical PMUT.

Development of crystallographic texture in chemical solution deposited lead zirconate titanate seed layers

AbstractDirect seeding of {001} textured lead zirconate titanate (PZT) on platinized silicon substrates was achieved by chemical solution deposition. The processing space for {001} PZT texturing was explored, under fixed PZT pyrolysis and crystallization conditions, by varying the lead content in solution, dopant species, and PZT layer thicknesses for deposition on platinized Si substrates with different platinum grain sizes. Strong {001} texture was achieved on fine‐grained (25 nm) platinum deposited at room temperature and dense, large‐grained platinum (80 nm) deposited at elevated temperature. Increases in lead content of solutions (from lead excesses of 10 at.% to 16 at.%) reduced surface pyrochlore coverage, with no substantial influence on orientation or grain size. Seed layer texturing was found to be insensitive to doping (Mn and Nb) on room temperature platinum, although niobium doping increased pyrochlore coverage. Conversely, on platinum deposited at high temperature, manganese doping reduced the perovskite nucleation, producing a rosette microstructure. Undoped seed layers from 30 to 70 nm thick were found to be strongly {001} textured while thicker layers were {111} textured and thinner layers were poorly crystallized.

Performance of ZnO based piezo-generators under controlled compression

This paper reports on the fabrication and characterization of ZnO based vertically integrated nanogenerator (VING) devices under controlled compression. The basic NG structure is a composite material integrating hydrothermally grown vertical piezoelectric zinc oxide (ZnO) nanowires (NWs) into a dielectric matrix (PMMA). A specific characterization set-up has been developed to control the applied compression and the perpendicularity of the applied force on the devices. The role of different fabrication parameters has been evaluated experimentally and compared with previously reported theoretical models, including the thickness of the top PMMA layer and the density of the NWs array in the matrix. Finally, the performance of the VING structure has been evaluated experimentally for different resistive loads obtaining a power density of 85 μW cm−3 considering only the active layer of the device. This has been compared to the performance of a commercial bulk layer of PZT (25 μW cm−3) under the same applied force of 5 N.