Piezoelectric Thick Films Research Articles

Piezoelectric Thick Film Formation Technology by Aerosol Deposition Method and Its Application to Vibration Power Generation Device

Piezoelectric Thick Film Formation Technology by Aerosol Deposition Method and Its Application to Vibration Power Generation Device

Numerical designs of piezoelectric thin-film vibration energy harvesters

To realize flexible and lightweight battery-free systems, we have investigated piezoelectric vibration energy harvesters (PVEHs) composed of piezoelectric thin-film cantilevers with bimorph or unimorph structures. To optimize dimensional parameters of PVEHs, we derived the theoretical equations of output power on the basis of time-resolved equivalent circuit models that are applicable to various types of vibrations with arbitrary waves. In this study, we have calculated the output power of the PVEHs with the shape of trapezoidal stainless-steel cantilevers on which Pb(Zr,Ti)O3 (PZT) thin films are deposited. A theoretical formula of the output power enables the optimization of not only the geometry of the trapezoidal cantilever, but also electrode length and substrate thickness. We fabricated the PVEHs of PZT thin films on stainless steel foils and confirmed that these calculation results were in good agreement with those of the experiments. The theoretical formula indicated that the output power was maximized when the electrode lengths were 66.7% (= 2/3), 76.2%, and 100% of cantilever length with geometries of the cantilever that were rectangular, trapezoidal (V/W = 1/3), and triangular, respectively, while the thickness of piezoelectric film was about 40% of substrate thickness. The output power increases with decreasing substrate thickness, because the reflection loss is reduced owing to the decrease in resonance frequency. The electrode length at which the reflection loss becomes minimum coincides with that at maximum output power, as confirmed by numerical calculation of the output impedance of PVEHs on Smith charts. On the other hand, we also confirmed that the reflection loss decreased to 0 when the piezoelectric coefficient |e31,f| of the piezoelectric thin films was increased to about 30 C/m2, while the output power was increased at the same time. With these electrical optimum solutions, we will be able to determine the optimal design of PVEHs in specific vibration environments.

Performance of a new piezoceramic thick film sensor for measurement and control of cutting forces during milling

Process monitoring and controlling with detailed real-time information such as the cutting force is required for improving the performance of milling processes. This paper presents a novel system for measuring the cutting force in the direct vicinity of the indexable insert. The outlined concept makes use of piezoelectric thick film sensors mounted directly below the insert. The unique design and features of the new sensor enable accurate and continuous force measurements as well as the indication of wear. The results of the experimental investigations are presented and compared to results of a conventional dynamometer.

Study on increasing output current of piezoelectric energy harvester by fabrication of multilayer thick film

Piezoelectric energy harvesting generally demonstrates low output power because its output current is low compared to its high output voltage. The low current and high impedance limit the applications of piezoelectric energy harvesting systems. Thus, it is necessary to increase the output current and reduce the internal impedance. This study presents the fabrication of multilayer piezoelectric thick films with high output currents. Single-layer and five-layer piezoelectric devices are prepared using the tape-casting process. The material properties of each lead zirconate titanate (PZT) ceramic are measured using an impedance analyzer and a d33 meter. The electrical properties of the piezoelectric devices were evaluated by a controllable strain module using vibration exciter. The capacitance of the single-layer device was 7.33 nF and that of the five-layer device was 241.04 nF, which was 32.88 times higher than that of the single-layer device. The open circuit voltage of the five-layer device decreased 6.09 times compared to the single-layer, but the short circuit current increased 5.30 times. The impedance matching load of the five layer device for maximum power transfer was averagely 34.05 times smaller than that of single-layer. Under maximum power transfer conditions, the current of the five-layer PZT device was 6.61 times larger than the single-layer, even though the output power of both devices was similar. Because of this capacitance and current increase, the energy stored in the 220 μF capacitor for 10 s using the five-layer device was 920% larger compared to the energy stored using a single-layer.

Effect of laser processing on physical properties of (Ba0.85Ca0.15Ti0.9Zr0.1O3) lead-free thick films fabricated by the electrophoretic deposition

In this work, we have fabricated lead-free piezoelectric Ba0.85Ca0.15Ti0.9Zr0.1O3 thick films by the electrophoretic deposition (EPD) followed by a continuous-wave CO2 laser annealing and demonstrated the effect of laser energy on the quality of the final product. Thick films annealed under optimized conditions, 50 W/15 min, show a controlled microstructure/density compared to those derived from higher laser power/annealing time/conventional sintering. The increase in laser power above this limit affects the grain growth kinetics and results in the compositional heterogeneities. From the results of Raman spectra, it was found that the film annealed under optimized conditions has a high degree of crystallinity and tetragonality, while the increase in laser fluence results in the growth of A1g mode. The controlled composition and microstructure, thus has resulted in the improved ferroelectricity with a remanent polarization 12 μC/cm2, on par with the bulk or larger than the films grown by the chemical solution deposition techniques. From the piezoresponse studies, we found that the film annealed at 75 W/5 min has weak ferroelectric nature with no switchable ferroelectric domains compared to those under optimized conditions. Subtle differences in phase transition temperatures and drop in ferroelectric polarization, for films annealed conventionally or at higher laser fluence, are related to porosity or site defects as well as compositional heterogeneities. Our study demonstrates that the combination of EPD and laser annealing is an effective way to achieve high quality piezoelectric thick films with a controlled composition, useful for energy harvesting applications.

Porous lead zirconate titanate ceramics with optimized acoustic properties for high-frequency ultrasonic transducer applications

Acoustic properties of porous PZT ceramics intended to be used as backing in high-frequency transducer applications are investigated using a novel method where an electroded piezoelectric thick film is deposited on the backing under test. Two backings with pore sizes 1.5 μm and 10 μm were obtained by sintering a mixture of ceramic powder and an organic template, their porosity was evaluated by scanning electron microscopy at 15%, leading to a density around 6.5 g/cm3. The electroacoustic impulse responses of these devices were measured considering the backing as a propagation medium, the initial thickness of which was chosen small enough to allow back-wall echoes to be detected and large enough to be able to separate the signals in time domain. Then the thickness of the backing was reduced (from around 2 mm to less than 1 mm) and the measurements were repeated. Acoustic properties were then deduced: attenuation coefficients reaching 4 dB/mm/MHz and group velocities around 3400 m/s were obtained, leading to an acoustic impedance around 22 MRa. Such combination of high attenuation and moderate acoustical impedance make these materials an interesting solution for high-resolution ultrasonic imaging transducers.

Electrophoretic deposition and properties of strontium-doped sodium potassium niobate thick films

We have processed strontium-modified potassium sodium niobate (KNNSr) piezoelectric thick films on metalized alumina by electrophoretic deposition and sintering for energy-harvesting applications. The deposition yield, the electric field in the close vicinity of the planar working electrode (calculated with a finite-element method) and the thickness profiles of the as-deposited layers were examined for ethanol-based suspensions with different conductivities, deposition times, inter-electrode distances and sizes of the counter electrode. Uniformly thick and defect-free, as-deposited KNNSr layers were processed from a suspension with a conductivity of 21.2μS/cm, deposited for 90s, for an inter-electrode distance of 3mm and a diameter of the counter electrode similar to the sample’s dimensions. KNNSr layers sintered at 1100°C with a thickness of 30μm and a relative density of 75% exhibited a dielectric permittivity of 325, dielectric losses of 0.04 at 10kHz and room temperature, and a d33 coefficient of 60pC/N.

Characterization of Kerfless Linear Arrays Based on PZT Thick Film.

Multielement transducers enabling novel cost-effective fabrication of imaging arrays for medical applications have been presented earlier. Due to the favorable low lateral coupling of the screen-printed PZT, the elements can be defined by the top electrode pattern only, leading to a kerfless design with low crosstalk between the elements. The thick-film-based linear arrays have proved to be compatible with a commercial ultrasonic scanner and to support linear array beamforming as well as phased array beamforming. The main objective of the presented work is to investigate the performance of the devices at the transducer level by extensive measurements of the test structures. The arrays have been characterized by several different measurement techniques. First, electrical impedance measurements on several elements in air and liquid have been conducted in order to support material parameter identification using the Krimholtz-Leedom-Matthaei model. It has been found that electromechanical coupling is at the level of 35%. The arrays have also been characterized by a pulse-echo system. The measured sensitivity is around -60 dB, and the fractional bandwidth is close to 60%, while the center frequency is about 12 MHz over the whole array. Finally, laser interferometry measurements have been conducted indicating very good displacement level as well as pressure. The in-depth characterization of the array structure has given insight into the performance parameters for the array based on PZT thick film, and the obtained information will be used to optimize the key parameters for the next generation of cost-effective arrays based on piezoelectric thick film.

Piezoelectric Thick Film Based on Bonding technologies for Energy Harvester

Piezoelectric Thick Film Based on Bonding technologies for Energy Harvester

自立電源無線センサモジュールを実現する圧電厚膜振動発電デバイス

自立電源無線センサモジュールを実現する圧電厚膜振動発電デバイス

High frequency and high intensity ultrasonic transducers for medical applications using oriented piezoelectric thick films by hydrothermal method

Recently, high-frequency ultrasonic transducers are proposed for medical applications using piezoelectric crystal. In this case, it is known that the high piezoelectric constant and the higher limitation of vibration velocity are important for high power application. Normally, the piezoelectric ceramics has limitation due to maximum vibration velocity. Thus it is very difficult to radiate for high intensity ultrasound with nonlinear acoustics due to the limitation of maximum vibration velocity. Therefore, we tried to develop a very high intensity and high frequency ultrasonic transducer using hydrothermal KNbO3 thick film. The piezoelectric constant was over 80 pm/V and the vibration velocity of thickness mode of KNbO3 thick film was 2.5 m/s or over at 20 MHz. This maximum vibration velocity is twice of reported piezoelectric materials. Then, a radiation sound-pressure from the prototype ultrasonic transducer with KNbO3 thick film was measured. The result of radiation ultrasound was 4 MPa or over in a wat...

Hybrid Energy Harvester Using Piezoelectric and Pyroelectric Properties of PVDF Nanocomposite Films

This paper reports a novel hybrid piezoelectric-pyroelectric energy harvester using a copper cantilever beam with PVDF thick films. Polyvinylidene fluoride (PVDF) is used as the piezoelectric material, which also has pyroelectric characteristics. We will present an experimental study of electrical output parameters and the resonance frequencies of different thick piezoelectric films attached at the clamped end of copper beam. The experiments were carried out with different plate piezoelectric films such as; polyvinylidene fluoride (PVDF), PVDF/PZT, and PVDF/PZT with multi walled carbon nanotubes (MWCNT) with the thickness of 0.2 mm. The output power was measured with changing the load resistance and the optimum value was found around 1 MΩ. The maximum output power obtained at resonance frequency of the optimum resistance was 0.39, 0.84, and 1.3 nW for PVDF, PVDF/PZT, and PVDF/PZT MWCNT, respectively. By heating the film as well with infrared lamp, the output voltage shall be enhanced. The results of La2O3 nanoparticles embedded in PVDF matrix will also be presented

Indentation response of piezoelectric films under frictional contact

Piezoelectric materials are available in a variety of shapes and forms in smart systems. One of the most common shapes for sensor or actuator applications is the film form. To gain a better understanding of the indentation behavior of these systems, this work analyzes piezoelectric films under different 3D frictional contact boundary conditions. For this purpose, the boundary element formulation presented by authors in Rodríguez-Tembleque, Buroni, and Sáez (2015) is used for modeling piezoelectric finitely thick and thin films under orthotropic frictional indentation conditions, including tangential loads. The formulation has been applied to analyze the influence of friction and tangential loads on the electromechanical response of finitely thick piezoelectric films, ranging from a piezoelectric half space configuration, where the contact radius is much smaller than the thickness of the film, to a thin film configuration. Results reveal that these variables have to be considered to study the indentation response of these advanced systems. In other case, we could over- or underestimate the piezoelectric response and its distribution over the contact zone.

Impact of layer and substrate properties on the surface acoustic wave velocity in scandium doped aluminum nitride based SAW devices on sapphire

This paper investigates the performance of surface acoustic wave (SAW) devices consisting of reactively sputter deposited scandium doped aluminum nitride (ScxAl1-xN) thin films as piezoelectric layers on sapphire substrates for wireless sensor or for RF-MEMS applications. To investigate the influence of piezoelectric film thickness on the device properties, samples with thickness ranging from 500 nm up to 3000 nm are fabricated. S21 measurements and simulations demonstrate that the phase velocity is predominantly influenced by the mass density of the electrode material rather than by the thickness of the piezoelectric film. Additionally, the wave propagation direction is varied by rotating the interdigital transducer structures with respect to the crystal orientation of the substrate. The phase velocity is about 2.5% higher for a-direction compared to m-direction of the sapphire substrate, which is in excellent agreement with the difference in the anisotropic Young's modulus of the substrate corresponding to these directions.

Unleashing the Full Sustainable Potential of Thick Films of Lead-Free Potassium Sodium Niobate (K0.5Na0.5NbO3) by Aqueous Electrophoretic Deposition.

A current challenge for the fabrication of functional oxide-based devices is related with the need of environmental and sustainable materials and processes. By considering both lead-free ferroelectrics of potassium sodium niobate (K0.5Na0.5NbO3, KNN) and aqueous-based electrophoretic deposition here we demonstrate that an eco-friendly aqueous solution-based process can be used to produce KNN thick coatings with improved electromechanical performance. KNN thick films on platinum substrates with thickness varying between 10 and 15 μm have a dielectric permittivity of 495, dielectric losses of 0.08 at 1 MHz, and a piezoelectric coefficient d33 of ∼70 pC/N. At TC these films display a relative permittivity of 2166 and loss tangent of 0.11 at 1 MHz. A comparison of the physical properties between these films and their bulk ceramics counterparts demonstrates the impact of the aqueous-based electrophoretic deposition (EPD) technique for the preparation of lead-free ferroelectric thick films. This opens the door to the possible development of high-performance, lead-free piezoelectric thick films by a sustainable low-cost process, expanding the applicability of lead-free piezoelectrics.

졸-침투와 감광성 직접-패턴 기술을 이용하여 스크린인쇄된 Pb(Zr,Ti)O3후막의 하이브리드 제작

In this paper, we propose a fabrication technique for enhanced electrical properties of piezoelectric thick films with excellent patterning property using sol-infiltration and a direct-patterning process. To achieve the needs of high- density and direct-patterning at a low sintering temperature (< 850 °C), a photosensitive lead zirconate titanate (PZT) solution was infiltrated into a screen-printed thick film. The direct-patterned PZT films were clearly formed on a locally screen-printed thick film, using a photomask and UV light. Because UV light is scattered in the screen-printed thick film of a porous powder-based structure, there are needs to optimize the photosensitive PZT sol infiltration process for obtaining the enhanced properties of PZT thick film. By optimizing the concentration of the photosensitive PZT sol, UV irradiation time, and solvent developing time, the hybrid films prepared with 0.35 M of PZT sol, 4 min of UV irradiation and 15 sec solvent developing time, showed a very dense with a large grain size at a low sintering temperature of 800 °C. It also illustrated enhanced electrical properties (remnant polarization, Pr, and coercive field, Ec). The Pr value was over four times higher than those of the screen-printed films. These films integrated on silicon wafer substrate could give a potential of applications in micro-sensors and -actuators.

Frequency dispersion of love waves in a piezoelectric nanofilm bonded on a semi-infinite elastic substrate

Research on the propagation of elastic waves in piezoelectric nanostructures is very limited. The frequency dispersion of Love waves in layered piezoelectric nanostructures has not yet been reported when surface effects are taken into account. Based on the surface elasticity theory, the propagation of Love waves with surface effects in a structure consisting of a nanosized piezoelectric film and a semi-infinite elastic substrate is investigated focusing on the frequency dispersion curves of different modes. The results show that under the electrically-open conditions, surface effects give rise to the dependence of Love wave dispersion on the film thickness when the thickness of the piezoelectric film reduces to nanometers. For a given wave frequency, phase velocity of Love waves in all dispersion modes exhibit obvious toward shift as the film thickness decreases or the surface parameters increase. Moreover, there may exist a cut-off frequency in the first mode dispersion below which Love waves will be evanescent in the structure due to surface effects. The cut-off frequency depends on the film thickness, the surface parameters and the bulk material properties.

Fabrication and Characterization of Vibration and Wind Energy Harvesters Using Multilayer Free-Standing Piezoelectric Thick Films

This article demonstrates the feasibility of fabricating energy harvesters based on piezoelectric cantilevers with a free-standing thick-film structure. Demonstrator devices have been designed, built, and evaluated in a range of mechanical coupling configurations to harvest energy from machinery vibrations and weak air flow. In terms of wideband vibration energy harvesters, arrays of the individual harvesters were assembled onto plastic test circuit boards integrated with diode bridge rectifiers. The harvesters were designed with different dimensions, and various tip masses were attached on the tip of the cantilevers to individually tune the resonant frequencies. The assembled harvesters were tested under harmonic vibration conditions. Great potential of harvesting vibration energy and broadening working bandwidth has been exhibited. In terms of the harvester for weak air flow, two individual cantilever devices were assembled on the chassis of a free-spinning fan. Permanent magnets were fixed on the blades of the fan as well as on the cantilevers. The device was tested in an open fluidic environment. The air flow was successfully transferred to axial oscillations, thus driving the cantilevers bending up and down. Possibilities of such devices being optimized to meet the requirements of real applications of self-powered wireless sensor networks can be foreseen.

Fabrication of piezoelectric thick films for development of micromechanical cantilevers

We fabricated a piezoelectric thick film, whose electromechanical properties are optimized, for development of micromechanical cantilever as a sensor and actuator. Specifically, we studied the electromechanical properties of piezoelectric thick films made of different kinds of piezoelectric powders with their different sizes. The electromechanical properties of piezoelectric thick film are optimized when it is made of both micro- and nano-sized piezoelectric particles. Moreover, we fabricated a micromechanical cantilever using piezoelectric thick film, and investigated the vibrational characteristics of piezoelectric thick film-based microcantilevers. It is shown that a cantilever made of optimized piezoelectric thick film exhibits the excellent vibrational properties such as high Q-factor even in a viscous fluid, and that the resonance behavior of such a cantilever is very stable when compared with cantilevers made of other piezoelectric thick films. Our study provides the design rule of piezoelectric thick film for further development of micromechanical devices based on such a piezoelectric film.

Non-180° domain contributions in Bi0.5(Na0.82K0.18)0.5TiO3 lead-free piezoelectric thick films

Piezoelectric responses of Bi0.5(Na0.82K0.18)0.5TiO3 (NKBT) ceramic films with thickness of 10–100μm have been studied in a wide range of ac electric field and frequency. By the Rayleigh law fit, the typical irreversible Rayleigh coefficient, α, for piezoelectric response is 39.69±0.41×10−18m2V−2, which is much larger than that of the piezoelectric thin films, indicating significantly enhanced non-180° domain wall motions in NKBT thick films. The logarithmic frequency dependence of the piezoelectric response is associated with domain wall pinning in NKBT thick films, and the frequency dispersion increases with increasing ac field amplitude, which is attributed to the relaxation of non-180° domains.