Lead Zirconate Titanate Thick Films Research Articles

Comparison of dielectric properties of sol–gel derived pure and calcium modified lead zirconate titanate ceramics and thick films of compositions near MPB

In this work, pure and calcium modified lead zirconate titanate thick composite films of compositions near morphotropic phase boundary (Pb(1−x)CaxZr0.52Ti0.48O3; where x = 0, 0.06, 0.1) have been fabricated on platinized silicon (Pt(111)/Ti/SiO2/Si) substrate using modified sol–gel technique and employing infiltration process. The XRD patterns of the films annealed at 750 °C possess pure perovskite phase. The films are dense, free of cracks and the thickness of the films is more than 25 µm as revealed by scanning electron microscopy (SEM). The films have high dielectric constant values at room temperature and though lower but comparable in magnitude with those for corresponding sol–gel derived bulk ceramic compositions. With increasing calcium concentration, both bulk samples and thick films show decreasing trend of room temperature dielectric constant. Temperature dependence of dielectric constant show that the ferroelectric-paraelectric phase transition in the case of thick films is gradual and broader while it is comparatively much sharper for the corresponding bulk samples. In sol–gel derived bulk samples the TC decreases with increasing calcium concentration while it is same for all the studied compositions of the thick films.

Fabrication of bimorph lead zirconate titanate thick films on metal substrates via the cold sintering-assisted process

A novel process was developed for the fabrication of 5–50 µm lead zirconate titanate (PZT) thick films on metal substrates. Tape cast PZT with a methyl cellulose binder was burned out at 275 °C, humidified, and then partially densified at 300 °C by cold sintering with a wet lead nitrate liquid phase. Lamination of the green tape on dense metal foils led to incomplete densification due to constrained sintering. However, when metal foils were replaced with tape cast Cu, fully sintered PZT/Cu/PZT composites were acquired after a secondary heat treatment at 800 °C. The PZT films has a relative permittivity over 500 and a loss tangent ~12% at 100 Hz because of a Cu2O interface between the PZT and Cu presumably formed during the cold sintering process. The polarization-electric field hysteresis loop shows a remanent polarization over 20 µC/cm2, and the e31,f of the samples is -4.7 C/m2.

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.

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.

Novel fabrication of PZT thick films by an oil-bath based hydrothermal method

Abstract This paper introduces an innovative way to prepare lead zirconate titanate thick films near the morphotropic phase boundary using oil-bath based hydrothermal method with magnetic stirring. Undergoing once nucleation process and four-time crystallization process, approximately 10 µm PZT thick films could be obtained. This PZT film performed good ferroelectric and dielectric property. At room temperature, the coercive field (E c ) and the remnant polarization (P r ) were 37.5 kV/cm and 7 μC/cm 2 , respectively. In the frequency range between 1 kHz to 1 MHz, dielectric constant decreased from 300 to 250 and the dielectric loss was below 0.1. These promising results suggest that the oil-bath based hydrothermal method is a good candidate for PZT film fabrication.

Low-frequency energy harvesters made from double-layer PZT thick films on titanium plate

A miniature piezoelectric energy harvester with bimorph configuration and low natural frequency is proposed in this article for vibration harvesting. The vibration energy harvester is fabricated from double-layer lead zirconate titanate (PZT) thick films and titanium (Ti) substrate via a dip-coating process. The high fracture toughness and strength of the Ti substrate were found to be conducive to forming a harvester with low nature frequency. Highly (100) oriented PZT films 1.71 µm in thickness were deposited on both sides of 50 µm-thick Ti substrate to fabricate the harvester. When the harvester was tested under 3 m s−2 vibration acceleration and an optimum load resistor of 47.5 kΩ, the measured resonant frequency was only 24.2 Hz, and the optimal output power was reached 50.9 µW.

Synthesizing nanostructured crack-free thick films of Fe-doped lead zirconate titanate by sol–gel dip coating method

Lead zirconate titanate is one of the most well-known ferroelectric oxides and has been widely used in nano/micro-electromechanical systems and piezoelectric industries. Doping the lead zirconate titanate thick films by Fe3+ as an acceptor dopant leads to hard lead zirconate titanate piezoelectrics for specific applications including high frequency transducers. In this article, Fe-doped lead zirconate titanate thick films with the thickness of 27 µm are synthesized by using a modified acetic acid/alcoholic based sol–gel method and applying diethanolamine as a complexing agent. Crystallographic measurements are performed considering lattice constants and lattice distortion of the films by means of X-ray diffraction. Pure perovskite phase is obtained by adding the dopant up to 5 at. % Fe. The tetragonal lattice distortion and lattice parameters decrease by adding Fe and reach to its minimum level of c t = 4.024 A and a t = 3.966 A at 3 at. % Fe. The surface morphology and grain size are surveyed using field emission scanning electron microscopy, which shows the reduction in grain size by adding the dopant. Polarization-voltage loops and dielectric constants of the films are calculated by electrical measurement and illustrate reduction in the polarization by increasing Fe dopant. The highest value of coercive voltage is achieved at 3 at. % Fe. Moreover, the lowest dielectric constant of 318 is obtained at 5 at. % Fe. Nanostructured crack-free Fe-doped PZT thick films are successfully prepared by using modified sol–gel route with different Fe dopant percentages (a) surface morphology of PF(3 %)ZT, (b) cross section of PZT thick film.

Optimum reaction conditions for lead zirconate titanate thick film deposition by ultrasound-assisted hydrothermal method

A hydrothermal method can be used to deposit lead zirconate titanate (PZT) films and has several advantages, such as a relatively low reaction temperature and high crystal quality. We developed an ultrasound-assisted hydrothermal method to promote the hydrothermal reactions, which is effective for thick-PZT-film deposition. The first ultrasound-assisted hydrothermal method we developed can synthesize a 7.5 µm PZT film on a titanium substrate. However, for a much thicker film, repeated depositions were required, and the optimum precursor solution for the first deposition was not suitable for repeated depositions. In this study, we attempted to find the optimum precursor solution for depositing a film of sufficient thickness by repeated depositions. As a result, we were able to synthesize a 23.6 µm PZT film on second deposition by changing the ratio of zirconium to titanium ions in the precursor solutions. In addition, a transverse effect transducer was fabricated under optimum conditions and its vibration properties were evaluated.

Dependence of the ferroelectric properties of modified spin-coating-derived PZT thick films on the crystalline orientation

The effects of crystalline orientation on the ferroelectric properties of lead zirconate titanate (PZT) thick films deposited on (111)-oriented Pt/Ti/SiO2/Si substrates by using a modified spincoating method have been studied. The texture and the microstructure of the thick films were characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, respectively. The XRD results implied that the texture of the PZT films was sensitive to the pyrolysis conditions after spin-coating, but less dependent on the film’s thickness. The texture had mainly a (111)-orientation for pyrolysis temperatures from 330 to 400 ◦C, and changes in the (100)- orientation occurred for pyrolysis temperatures at or above 450 ◦C after annealing at 650 ◦C for 5 min. The formation of a preferred texture could be explained by using the intermetallic phases and the internal stress energies between the substrate and the film. The ferroelectric properties of the PZT films fabricated by using this method have been found to be enhanced as compared to those of the PZT films fabricated by using the conventional spin-coating method and to be correlated to the microstructure of the film.

Photonic Sintering of Aerosol Jet Printed Lead Zirconate Titanate (PZT) Thick Films

Lead Zirconate Titanate (PZT) is a commonly used piezoelectric material due to its high piezoelectric response. We demonstrate a new method of printing and sintering micro‐scale PZT films with low substrate temperature increase. Self‐prepared PZT ink was Aerosol‐Jet printed on stainless steel substrates. After drying for 2 h in vacuum at 200°C, the printed PZT films were divided into two groups. The first group was traditionally sintered, using a thermal process at 1000°C for 1 h in an Argon environment. The second group was photonically sintered using repetitive sub‐msec pulses of high intensity broad spectrum light in an atmospheric environment. The highest measured substrate temperature during photonic sintering was 170.7°C, enabling processing on low melting point substrates. Ferroelectric measurements were performed with a low‐frequency sinusoidal signal. The remanent polarization (Pr) and coercive field (Ec) for thermally sintered PZT film were 17.1 μC/cm2 and 6.3 kV/cm, respectively. The photonically sintered film had 32.4 μC/cm2 Pr and 6.7 kV/cm Ec. After poling the samples with 20 kV/cm electric field for 2 h at 150°C, the piezoelectric voltage constant (g33) was measured for the two film groups yielding −16.9 × 10−3 (V·m)·N−1 (thermally sintered) and −17.9 × 10−3 (V·m)·N−1 (photonically sintered). Both factors indicate the PZT films were successfully sintered using both methods, with the photonically sintered material exhibiting superior electrical properties. To further validate photonic sintering of PZT on low melting point substrates, the process and measurements were repeated using a polyethylene terephthalate (PET) substrate. The measured Pr and Ec were 23.1 μC/cm2 and 5.1 kV/cm, respectively. The g33 was −17.3 × 10−3 (V·m)·N−1. Photonic sintering of thick film PZT directly on low melting point substrates eliminates the need for complex layer transfer processes often associated with flexible PZT transducers.

Fabrication of Nb-doped lead zirconate titanate thick films synthesized by sol–gel dip coating method

Modifying the lead zirconate titanate thick films by Nb5+ can thoroughly optimize the properties of the thick films in micro-electromechanical systems, sensors, and microactuators. In this article, the Nb5+ is doped in sol–gel synthesized thick films of PZT with the thickness of more than 27 µm. In order to produce the thick films, a new modified sol–gel method based on the niobium chloride precursor is applied. The lattice constants, lattice distortion, and the preferred-orientation of the films are measured by means of X-ray diffraction. The surface morphology and grain size of the films are examined by field emission scanning electron microscopy. The results demonstrated the formation of pure perovskite phase with the tetragonal lattice parameters of ct = 4.114 A and at = 4.039 A and the average grain size of 28 nm in the sample with 2 at.% Nb. Moreover, the hysteresis loops and dielectric constants of the films are compared by electrical measurements. The results illustrated 1.23-fold increase in remanent (from 5.7 µC cm−2 for undoped sample to 12.7 µC cm−2 for 2 at.% Nb) and 6.65-fold increase in dielectric constant (from 275 for undoped sample to 2080 for 3 at.% Nb).

에어로졸 증착법에 의한 압전 PZT 후막의 전기적 특성

Lead zirconate titanate (PZT) thick films with thickness of were fabricated on silicon substrate by aerosol deposition method. As-deposited films on silicon were annealed at the temperatures of . The electrical properties of films deposited by PZT powders were characterized using impedance analyzer and Sawyer-Tower circuit. The PZT powder was prepared by both conventional solid reaction process and sol-gel process. The remanent polarization, coercive field, and dielectric constant of the thick film with solid reaction process were , 30 kV/cm and 1320, respectively. On the other hand, the PZT films by sol-gel process showed a poor dielectric constant of 635. The reason was probably due to the presence of pores produced from organic residue during annealing.

Micro-Positioning Stages for Adaptive Optics Based on Piezoelectric Thick Film Actuators

Piezoceramic actuators based on thick film technology offer the opportunity of integrated solutions for smart microsystems. Especially in adaptive micro-optics, where the height of devices is limited, outgassing has to be inhibited and complex actuator structures are required, screen printed actuators are of great interest. The paper highlights our recent research on micro-positioning stages for integration into a plenoptic camera. The first concept is based on through-thickness polarized lead zirconate titanate (PZT) thick films printed on a 45 mm × 44 mm × 0.17 mm LTCC (Low Temperature Cofired Ceramics) frame with 4 mm wide legs. Driving with an electrical field of 2 kV/mm resulted in an upright stroke of 115 μm. The second concept combines through-thickness and in-plane polarized thick films on four cantilever beams of an Al2O3 based micro-positioning stage. Because of the combination of d31- and d33-mode of excitation, each cantilever beam will provide an s-shaped bending profile allowing for a planar and tilt free lift of 130 μm at 1.66 kV/mm. Both actuator concepts were exploited to adjust position of a micro-lens array between main lens and image sensor in a plenoptic camera setup. With that, working range of the plenoptic camera could be extended.

Processing and electromechanical properties of lead zirconate titanate thick films by electrophoretic deposition

Electrophoretic deposition (EPD) was used for the fabrication of piezoelectric [lead zirconate titanate (PZT)] thick films on alumina substrates. The EPD was performed in constant current mode from an ethanol based suspension consisting of PZT and PbO particles. The influence of addition of ethyl cellulose (EC) and sintering temperature on the thickness, density, homogeneity and functional response of PZT thick films is studied. Results show that the highest electromechanical performance is obtained for the PZT thick films sintered at 900 or 950°C, with a thickness coupling factor kt of 50%. The addition of EC influenced the thickness of the PZT thick films but had only minor effect on the porosity content for sintering temperatures over 900°C. Moreover, elastic constants of the thick films based on the suspension with EC were lower, which leads to lower acoustic impedance (15 MRa) while maintaining high (kt) value. In this last case, a better acoustic matching can be expected with propagation media such as water or biological tissues for ultrasound medical imaging applications.

Preparation and characterization of lead zirconate titanate thick films prepared by chemical solution deposition for MEMS applications

Lead zirconate titanate (PbZrxTi1−xO3, PZT) films are widely used in silicon based microelectromechanical systems (MEMS) due to their high piezoelectric and electromechanical coupling coefficient. Si3N4 is often needed as a masking layer to protect Si during wet etching. In this paper, the preparation and characterization of Pb(Zr0.52Ti0.48)O3 thick films deposited on Pt/Ti/Si3N4/SiO2/Si substrate by chemical solution deposition were studied. PZT films with a thickness of 2μm were spin-coated on the substrates and pyrolyzed at 350°C, and then annealed at 650°C. PZT thick films exhibit highly (100) preferential orientation. The dielectric constant and loss tangent of the films are 2370 and 0.046 at 1kHz, respectively. The remnant polarization (Pr) and the coercive fields (Ec) are 32μC/cm2 and 56kV/cm, respectively. PZT films on patterned Si wafers have been studied for the applications on biosensors and medical ultrasound transducers.

Effects of Pb5Ge3O11 on pyroelectric lead–zirconate–titanate thick films deposited on silicon substrate by electrophoresis deposition

The effects of Pb5Ge3O11 (PGO) sintering additive on the sintering temperature (Ts) and pyroelectric properties of 1 × 1 mm2 lead–zirconate–titanate (PZT) thick films on Pt/Ti/SiO2/Si substrates were studied. The pattern of PGO-added PZT thick films were formed directly by electrophoresis deposition (EPD). The PGO percentage and Ts were optimized at the range from 0 to 9 wt % and 700 to 900 °C, respectively. The energy dispersive spectrometer (EDS) results showed that the diffusion between Si and PZT were weaken gradually as the Ts decreased. The sintered PZT films sintered at 800 °C with 3 wt % PGO exhibited room-temperature pyroelectric coefficient (Pc) of 1.73 × 10−8 C/(cm2·K), figure of merit for detectivity (FD) of 1.9 × 10−5 Pa−0.5, permittivity of 330 and dielectric loss of 1.5% (1 kHz), respectively. These results demonstrate that the directly patterned PGO-added PZT thick films fabricated by EPD show potential application in MEMS detectors.

Hybrid fabrication of piezoelectric thick films using a sol-infiltration and photosensitive direct-patterning technique

We propose a hybrid fabrication technique for piezoelectric thick films using sol-infiltration and a direct-patterning process. To achieve the demands of high-density and direct-patterning at a low sintering temperature, a photosensitive lead zirconate titanate (PZT) solution was infiltrated into a lead zinc niobate–lead zirconate titanate (PZN–PZT) thick film. The direct-patterned PZT films were formed on a locally screen-printed thick film, using a photomask and UV light. By optimizing the thickness of the photosensitive PZT layer, the hybrid films that were prepared with a 120-s soaking time of PZT sol showed a very dense and uniform microstructure with a large grain size at a low sintering temperature of 800 °C. It also had enhanced electrical properties. The measured remnant polarization (Pr) and coercive field (Ec) were 14.61 μC cm−2 and 24.16 kV cm−1, respectively. The Pr value was over four times greater than those of the screen-printed films. We fabricated array-type piezoelectric resonators with direct-patterned PZN–PZT thick films to show the ability of the direct-patterning of the PZT thick film on a silicon wafer for actuator and sensor application, especially for mass production.

Sol-Gel 법에 의한 압전 PZT 후막의 제조

Lead zirconate titanate (PZT) thick films with thicknesses of 20-100 ㎛ were fabricated on silicon substrates using an aerosol deposition method. A PZT powder solution was prepared using a sol-gel process. The average diameters (d50) obtained were 1.67, 1.98, and 2.40 μm when the pyrolysis temperatures were 300°C, 350° C, and 450°C respectively. The as-deposited film had a uniform microstructure without any cracks or pores. The as-deposited films on silicon were annealed at a temperature of 700°C. The 20-㎛ -thick PZT film showed good adherence between the PZT film and substrate, with no tearing observed in the conventional solid phase process. This was probably because the presence of pores produced from organic residue during annealing relieved the residual stresses in the deposited film.

X-ray diffraction measurement of residual stress in sol-gel grown lead zirconate titanate thick films on nickel-based super alloy substrate

Residual compressive stress of Pb(Zr0.52Ti0.48)O3 thick films was investigated using residual strains derived from X-ray diffraction patterns. Sin2ψ method was applied for the 5, 10 and 15 µm sol-gel derived thick films annealed at 700°C for 1 hr as high frequency structural health monitoring square-shape transducers of 10×10 mm, deposited onto the curved nickel-based super alloy substrates. A triaxial model was proposed based on piezoelectric constitutive equations, and Bragg’s law at a large diffraction angle (∼89o) was utilized considering the electromechanical coupling factor as well as elastic, dielectric and piezoelectric constants. Thickness variations led to a significant change in residual stress magnitudes delineated from more-accurate triaxial model compared to small angle plane-stress results not considering the piezoelectric coupling effects.

3J2-3 Vibration properties of lead zirconate titanate thick film transducer fabricated by ultrasonic assisted hydrothermal method

3J2-3 Vibration properties of lead zirconate titanate thick film transducer fabricated by ultrasonic assisted hydrothermal method