PZT Thick Films Research Articles

Improved properties of Pb(Zr0.52Ti0.48)O3 films by hot plate annealing on LaNiO3 bottom electrode

Pb(Zr0.52Ti0.48)O3 (PZT) perovskite ferroelectric thin films were fabricated on LaNiO3 buffer silicon substrate by sol–gel spin coating technique. The thickness of PZT films was about 150 nm, and the thickness of LNO films as electrodes was about 120 nm. The prepared PZT thin films were annealed by hot plate annealing and conventional electric furnace annealing at various temperatures for 30 min. The microstructure of annealed films was analyzed by different techniques. The obtained results demonstrated that the perovskite phase can be achieved in films by both methods of annealing. Structural and morphological characterizations substantiated that hot plate annealing method can facilitate the formation of perovskite phase of PZT films than the electric furnace annealing. Consequently, the films annealed using hot plate exhibited more excellent electrical properties. The higher dielectric permittivity, remnant polarization, and the lower dielectric dissipation were observed for the thin films annealed at 550 °C by the hot plate. The values of remnant polarization and coercive field of PZT annealed on the hot plate were 36.4 μC/cm2 and 168 kV/cm, respectively. These results demonstrated that the crystallization of ferroelectric PZT films was improved by hot plate annealing.

Microstructural and electrical properties of nanostructured lead zirconate titanate composite thick films processed for MEMS applications via hybrid sol–gel approach

An alternative chemical solution processing version of thick and crack free PZT films was developed. PZT films were equally deposited from pure sol and composite suspension on ITO-coated corning glass substrates by dip-coating process and were sintered at various temperatures. The PZT composite sol–gel suspension/slurry was optimized to dip-coating to form thick films with nearly constant thickness and limited cracking. The XRD spectra indicate that the 0–3 ceramic/ceramic composites films possess single-phase perovskite type. SEM micrographs of thick film cross-sections displayed composite structures with no observable boundary between layers. The optimized PZT layer revealed a capacitance resultant to a permitivity of Ɛr = 1282 and tang(δ) = 0.17 at 100 Hz. The remnant polarization, and coercive field for the same sample estimated from the ferroelectric P–E hysteresis loop were 30 μC cm−2, and 17 kV cm−1, respectively. The ferroelectric and dielectric constant values were equivalent to those reported for bulk material.

Study on the properties of Pb(Zr,Ti)O3 thin films grown alternately by pulsed laser deposition and sol-gel method

In order to prepare good quality Pb(Zr,Ti)O3 (PZT) thin films, we consider the method of alternately growing PZT thin films on Pt (111)/Ti/SiO2/Si (100) substrates by pulsed laser deposition (PLD) and sol-gel. In this work, we conducted comparative experiments on different film preparation methods, and 1.0 um thick PZT film was grown on platinized silicon wafers by an alternate PLD and sol-gel method. The microstructure and electrical properties of the films is analyzed. Through the study of X-ray diffraction, SEM, AFM, PFM, and ferroelectric testing, it is found that the alternating growth of a film by the alternate PLD and sol-gel method has good compactness, excellent ferroelectric properties, and smaller leakage current compared to film prepared by the sol-gel method alone.

Ultra-thin lead oxide piezoelectric layers for reduced environmental contamination using a liquid metal-based process

Mitigation of the health hazards caused by Pb is necessary. A liquid metal-based synthesis method delivers unit-cell-thick layers of PbO with comparable piezoelectric response and band gap to PZT thick films while posing reduced toxicity.

Studies on ferroelectric and nanomechanical response of single-layered PZT thick film for energy harvester applications

We have made an attempt to fabricate free standing warpage free PZT thick films of 100 µm thickness by tape casting method. The poly crystalline nature and nanoscale polarization switching of free standing thick film were confirmed using X-ray diffraction technique and piezo force microscopy, respectively. The piezoelectric coefficient (d33) of 100 µm free-standing Pb(Zr0.56Ti0.44)O3 [PZT] thick film was calculated using double beam laser interferometer and found to be 400 pm/V. From the results, it indicates that free-standing PZT thick films are suitable candidate for miniaturization of harvesting device by directly bonding them on microsystem components for microelectromechanical systems (MEMS) applications.

Low thermal budget lead zirconate titanate thick films integrated on Si for piezo-MEMS applications

Piezoelectric cantilevers made from ferroelectric thick films are commonly used as key components in many prototypical piezo-MEMS devices, including sensors, micro-actuators and piezoelectric energy harvesters. In this work, transverse piezoelectric performance of rapid thermal annealed Pb(Zr0.53Ti0.47)O3 (PZT) thick film (~1-2 μm) were characterized. These films were sputtered on LaNiO3 buffered Pt/Ti/SiO2/(100) Si substrates at 350 °C followed by a rapid thermal process (RTP) with different annealing time (30 s to 15 min) at the high temperature end (700 °C), and then patterned into rectangular prism-shaped cantilevers. Such a two-step process yields highly (001)-oriented perovskite PZT films with good overall electrical properties (ferroelectric, dielectric and piezoelectric) close to those of an epitaxial PZT film, yet on a much reduced thermal budget. With the elementary and chemical valence information from EDS and XPS analysis, an optimal annealing time was determined for the PZT thick film cantilevers to have both an outstanding piezoelectric performance (actuating, sensing or energy harvesting), and a good compatibility with the Si technology (a brief exposure to a high temperature). This study promotes the integration of large piezoelectricity into Si-based MEMS.

Microstructural comparison between precursor-based and particle-based PZT ceramic coatings

Piezoelectric materials are used in several applications, including sensors and actuators. Perovskite type ferroelectrics, specially, lead zirconate titanate (PZT), due to its excellent dielectric, piezoelectric and ferroelectric properties are usually employed. In this work, a series of Spin Coated PZT thick films were deposited on alumina and stainless steel substrates. These PZT-based films were obtained using inks containing either particles or a precursor that were synthesised using a chemical method. In order to consolidate the deposit as a thick film, a thermal treatment is required after deposition on a substrate. Under temperature exposure, the PZT particles tend to sinter after the elimination of the organic vehicle. Moreover, the PZT precursor transforms to crystalline PZT. Films based on the PZT precursor exhibited many cracks after treatment, while those constituted by PZT particles required sintering temperatures higher than 1000 °C which resulted in unstable PZT structures. As an alternative, slurries forming mixtures of PZT precursor and particles, varying their relative proportions, were studied to improve the properties of the films. Films generated in this study were characterized by SEM and X-ray diffractometry.

Energy harvesting performance of unimorph piezoelectric cantilever generator using interdigitated electrode lead zirconate titanate laminate

An unimorph piezoelectric cantilever generator with an interdigitated electrode (IDE) was developed for application to vibration energy harvesters driven in longitudinal mode. Lead zirconate titanate (PZT) thick film was fabricated by lamination of 10 sheets printed with Ag IDE; the laminated film was subsequently cofired at 850 °C for 2 h. Compared with a conventional IDE PZT thick film, the approximately 270 ㎛-thick cofired IDE PZT laminate revealed a significantly increased capacitance due to reduction of transition area. The use of multilayered IDE could result in the enhancement of energy harvesting performance for unimorph piezoelectric cantilever generator using PZT laminate. Optimized bending resonance frequency was obtained at 78 Hz for the unimorph piezoelectric cantilever generator with tip mass of 2.3 g driven in longitudinal vibration mode. Its energy harvesting performance was characterized as having a high power density of 26.7 mW/cm3 across the resistive load of 80 kΩ, corresponding to a normalized power factor of 6.7 mW/G2·cm3.

Large piezoelectricity on Si from highly (001)-oriented PZT thick films via a CMOS-compatible sputtering/RTP process

Integration of lead zirconate titanate (PZT) ferroelectrics into CMOS-Si technology has become a perennial challenge due to the continuously shrinking thermal budget in semiconductor processing. In this work, Pb(Zr0.53Ti0.47)O3 (PZT) thick films (∼1 µm) were prepared on LaNiO3 buffered (111)Pt/Ti/SiO2/(100) Si substrates via a low temperature (350 °C) sputtering deposition followed by a rapid thermal process (RTP). This two-step fabrication process resulted in a highly (001)-oriented perovskite PZT film with a dense, fine-grain morphology and reduced strains, hence an optimal electrical performance intrinsic to the chemical composition was achieved. EDS and XPS analyses verified a desirable evolution of the chemical stoichiometry in the RTP, as well as the expected chemical bonding states of the elements in the annealed films. Moreover, prototypical piezoelectric thin film cantilevers fabricated from the PZT/LaNiO3/Pt/Ti/SiO2/(100)Si heterostructure yielded a large transverse piezoelectric coefficient (e31,f) up to 15.7 C/m2, together with a high coupling coefficient k2∼0.23 for energy conversion efficiency. The PZT films showed high e31,f coefficients (∼10 C/m2) even when the RTP annealing time was reduced down to 2 min. Such a piezoelectric performance is close to the highest ones reported in the literature from epitaxial or highly-oriented PZT films, which require a much higher thermal budget for processing. These high quality PZT films open up many possibilities for the integration of piezoelectricity into Si-based micro-electro-mechanical systems (MEMS).

PZT/PZT and PZT/BiT Composite Piezo-Sensors in Aerospace SHM Applications: Photochemical Metal Organic + Infiltration Deposition and Characterization.

The composition of fine-ground lead zirconate-titanate powder Pb(Zr0.52Ti0.48)O3, suspended in PZT and bismuth titanate (BiT) solutions, is deposited on the curved surface of IN718 and IN738 nickel-based supper alloy substrates up to 100 µm thickness. Photochemical metal organic and infiltration techniques are implemented to produce smooth, semi-dense, and crack-free random orientated thick piezoelectric films as piezo-sensors, free of any dopants or thickening polymers. Every single layer of the deposited films is heated at 200 °C with 10 wt.% excess PbO, irradiated by ultraviolet lamp (365 nm, 6 watt) for 10 min, pyrolyzed at 400 °C, and subsequently annealed at 700 °C for one hour. This process is repeated successively until reaching the desired thickness. Au and Pt thin films are deposited as the bottom and top electrodes using evaporation and sputtering methods, respectively. PZT/PZT and PZT/BiT composite films are then characterized and compared to similar PZT and BiT thick films deposited on the similar substrates. The effect of the composition and deposition process is also investigated on the crystalline phase development and microstructure morphology as well as the dielectric, ferroelectric, and piezoelectric properties of piezo-films. The maximum remnant polarization of Pr = 22.37 ± 0.01, 30.01 ± 0.01 µC/cm2, the permittivity of εr = 298 ± 3, 566 ± 5, and piezoelectric charge coefficient of d33 = 126, 148 m/V were measured versus the minimum coercive field of Ec = 50, 20 kV/cm for the PZT/PZT and PZT/BiT thick films, respectively. The thick film piezo-sensors are developed to be potentially used at frequency bandwidth of 1–5 MHz for rotary structural health monitoring and also in other industrial or medical applications as a transceiver.

Piezoelectric Property Enhancement of PZT Thick Film via Pulsed Flash Poling during Sintering

Lead zirconate titanate (PZT) is a widely used piezoelectric material due to its high piezoelectric response. High-temperature thermal sintering and poling are two important steps to obtain a high ...

Improved ferroelectric and piezoelectric properties of tape casted free standing PSLZT thick films

We have synthesized Sr and La substituted Pb(1-x-3y/2)SrxLay(Zrz, Ti(1−z))O3 ceramics with x = 0.06, y = 0.01, 0.03, 0.05, z = 0.56 by solid-oxide route. Compacted discs were sintered at optimized temperature of 1280 °C for 2 h and its phase formation was confirmed by XRD analysis. Rietveld refinement confirmed that for the composition with y = 0.03 coexistence of tetragonal and rhombohedral phases comparatively closer to MPB. Dielectric and ferroelectric properties of discs were investigated thoroughly as a function of La content. Among the three compositions, ceramics with y = 0.03 (PSLZT) exhibit higher piezoelectric voltage coefficient (g33) of 30 mV.m/N which is relatively high compared to commercial PZT compositions. This composition was further utilized to fabricate free-standing piezoelectric thick films of 100 μm thickness using tape casting method with optimized slurry formulation. Warpage free PZT thick films with Pt electrodes were achieved with better density by co-sintering at 1060 °C for 2 h. Free standing thick films were characterized for their structural, microstructural, ferroelectric and piezoelectric properties and compared with bulk ceramic properties. The relative dielectric constant of 1250 with loss tangent of 0.02–0.03, remnant polarization of about 19 μC cm−2, piezoelectric charge coefficient of 300–325 pC/N and piezoelectric voltage coefficient up to 27 mV.m/N have been observed. These results indicate piezoelectric voltage coefficient of PSLZT free standing thick films is comparable to that of its bulk ceramic counterpart.

Fabrication and characterization of miniature nonlinear piezoelectric harvester applied for low frequency and weak vibration

Abstract In order to collect energy from human activities, piezoelectric energy harvesters should have a flexible structure, low resonant frequency and wide frequency bandwidth. In this paper, the fabrication and characterization of a metal-based Pb(Zr,Ti)O3 (PZT) bimorph thick film energy harvester. PZT thick films were deposited on cantilever-shaped titanium (Ti) substrate via a dip-coating process. The electrical properties of the PZT films sintered at different temperatures were investigated. The nonlinear piezoelectric energy harvester has the following advantages: it is suitable for low frequency, weak vibration, and wide frequency bandwidth. The maximum open-circuit voltage of the piezoelectric energy harvester is 1.6 V and the output power is 0.85 μW with 150 kΩ load resistance at low resonant frequency of 17.6 Hz when the input vibration acceleration was 0.12 g. In addition, the frequency bandwidth is broadened from 0 to 8.4 Hz as the input acceleration increases from 0.05 g to 0.12 g.

Dielectric properties and resistive switching characteristics of lead zirconate titanate/hafnia heterostructures

We report the dielectric response and resistive switching properties of bilayers of PbZr0.40Ti0.60O3 [PZT (40:60)] and HfO2 of varying thickness on platinized Si substrates. PZT (40:60) and HfO2 films were grown using chemical solution deposition and atomic layer deposition, respectively. We show here that the addition of an interposed linear dielectric layer with a high permittivity between the ferroelectric film and the top electrode modifies the polarization and resistive switching characteristics of the multilayer stack. We observe an increase in the coercive field by 45% for PZT films of 250 nm thickness with a 20 nm HfO2 layer compared to 250 nm thick PZT films grown under identical conditions. Simultaneously, the dielectric constant decreases by 43% from 409 to 175 for a 250 nm PZT film with 20 nm HfO2, accompanied by a significant improvement in the leakage current density from 5.6 × 10−4 A/cm2 to 8.7 × 10−8 A/cm2. Our resistance measurements show that there are two separate resistance states that are accessible with at least an order of magnitude in resistance difference from 5 × 108 to 5 × 109 Ω. We show that the dielectric response and the coercivity of the bilayer system can be explained by a capacitors-in-series model. This indicates that the PZT and the HfO2 layer could effectively be considered decoupled, presumably due to bound/trapped charges at the interlayer interface. This charged ferroelectric/dielectric interface could be the reason for the intermediate resistance states which could be used as multistate resistive memories in neuromorphic computing applications.

Printed PZT Thick Films Implemented for Functionalized Gas Sensors

Attractive for MEMS, PZT thick films are often microstructured on Si supporting platforms to span the gap between ceramics and thin film technologies. Printing process might lead to lower cost than ceramic process to open routes for MEMS applications. In this paper processing by screen-printing of Au/PZT/Au thick-films supported on alumina or completely released from the substrate are described. Investigations of the film microstructures nevertheless show lower densification than those of bulk ceramics. Prior to selective coating deposition, routes to improve the reduction of the film’s porosity are proposed.

High-performance low-frequency MEMS energy harvester via partially covering PZT thick film

This paper proposes a high-performance and low-frequency MEMS piezoelectric energy harvester (PEH) via partially covering PZT thick film on beryllium bronze substrate. The simulated results of fully and partially covered structures show that the PEH with partially covering PZT thick film contributes to high performance due to more uniform stress distribution. In the experiment, the fabricated PEH with partially covered PZT thick film generates the maximum output voltage of 29.1 V, and the maximum power of 79.36 µW and power density of 16.5 mW cm−3 at the resonant frequency of 64.6 Hz and the excited acceleration amplitude of 0.7 g. The normalized power density of the harvester can reach 365.6 µW g−1 Hz−1 cm−3, which has a great improvement compared to other reported PEHs with fully covering piezoelectric layer. Meanwhile, the device is measured continuously under 0.7 g acceleration for 1 h and shows a good stability. It indicates that it has a potential application in self-powered electronic devices or systems to promote the rapid development of internet of things.

Development and characterization of thinned PZT bulk technology based actuators devoted to a 6-DOF micropositioning platform

Piezoelectric actuators are widespread in the design of micro/nanorobotic tools and microsystems, as they have a very interesting electromechanical coupling factor, in addition to their high dynamics and resolution performances. Studies toward the integration of such actuators in complex micromechatronic systems require the size reduction of these actuators while retaining a wide range of performances. Two main fabrication processes are currently used for the fabrication of piezoelectric actuators, providing very different behaviors: (i) the use of a bulk layers and (ii) the use of thin film growth. In this study, we propose to develop micropositioning actuators and platform whose performances are a trade-off between the performances from these two technologies. The proposed trade-off technology allows the development of microsystems with high stiffness, high torque and high dynamics (from technology (i)), as well as, large motion, low voltage and small size (from technology (ii)). Using this technology we designed and fabricated a thick film PZT platform containing eight unimorph beam bending actuators. The Platform allows a high level of performances, both in the static (displacement) and dynamic (first resonance frequency) regimes. The purpose of the fabricated platform is to improve the micromanipulation and microassembly processes, to the point where approaching and manipulating very small object with a high precision will be a very fast and simple operation. These devices were obtained through a room temperature mechanical thinning of a PZT thick layers, after the deposition of Nickel on the bottom side. The piezoelectric beam bending actuators have a 80 μm thick PZT layer on top of a 10 μm thick Nickel layer, a length of 5 mm and a width of 0.5 mm. Experimental characterization has shown that the static displacements obtained are in excess of 1.33 μm/V and the resonance frequencies are up to 1814 Hz, which are very convenient in high dynamics micropositioning applications such as microrobotics and microassembly tasks.

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.

Fabrication and characterisation of substrate-free PZT thick films

This paper reports the preparation of dense and substrate-free PZT thick films. Electrohydrodynamic jet deposition and sol infiltration were utilized to produce dense PZT thick film, then wet chemical etching was employed to successfully remove the silicon substrate. Subsequently, a pure PZT thick film having a thickness of 14 µm without substrate was produced. The piezoresponse force microscopy technique was used to examine the piezoelectric constant (d33, f), it was found that the d33 was increased from 71 pm V−1 to 140 pm V−1, having a double increase. It was also observed that the remnant polarization (Pr) and relative permittivity (εr) of PZT film were distinctly improved after the removal of silicon substrate. The experimental result shows that the substrate clamping had great effects on the electrical properties of PZT films and its effect value was evaluated. In addition, the systematic theoretical analysis of the substrate clamping on film was deeply studied. The theoretical analysis agrees well with the experiment results, which can be used to estimate the effect value caused by the substrate clamping.

Determination of the Steady State Leakage Current in Structures with Ferroelectric Ceramic Films

Steady state leakage currents have been investigated in capacitor structures with ferroelectric solgel films of lead zirconate titanate (PZT) formed on silicon substrates with a lower Pt electrode. It is established that Pt/PZT/Hg structures, regardless of the PZT film thickness, are characterized by the presence of a rectifying contact similar to p–n junction. The steady state leakage current in the forward direction increases with a decrease in the film thickness and is determined by the ferroelectric bulk conductivity.