Showing papers on "Piezoelectricity published in 1999"
TL;DR: Ferroelectric ceramics have been the heart and soul of several multibillion dollar industries, ranging from high-dielectric-constant capacitors to later developments in piezoelectric transducers, positive temperature coefficient devices, and electrooptic light valves as mentioned in this paper.
Abstract: Ferroelectric ceramics were born in the early 1940s with the discovery of the phenomenon of ferroelectricity as the source of the unusually high dielectric constant in ceramic barium titanate capacitors. Since that time, they have been the heart and soul of several multibillion dollar industries, ranging from high-dielectric-constant capacitors to later developments in piezoelectric transducers, positive temperature coefficient devices, and electrooptic light valves. Materials based on two compositional systems, barium titanate and lead zirconate titanate, have dominated the field throughout their history. The more recent developments in the field of ferroelectric ceramics, such as medical ultrasonic composites, high-displacement piezoelectric actuators (Moonies, RAINBOWS), photostrictors, and thin and thick films for piezoelectric and integrated-circuit applications have served to keep the industry young amidst its growing maturity. Various ceramic formulations, their form (bulk, films), fabrication, function (properties), and future are described in relation to their ferroelectric nature and specific areas of application.
3,442 citations
TL;DR: In this paper, a thin-film bulk acoustic resonator (TFBAR) with fundamental resonance at 3.6 GHz has been fabricated to assess resonator properties, and the material parameters derived from the thickness resonance were a coupling factor k=0.23 and a sound velocity vs.
Abstract: Aluminum nitride thin films have been grown by reactive magnetron sputter technique using a pulsed power supply. The highly (002)-textured columnar films deposited on platinized silicon substrates exhibited quasi-single-crystal piezoelectric properties. The effective d33 was measured as 3.4 pm/V, the effective e31 as 1.0 C/m2. The pyroelectric coefficient turned out to be positive (4.8 μC m−2 K−1) due to a dominating piezoelectric contribution. Thin-film bulk acoustic resonators (TFBAR) with fundamental resonance at 3.6 GHz have been fabricated to assess resonator properties. The material parameters derived from the thickness resonance were a coupling factor k=0.23 and a sound velocity vs=11 400 m/s. With a quality factor Q of 300, the TFBARs proved to be apt for filter applications. The temperature coefficient of the frequency could be tuned to practically 0 ppm/K.
415 citations
TL;DR: In this paper, the authors investigated the piezoelectric properties of barium titanate single crystals at room temperature as a function of crystallographic orientation, and showed that electric field exposure below 6 kV/cm resulted in a high d33 of 203 pC/N and a hysteresis-free strain vs electric-field behavior, which suggested the formation of an engineered domain configuration.
Abstract: Piezoelectric properties of barium titanate single crystals were investigated at room temperature as a function of crystallographic orientation. When a unipolar electric field was applied along [001], its strain vs electric-field curve showed a large hysteresis, and finally barium titanate crystal became to single-domain state with piezoelectric constant d33 of 125 pC/N over 20 kV/cm. On the other hand, electric-field exposure below 6 kV/cm along [111] resulted in a high d33 of 203 pC/N and a hysteresis-free strain vs electric-field behavior, which suggested the formation of an engineered domain configuration in a tetragonal barium titanate crystal. Moreover, when an electric field over 6 kV/cm was applied along [111], two discontinuous changes were observed in its strain vs electric-field curve. In situ domain observation and Raman measurement under an electric field suggested an electric-field-induced phase transition from tetragonal to monoclinic at around 10 kV/cm, and that from monoclinic to rhombohedral at around 30 kV/cm. Moreover, in a monoclinic barium titanate crystal, electric-field exposure along [111] resulted in the formation of another new engineered domain configuration with d33 of 295 pC/N.
351 citations
TL;DR: The effective piezoelectric transverse coefficient e(31,f) was measured on various lead zirconate-titanate (PZT) and aluminum nitride thin films.
Abstract: The effective piezoelectric transverse coefficient e(31,f) was measured on various lead zirconate-titanate (PZT) and aluminum nitride thin films. The measurement set-up is based on the collection of the electric charges created by the forced deflection of a Si cantilever coated with a piezoelectric material. The maximum value was obtained from a tetragonal composition of PZT (45/55 Zr/Ti ratio) and was equal to 8.3 C/m(2). The ALN layer exhibited 97% of the theoretical value calculated from single crystal data, i.e., e(31,f)- = 1.02 C/m(2) (C) 1999 Elsevier Science S.A. All rights reserved.
269 citations
TL;DR: In this article, a new solution to the force, displacements, and charges developed in piezoelectric beams is derived, which determines the neutral axis where the bending strains are zero and results in a closed form solution (without matrix inversion).
Abstract: A new solution to the force, displacements, and charges developed in piezoelectric beams is derived. Differing from previous solutions, this development determines the neutral axis where the bending strains are zero and results in a closed form solution (without matrix inversion). With the closed form, simplifications become evident which increase understanding and facilitate calculations. These equations are than expanded to account for axial, built-in strains in the beam. A design example where axial forces exerted by the piezoelectric layer are important is presented.
254 citations
TL;DR: Calculation results on four unimorph actuators indicate that the use of stiffer elastic material is preferred to increase electromechanical coupling and output mechanical energy in unimorph automaton actuators.
Abstract: Electromechanical coupling mechanisms in piezoelectric bending actuators are discussed in this paper based on the constitutive equations of cantilever bimorph and unimorph actuators. Three actuator characteristic parameters, (e.g., electromechanical coupling coefficient, maximum energy transmission coefficient, and maximum mechanical output energy) are discussed for cantilever bimorph and unimorph actuators. In the case of the bimorph actuator, if the effect of the bonding layer is negligible, these parameters are directly related to the transverse coupling factor lest. In the case of the unimorph actuator, these parameters also depend on the Young's modulus and the thickness of the elastic layer. Maximum values for these parameters can be obtained by choosing proper thickness ratio and Young's modulus ratio of elastic and piezoelectric layers. Calculation results on four unimorph actuators indicate that the use of stiffer elastic material is preferred to increase electromechanical coupling and output mechanical energy in unimorph actuators.
236 citations
TL;DR: In this paper, measurements of piezoelectric coefficients d33 and d31 in wurtzite GaN and AlN using an interferometric technique are presented.
Abstract: Measurements of piezoelectric coefficients d33 and d31 in wurtzite GaN and AlN using an interferometric technique are presented. We report on the clamped values, d33c of these coefficients found in GaN and AlN thin films, and we derive the respective bulk values, d33b. The clamped value of d33c in GaN single crystal films is 2.8±0.1 pm V−1 which is 30% higher than in polycrystalline films grown by laser assisted chemical vapor deposition. The value of d33b in bulk single crystal GaN is found to be 3.7±0.1 pm V−1. The value of d33c in plasma assisted and laser assisted chemical vapor deposited AlN films was 3.2±0.3 and 4.0±0.1 pm V−1, respectively. The bulk value estimate of d33b in AlN of 5.6±0.2 pm V−1 was deduced. The values of d31, both clamped and bulk, were calculated for wurtzite GaN and AlN. We have also calculated the values of d14 in cubic phase film and bulk GaN and AlN. Interferometric measurements of the inverse piezoelectric effect provide a simple method of identifying the positive direction...
226 citations
TL;DR: In this paper, the nonlinear electromechanical behavior of cantilevered piezoelectric ceramic bimorph, unimorph, and reduced and internally biased oxide wafer actuators is studied in a wide electric field and frequency range.
Abstract: The nonlinear electromechanical behavior of cantilevered piezoelectric ceramic bimorph, unimorph, and reduced and internally biased oxide wafer actuators is studied in a wide electric field and frequency range. It is found that under quasistatic condition, linear relationships between actuator tip displacement-electric field, and blocking force-electric field are only valid under weak field driving. With increasing the driving field, electromechanical nonlinearity begins to contribute significantly to the actuator performance because of ferroelectric hysteresis behavior associated with piezoelectric lead zirconate titanate (PZT)-type ceramic materials. The bending resonance frequencies of all these actuators vary with the magnitude of the electric field. The decrease of resonance frequency with electric field is explained by the increase of elastic compliance of PZT ceramic due to elastic nonlinearity. Mechanical quality factors of the actuators also depend on the magnitude of electric field strength. No significant temperature increase is observed when actuators are driven near resonance frequency under high electric field.
225 citations
TL;DR: In this article, the authors show that simple heat conduction from porous silicon to air results in high-intensity ultrasound without the need for any mechanical vibrational system, achieving an acoustic pressure of 0.1
Abstract: The most common mechanism1 for generating ultrasound in air is via a piezoelectric transducer, whereby an electrical signal is converted directly into a mechanical vibration. But the acoustic pressure so generated is usually limited to less than 10 Pa, the frequency bandwidth of most piezoelectric ceramics is narrow, and it is difficult to assemble such transducers into a fine-scale phase array with no crosstalk2,3. An alternative strategy using micromachined electrostatic diaphragms is showing some promise4,5, but the high voltages required and the mechanical weakness of the diaphragms may prove problematic for applications. Here we show that simple heat conduction from porous silicon to air results in high-intensity ultrasound without the need for any mechanical vibrational system. Our non-optimized device generates an acoustic pressure of 0.1 Pa at a power consumption of 1 W cm−2, and exhibits a flat frequency response up to at least 100 kHz. We expect that substantial improvements in efficiency should be possible. Moreover, as this material lends itself to integration with conventional electronic circuitry, it should be relatively straightforward to develop finely structured phase arrays of these devices, which would give control over the wavefront of the acoustic emissions.
216 citations
TL;DR: In this paper, the electric field dependence of the piezoelectric properties of rhombohedral 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3 crystals was investigated as a function of orientation with respect to the prototypic (cubic) axes.
Abstract: The electric field dependence of the piezoelectric properties of rhombohedral 0.955Pb(Zn1/3Nb2/3)O3–0.045PbTiO3 crystals were investigated as a function of orientation with respect to the prototypic (cubic) axes. For 〈111〉 oriented fields, depolarization and subsequent domain reorientation resulted in an apparent maximum in the piezoelectric coefficients occurring at ∼5 kV/cm, followed by nonhysteretic dij saturation, indicating a single domain state under bias. By extrapolation, single domain values for the piezoelectric coefficients d33 and d31 were determined to be 125 and −35 pC/N, respectively. The hydrostatic piezoelectric coefficient dh for single domain crystals was calculated to be ∼55 pC/N, coincident with the experimentally determined values under hydrostatic pressure. For 〈001〉 oriented fields, piezoelectric coefficients d33〈001〉 and d31〈001〉 as high as 2250 and −1000 pC/N were determined, respectively. Although a high value of dh〈001〉 (∼250 pC/N) was expected, the experimentally determined va...
214 citations
TL;DR: This paper presents the derivation of the constitutive equations of a symmetrical triple layer piezoelectric bender under different excitation conditions and analysis on the electromechanical behavior of the triple layer Piezoelectic bender is made.
Abstract: Piezoelectric triple layer benders, with a structure of two piezoelectric top and bottom layers sandwiched by a non-piezoelectric elastic central layer, are one of the most commonly used piezoelectric devices. In this paper, we present the derivation of the constitutive equations of a symmetrical triple layer piezoelectric bender under different excitation conditions. The constitutive equations are presented by a 4/spl times/4 matrix with an external moment M, an external tip force F, a uniform load p, and an applied electric voltage V as the extensive parameters, with the generated tip angular deflection (slope) /spl alpha/, tip deflection /spl delta/, volume displacement v, and electric charge Q as the internal parameters. Further analysis on the electromechanical behavior of the triple layer piezoelectric bender can be made on the constitutive equations.
TL;DR: In this paper, the authors analyzed the efficiency of piezoelectric ceramic for electric power generation and found that most energy is stored in the ceramic and returned to the mechanical port.
Abstract: This paper analyzes the efficiency of piezoelectric ceramic for purposes of electric power generation. An analytical model is presented which suggests that the primary problem of using PZT for electric power generation is that most energy is stored in the ceramic and returned to the mechanical port. The efficiency as a function of force input frequency and resistive load are derived based upon a linearized model of a commercially available PZT stack. The analysis yields counterintuitive results in that maximum efficiency occurs in a low frequency region, several orders of magnitude below the structural resonance of the stack. The analytical results are followed by presentation of experimental data that substantiate the model. The model is then utilized to show that. due to hysteresis in the ceramic, the efficiency of energy transfer is dependent on the amplitude of force input, and that greatest efficiencies can be achieved with maximum input forces.
TL;DR: In this article, a consistent experimental program has been developed to investigate the mechanical and electrical properties of polyvinylidene fluoride (PVDF), and the results of the study indicate that this piezoelectric polymer can be characterized as an orthotropic, thermorheologically simple material with constant PDE strain coefficients over the experimental range of stresses, frequencies and temperatures.
Abstract: A consistent experimental program has been developed to investigate the mechanical and electrical properties of polyvinylidene fluoride (PVDF). The results of the study indicate that this piezoelectric polymer can be characterized as an orthotropic, thermorheologically simple material with constant piezoelectric strain coefficients over the experimental range of stresses, frequencies and temperatures. The mechanical properties of PVDF are time-dependent and, under certain loading and temperature conditions, can be treated using the principles of linear hereditary viscoelasticity.
TL;DR: Although soft PZT ceramics can be easily stress depoled (losing piezoelectricity), a DC bias electric field can be employed to maintain the ceramic poling state so that the ceramic can be used at high stresses without depoling.
Abstract: In lead zirconate titanate piezoceramics, external stresses can cause substantial changes in the piezoelectric coefficients, dielectric constant, and elastic compliance due to nonlinear effects and stress depoling effects. In both soft and hard PZT piezoceramics, the aging can produce a memory effect that will facilitate the recovery of the poled state in the ceramics from momentary electric or stress depoling. In hard PZT ceramics, the local defect fields built up during the aging process can stabilize the ceramic against external stress depoling that results in a marked increase in the piezoelectric coefficient and electromechanical coupling factor in the ceramic under the stress. Although soft PZT ceramics can be easily stress depoled (losing piezoelectricity), a DC bias electric field, parallel to the original poling direction, can be employed to maintain the ceramic poling state so that the ceramic can be used at high stresses without depoling.
17 Oct 1999
TL;DR: In this paper, the parameters of the KLM and Mason's equivalent circuits in the thickness mode were compared under various boundary conditions with and without acoustic layers to the analytical solutions of the wave equation.
Abstract: The parameters of the KLM and Mason's equivalent circuits in the thickness mode are presented to include dielectric, elastic and piezoelectric loss. The models are compared under various boundary conditions with and without acoustic layers to the analytical solutions of the wave equation. We show that in all cases equivalence is found between the analytical solution and the KLM and Mason's equivalent circuit models. It is noted that in order to maintain consistency with the linear equations of piezoelectricity and the wave equation care is required when applying complex coefficients to the models. The effect of the piezoelectric loss component on the power dissipated in the transducer is presented for loaded and unloaded transducers to determine the significance of the piezoelectric loss to transducer designers. The effect of the piezoelectric loss on the insertion loss was found to be small.
TL;DR: In this article, the pyroelectric responses of ferroelectric Langmuir-Blodgett polymer films are less than the largest values measured with bulk films of the same composition.
Abstract: The piezoelectric and pyroelectric responses of ferroelectric Langmuir–Blodgett polymer films are less than the largest values measured with bulk films of the same composition. The films of the crystalline copolymer poly(vinylidene fluoride trifluoroethylene) fabricated by the Langmuir–Blodgett technique are 30 ML thick (15 nm) and are highly crystalline and oriented with polarization perpendicular to the film. Both piezoelectric and pyroelectric measurements show reversible ferroelectric switching. The films are suitable for use in pyroelectric infrared imaging and in piezoelectric acoustic transducers.
TL;DR: In this article, the photoluminescence decay time of excitons is used as a probe of internal electric fields in GaN-(Ga, Al)N quantum wells in various configurations of strain, well widths, and barrier widths.
Abstract: Very strong coefficients for spontaneous and piezoelectric polarizations have recently been predicted for III-V nitride semiconductors with natural wurtzite symmetry. Such polarizations influence significantly the mechanisms of radiative emissions in quantum-confinement heterostructures based on these materials. The photoluminescence decay time of excitons is used as a probe of internal electric fields in GaN-(Ga, Al)N quantum wells in various configurations of strain, well widths, and barrier widths. The measured decays are not only controlled by radiative lifetimes, which depend on the fields inside GaN wells but also on the nonradiative escape of carriers through Ga1 - xAlyN barriers, which depends on their widths and on the electric field in these layers. It is shown in particular that the magnitude of the held in the wells is not a simple function of the strain of these layers via the only piezoelectric effect, but rather the result of the interplay of spontaneous and piezoelectric polarizations in both well and barrier materials. [S0163-1829(99)02923-9].
TL;DR: In this article, the authors proposed a piezoelectric composites with product properties, which includes different assets of the phases and the interaction between the phases, determining the inhomogeneous distribution of stress, is essential.
TL;DR: In this paper, the authors studied the two-dimensional crack problem in a piezoelectric material containing an elliptic hole subjected to uniform remote loads and showed that the field intensity factors are the same as that of isotropic material.
TL;DR: In this article, a pneumatic pressure rig was designed to measure the effective d33 coefficient of thin film piezoelectrics by applying a known stress and monitoring the induced charge.
Abstract: A pneumatic pressure rig was designed to measure the effective d33 coefficient of thin film piezoelectrics by applying a known stress and monitoring the induced charge. It was found that the stress state imposed included components both perpendicular and parallel to the film plane. The later were due to friction and could largely be relieved through sliding of the O-rings to their equilibrium positions for a given pressure. The induced charge stabilized as equilibrium was reached and most of it was produced by the normal component of the stress. By minimizing the surface friction and compensating for the remnant in-plane stress, very good agreement was obtained among the d33 values measured by the Berlincourt method, double-beam interferometry and this method for a bulk lead zirconate titanate (PZT) sample. The d33 value of PZT thin films made by sol-gel processing was also measured. The as deposited films usually showed very weak piezoelectricity with d33 values ranging from 0 to 10 pC/N, indicating little pre-existing alignment of the domains. With increasing poling field, the d33 value also increased and saturated at poling fields exceeding three times the coercive field. Typically, films with thicknesses around 1 μm had d33 values of 100 pC/N. Good agreement between double-beam interferometry and this technique was also obtained for thin films. The small difference between the two measurements is attributed to the effect of mechanical boundary conditions on the effective d33 coefficient.
TL;DR: In this article, a finite element formulation of the piezoelectric vibrations of quartz resonators based on Mindlin plate theory is derived, and the vibration frequency, the vibration mode shapes and the electric potential distribution are obtained.
TL;DR: In this article, the electromechanical coupling factor, k 33 in the longitudinal mode was found to be 0.55, 0.43 and 0.47 for BNBT-6, BNTN-3 and KTNS, respectively.
Abstract: The use of lead-free materials in piezoelectric ceramics has recently become a very important issue in environmental protection of the earth. Some lead-free piezoelectric materials, namely bismuth sodium titanate, (Bi1/2Na1/2)TiO3 (BNT) – based solid solution ceramics, such as (1-a)BNT-a·BaTiO3 [BNBT], (1-b)BNT-b·NaNbO3 [BNTN] and a(Bi1/2Na1/2)TiO3-b KNbO3-c 1/2(Bi2O3·Sc2O3) [KTNS] (a+b+c=1) systems, were studied for their dielectric, ferroelectric and piezoelectric properties as candidates for a new family of lead-free piezoelectric ceramics. The electromechanical coupling factor, k 33 in the longitudinal mode was found to be 0.55, 0.43 and 0.47 for BNBT-6. BNTN-3 and KTNS, respectively. On particular, the amount of modified Bi3+ ions has an effect on k 33. Consequently these ceramics are potential candidates as lead-free piezoelectric ceramics.
TL;DR: In this article, the sensing effect of cantilever mounted piezoelectric bimorph unimorph and triple layer benders subjected to external mechanical excitations is discussed based on the constitutive equations of these bending devices.
Abstract: Piezoelectric bending mode elements such as bimorph and unimorph benders can be used as both actuation and sensing elements for a wide range of applications. As actuation elements, these devices convert electric input energy into output mechanical energy. As sensing elements, they convert external mechanical stimuli into electrical charge or voltage. In this article, the sensing effect of cantilever mounted piezoelectric bimorph unimorph and triple layer benders subjected to external mechanical excitations are discussed. General analytical expressions relating generated electric voltage (or charge) to the applied mechanical input excitations (moment M, tip force F, and body force p) are derived based on the constitutive equations of these bending devices. It is found that the clamping effect of each component in the bender devices decreases the dielectric constant. The bimorph bender has a higher voltage sensitivity than the unimorph or triple layer bender with the same geometrical dimensions. The dependence of voltage and charge sensitivities on the thickness ratio and the Young’s modulus ratio of the elastic layer and piezoelectric layer under different conditions are discussed and compared for the unimorph and triple layer benders.
TL;DR: In this paper, scaling of the ferroelectric and piezoelectric properties in Pt/SrBi2Ta2O9/Pt thin films was studied using focused ion beam milling.
Abstract: Scaling of the ferroelectric and piezoelectric properties in Pt/SrBi2Ta2O9/Pt thin films was studied. Focused ion beam milling was used to fabricate submicron devices (1×1, 0.5×0.5, 0.25×0.25, 0.09×0.09, and 0.07×0.07 μm2) and scanning force microscopy was used to examine their piezoelectric response. It was found that capacitors as small as 0.09×0.09 μm2 exhibit good piezoelectric/ferroelectric properties and that submicron (0.25×0.25 μm2) capacitors show resistance to bipolar fatigue with up to at least 109 cycles. The results were compared with similar capacitor structures milled in the Pb1.0(Nb0.04Zr0.28Ti0.68)O3 system where structures as small as 0.07×0.07 μm2 were analyzed.
TL;DR: In this paper, the surface potential of a thin ferroelectric thin film was measured using scanning probe microscopy with a small oscillating voltage between the probe tip and the substrate.
Abstract: Scanning probe microscopy was used to form local polarized domains in ferroelectric thin films by applying a voltage between the gold-coated cantilever and the conductive substrate in contact mode. Two methods of visualizing the poled areas are described. The first is to detect the piezoelectric response of the films by applying a small oscillating voltage between the probe tip and the substrate. This measurement determines the local ferroelectric polarity and domain structure directly. The second method is to measure the surface potential of the poled films using scanning Maxwell stress microscopy. This does not directly address the ferroelectric behavior of the film, but rather the potential due to surface charge. We determined the surface potential dependence on pulse voltage and duration applied to the ferroelectric film. The results demonstrate that the charged area will increase rapidly, but the surface potential will saturate as the pulse voltage and duration are increased. The resultant stable loc...
TL;DR: The effect of heteroepitaxy-induced constraint on the structure and piezoelectric properties of the relaxor ferroelectric lead magnesium niobate-lead titanate (PMN-PT) was investigated in this paper.
Abstract: The effect of heteroepitaxy-induced constraint on the structure and piezoelectric properties of the relaxor ferroelectric lead magnesium niobate–lead titanate (PMN–PT) were investigated. Relaxor PMN–PT epitaxial thin films with oxide electrodes were grown by pulsed-laser deposition on (100) LaAlO3 substrates. We observe a systematic decrease in the phase transition temperature (temperature at which a maximum in dielectric response occurs), from around 250 to around 60 °C as the relaxor thickness is increased from 100 to 400 nm. This is accompanied by an increase in the relative dielectric constant (er), measured at room temperature and 10 kHz, from 300 to 2000. The piezoelectric coefficient d33 measured using a scanned probe microscope, increase by almost an order of magnitude with increasing film thickness.
TL;DR: In this article, the authors studied the piezoelectric properties of lead-free bismuth layer structure oxide, SrBi4Ti4O15 (SBT) based ceramics, and found that the maximum value of Q (Qmax ) between resonant frequency and anti-resonant frequency was larger than that of SBT.
Abstract: Piezoelectric properties of lead-free bismuth layer structure oxide, SrBi4Ti4O15 (SBT) based ceramics, were studied. By means of La substitution and Mn addition, the maximum value of Q (Qmax ) between resonant frequency and anti-resonant frequency was larger than that of SBT. These materials could be utilized in practical applications as substitutes for lead titanate based ceramics (PT) and lead zirconate titanate based ceramics (PZT) which are used mainly in resonators. The reason for the higher Qmax value was identified by microstructual analysis as being due to the absence of a defect structure.
TL;DR: In this article, the authors deal with the modelling of 1 − 3 and 0 − 3 composites made of piezoceramic fibres embedded in a soft non-piezoelectric matrix.
TL;DR: In this paper, the direct piezoelectric effect is incorporated into beam theory via suitable approximations for the axial components of the electric field or the electric displacement, respectively.
Abstract: Free transverse vibrations of smart beams are considered where distributed actuators and sensors are realized by means of piezoelastic layers. Utilizing a variational formulation, the direct piezoelectric effect is incorporated into beam theory via suitable approximations for the axial components of the electric field or the electric displacement, respectively. Influence of shear and rotatory inertia is taken into account in the manner suggested by Timoshenko. It is shown that the correction for electrical coupling leads to effective stiffness parameters. This advantageous behavior is utilized for studying its influence on natural frequencies of smart beams with various boundary conditions.
TL;DR: In this paper, a W6+ ion substitution and an addition of a small amount of Cr2O3 was used to improve the piezoelectric properties of bismuth titanate Ceramics.
Abstract: Ceramics of bismuth titanate family Bi4Ti3O12 were prepared by the classic sintering process. A composition with a W6+ ion substitution and an addition of a small amount of Cr2O3 was perfected. Piezoelectric properties of this material studied as a function of temperature showed a good stability up to 500°C. A sensor device was manufactured like a buzzer. Its response to an acoustic signal was studied up to 300°C. The electric and piezoelectric study of the material deposited as a thick film shows the possibility to obtain a sensor prepared with this technology working at higher temperatures.