Effects of coupled vibrations on the parameters of tangentially polarized stripe-electroded piezoelectric cylinders (L)

The effects of coupled vibrations on the piezoelectric properties and electroacoustic transducer performance of radially polarized hollow cylindrical elements as a function of the choice of height-to-diameter ratio have been well documented [J. Acoust. Soc. Am. 120(3), 1374-1380 (2006); J. Acoust. Soc. Am. 122(6), 3419-3427 (2007)]. This letter presents experimental work on the effects of coupled (circumferential, axial, and flexural) vibrations on the resonance frequencies, effective electromechanical coupling coefficient, and acoustical performance of tangentially polarized piezoceramic cylindrical elements. Comparisons are made with analytical predictions of the properties of uniformly circumferentially polarized cylinders.     

Effective elastic properties of piezoelectric composites with radially polarized cylinders

Effective elastic properties of piezoelectric composites containing an infinitely long, radially polarized cylinder embedded in an isotropic non-piezoelectric matrix are theoretically investigated under an external strain field. Analytical solutions of elastic displacement and electric potentials are exactly derived, and the effective elastic responses are formulated in the dilute limit. Meanwhile, a vanishing piezoelectric response mechanism is revealed in the piezoelectric composite containing radially polarized cylinders. Furthermore, it is shown that the effective elastic properties can be enhanced (or reduced) due to the increase of the piezoelectric (or dielectric) constants of the cylinders.     

Wave propagation in axially polarized piezoelectric hollow cylinders of sector cross section

In this paper, the problem of electroelastic waves propagating in piezoelectric hollow cylinders of sector cross section is studied for the case when the boundary surfaces of sector cut are covered by non-extensible membranes. The three-dimensional linear equations of motion for the piezoelectric cylinder are analytically integrated and different boundary conditions on the cylindrical surfaces yield frequency equations, which relate the frequencies of elastic waves to their wavenumbers. Numerical results for waveguides with various boundary conditions are presented to illustrate the approach. Analysis of the dispersion spectra is carried out, and cutoff frequencies are obtained and characterized; mode asymptotic behavior and amplitude distributions of wave characteristics are analyzed. The main effects of their transformation by variation of the angular measure and the ratio of inner and outer radii are discussed. The results obtained are in good agreement with the results for the special case of a hollow semicircular cylinder.     

Forced responses of solid axially polarized piezoelectric ceramic finite cylinders with internal losses

A method is presented to determine the forced responses of piezoelectric cylinders using weighted sums of only certain exact solutions to the equations of motion and the Gauss electrostatic conditions. One infinite set of solutions is chosen such that each field variable is expressed in terms of Bessel functions that form a complete set in the radial direction. Another infinite set of solutions is chosen such that each field variable is expressed in terms of trigonometric functions that form a complete set in the axial direction. Another solution is used to account for the electric field that can exist even when there is no vibration. The weights are determined by using the orthogonal properties of the functions and are used to satisfy specified, arbitrary, axisymmetric boundary conditions on all the surfaces. Special cases including simultaneous mechanical and electrical excitation of cylinders are presented. All numerical results are in excellent agreement with those obtained using the finite element software ATILA. For example, the five lowest frequencies at which the conductance and susceptance of a stress-free cylinder, of length 10 mm and radius 5 mm, reach a local maximum or minimum differ by less than 0.01% from those computed using ATILA.     

Vibrations of radially polarized composite piezoceramic cylinders and disks

Eigenfrequency equations are derived for the resonance and antiresonance of long tubes and thin disks composed of n radially polarized piezoceramic materials bonded at their cylindrical interfaces. Numerical solutions are presented for steel/PZT-4/steel transducers, along with the corresponding effective electromechanical coupling factors. The results obtained provide for an efficient design of piezoceramic bandpass filters and other composite transducer devices.     

厚壁径向极化压电陶瓷薄圆环的研究

本文对厚壁径向极化压电陶瓷薄圆环进行了研究,得出了振子的谐振和反谐振频率的理论方程,并用有限元法分析了和实验测试了径向振动模态,给出了理论、有限元法和实验数据的一个对比。结果表明:本文的理论较为完善,对实际运用有一定的指导意义。     

Preparation and characterization of in-plane polarized PZT piezoelectric diaphragms

The preparation and characterization of in-plane polarized lead zirconate titanate （PZT） piezoelectric diaphragms for sensors and actuators applications are demonstrated in this letter. The single phase PZT films can be obtained on SiO2-passivated silicon substrates via sol-gel technique, in which PbTiO3 （PT） films are used as seed layers. Al reflective layer is deposited and patterned into concentric interdigitated top electrode by lithographic process, subsequently. The diaphragms are released using orientation-dependent wet etching （ODE） method. The size of the diaphragms is 5 mm in diameter and the outer interdigitated （IDT） electrode diameter （4.25 mm） is fixed at 85~ of the diaphragm diameter. The three-dimensional （3D） profiles results indicate that the measured maximum central deflection at 15 V is approximately 9 μm. Sensing measurements show that the capacitance continually decreases with an increase of applied force, while the case of induced charge exhibits a reverse tendency.     

复合圆环弯曲振动四极子模态分析

针对压电圆环弯曲振动机电转换性能较差的问题,提出了一种复合圆环弯曲振动换能器,它由一个径向极化的压电陶瓷内圆环和一个金属外圆环复合而成。基于能量原理推导得到了复合圆环弯曲振动的谐振频率和有效机电耦合系数,探讨了弯曲振动四极子模态特性与其结构尺寸间的关系。当压电圆环尺寸不变时,随外侧金属圆环壁厚增加,复合圆环弯曲振动四极子模态谐振频率上升,有效机电耦合系数迅速上升到极大值后缓慢下降。最后,设计制作了圆环换能器并对其谐振频率和有效机电耦合系数进行了实验测试,测试结果与解析结果和数值模拟结果吻合得较好。     

Axial vibration characteristics of a cylindrical, radially polarized piezoelectric transducer with different electrode patterns

A circular cylindrical piezoelectric transducer with radial polarization is proposed. The axial vibration characteristics of the transducer are studied by three different methods: analytical calculation, FEM simulation and experiment. The symmetric and asymmetric excitation conditions are discussed in the Haskins and Walsh model. For the resonance frequencies of the transducer, the results from the above three methods coincide well with each other. For the vibration amplitude, there are some deviations between the FEM simulation and measurement results; some possible reasons for this are discussed. The influence of the electrode patterns on the excitation modes are also investigated in detail. Based on the study described in this paper, the research methodology for a cylindrical piezoelectric transducer is clarified.     

Transport properties of arrays of intersecting cylinders

Formalisms are presented which enable the accurate calculation of the polarizability of an isolated square prism, and of the transport properties of square arrays of both circular cylinders and square prisms, over the entire range of volume fractions. For volume fractions close to zero and to unity, the results are shown to agree with dipolar formulae based on the appropriate polarizability. For volume fractions close to touching, the transport property varies rapidly but smoothly through the multipolar region. The results are shown to be in good qualitative agreement with experimental curves.     

Analysis of the magnetic field, force, and torque for two-dimensional Halbach cylinders

The Halbach cylinder is a construction of permanent magnets used in applications such as nuclear magnetic resonance apparatus, accelerator magnets and magnetic cooling devices. In this paper the analytical expression for the magnetic vector potential, magnetic flux density and magnetic field for a two dimensional Halbach cylinder are derived. The remanent flux density of a Halbach magnet is characterized by the integer p. For a number of applications the force and torque between two concentric Halbach cylinders are important. These quantities are calculated and the force is shown to be zero except for the case where p for the inner magnet is one minus p for the outer magnet. Also the force is shown never to be balancing. The torque is shown to be zero unless the inner magnet p is equal to minus the outer magnet p. Thus there can never be a force and a torque in the same system.     

Structural,spectral and dielectric properties of piezoelectric–piezomagnetic composites

Composite materials of spinel ferrite (SF) NiZnFe₂O₄ (NZF) and barium titanate (BT) BaTiO₃ were prepared by double sintering ceramic technique. X-ray diffraction patterns for the composite system (1–x) NZF+x BT, showed the presence of mainly of 2 phases, hence confirming the successful preparation of the composite. Some structural and microstructural parameters like porosity, X-ray density, particle size and lattice constant were deduced from the analysis of X-ray data for both phases. Scan electron microscope (SEM) analysis shows nearly a homogeneous microstructure with good dispersion of BT grains as well as the presence of some pores. There was also an enlargement of BT grains with increasing its content. Infra red (IR) spectra of the composite system indicate that BT content affects the intermolecular character of the SF phase. A rise in the dielectric constant occurred at high temperature which was attributed to the effect of space change resulting from the increase of the change carriers in the paramagnetic region. The dielectric loss (tan δ) decreased by increasing BT content.     

Plasma crystallization of polymer-ferroelectric/piezoelectric ceramic composites and their piezoelectric properties

Physics of the Solid State - The crystallization of “polymer-ferroelectric/piezoelectric ceramic” composites under the action of an electric discharge plasma and temperature is...     

Diffraction study of the piezoelectric properties of low quartz

The effect of a static electric field on the crystal structure of -quartz has been determined by Xray diffraction on single crystals. By a stroboscopic technique rocking curves are measured quasi simultaneously for zero field and for two opposite strong fields (28.8 kV/cm) applied in the direction of the crystallographic a-axis. The relative intensity-changes of high order reflections (i.e. sensitive to the core electrons) were measured and analysed by a least squares method technique. The analysis indicates that the bond distances Si-O are very little affected by the field, but both a deformation and a reorientation of the SiO₄ tetrahedra are induced. The model is qualitatively in agreement with the small amplitudes of the induced polarisation and the piezoelectric coefficients.Received: 22 September 2004, Published online: 23 December 2004PACS: 61.10.Nz X-ray diffraction - 77.65.-j Piezoelectricity and electromechanical effects - 77.22.Ej Polarization and depolarization - 07.85.Qe Synchrotron radiation instrumentation     

Characterizing polarization properties of radially polarized beams

In the present work two methods of characterizing polarization properties of well-known radially polarized beams are discussed in both theoretical aspect and experimental aspect. A rotating linear polarizer used behind the beam is known to be used to qualitatively characterize the polarization properties of a radially polarized beam. In this paper for the first time we give the mathematic model of this characterization process. The proposed model helps to analyze the known experimental results. On the other hand two global parameters have been previously proved to be used to characterize the linear or circular polarization content of the radially polarized beams. In this paper for the first time we propose the theoretical model of determining the two parameters in experiments. Some experimental results on characterizing the polarization properties of the real radially polarized beam produced by using different approaches are shown.     

Measurements of the thermal, dielectric, piezoelectric, pyroelectric and elastic properties of porous PZT samples

The introduction of porosity into ferroelectric ceramics has been of great interest in recent years. In particular, studies of porous lead-zirconate-titanate ceramic (PZT) have been made. In the research reported, samples of Ferroperm Pz27 with porosities of 20, 25 and 30% were studied. Very complete measurements were made of all of the physical properties relevant for ferroelectric applications including thermal conductivity and diffusivity, heat capacity, dielectric, pyroelectric, piezoelectric and elastic properties. Scanning electron micrographs indicated a change from 3-0 to 3-3 connectivity with increasing porosity. Although most of the physical properties are degraded by the presence of porosity, both piezoelectric and pyroelectric figures-of-merit are improved because of the markedly reduced relative permittivity. Porous ferroelectric ceramics are very promising materials for a number of applications.     

Diserine sulfate monohydrate: Symmetry, piezoelectric properties, and phase transitions

A new compound, diserine sulfate monohydrate, was synthesized, and single crystals of this compound were grown. X-ray diffraction studies were carried out, and the temperature dependences of the piezoelectric response of these crystals were measured. A conclusion was drawn that the crystals are orthorhombic with the space symmetry group C _1v -Pmm2 and that they apparently undergo phase transitions at 340 and 255 K.     

Investigation on the bulk crystal growth,crystalline perfection,refractive index and piezoelectric properties of borate single crystals for piezoelectric and electro-optic applications

Low solubility potassium pentaborate tetrahydrate (KB5), ammonium pentaborate tetrahydrate (AB5) and mixed (KAB5) single crystals have been grown by the Sankaranarayanan-Ramasamy (SR) method. The crystal structures and space groups have been confirmed by powder XRD analysis. The direction of the grown crystal was confirmed by the back reflection X-ray Laue pattern. The crystalline perfection (CP) of the crystals have been evaluated using HRXRD studies. The transmittance spectra of the grown crystals were recorded by UV–Vis-NIR transmission studies showing that all the crystals have 90% transmittance in the entire visible region and found that the crystals' cut off wavelengths were below 200 nm. The optical studies such as refractive index (RI) and birefringence interferometry (BI) were reported. The RI for five different wavelengths of KB5, AB5 and KAB5 crystals were analyzed using the prism coupling method (PCM). Electromechanical behavior of the grown crystals was observed using piezoelectric coefficient (d₃₃) measurement. Vickers Microhardness (VMH) measurement carried out at 30 °C shows increased hardness as the load increases.