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Low-consumption ceramics processing routes are expected to replace conventional ones due to environmental concerns. In this context, flash sintering is garnering interest because it allows dense ceramics to be obtained in just a few minutes and at relatively low temperatures. This is particularly interesting for sintering alkaline-based compounds due to the easy volatilization of these elements. In this work, current-controlled flash sintering is used to obtain potassium-sodium niobate (KNN)-based piezoceramics with refined microstructure and suitable stoichiometry, leading to improved functional properties. KNN-based materials are currently outstanding lead-free piezoceramics, with their properties highly sensitive to the proper construction of the polymorphic phase boundary, as in the case of the first promising composition (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3. Results of this work show that sintering parameters may determine the polymorphic behavior of this system, thereby evincing flash sintering allows polymorphic phase boundary to be fine-tuned. It is demonstrated that the convergence of microstructure refinement and compositional control holds the potential for enhancing properties through a proper electric current control during flash sintering., Postprint (author's final draft)

Purpose. To investigate the frequency dependence of the electrical conductivity in piezoelectric ceramics based on solid solutions of lead-zirconate titanate oxides.Methodology. To obtain the frequency dependence of the electrical conductivity in piezoelectric ceramics based on solid solutions of lead-zirconate titanate oxides, we used a technique for measuring the resistance of a sample with electrodes deposited on its opposite faces. Using the obtained resistance value, the value of the electrical conductivity of the sample was calculated at various frequencies.Findings. The frequency dependence of the specific electrical conductivity in PZT-22 piezoceramics based on solid solutions of lead-zirconate titanate oxides in the frequency range of 0 < ν < 60 kHz has been obtained by the authors. The specific electrical conductivity in PZT-22 piezoceramics increased over the entire range of frequencies studied. A sharp increase in specific electrical conductivity was observed at frequencies up to 20 kHz. At frequencies of ν > 20 kHz the increase in specific electrical conductivity ceased and at frequencies of ν > 30 kHz its value reached saturation. The maximum value of specific electrical conductivity γ = 0.55 . 10-6 Ohm-1.m-1 was obtained at a frequency of 60 kHz. The frequency dependence of the specific electrical conductivity in PZT-22 piezoceramics in the frequency range of 0 < ν < 60 kHz is analyzed. It was found that the specific electrical conductivity in PZT-22 piezoceramics increases according to a power law in the frequency range of 0 < ν < 10 kHz. The mechanism of changing the electrical conductivity in PZT piezoceramics with increasing frequency of the electric field is discussed. A formula is obtained that satisfactorily describes the experimental dependence of the specific electrical conductivity in PZT-22 piezoceramics on the frequency of an alternating voltage in the frequency range of 0 < ν < 10 kHz and which corresponds t, Цель работы. Исследовать частотную зависимость электрической проводимости пьезокерамики на основе твердых растворов оксидов цирконата-титаната свинца.Методы исследования. Для получения частотной зависимости электрической проводимости пьезокерамики на основе твердых растворов оксидов цирконата-титаната свинца использовалась методика измерения сопротивления образца с нанесенными на его противоположные грани электродами. По полученному значению сопротивления вычислялось значение электрической проводимости образца при различных частотах.Полученные результаты. Авторами получена частотная зависимость удельной электрической проводимости пьезокерамики ЦТС-22 на основе твердых растворов оксидов цирконата-титаната свинца в диапазоне частот 0 < ν < 60 кГц. Удельная электрическая проводимость пьезокерамики ЦТС-22 увеличивалась во всем диапазоне исследованных частот. При частотах до 20 кГц наблюдался резкий рост удельной электрической проводимости. При частотах ν > 20 кГц увеличение удельной электрической проводимости прекращалось, и при частотах ν > 30 кГц ее значение выходило на насыщение. Максимальное значение удельной электрической проводимости γ = 0,55 . 10-6 Ом-1.м-1 было получено при частоте 60 кГц. Проведен анализ частотной зависимости удельной электрической проводимости пьезокерамики ЦТС-22 в диапазоне частот 0 < ν < 60 кГц. Установлено, что в диапазоне частот 0 < ν < 10 кГц удельная электрическая проводимость пьезокерамики ЦТС-22 увеличивается по степенному закону. Обсуждается механизм изменения электрической проводимости пьезокерамики ЦТС при увеличении частоты электрического поля. Получена формула, удовлетворительно описывающая экспериментальную зависимость удельной электрической проводимости пьезокерамики ЦТС-22 от частоты переменного напряжения в диапазоне частот 0 < ν < 10 кГц и которая соответствует степенному закону А. Иончера. Удельная электрическая проводимость не поляризованной пьезокерамики ЦТС-19 увеличивается в диапазоне час, Мета роботи. Дослідити частотну залежність електричної провідності п'єзокераміки на основі твердих розчинів оксидів цирконата-титанату свинцю.Методи дослідження. Для отримання частотної залежності електричної провідності п'єзокераміки на основі твердих розчинів оксидів цирконата-титанату свинцю використовувалась методика вимірювання опору зразка з нанесеними на його протилежні грані електродами. За отриманого значення опору обчислювалося значення питомої електричної провідності зразка при різних частотах.Отримані результати. Авторами отримана частотна залежність питомої електричної провідності п'єзокераміки ЦТС-22 на основі твердих розчинів оксидів цирконата-титанату свинцю в діапазоні частот 0 < ν < 60 кГц. Питома електрична провідність п'єзокераміки ЦТС-22 збільшувалася у всьому діапазоні досліджених частот. При частотах до 20 кГц спостерігалося різке зростання питомої електричної провідності. При частотах ν > 20 кГц збільшення питомої електричної провідності припинялося, і при частотах ν > 30 кГц її значення виходило на насичення. Максимальне значення питомої електричної провідності γ = 0,55. 10-6 Ом-1.м-1 було отримано при частоті 60 кГц. Проведено аналіз частотної залежності питомої електричної провідності п'єзокераміки ЦТС-22 в діапазоні частот 0 < ν < 60 кГц. Встановлено, що в діапазоні частот 0 < ν < 10 кГц питома електрична провідність п'єзокераміки ЦТС-22 збільшується за степеневим законом. Обговорюється механізм зміни електричної провідності п'єзокераміки ЦТС при збільшенні частоти електричного поля. Отримана формула, задовільно описує експериментальну залежність питомої електричної провідності п'єзокераміки ЦТС-22 від частоти змінної напруги в діапазоні частот 0 <ν <10 кГц і яка відповідає степеневому закону А. Іончера. Питома електрична провідність не поляризованої п'єзокераміки ЦТС-19 збільшується в діапазоні частот 0 < ν < 100 кГц. В діапазоні частот 0 < ν < 20 кГц спостерігається степенева залежність, а при ч

An efficient long-term storage of cryogenic propellants is a challenge for future space exploration missions. The vapour bubbles formed as a result of boil-off in the tank walls can generate foam structures, which could be hazardous in different operations in orbit. A recently proposed approach to control the dynamics of bubbles is based on the generation of an acoustic field by means of a piezoelectric transducer. This technology needs to be validated at cryogenic temperatures in order to be applicable in space. In this perspective, different piezoelectric elements and matching layer materials have been tested at cryogenic temperatures to assess their performance at such environmental conditions. We consider the use of soft PZT piezoceramics coupled with an epoxy resin as the matching layer. Experimental data reveal that epoxy resin-based acoustic matching layers exhibit a linear increase in the transmittance of the acoustic amplitude at cryogenic conditions. The peak-to-peak amplitude increases as temperature decreases up to a factor of 1.6. This result opens the possibility of generating and transmitting acoustic waves at cryogenic temperatures, which could be used in the recently proposed technology to control the dynamics of vapour bubbles in cryogenic fuel tanks., Postprint (author's final draft)

Piezoelectric materials possess nonlinear behavior when actuated in a large electric field and show a large deflection when embedded inside a composite laminate such as a LIghtweight Piezoelectric Composite Actuator. Linear and nonlinear COMSOL multi-physics finite element models were developed and validated using the actuation response of three different layups of LIghtweight Piezoelectric Composite Actuators under a cantilever beam configuration. The linear model incorporated the linear piezoelectric coefficient given from the manufacturer, while the nonlinear model incorporated the nonlinear piezoelectric coefficient plus permanent strain offset in the piezoelectric material as a result of a high applied electric field. The linear model significantly underestimated the experimental values of the actuator response and it showed that taking nonlinearity and permanent strain offset into account is an essential practice when an actuator is operated in high electric fields and accurate prediction is required., Structural Integrity & Composites

The origins of high piezoelectric properties in the lead-free (K,Na)NbO3-based tetragonal composition (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3 (KNL-NTS) is investigated by quantifying the intrinsic and extrinsic contributions from high energy X-ray diffraction measurements. The applied methodology, which allows discerning between the intrinsic contribution, related to the field induced lattice distortion, and the extrinsic contributions, related to non-180° domain wall motion, is widely described in this work. The non-180° domain reorientation of the KNL-NTS piezoceramic is quantify from the integrated intensities of the 002 and 200 reflections obtained from line profile, while the shifts in peak position versus the applied electric field is used to obtain the lattice strain contribution. Large non-180° domain wall contribution to the electric field induced macroscopic strain (80% of the macroscopic strain) is verified in KNL-NTS., Postprint (author's final draft)

Piezoelectric ceramics have been widely used in the commercial applications of actuators, sensors, etc. Nowadays, Pb(Zr,Ti)O3-based (PZT) ceramics, which contain ≥ 60 wt.% of lead, dominate the market due to their excellent electromechanical properties. The large electric field induced polarization and strain developed in PZT piezoceramics are intimately related to the morphotropic phase boundary (MPB). This has been attributed to the coexistence of tetragonal and rhombohedral perovskite phases. However, toxic lead severely threatens the environment and human health, as a significant amount of lead is released into the air during the fabrication and disposal. Thus, there is an urgent demand worldwide to develop new kinds of green materials, lead-free ceramics, to replace the PZT lead-based compositions with comparable electrical properties. For the past decade, the study has been focused on the BaTiO3-based (BTO), (K0.5Na0.5)NbO3-based (KNN), and (Bi1/2Na1/2)TiO3-based (BNT) solid solutions. Despite the extensive efforts worldwide, the performances of lead-free materials have yet to reach the level of PZT ceramics. In this thesis research, new chemical modifications have been explored and introduced to the lead-free compositions. It is elucidated that the dielectric, ferroelectric and piezoelectric properties are associated with the phase presence and microstructure. Therefore, understanding the structure behavior is the key to enhance the electrical properties efficiently. Usually, the bottleneck for industry application of lead-free materials is the narrow working temperature range, the weak piezoelectric response and the low electric field induced strain. It is well known that the best way to overcome these shortcomings is to form a solid solution by combining two different compounds. Another common way is to decrease the grain size to a submicron level. The results from this dissertation demonstrate that the (Bi1/2A1/2)TiO3 type doping compounds (A = Ag, Li, Na

The phase structure, piezoelectric, dielectric, and ferroelectric properties of (0.80-x)PMN-0.10PFN-0.10PZ-xPT were investigated systematically. The morphotropic phase boundary (MPB) was confirmed to be 0.30

The phase structure, piezoelectric, dielectric, and ferroelectric properties of (0.80-x)PMN-0.10PFN-0.10PZ-xPT were investigated systematically. The morphotropic phase boundary (MPB) was confirmed to be 0.30

The phase structure, piezoelectric, dielectric, and ferroelectric properties of (0.80-x)PMN-0.10PFN-0.10PZ-xPT were investigated systematically. The morphotropic phase boundary (MPB) was confirmed to be 0.30

The phase structure, piezoelectric, dielectric, and ferroelectric properties of (0.80-x)PMN-0.10PFN-0.10PZ-xPT were investigated systematically. The morphotropic phase boundary (MPB) was confirmed to be 0.30

The purpose of this study is to evaluate modeling of piezoceramic materials with maximum efficiency; that is high fidelity with shortest computer run time. To do this, the modeler varied the number of element layers and element types in each part to find the most efficient combination that would produce accurate bending in an activated piezoelectric material with less than 1% displacement error. A cantilever beam model, based on an example in the ABAQUS manual, was developed. The number of element layers varied from one to 10 per part. Low order, high order, and shell and brick elements with various hourglass controls were employed. Results show that the best combination of high accuracy and short run time was a model with a single layer of high order bricks for the piezoelectric layers and a single layer of low order bricks with enhanced hourglass control for the beam layer., The original document contains color images.

We report the piezoelectric and ferroelectric properties of (Na0.5Bi0.5TiO3)(x)-(BaTiO3)(y)-(Na0.5K0.5NbO3)(1-x-y) ceramics for Na0.5K0.5NbO3 rich end of composition (x, y <= 0.04 mol. %). These compositions were found to exhibit significantly improved thermal stability of piezoresponse. Variation of dielectric constant as a function of temperature revealed that orthorhombic-tetragonal (To-t) and tetragonal-cubic (T-c) transition temperatures for these compositions were in the vicinity of 0 degrees C and 330 degrees C, respectively. Dynamic scaling and temperature dependent X-ray diffraction analysis were conducted. Results are discussed in terms of intrinsic and extrinsic contributions to the piezoelectric response explaining the temperature dependent behavior. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773983]

In this work, the piezoelectric properties at high electric fields of dielectrophoretically aligned PZT—polymer composites containing high aspect ratio particles (such as short fibers) are presented. Polarization and strain as a function of electric field are evaluated. The properties of the composites are compared to those of PZT-polymer composites with equiaxed particles, continuous PZT fiber-polymer composites, and bulk PZT ceramics. From high-field polarization and strain measurements, the effective field dependent permittivity and piezoelectric charge constant in the poling direction are determined for dielectrophoresis structured PZT-polymer composites, continuous PZT fiber-polymer composites, and bulk PZT ceramics. The changes in dielectric properties of the inclusions and the matrix at high fields influence the dielectric and piezoelectric properties of the composites. It is found that the permittivity and piezoelectric charge constants increase towards a maximum at an applied field of around 2.5-5?kV/mm. The electric field at which the maximum occurs depends on the aspect ratio and degree of alignment of the inclusions. Experimental values of d33 at low and high applied fields are compared to a model describing the composites as a continuous polymer matrix containing PZT particles of various aspect ratios arranged into chains. Thickness mode coupling factors were determined from measured impedance data using fitted equivalent circuit model simulations. The relatively high piezoelectric strain constants, voltage constants, and thickness coupling factors indicate that such aligned short fiber composites could be useful as flexible large area transducers. Erratum published 5 March 2015: http://dx.doi.org/10.1063/1.4914113, Aerospace Structures & Materials, Aerospace Engineering

The meso-scale surface roughness of piezoelectric fiber composites can be manipulated by applying an electric field to a piezocomposite with a polished surface. In the absence of an applied voltage, the tips of the embedded piezoelectric ceramic fibers are below the surface of the piezocomposite and a silicon wafer counter surface rests solely on the matrix region of the piezocomposite surface. When actuated, the piezoelectric ceramic fibers protrude from the surface and the wafer rests solely on these protrusions. A threefold decrease in engineering static friction coefficient upon actuation of the piezocomposite was observed: from ?*?=?1.65 to ?*?=?0.50. These experimental results could be linked to the change in contact surface area and roughness using capillary adhesion theory, which relates the adhesive force to the number and size of the contacting asperities for the different surface states, Aerospace Structures & Materials, Aerospace Engineering

Synchronized switch damping on inductor offers a high damping performance in a broad frequency range. It consists of an inductor and resistor in a serial configuration, which are connected and disconnected from the piezoceramics in an alternating manner by a switch. When the switch is triggered by the vibration itself, it adapts to different excitation frequencies especially in the low frequency range. This article presents a detailed study of the damping performance of the synchronized switch damping on inductor technique. Calculations are performed in a normalized way. The optimal tuning of synchronized switch damping on inductor network parameters is derived, and the corresponding maximum damping performance is obtained. The results are further compared to standard linear inductance-resistance networks. For a validation of the theoretical results, measurements on a clamped beam test rig are performed. Therefore, the synchronized switch damping on inductor circuit is realized as a synthetic impedance in a DSpace environment. The measurement results are in good agreement with the theoretical calculations. © The Author(s) 2012.

The meso-scale surface roughness of piezoelectric fiber composites can be manipulated by applying an electric field to a piezocomposite with a polished surface. In the absence of an applied voltage, the tips of the embedded piezoelectric ceramic fibers are below the surface of the piezocomposite and a silicon wafer counter surface rests solely on the matrix region of the piezocomposite surface. When actuated, the piezoelectric ceramic fibers protrude from the surface and the wafer rests solely on these protrusions. A threefold decrease in engineering static friction coefficient upon actuation of the piezocomposite was observed: from ?*?=?1.65 to ?*?=?0.50. These experimental results could be linked to the change in contact surface area and roughness using capillary adhesion theory, which relates the adhesive force to the number and size of the contacting asperities for the different surface states, Aerospace Structures & Materials, Aerospace Engineering

In this work, the piezoelectric properties at high electric fields of dielectrophoretically aligned PZT—polymer composites containing high aspect ratio particles (such as short fibers) are presented. Polarization and strain as a function of electric field are evaluated. The properties of the composites are compared to those of PZT-polymer composites with equiaxed particles, continuous PZT fiber-polymer composites, and bulk PZT ceramics. From high-field polarization and strain measurements, the effective field dependent permittivity and piezoelectric charge constant in the poling direction are determined for dielectrophoresis structured PZT-polymer composites, continuous PZT fiber-polymer composites, and bulk PZT ceramics. The changes in dielectric properties of the inclusions and the matrix at high fields influence the dielectric and piezoelectric properties of the composites. It is found that the permittivity and piezoelectric charge constants increase towards a maximum at an applied field of around 2.5-5?kV/mm. The electric field at which the maximum occurs depends on the aspect ratio and degree of alignment of the inclusions. Experimental values of d33 at low and high applied fields are compared to a model describing the composites as a continuous polymer matrix containing PZT particles of various aspect ratios arranged into chains. Thickness mode coupling factors were determined from measured impedance data using fitted equivalent circuit model simulations. The relatively high piezoelectric strain constants, voltage constants, and thickness coupling factors indicate that such aligned short fiber composites could be useful as flexible large area transducers. Erratum published 5 March 2015: http://dx.doi.org/10.1063/1.4914113, Aerospace Structures & Materials, Aerospace Engineering

We report the piezoelectric and ferroelectric properties of (Na0.5Bi0.5TiO3)(x)-(BaTiO3)(y)-(Na0.5K0.5NbO3)(1-x-y) ceramics for Na0.5K0.5NbO3 rich end of composition (x, y <= 0.04 mol. %). These compositions were found to exhibit significantly improved thermal stability of piezoresponse. Variation of dielectric constant as a function of temperature revealed that orthorhombic-tetragonal (To-t) and tetragonal-cubic (T-c) transition temperatures for these compositions were in the vicinity of 0 degrees C and 330 degrees C, respectively. Dynamic scaling and temperature dependent X-ray diffraction analysis were conducted. Results are discussed in terms of intrinsic and extrinsic contributions to the piezoelectric response explaining the temperature dependent behavior. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773983]

Synchronized switch damping on inductor offers a high damping performance in a broad frequency range. It consists of an inductor and resistor in a serial configuration, which are connected and disconnected from the piezoceramics in an alternating manner by a switch. When the switch is triggered by the vibration itself, it adapts to different excitation frequencies especially in the low frequency range. This article presents a detailed study of the damping performance of the synchronized switch damping on inductor technique. Calculations are performed in a normalized way. The optimal tuning of synchronized switch damping on inductor network parameters is derived, and the corresponding maximum damping performance is obtained. The results are further compared to standard linear inductance-resistance networks. For a validation of the theoretical results, measurements on a clamped beam test rig are performed. Therefore, the synchronized switch damping on inductor circuit is realized as a synthetic impedance in a DSpace environment. The measurement results are in good agreement with the theoretical calculations. © The Author(s) 2012.

Presented at the 2nd Multifunctional Materials for Defense Workshop in conjunction with the 2012 Annual Grantees'/Contractors' Meeting for AFOSR Program on Mechanics of Multifunctional Materials & Microsystems held 30 July - 3 August 2012 in Arlington, VA. Sponsored by AFRL, AFOSR, ARO, NRL, ONR, and ARL. U.S. Government or Federal Rights License

Piezoelectric composites were prepared by dielectrophoretic alignment of high aspect ratio piezoelectric particles in a thermosetting polymer matrix. A high level of alignment was achieved in the cured composite from a resin containing randomly oriented high aspect ratio particles. Upon application of an electric field during curing of the resin, the particles were found to rotate with their long axes in the direction of the electric field, before coalescing to form chains. The dielectric and piezoelectric properties of the structured composites are well described by an analytical model for composites containing particles arranged into chains. The influence of degree of rotation and aspect ratio of the individual particles as well as their spacing is described with this model. The results correlate with the experimental values for both permittivity and piezoelectric constants in the poling direction. Dielectric and piezoelectric properties were significantly improved with respect to randomly dispersed piezoelectric ceramic powder–polymer composites and the maximum g33 was shifted to a lower volume fraction. The results could have implications for development of dielectric and piezoelectric (nano-)fiber composites for dielectrics such as embedded capcitors, as well as piezoelectrics for sensing and energy harvesting applications., Aerospace Materials & Manufacturing, Aerospace Engineering

Piezoelectric composites were prepared by dielectrophoretic alignment of high aspect ratio piezoelectric particles in a thermosetting polymer matrix. A high level of alignment was achieved in the cured composite from a resin containing randomly oriented high aspect ratio particles. Upon application of an electric field during curing of the resin, the particles were found to rotate with their long axes in the direction of the electric field, before coalescing to form chains. The dielectric and piezoelectric properties of the structured composites are well described by an analytical model for composites containing particles arranged into chains. The influence of degree of rotation and aspect ratio of the individual particles as well as their spacing is described with this model. The results correlate with the experimental values for both permittivity and piezoelectric constants in the poling direction. Dielectric and piezoelectric properties were significantly improved with respect to randomly dispersed piezoelectric ceramic powder–polymer composites and the maximum g33 was shifted to a lower volume fraction. The results could have implications for development of dielectric and piezoelectric (nano-)fiber composites for dielectrics such as embedded capcitors, as well as piezoelectrics for sensing and energy harvesting applications., Aerospace Materials & Manufacturing, Aerospace Engineering

We present a modular high-vacuum setup for the electrical characterization of single molecules down to liquid helium temperatures. The experimental design is based on microfabricated mechanically controllable break junctions, which offer control over the distance of two electrodes via the bending of a flexible substrate. The actuator part of the setup is divided into two stages. The slow stage is based on a differential screw drive with a large bending range. An amplified piezoceramic actuator forms the fast stage of the setup, which can operate at bending speeds of up to 800 ?m/s. In our microfabricated break junctions this is translated into breaking speeds of several 10 nm/s, sufficient for the fast acquisition of large statistical datasets. The bandwidth of the measurement electronics has been optimized to enable fast dI/dV spectroscopy on molecular junctions with resistances up to 100 M?. The performance of the setup is demonstrated for a ?-conjugated oligo(phenyleneethynylene)-dithiol molecule., QN/Quantum Nanoscience, Applied Sciences

We present a modular high-vacuum setup for the electrical characterization of single molecules down to liquid helium temperatures. The experimental design is based on microfabricated mechanically controllable break junctions, which offer control over the distance of two electrodes via the bending of a flexible substrate. The actuator part of the setup is divided into two stages. The slow stage is based on a differential screw drive with a large bending range. An amplified piezoceramic actuator forms the fast stage of the setup, which can operate at bending speeds of up to 800 ?m/s. In our microfabricated break junctions this is translated into breaking speeds of several 10 nm/s, sufficient for the fast acquisition of large statistical datasets. The bandwidth of the measurement electronics has been optimized to enable fast dI/dV spectroscopy on molecular junctions with resistances up to 100 M?. The performance of the setup is demonstrated for a ?-conjugated oligo(phenyleneethynylene)-dithiol molecule., QN/Quantum Nanoscience, Applied Sciences

The determination of the characteristic frequencies of an electromechanical resonance is not enough data to obtain material properties of piezoceramics, including all losses, from complex impedance measurements. Besides, values of impedance around resonance and antiresonance frequencies are also required to determine the material losses. Uncoupled resonances are needed for this purpose. The shear plates used for the material characterization present unavoidable mode coupling of the shear mode and other modes of the plate. A study of the evolution of the complex material coefficients as the coupling of modes evolves with the change in the aspect ratio (lateral dimension/thickness) of the plate is presented here. These are obtained by Alemany et al. software. A soft commercial PZT ceramic was used in this study and a number of shear plates amenable to material characterization were obtained in the range of aspect ratios below 15. The validity of the material properties for 3-D modelling of piezoceramics is assessed by means of Finite Element Analysis (FEA), which shows that uncoupled resonances are virtually pure thickness driven shear modes.

This letter investigates the nonlinear response of a bimorph energy harvester comprised of lead zirconate titanate (PZT-5A) laminates. For near resonant excitations, we demonstrate significant intrinsic nonlinear behavior despite geometrically linear motion. Fourth order elastic and electroelastic tensor values for PZT-5A are identified following methods recently published concerning a PZT-5H bimorph. A response trend indicative of a nonlinear dissipative mechanism is discussed as well as the inadequacy of linear modeling. The PZT-5A bimorph exhibits an increased softening frequency response in comparison to PZT-5H. The results contained herein are also applicable to electroelastic sensor and actuator technologies. (C) 2010 American Institute of Physics. [doi:10.1063/1.3530449]

This letter investigates the power generation and shunt damping performance of the single crystal piezoelectric ceramic lead magnesium niobate-lead zirconate titanate (PMN-PZT) analytically and experimentally. PMN-PZT is a recently developed interface for energy harvesting and shunt damping with its large piezoelectric constant (-2252 pm/V) and coupling coefficient (0.95) for the transverse piezoelectric mode. A unimorph PMN-PZT cantilever with an aluminum substrate is tested under base excitation and its electromechanical response is predicted with a coupled distributed parameter model. The power generation performance of the device is 138 mu W/(g(2) cm(3)) at 1744 Hz, causing 84% tip vibration attenuation due to the resistive shunt damping effect.

In this work, the contribution of the extrinsic effect to the macroscopic properties in soft and hard lead zirconate titanate ceramics is directly evaluated. Close to the room temperature, poled hard ceramics show an anomalous behavior, which is notably different from that of soft ceramics, not only in dielectric but also in piezoelectric and elastic responses. Hence, at room temperature their properties are thermally stable and the losses are unusually low. It is suggested that two mechanisms are present, with one mechanism inhibiting the other., Peer Reviewed, Postprint (published version)

Resonant sensors are based on the adsorption of a mass delta m of the biological or chemical agent on the surface of the resonant element. Corresponding antibodies with efficiency x are deployed on the resonator face. The adsorption gets detected by a reduction y =delta omega/omega =-kappa delta m/m of the resonance frequency omega of the ZnO crystal. However, the latter is also subject to fundamental Q1/f frequency fluctuations with spectrum S-y(f). The quantum 1/f limit of detection is given by (delta m/m)(min)=(2ln2)(1/2)[S-y(1Hz)](1/2)/kappa., QC 20110628

Se estudia la dependencia entre la constante dieléctrica y las pérdidas con el campo eléctrico aplicado, así como entre la constante dieléctrica y las pérdidas dieléctricas. Los resultados muestran que las cerámicas PZT duras no pueden ser decritas por el modelo de Rayleigh, pues la respuesta histerética de estos materiales no puede ser atribuida exclusivamente a la contribución de procesos irreversibles. Las medidas experimentales muestran la existencia de procesos reversibles, relacionados con movimientos de arqueo de dominios que contribuyen a la constante dieléctrica sin producir pérdidas. Esta contribución reversible es independiente del envejecimiento de la cerámica., Peer Reviewed

Ceramics of composition Bi3TiNbO9 (BTN) and perovskite-layered structure (Aurivillius type) [B. Aurivillius, Ark. Kemi 1, 463 (1949)] were processed by natural sintering and hot pressing from amorphous precursors. Precursors were obtained by mechanochemical activation of stoichiometric mixtures of oxides. These materials are in general interesting for their use as high-temperature piezoelectrics. Among them, BTN possesses the highest ferroparaelectric phase-transition temperature (>900 °C). The transition temperature establishes the working limit of the ceramic and the electric properties, especially the dc conductivity, affect on its polarizability. In this work, dielectric studies of BTN ceramics with controlled texture and microstructure have been made at 1, 100 KHz, and 1 MHZ and in the temperature range from 200 °C up to the ferroparaelectric transition temperature. Values of ~250 at 200 °C are achieved in ceramics hot pressed at temperatures as low as 700 °C for 1 h.

[EN] The environmental protection issues are driving forces nowadays in the scientific research on materials. From this point of view, it is a need to find alternatives to the present commercial piezoceramics, based on lead titanates-zirconates. The production of these materials requires handling of big amounts of lead oxide, which is highly toxic. Alkaline niobate piezoceramics are considered a good alternative for the future substitution of commercial piezoceramics by lead-free materials. However, the processing of these ceramics is difficult by conventional ceramic routes. There is a need to search for new routes of processing. The mechanochemical activation was used in this work for the first time to get Na1-xLixNbO3 ceramics in the Na rich region. Stoichiometric mixtures of Na2CO3 or Na2O, Li2CO3 and Nb2O5 were activated in a vibrating mill. A progressive broadening of the X-ray diffraction peaks of the mixtures was observed as the milling time increased. Nevertheless, the precursors did not became fully amorphous. The thermal evolution of the activated precursors was also tested. Ceramics were obtained by sintering or hot pressing and their piezoelectric properties were studied., [ES] La protección medioambiental es uno de los factores que impulsan diversas áreas de la investigación en materiales. Existe la necesidad de la búsqueda de alternativas a las cerámicas ferro-piezoeléctricas comerciales basadas en los titanatos-circonatos de plomo, que requieren el manejo de grandes cantidades de óxido de plomo, muy tóxico, en su procesado. Los niobatos alcalinos se consideran buenos candidatos para esta sustitución. Sin embargo, es difícil conseguir cerámicas con altas densificaciones. De aquí la necesidad de investigar nuevas rutas de procesado. La activación mecanoquímica se ha utilizado por primera vez en este trabajo para obtener cerámicas de Na1-xLixNbO3, en la región rica en Na. Se han activado mecanoquímicamente mezclas estequiométricas de Na2CO3 o Na2O, Li2CO3 y Nb2O5 en un molino vibratorio. Se ha observado el progresivo ensanchamiento de los picos de difracción de rayos X de las mezclas a medida que se aumentaba el tiempo de molienda, pero los precursores no llegan a ser amorfos para la difracción de rayos X. A partir de estos precursores se han obtenido cerámicas mediante sinterización o prensado en caliente y estudiado sus propiedades piezoeléctricas.

This paper describes the optimization of a piezoelectric-driven synthetic jet actuator based on a Lumped Element Modeling (LEM). To simplify the problem, this papers splits the optimization problem into two parts. First, a constrained optimization of the cavity volume and orifice dimensions of two baseline synthetic jets, each with a given piezoelectric diaphragm, is conducted using two different objective functions. One seeks to improve the centerline output velocity over a broad frequency range, and the other maximizes the centerline velocity at a prescribed resonant frequency of the device. Significant improvements are achieved using both objective functions for both synthetic jets. Second, the two baseline piezoelectric diaphragms have been optimized using two configurations. One uses the standard inner-disc piezoceramic patch bonded to a metal shim, while the other employs an outer piezoceramic ring. In each case, the objective is to maximize the achievable volume displacement of the diaphragm at the coercive electric field strength of the piezoceramic, while the natural frequency of the piezoelectric diaphragm is constrained to be greater than or equal to the baseline designs. Both configurations yield modest (~5%) improvements for one diaphragm and significant improvements for the other diaphragm (>50%)., Presented at the Aerospace Sciences Meeting and Exhibit (41st) held in Reno, NV on 6-9 Jan 2003. Published in the Proceedings of the Aerospace Sciences Meeting and Exhibit (41st), Paper AIAA 2003-0635, 2003. Sponsored in part by NASA Langley. The original document contains color images.

To meet the requirements of development for smart or intelligent structures in civil engineering, new functional materials that have good compatibility with civil engineering structural materials are needed. In this study, for the first time in the field of piezoelectric materials, cement-based 0-3 piezoelectric (PZT) composites were fabricated by the normal mixing and spreading method. The new materials have very good compatibility with portland cement concrete. The cement-based 0-3 piezoelectric composites were shown to have a slightly higher piezoelectric factor and electromechanical coefficient than those of 0-3 PZT/polymer composites with a similar content of PZT particles; thus, they are adequate for sensor application. There is potential for the application of cement-based 0-3 PZT composites in civil engineering because of their better piezoelectric properties and good compatibility with portland cement concrete.

To meet the requirements of development for smart or intelligent structures in civil engineering, new functional materials that have good compatibility with civil engineering structural materials are needed. In this study, for the first time in the field of piezoelectric materials, cement-based 0-3 piezoelectric (PZT) composites were fabricated by the normal mixing and spreading method. The new materials have very good compatibility with portland cement concrete. The cement-based 0-3 piezoelectric composites were shown to have a slightly higher piezoelectric factor and electromechanical coefficient than those of 0-3 PZT/polymer composites with a similar content of PZT particles; thus, they are adequate for sensor application. There is potential for the application of cement-based 0-3 PZT composites in civil engineering because of their better piezoelectric properties and good compatibility with portland cement concrete.

To meet the requirements of development for smart or intelligent structures in civil engineering, new functional materials that have good compatibility with civil engineering structural materials are needed. In this study, for the first time in the field of piezoelectric materials, cement-based 0-3 piezoelectric (PZT) composites were fabricated by the normal mixing and spreading method. The new materials have very good compatibility with portland cement concrete. The cement-based 0-3 piezoelectric composites were shown to have a slightly higher piezoelectric factor and electromechanical coefficient than those of 0-3 PZT/polymer composites with a similar content of PZT particles; thus, they are adequate for sensor application. There is potential for the application of cement-based 0-3 PZT composites in civil engineering because of their better piezoelectric properties and good compatibility with portland cement concrete.

Experimental results of the sensory effect of a cement matrix 2-2 piezoelectric composite are presented. The purpose of the research is to develop a self-sensing actuator exclusively for use in intelligent structures in the civil engineering field. The composite was fabricated by casting cement-based mortar into a series of pre-arranged piezoelectric thin plates. Different from most research work on piezoelectric materials, the current research focuses on the electromechanical properties and mechanical properties of the piezoelectric composite at relatively low frequencies (0.1 to 50 Hz) due to the special requirements for intelligent structures in the civil engineering field. In this frequency range, linear elastic behavior was observed for the composite. Viscosity or hysteresis, which often exists in some polymer matrix piezoelectric composites, was not observed. A complex math form was adopted to characterize the piezoelectric coefficients. It was found that the magnitude of the composite piezoelectric coefficients exhibited a linear dependency on the frequency, while the phase had an asymptotic dependency on the frequency. In the load range used, no dependency of the piezoelectric coefficients on load level was found for the composite.

Experimental results of the sensory effect of a cement matrix 2-2 piezoelectric composite are presented. The purpose of the research is to develop a self-sensing actuator exclusively for use in intelligent structures in the civil engineering field. The composite was fabricated by casting cement-based mortar into a series of pre-arranged piezoelectric thin plates. Different from most research work on piezoelectric materials, the current research focuses on the electromechanical properties and mechanical properties of the piezoelectric composite at relatively low frequencies (0.1 to 50 Hz) due to the special requirements for intelligent structures in the civil engineering field. In this frequency range, linear elastic behavior was observed for the composite. Viscosity or hysteresis, which often exists in some polymer matrix piezoelectric composites, was not observed. A complex math form was adopted to characterize the piezoelectric coefficients. It was found that the magnitude of the composite piezoelectric coefficients exhibited a linear dependency on the frequency, while the phase had an asymptotic dependency on the frequency. In the load range used, no dependency of the piezoelectric coefficients on load level was found for the composite.

Experimental results of the sensory effect of a cement matrix 2-2 piezoelectric composite are presented. The purpose of the research is to develop a self-sensing actuator exclusively for use in intelligent structures in the civil engineering field. The composite was fabricated by casting cement-based mortar into a series of pre-arranged piezoelectric thin plates. Different from most research work on piezoelectric materials, the current research focuses on the electromechanical properties and mechanical properties of the piezoelectric composite at relatively low frequencies (0.1 to 50 Hz) due to the special requirements for intelligent structures in the civil engineering field. In this frequency range, linear elastic behavior was observed for the composite. Viscosity or hysteresis, which often exists in some polymer matrix piezoelectric composites, was not observed. A complex math form was adopted to characterize the piezoelectric coefficients. It was found that the magnitude of the composite piezoelectric coefficients exhibited a linear dependency on the frequency, while the phase had an asymptotic dependency on the frequency. In the load range used, no dependency of the piezoelectric coefficients on load level was found for the composite.

This study evaluates the effectiveness of actively controlled piezoceramics with positive position feedback (PPF) for reducing structural vibrations. A comparison is made between active control with PPF and a parallel resistor-inductor (RLC) shunt technique. The primary objectives of this study are to: 1. Explore the feasibility of using smart materials and fiber optics for simultaneous health monitoring and active damping of a representative aircraft panel. 2. Determine how optical fiber sensors may be used to detect vibration modes of an aircraft panel by investigating their use on a representative test article. 3. Determine how piezoelectric patches may be used to detect and counteract fundamental resonances of a representative test article. 4. Determine a control algorithm and hardware system to increase substantially the damping in the fundamental mode of the representative test article over a wide temperature range. 5. Develop a health-monitoring algorithm based on fiber optic sensors to detect impedance changes in a representative test article. 6. Make a comparison between active control with PPF and an RLC shunt technique. To achieve the objectives of this study, a special test rig was used to evaluate the performance of piezoelectric materials (PZTs) for vibration suppression. The test rig was used to rigidly clamp a flat 20-guage steel plate, and then excite the plate in various frequency ranges with an electromagnetic shaker. For each test, a data acquisition system was used to acquire the data to evaluate the performance of each PPF controller. Once the data was obtained, a comparison was made between active damping with PPF and passive damping with the RLC shunt technique. The active damping technique used for this study combined piezoelectric actuators with fiber optic sensors to achieve simultaneous active control and health monitoring of a test plate. The results of the active damping tests show that piezoelectric materials can provide substantial na

Weight is a critical parameter in the design of any system launched into space. Current launch costs are on the order of 10,000 dollars per pound of payload capacity. Reducing weight and thus increasing payload capacity is always in the forefront of the design process. One method of increasing the payload capacity of launch vehicles is to reduce the acoustic environment in the interior of the fairing. A major problem is that passive methods currently used for noise suppression do not exhibit significant energy dissipation at low frequencies. This motivates the use of active noise control. Using active noise control for frequencies below 200 to 300 Hz in addition to the passive control means has potential to provide broadband noise suppression and thus a smoother, cheaper ride for any payload. The problem with this technique is that active noise control commonly uses electromagnetic speakers as the control element. The weight of the speaker adds more cost to the application due to the approximate cost per pound to send a launch vehicle and payload to space. At 10,000 dollars per pound of payload capacity, the added cost spent on protecting the payload can potentially reduce the amount of payload capacity a customer receives due to monies spent on non-payload mass. Therefore, necessity dictates a light weight noise control solution. This work investigates the feasibility of a transducer with less mass than that of a conventional loudspeaker which dissipates energy at the acoustic resonances of an enclosed cavity. The test setup involves using the transducer to lower the sound pressure levels of acoustic resonances which are excited by an external source, thus simulating the launch phase of a launch vehicle. The transducer is used as an actuator to add damping through feedback control. The transducer is comprised of three thin flexures that are actuated by piezoceramic material attached to both sides. The flexures actuate a speaker cone that is attached to the end of t

Aircraft and satellite structures are exposed to a wide range of temperatures during normal operation cycles. These fluctuations in temperature may result in significant changes of the structural dynamics. Aircraft, automotive, and satellite structures are also subject to various vibration sources. Passive and active vibration suppression techniques have been developed to minimize acoustic noise and fatigue stress damage. Featuring low weight solutions and high performance, active control techniques are becoming increasingly common. Structures with varying dynamics require more sophisticated active control techniques, such as adaptive control. This research uses a special vibration test rig for evaluating the performance of different vibration suppression systems on a representative aircraft panel. The test panel is clamped rigidly in a frame and can be excited in various frequencies with an electromagnetic shaker. To simulate temperature fluctuations the temperature on the panel can be increased up to 65°C (150°F). Smart material based sensors and actuators are used to interface the mechanical system with the electronic controller. The active controller utilizes three positive position feedback (PPF) filters implemented through a digital signal processor board. This research develops two different adaptation methods to perform vibration suppression in the presence of thermally induced frequency changes of the representative panel. To adjust the PPF filter parameters an open-loop adaptation method and an auto-tuning method are investigated. The open-loop adaptation method uses a measurement of the plate temperature and a look-up table with pre-determined parameters to update the filters accordingly. The auto-tuning methods identifies the frequencies of the poles and zeros in the structure's collocated transfer function. From the knowledge of the pole and zero locations the optimal PPF parameters are calculated online. The results show that both adaptation methods ar

This study evaluates the effectiveness of actively controlled piezoceramics with positive position feedback (PPF) for reducing structural vibrations. A comparison is made between active control with PPF and a parallel resistor-inductor (RLC) shunt technique. The primary objectives of this study are to: 1. Explore the feasibility of using smart materials and fiber optics for simultaneous health monitoring and active damping of a representative aircraft panel. 2. Determine how optical fiber sensors may be used to detect vibration modes of an aircraft panel by investigating their use on a representative test article. 3. Determine how piezoelectric patches may be used to detect and counteract fundamental resonances of a representative test article. 4. Determine a control algorithm and hardware system to increase substantially the damping in the fundamental mode of the representative test article over a wide temperature range. 5. Develop a health-monitoring algorithm based on fiber optic sensors to detect impedance changes in a representative test article. 6. Make a comparison between active control with PPF and an RLC shunt technique. To achieve the objectives of this study, a special test rig was used to evaluate the performance of piezoelectric materials (PZTs) for vibration suppression. The test rig was used to rigidly clamp a flat 20-guage steel plate, and then excite the plate in various frequency ranges with an electromagnetic shaker. For each test, a data acquisition system was used to acquire the data to evaluate the performance of each PPF controller. Once the data was obtained, a comparison was made between active damping with PPF and passive damping with the RLC shunt technique. The active damping technique used for this study combined piezoelectric actuators with fiber optic sensors to achieve simultaneous active control and health monitoring of a test plate. The results of the active damping tests show that piezoelectric materials can provide substantial na

Piezoelectricity was first discovered by the Curie brothers in 1880. During the 1940s, piezoelectric ceramic materials were first used in commercial devices, and new materials and other applications have continued to develop over the years. Most recently, however, relaxor-based ferroelectric single crystals have been produced. In most cases, these single-crystal material properties, exceed those of conventional piezoelectric ceramics. The purpose of this study was to determine the current commercial and military uses of the piezoelectric materials, the properties that are important to these uses, and the impact of substituting single-crystal materials for the piezoelectric materials. Service and Defense agency piezoelectric development programs are discussed, as is the possibility of restructuring these programs to take advantage of the single-crystal materials. Novel military uses for single-crystal piezoelectric materials are given, and important commercial applications for single-crystal piezoelectric materials are identified. Finally, issues such as design modifications needed to produce devices using the single crystals are addressed.

The Navy has an immediate need for large-scale, 3D, nonlinear simulations of broadband sonar projectors. The example considered here is a volume array of high-power, electrostrictive (PMN) flextensionals. Analysis and design of these complex arrays are clearly pushing the limits of simplified models. The analytical burden should be shifted from clever but overextended designers to computers. Very large-scale models, broadband response and nonlinearity favor explicit time-domain methods over implicit time- or frequency-domain methods. We demonstrate comprehensive finite element modeling of an icosahedral array of 12 electrostrictive flextensionals. Behavior of the PMN driver is illustrated with a 1D finite element (nonlinear harmonic oscillator) and generalized to a 3D element. Full-scale, SMP simulations are shown for individual flextensionals and the icosahedral array including tow-body structure., Presented at the IEEE International Ultrasonics Symposium, held in Toronto, Ontario on 5-8 October 1997. Publiashed in the Proceedings of the IEEE International Ultrasonics Symposium, October 1997. The original document contains color images.

Smart materials such as SMA and piezoelectric materials offer promising applications in many adaptive structures enabling the development of new structural control. Potential applications include shape control of large space structures, active noise and vibration control, flutter suppression, and microservoelasticity in flight vehicles. To deliver the maximum actuation power, piezoelectric actuators are subjected to high electric fields and strains. The development of reliability and life prediction methodologies for piezoceramics is of vital importance to the technology of smart structures. The result of this research concerning the behavior of fracture and fatigue crack growth in PZT piezoceramics under combined electrical and mechanical loads is an important step to the aforementioned goal.

The Office of Naval Research (ONR) and Office of Naval Research European Office (ONR Europe) recently sponsored an international workshop on advances in piezoelectric materials and current research thrusts in Europe. 'Perspectives on Piezoelectric Materials Research' was held at Elvetham Hall, near Basingstoke, England, 21-24 February 1993. The 27 invited delegates were drawn from industry, academia, and government research organizations in nine countries Denmark, France, the Federal Republic of Germany (FRG), Italy, Slovenia, Spain, Switzerland, the United Kingdom (U.K.), and the United States (U.S.). Abstracts and viewgraphs from the international meeting have been included in this report. Piezoelectric, Polycrystalline, Poling, Curie point, Magnetics

This thesis details the further refinement of the Naval Postgraduate School's Flexible Spacecraft Simulator and the first successful experimental control of the flexible system. The major emphasis of this work has been the development of a system to provide active damping to aid in control of the flexible modes of the system. The completed design of the circuit and the choice and placement of the piezoceramic sensors and actuators are presented. Verification of the computer model of the flexible system without active damping was completed and comparisons between the analytical and the experimental results are presented for simple proportional-derivative (PD) control using the main body angular position and rate.

Tématem diplomové práce je syntéza a následná příprava bezolovnaté piezokeramiky s perovskitovou strukturou, konkrétně draselno-sodného niobátu (KNN). V teoretické části jsou popsány možnosti syntéz KNN prášku, jeho tvarování a slinování. Experimentální část se věnuje třem typům popsaných syntéz – reakci v pevné fázi, hydrotermální syntéze, sol-gel syntéze, následnému zpracování vzniklých KNN prášků pomocí uniaxálního lisování, metody CIP (cold isostatic pressure), slinování (klasické v peci, případně SPS – spark plasma sintering) takto připravených těles a jejich následné vlastnosti – hustota, velikost zrna a nábojová konstanta. Pomocí každé z metod byl připraven čistý KNN prášek, který byl tvarován a slinován. Nejlepších vlastností dosahovaly vzorky slinuté pomocí SPS, které vykazovaly nejvyšší hustotu a nejnižší nárůst zrna., The topic of this thesis is synthesis and preparation of lead-free pizoceramic with perovskite structure, in particular potassium-sodium niobate (KNN). In theoretical part are described possibilities of KNN synthesis and of it’s shaping and sintering. Experimental part deals with three types of synthesis described in the theretical part – solid state reaction, hydrothermal synthesis, sol-gel synthesis, and subconsequentional shaping of prepared powders by uniaxial pressing, cold isostatic pressure method, sintering (classical in oven, in some cases SPS – spark plasma sintering) of such green body and their following properties like relative density, grain size or charge constant. Preparation of KNN powder by each described method took place, followed by shaping and sintering. Best properties were shown by SPS sintered samples, which reached the highest density and lowest grain growth.

Tato práce se zabývá simulačním modelováním a analýzou piezoelektrického tlačítkového generátoru energie. Model tohoto generátoru byl vytvořen v prostředí ANSYS. Součástí této práce je i stručné seznámení s piezo problematikou., This thesis focuses on simulation modelling of a piezoelectric button power generator. A model of this generator is created in the programme ANSYS. An introductory chapter on piezoelectricity is also included.