Showing papers on "Piezoelectricity published in 1995"

Dielectric Materials and Applications

Abstract: Theory dielectric measuring techniques dielectric materials and their applications - dielectric materials insulation strengths of high pressure gases and of vacuum liquid dielectrics plastics as dielectrics ceramics dielectrics in equipment dielectrics in power and distribution equipment dielectrics in electronic equipment dielectrics in capacitors rubber and plastics in cables problems of the cable engineer dielectric materials as devices rectifiers piezoelectric transducers and resonators magnetic and dielectric amplifiers memory devices dielectric requirements of the armed forces tables of dielectric materials

Sensors based on piezoelectric resonators

Abstract: A review of sensors based on piezoelectric crystal resonators is presented. The survey focuses on the fundamental resonator modes rather than on the variety of surrounding support configurations in special sensor applications. First, the general properties of vibrating crystal sensors and their inherent superiority are described. The sensor concepts utilizing either homogeneous resonators with temperature and pressure (stress) as primary measurants or composite resonators with areal mass density and viscoelastic properties of the 'foreign' layer as primary measurands are discriminated. A comparison between bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators with respect to their primary sensitivity functions and principal capabilities for sensor applications is given and the importance of recent investigations on Lamb wave and horizontal polarized shear wave (HPLW) interdigital transducer (IDT) resonators is acknowledged. The importance of mode purity for high dynamic range sensors based on resonators and some aspects of the demand on specialized electronics are emphasized. The present state of established sensors based on primary sensitivities, e.g., quartz-crystal thermometers, pressure transducers, thin-film thickness and deposition-rate monitors, viscoelastic layer analysers (crystal/liquid composite resonators) is reviewed. A selection of the most promising recently investigated vibrating crystal sensors utilizing indirect sensitivities is described, including the wide field of analyte-selective coatings and resonator-based immunosensors or immunoassays. Finally, the potential of alternative piezoelectric materials for future sensor developments is briefly discussed.

Modeling of a three-layer piezoelectric bimorph beam with hysteresis

Abstract: Piezoelectric actuators are usually stacked or bimorph in configuration. In this paper the mechanics of a three-layer piezoelectric bimorph is discussed and its dynamic model with hysteresis is presented. The results can be used to analyze piezoelectric actuators constructed with three-layer piezoelectric bimorphs. A piezoelectric bimorph actuator has been fabricated and experiments have been carried out to verify the model. The calculated results of this model closely matched the tested results. This model can also be used with other types of piezoelectric actuators with a slight modification.

Exact free‐vibration analysis of laminated plates with embedded piezoelectric layers

Abstract: Exact solutions are developed for predicting the coupled electromechanical vibration characteristics of simply supported laminated piezoelectric plates composed of orthorhombic layers. The three‐dimensional equations of motion and the charge equation are solved using the assumptions of the linear theory of piezoelectricity. The through‐thickness distributions for the displacements and electrostatic potential are functions of eight constants for each layer of the laminate. Enforcing the continuity and surface conditions results in a linear system of equations representing the behavior of the complete laminate. The determinant of this system must be zero at a resonant frequency. The natural frequencies are found numerically by first incrementally stepping through the frequency spectrum and refining the final frequencies using bisection. Representative frequencies and mode shapes are presented for a variety of lamination schemes and aspect ratios.

Coupled layerwise analysis of composite beams with embedded piezoelectric sensors and actuators

Abstract: Unified mechanics are developed with the capability to model both sensory and active composite laminates with embedded piezoelectric layers. Two discretelayer (or layerwise) formulations enable analysis of both global and local electromechanical response. The first assumes constant through-the-thickness displacement, while the second permits piecewise continuous variation. The mechanics include the contributions from elastic, piezoelectric and dielectric components. The incorporation of electric potential into the state variables permits representation of general electromechanical boundary conditions. Approximate finite element solutions for the static and freevibration analysis of beams are presented. Applications on composite beams demonstrate the capability to represent either sensory or active structures, and to model the complicated stressstrain fields, the interactions between passive/active layers and interfacial phenomena between sensors and composite plies. The capability to predict the dynamic c...

Electrical properties’ maxima in thin films of the lead zirconate–lead titanate solid solution system

Abstract: The piezoelectric strain coefficients have been measured as a function of composition for films in the PbZrO3–PbTiO3 (PZT) solid solution system, using a double‐beam laser interferometry technique. This compositional dependence of piezoelectric, and the associated dielectric and ferroelectric properties for films 1 μm in thickness with varying Zr/Ti ratio, deposited on platinized silicon substrates using a modified sol‐gel route, corresponds to data reported for undoped PZT ceramics with respect to the effective morphotropic phase boundary composition. Films with composition near the morphotropic phase boundary, Pb(Zr0.52Ti0.48)O3, show enhanced values of the longitudinal piezoelectric coefficient, 194 pC/N; dielectric permittivity, 1310; and remanent polarization, 36 μC/cm2.

Precision position control of piezoelectric actuators using charge feedback

Abstract: The issue of precision position control is critical if piezoelectric actuator technology is to be applied in increasingly demanding applications. In one particular application, the NASA NAOMI project, piezoelectric actuators have been proposed as the pointing and focusing elements for thousands of small mirror-lenslets because of their fast response time and load- carrying ability. In this application the positions of these actuators must be precisely controlled both statically and dynamically to the nanometer level. This requirement necessitates a careful study of the concept and design of the driving electronics of the system. This paper is focused on finding an appropriate method for driving piezoelectric stack actuators for ultraprecision position and motion control. In this paper the theoretical basis of the electrical control of piezoelectric stack actuators is derived using the fundamental physical laws governing dielectrics and piezoceramics. It is shown that the relationships used for voltage control of piezoelectric actuators result from an approximation of the constitutive equations. An exact input/output relationship for piezoelectric actuators is derived and shows that displacement relies fundamentally on charge, not voltage. Experimental verification was obtained to illustrate the differences between driving piezoactuators with voltage control and charge control.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Design of Passive Damping Systems

Abstract: This paper presents a brief review of techniques for designed-in passive damping for vibration control. Designed-in passive damping for structures is usually based on one of four damping technologies : viscoelastic materials, viscous fluids, magnetics, or passive piezoelectrics. These methods are discussed and compared. The technology of using viscoelastic materials for passive damping is discussed in more detail than the other methods since it is presently the most widely used type of damping technology. Testing and characterization of viscoelastic materials and design methods for passive damping are discussed. An example showing the benefits of a passive damping treatment applied to a stiffened panel under an acoustic load is presented.

Saint-Venant's Principle in Linear Piezoelectricity

Abstract: Toupin's version of Saint-Venant's principle in linear elasticity is generalized to the case of linear piezoelectricity. That is, it is shown that, for a straight prismatic bar made of a linear piezoelectric material and loaded by a self-equilibrated system at one end only, the internal energy stored in the portion of the bar which is beyond a distance s from the loaded end decreases exponentially with the distance s.

Dielectric, ferroelectric, and piezoelectric properties of lead zirconate titanate thick films on silicon substrates

Abstract: This article reports the fabrication of thick films of lead zirconate titanate (PZT) on platinum‐buffered silicon substrates by screen printing. Crack‐free films, up to 12 μm on a single pass, show a dielectric permittivity of 200, tangent losses of 0.05, remanent polarization of 2.5 μC/cm2, and coercive field of 40 kV/cm. The field‐induced longitudinal piezoelectric coefficient d33 at 40 kV/cm dc bias and 4 kV/cm alternating field corresponded to 50 pC/N. The magnitude of the piezoelectric voltage coefficient g33, computed from the strain coefficient and dielectric permittivity, under the same conditions, was found to be 36×10−3 V m/N, higher than that of a poled PZT bulk ceramic in comparison. These results are promising for a broad variety of sensor applications.

Piezoelectric ultrasonic motors

Abstract: Piezoelectric ultrasonic motors are a new type of actuator. They are characterized by high torque at low rotational speed, simple mechanical design and good controllability. They also provide a high holding torque even if no power is applied. Compared to electromagnetic actuators the torque per volume ratio of piezoelectric ultrasonic motors can be higher by an order of magnitude. Recently various types of piezoelectric ultrasonic motors have been developed for industrial applications such as cameralens drive or as actuator in the head restraint of automobile seats. This paper describes several types of piezoelectric ultrasonic motors. In the first part the working principle of the travelling wave motor is explained. In the second part other types of piezoelectric ultrasonic motors are described and classified with respect to the vibration modes and contact mechanisms used in their design. Finally some open problems in piezoelectric ultrasonic motor research are addressed.

Automatic determination of complex constants of piezoelectric lossy materials in the radial mode

Abstract: An iterative automatic method is described for the characterization of lossy piezoelectric materials in the radial resonance mode based on the use of the more general expression for the complex admittance. From the experimental data of Y at four adequately selected frequencies, the constants of the material are determined with the necessary accuracy to reproduce the piezoelectric behaviour of the sample around resonance. The IEEE-176 Standard procedure has been automatized for the initial estimation of the real parts of the elastic constants. The method is applicable even to those materials in which said standard does not allow one to determine the piezoelectric constants.

Suppression of nonlinear panel flutter with piezoelectric actuators using finite element method

Abstract: An optimal control design is presented to actively suppress large-amplitude, limit-cycle flutter motions of rectangular isotropic plates at supersonic speeds using piezoelectric actuators. The nonlinear panel flutter equations based on the finite element method are derived for isotropic plates with piezoelectric layers subjected to aerodynamic and thermal loads. A model reduction is performed to the finite element system equations of motion for the control design and the time domain simulation. An optimal controller is developed based on the linearized modal equations, and the norms of the feedback control gain are employed to provide the optimal shape and location of the piezoelectric actuators. Numerical simulations based on the reduced nonlinear panel flutter model show that the critical dynamic pressure can be increased three to four times by the piezoelectric actuation. Within the increased critical dynamic pressure, the limit-cycle motions can be completely suppressed. The results demonstrate that piezoelectric materials are effective in panel flutter suppression.

Effect of poling on piezoelectric properties of lead zirconate titanate thin films formed by sputtering

Abstract: Lead zirconate titanate (PZT) thin film was formed on Pt/Ta/Si3N4/Si(100) substrate at 400 °C by sputtering and then annealed at 650 °C in air The PZT film was 1 μm thick and had dielectric permittivity of 980, loss tangent of 005, remanent polarization of 31 μC/cm2, and coercive field of 110 kV/cm Piezoelectric property of the film formed on silicon cantilever was estimated from the converse effect Poling at 5 kV/mm increased the property by a factor of 12 to 34, resulting in converse piezoelectric constant (d31) varying from −84 to −102 pC/N

Electromechanical Properties of Relaxor Ferroelectric Lead Magnesium Niobate-Lead Titanate Ceramics

Abstract: In this paper, the results of a recent investigation of the dependence of the induced piezoelectric activity on temperature, electric bias field, and frequency and the electrostrictive response in the relaxor ferroelectric lead magnesium niobate-lead titanate ceramics ( (1- x)(Pb(Mg1/3Nb2/3)O3)- x(PbTiO3)) at compositions below 30% PT are presented. It was observed that the electrostrictive strain at temperatures near the dielectric constant maximum T max increases monotonically with increased PT content. For PMN:PT at compositions near 30% PT, the electrostrictive strain under a 10 kV/cm electric field can reach about 0.15% with very little hysteresis. An exceptionally large piezoelectric response with an effective piezoelectric d33 coefficient in the electric field induced state of over 1,800 pC/N could be achieved for selected PMN:PT compositions and electric bias fields.

Compensation of hysteresis in solid-state actuators

Abstract: In order to control piezoelectric or magnetostrictive solid-state actuators in a hysteresis-free way, the electric or magnetic polarization in the active material must be controlled. The actuating signal is modified by an inverse system so as to show a hysteresis-free, linear transfer characteristic by the concatenation of the inverse system with the actuator. The hysteresis is described by a Preisach model. Measurements of magnetostrictive Terfenol-D demonstrate that almost complete compensation of the flux density/field strength characteristic curve can be obtained.

Application of lead zirconate titanate thin film displacement sensors for the atomic force microscope

Abstract: Elimination of optical and tunneling displacement sensors from the atomic force microscope (AFM) is an important breakthrough for improved performance of the AFM. The interaction of an oscillating tip and a surface has become a popular tool for obtaining information which could not be obtained by the conventional repulsive force AFM mode. In this application, lead zirconate titanate (PZT) is one of the most promising materials with large piezoelectric constants which can be used not only for detecting distortions such as the displacement detection of an AFM cantilever, but also oscillations of the cantilever. However, incorporating PZT into the microfabrication process to make the AFM cantilever has not been easily accomplished because PZT has a delicate chemical nature. We have successfully developed an AFM with a microfabricated cantilever which had a PZT thin film applied for displacement sensing. The linearity of the output signal was sufficient for displacement sensing. Images of a compact disk were ...

Thin film actuated mirror array

Abstract: A thin film actuated mirror for an actuated mirror array (10) includes a pedestal (14) and at least one piezoelectric structure (12) cantilevered from the pedestal. The piezoelectric structure includes a layer of piezoelectric material (18) having two opposing surfaces (24, 26). Each of two metal electrodes (20, 22) are mounted on a respective one of the opposing surfaces of the piezoelectric material layer. An electrical signal is applied across the piezoelectric material, between the electrodes, causing deformation of the piezoelectric material. The thin film actuated mirror further includes a mirror surface (32) interconnected to the piezoelectric material layer such that the mirror surface deforms in response to the deformation of the piezoelectric material layer.

Atomic force microscope for high speed imaging including integral actuator and sensor

Abstract: A cantilever for a scanning probe microscope (SPM) includes a piezoelectric element in a thicker, less flexible section near the fixed base of the cantilever and a piezoresistor in a thinner, more flexible section near the free end of the cantilever. When the SPM operates in the constant force mode, the piezoelectric element is used to control the tip-sample separation. Since the resonant frequency of the piezoelectric element is substantially higher than that of conventional piezoelectric tube scanners, much higher scan rates can be achieved. When the SPM operates in the dynamic or intermittent contact mode, a superimposed AD-DC signal is applied to the piezoelectric element, and the latter is used to vibrate the cantilever as well as to control the tip-sample spacing. In another embodiment the cantilever is supported on a knife edge and vibrates at a third or higher order resonant frequency.

Simple, high‐resolution interferometer for the measurement of frequency‐dependent complex piezoelectric responses in ferroelectric ceramics

Abstract: In this paper, we report the development of a simple but precise piezoelectric spectrometer using a Michelson–Morley interferometer. The measurement system has been developed to study the frequency and temperature dependence of the complex piezoelectric and electrostriction coefficients of ferroelectric materials. The spectral data are collected by computer and has significantly wider frequency range and lower noise than other such systems. Results are reported for a quartz sample, a La‐modified lead zirconate titanate ferroelectric, and a lead zirconate titanate sol‐gel derived ferroelectric thin film.

Effects of grain shape anisotropy, porosity, and microcracks on the elastic and dielectric constants of polycrystalline piezoelectric ceramics

Abstract: A theoretical approach is proposed to estimate the effects of grain shape anisotropy on the overall response of polycrystalline piezoelectric ceramics. The self‐consistent approach is applicable to a polycrystal with arbitrary grain shapes, orientations, and anisotropy, but emphasis is placed on the effective bulk and shear moduli and the dielectric constant of a polycrystal consisting of randomly oriented piezoelectric grains. Because typical piezoelectric ceramics often contain substantial porosity, the effects of randomly oriented pores of various shapes on the overall electroelastic properties are considered. Analytical predictions are compared to simplified predictions which ignore the effects of piezoelectricity at the grain level and the effects of grain shape. Analytical predictions are in good agreement with measurements for unpoled, porous BaTiO3 polycrystals. A FORTRAN computer program developed to implement the theory is available upon request from the author.

The Green function for a piezoelectric piezomagnetic magnetoelectric anisotropic elastic medium with an elliptic hole or rigid inclusion

Abstract: By extending the Stroh sextic formalism to a ten-dimensional formalism, it is shown that the Green function for an elliptic hole or rigid inclusion in an anisotropic elastic medium can be modified easily for an anisotropic medium with piezoelectric, piezomagnetic and magnetoelectric coupling.

On the dynamic fracture of piezoelectric materials

Abstract: Some problems in the fracture theory of piezoelectric materials are studied in the quasielectrostatic approximation. Asymptotic near-tip expressions for mechanical and electric fields are obtained, using a complex-variable approach. A closure-integral formula for the quasielectrostatic energy release rate is given, which permits the evaluation of this energy by the solution previously obtained. The connection between two electroelastic crack-extension forces provided by different forms of the energy balance is established. For the antiplane fracture of a transversely isotropic piezoelectric solid the stress and electrical intensity factors are obtained for small time values. The use of a Griffith-type propagation criterion leads to a differential equation for the crack-tip trajectory which is numerically solved and the solution dependence on the applied electric field is investigated

GaN linear electro‐optic effect

Abstract: Measurements of the linear (Pockels) electro‐optical coefficient of wurtzite GaN are reported. The values for the electro‐optic coefficients r33 and r31 are 1.91±0.35 and 0.57±0.11 pm/V at 633 nm, respectively, in agreement with extrapolations from measured second‐harmonic generation coefficients (χ33(2)=−20±6 pm/V and χ31(2)=10±3 pm/V) suggesting that the dominant contributions are electronic in origin. Measurements were performed using a Mach–Zehnder interferometer with LiNbO3 as a reference material. Piezoelectric effects were also observed.

Comparison of the anisotropy of apparent integrated ultrasonic backscatter from fixed human tendon and fixed human myocardium.

Abstract: The content and organization of collagen in the cardiac interstitium may represent significant determinants of the ultrasonic scattering properties of myocardium. This study was designed to investigate the anisotropic backscattering properties of a fibrous soft tissue exhibiting an ordered arrangement of fibers similar to myocardium, but possessing a substantially greater content of collagen. Human Achilles tendon was chosen for this study because it possesses a simple unidirectional arrangement of fibers and a high content of collagen compared to normal myocardium. Integrated (frequency-averaged) backscatter was measured from ten formalin fixed samples of tendon as a function of insonifying angle relative to the fiber axis of the tissue. The samples were insonified in a water bath using a 5-MHz center frequency piezoelectric transducer. Maximum backscatter occurred for insonification perpendicular to the fibers, and minimum backscatter occurred for insonification parallel to the fibers. The mean peak to nadir variation, or magnitude of anisotropy, of integrated backscatter for the ten formalin fixed samples of tendon was 36.3 dB. This compares to 14.5 dB for formalin fixed human myocardium measured in an earlier study by our laboratory.