Piezoelectric Thick Films Research Articles

Fabrication and Resonant Behavior of PZT Thick Film Cantilever for BioChip

PZT(52/48) thick films with an Pb-based complex oxide (PCW) additive were prepared on Pt/TiO 2 /YSZ/SiO 2 /Si substrate by new hybrid method based on the screen printing. It is found that solinfiltration for thick films fabrication process significantly improves the electrical properties due to the improved structural compactness. By applying these high quality piezoelectric thick films on micro cantilever devices, a highly sensitive thick film cantilever for mass(ng- ¯ ) detection devices is successfully fabricated. Resonant frequency and displacement of PZT-0.12PCW thick film cantilever for biochip are measured by laser vibrometer system as a function of cantilever size (width, length). We change the added mass from 4ng to 5 ¯ through Au deposition. The shorter cantilever is more sensitive for mass change and it is found that the sensitivity of cantilever decreases due to viscous damping effect in liquid. Finally, the application of these PZT-0.12PCW thick film cantilever devices to a protein detector is discussed.

Processing and Properties of Screen-Printed Lead Zirconate Titanate Piezoelectric Thick Films on Electroded Silicon

The printing of lead zirconate titanate (PZT, Pb(Zr,Ti)O3) piezoelectric thick films on silicon substrates is being studied for potential use as microactuators, microsensors, and microtransducers. A fundamental challenge in the fabrication of useful PZT thick-film devices on silicon is to sinter the PZT to high density at sufficiently low temperature to avoid mechanical or chemical degradation of the silicon substrate. The goal of the present study is to develop and implement suitable electrodes and PZT sintering aids that yield attractive piezoelectric properties for devices while minimizing reactions between the silicon, the bottom electrode, and the PZT thick film. A B2O3-Bi2O3-CdO sintering aid has been found to be superior to borosilicate glass, and the use of a gold/platinum bilayer bottom electrode has resulted in better thermal stability of the electrode/film structure. Films sintered at 900°C for 1 h have relative permittivity of 970 (at 1 kHz), remnant polarization of 20 μC/cm2, coercive field of 30 kV/cm, and weak-field piezoelectric coefficient d33 of 110 pm/V.

Estimation of Hydrothermally Deposited Lead Zirconate Titanate (PZT) Thin-Film

The mechanical output of piezoelectric vibrators, particularly actuators, is determined by the limit of the vibration velocity. To obtain large vibration velocity, it is important to deposit a thick piezoelectric film. We have succeeded in depositing thick lead zirconate titanate (PZT) films by the hydrothermal method. The thicknesses of the films were 2 µm, 9.8 µm, 20 µm and 30 µm when the reaction times were 2, 5, 10, and 15, respectively. We have also estimated Young's modulus of the PZT films from the resonance frequency of the bimorph vibrators. From the measurement results, Young's modulus of the PZT film was 1.3×1010 N/m2. This value corresponded to only 16% of that of bulk PZT. The piezoelectric constants of hydrothermally deposited PZT film were inferior to those of bulk PZT. To obtain much larger constants, it is necessary to obtain larger Young's modulus.

Fabrication of low firing piezoelectric ceramics and their applications

The Low-firing PZT, PNN-PZT, PMN-PNN-PZT systems piezoelectric ceramics with high performance have been studied systematically. By doping suitable additives and optimizing processing, excellent piezoelectric properties could be obtained: Kp=0.50∽0.74, d33=(300∽705)×10−12C/N, ϵ33 T /ϵ0 =800∽4100, tanδ=(40∽250)×10−4. The microstructure and the mechanism of transition liquid phase sintering were also investigated. The low firing piezoelectric ceramics have been used for multilayer piezoelectric transformers, ultrasonic motors and thick film devices.

F-1327 スクリーン印刷法によるPZT-PZN圧電体厚膜の低温形成とアクチュエータの特性(S49-2&S48 マイクロエネルギー(2)/精密機器マイクロメカトロニクス)(S49 マイクロエネルギー)

F-1327 スクリーン印刷法によるPZT-PZN圧電体厚膜の低温形成とアクチュエータの特性(S49-2&S48 マイクロエネルギー(2)/精密機器マイクロメカトロニクス)(S49 マイクロエネルギー)

Electrical properties of 3-component piezoelectric thick films by screen printing method

PZT(52/48) thick films with Pb-based complex oxide (PCW) additive were prepared on Pt/TiO2/YSZ/SiO2/Si substrate by screen printing method. PCW addition and PZT sol application are performed to fabricate high density PZT thick film and to lower sintering temperature. With the increase of sintering temperature, electrical properties of screen-printed films were improved. Further, for the sol-gel treated thick films, the electrical properties were improved as compared to only screen-printed films. For the PZT-0.12PCW thick films with sol-treated and sintered at 900°C, the remanent polarization (Pr) was about 23.8 μC/cm2 at the applied filed of 150 kV/cm2, the dielectric permittivity (Ωr) was 1024 at the frequency of 100 kHz, and the piezoelectric coefficient (d33) was 339 pC/N at the applied pressure of 1 atm. Finally, the application of these PZT thick films to piezoelectric actuator is described.

Formation of Pb(Zr, Ti)O3–Pb(Zn, Nb)O3 System Piezoelectric Thick Films in Low-Temperature Firing Process

Piezoelectric thick-films of 0.7Pb(Zr, Ti)O3–0.3Pb(Zn, Nb)O3 were prepared on ZrO2 ceramic substrates by firing the printed paste at 800–950°C. As a source material for the paste, glass-ceramics composed of a lead-based glass and nucleation initiators of TiO2 and ZrO2 were used together with the mother material of Pb(Zr, Ti)O3–Pb(Zn, Nb)O3. The piezoelectric properties were evaluated with a unimorph actuator formed on the ZrO2 thin substrate. The remanent polarization was 11 to 12 µC/cm2. The coercive field was 13 to 14 kV/cm and the piezoelectric constant d33 was 260 to 320 pC/N. Thick-film material consisting of Pb(Zn, Nb)O3 modified PZT powder and glass-ceramics containing nucleation initiators are very useful for obtaining densification in low-temperature firing and excellent piezoelectric properties.

Processing of PZT piezoelectric thick films on silicon for microelectromechancial systems

Thick-film printed lead zirconate titanate (PZT) structures can be combined with micromachined silicon structures and offer relatively large actuation forces compared to alternative techniques. This paper describes the initial investigation into the compatibility issues of micromachining silicon wafers with PZT layers printed on the surface. It assesses the effect of many standard photolithography and micromachining upon the printed PZT layer. In particular the adhesion of the printed layer to the substrate and its internal structure have been studied after exposure to each process. Standard photolithography using positive resists has been found to destroy the adhesion of the platinum electrode and an alternative masking technique using a thick-film printed dielectric polymer has been developed. Aluminium top electrodes have been fabricated using this masking technique combined with ion beam milling. Finally many standard micromachining etching processes have been carried out on a range of silicon substrates incorporating platinum electrode/thick-film PZT structures. Wet silicon and silicon dioxide etches were found to be unsuitable since they also attacked the adhesion of the bottom electrode. Plasma etching processes appear to be well suited for the combination of materials since there is a wide range of etches available that do not affect the PZT. These can therefore be used for the micromachining of the silicon substrate after thick-film processing greatly expanding the range of applications suited to this combination of technologies.

Effect of grain sizes on piezoelectric properties of multilayer thick film actuators

A unique piezoelectric multilayer thick film actuator for computer hard disk drives has been designed and fabricated using the screen printing technology. Dielectric and piezoelectric properties of such PZT thick film actuators with grain sizes ranging from 0.8 to 3.0 μm have been investigated. Under an applied electric voltage of 6V. displacement values of 0.25 μm, 0.44 μm, and 0.55 μm and corresponding resonance frequencies of 58.0 kHz, 61.4 kHz, and 65.6 kHz are obtained in those PZT multilayer actuators with grain sizes of 0.8 μm, 1.3 μm, and 3.0 μm, respectively. The correlation between processing parameters with grain sizes and piezoelectric properties is discussed.

Electrical properties of direct deposited piezoelectric thick film formed by gas deposition method annealing effect of the deposited films

Ultrafine particles jetting with the velocities of several hundreds m/s are accumulated on the metal and ceramic substrate via impact adhesion. Recently, the application of this phenomenon as a thick film formation method has been investigated for micro electro mechanical systems (MEMS) and micro devices. The gas deposition method is one of the thick film formation method based on impact adhesion of ultrafine particle. In this paper, the optimum annealing condition for the deposited Pb(Zr,Ti)O3 film with thickness over 10 μ m is reported. For the deposited films after annealing at 600°C for 1 hour, the remanent polarization of 20 μ C/ cm2 and the coercive filed of 44.7kV/cm was obtained.

Ferroelectric Ceramics: History and Technology

Ferroelectric ceramics were born in the early 1940s with the discovery of the phenomenon of ferroelectricity as the source of the unusually high dielectric constant in ceramic barium titanate capacitors. Since that time, they have been the heart and soul of several multibillion dollar industries, ranging from high‐dielectric‐constant capacitors to later developments in piezoelectric transducers, positive temperature coefficient devices, and electrooptic light valves. Materials based on two compositional systems, barium titanate and lead zirconate titanate, have dominated the field throughout their history. The more recent developments in the field of ferroelectric ceramics, such as medical ultrasonic composites, high‐displacement piezoelectric actuators (Moonies, RAINBOWS), photostrictors, and thin and thick films for piezoelectric and integrated‐circuit applications have served to keep the industry young amidst its growing maturity. Various ceramic formulations, their form (bulk, films), fabrication, function (properties), and future are described in relation to their ferroelectric nature and specific areas of application.

The Dielectric Properties of the Piezoelectric PZT Thick Films

The piezoelectric PZT thick films were fabricated by spinning and painting techniques in our laboratory. The purpose of this paper is to study the characteristics of the piezoelectric films that could be used as the sensors in devices, smart materials and structures. The effects of processing methods and processing conditions on dielectric properties of thick films are investigated. The temperature dependencies of the dielectric constants and the loss of the sample are measured before and after poling. Our experimental results might provide a better understanding of the behavior of these types of materials regarding their applications in monitoring, active controlling and diagnosing.

Electromechanical characterization and modelling of piezoelectric thick films

Polycrystalline Pb(Zr x Ti 1-x )O 3 thick films have been prepared by spin-on and rapid sintering in a conventional oven. The remanent polarization and coercive field of a 80 μm thick film are studied versus the applied field. Modellings from the admittance curves and from a modified Mason circuit can explain that the weaker electromechanical characteristics of the PZT layer against the bulk material are due both to the porosity and to the existence of an inactive layer. A characterization by the beam method shows a good correlation between the theoretical and experimental resonance frequencies.

Preparation of Piezoelectric Thick Films using a Jet Printing System

Pb(Zr, Ti)O3 piezoelectric thick films were prepared on Pt/Cr/SiO2/Si substrate using an improved jet printing system (JPS). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis and measurements of electrical properties, including dielectricity, ferroelectricity and piezoelectricity, were carried out on these films. A very high deposition rate of 3 µm/min and films with thicknesses above 100 µm were obtained without peeling. However, the films prepared in this fashion demonstrate lower piezoelectric behavior than bulk PZT ceramics. The reason for this has been explored using element analysis. Furthermore, we have developed a mask depositing technique as a surface leveling.

The preparation of piezoceramic–polymer thick films and their application as micromechanical actuators

There is currently considerable interest in the development of piezoelectric materials with properties that cannot at present be attained with single-phase materials. Composite piezoelectric thick films have been prepared and characterized. These films, deposited directly onto metallized glass cantilevers, have been shown to be effective as micro-actuators.

Self-resonant piezoelectric thick filmsfor sensing applications

The behaviour of piezoelectric thick films based on a PZT paste screen-printed and fired on alumina substrates has been investigated around their resonant frequencies. Experimental results relative to circular layers are reported, which show the influences on the impedance spectra around resonance owing to lead oxide content in the paste, layer thickness and poling field. These early results suggest that this, so far overlooked region of operation, might be advantageously exploited for sensing applications, stimulating the migration in the low-cost field of thick film technology of operating principles and devices from more costly technologies.

Elastic surface wave devices based on piezoelectric thick-films

A study has been performed for the development of elastic-waves structures, involving screen printed and fired piezoelectric layers on nonpiezoelectric substrates, intended for new families of thick film sensors. This study approached the electroacoustic effects, i.e., the coupling between electromechanical parameters of the layers and elastic properties of the substrate, related to the wave propagation. In this work, particular attention is devoted to devices implemented on alumina substrates where SAW as well as (symmetric and antisymmetric) Lamb's waves are generated. The realization processes and the performance characteristics of these structures are presented.

The use of composite piezoelectric thick films for actuation and control of miniature cantilevers

A control and actuation system is described which utilises a single active piezoelectric composite thick film and optical vibration sensing. This system enables unwanted vibrations of the cantilever to be cancelled, whilst maintaining the ability to deflect the cantilever statically or dynamically as required. The use of such piezoelectric elements in scanning probe microscopes is duscussed.

A novel torque sensor based on elastic waves generated and detected by piezoelectric thick films

Abstract Screen-printed and fired PZT-based films have been used as the source and detectors of elastic waves near the surface of a torsional shaft. The change in wave propagation velocity due to applied torques has been taken as the operating principle of a torque sensor. The new opportunities opened by piezoelectric thick-film materials in the implementation of this novel sensor are demonstrated.

Thick-film acoustic wave sensor structure

The scope for thick-film sensor development has largely been limited by the lack of special-purpose sensing pastes. Using a new piezoelectric thick-film we have developed a novel acoustic wave sensor which allows an expansion of the technology into areas previously overlooked.