Potential distribution in a bounded piezoelectric in the presence of the photothermoacoustic effect

The photothermoacoustic effect in a bounded piezoelectric is studied theoretically and experimentally. Calculations are made of the potential distribution over the thickness and the potential difference in a thin piezoelectric layer as a function of the coordinate of this layer. The amplitude distribution of the potential oscillations over the thickness of the piezoelectric reveals two maxima. The phase of the oscillations at these maxima is shifted by approximately 180°. It is shown that the potential difference on the opposite surfaces of the plate is zero regardless of the propagation constant of the thermal wave. An experiment was carried out using a layered disk formed by seven identical piezoelements. The amplitude and phase shift of the potential difference were investigated for each element at different light modulation frequencies. The experimental results show good agreement with the theory. Zh. Tekh. Fiz. 68, 75–79 (January 1998)     

Influence of nonparallelism of the surfaces of a piezoelectric layer on the frequency band of an electroacoustic piezoelectric transducer

The influence of nonparallelism of the surfaces of a piezoelectric transducer on its impedance and frequency band is analyzed theoretically. The model of a wedge-shaped piezoelectric layer taken for the analysis consists of a set of n plane-parallel elements arranged in succession along the length of the transducer with a gradual increase in the thickness of the piezoelectric layer. The analysis performed demonstrates the possibility of significantly expanding the band of working frequencies of a piezoelectric transducer when its electroacoustic conversion efficiency is reduced. In some cases, however, a decrease in conversion efficiency can be employed to optimize an acoustic device, for example, in creating a filter-type piezoelectric transducer, where electromagnetic energy is converted into acoustic energy successively from one cell of the filter to another. The proposed method for expanding the frequency band can be useful, for example, in creating high-frequency acousto-optic Bragg cells. Zh. Tekh. Fiz. 69, 72–73 (March 1999)     

Theory of the generation of mechanical vibrations by laser radiation in solids containing internal stresses on the basis of the thermoelastic effect

The behavior of the nonsteady deformations in solids containing internal stresses under irradiation by temporally modulated laser radiation is analyzed. In the framework of the nonlinear theory of thermoelasticity a model is proposed for the excitation of mechanical vibrations with allowance for the dependence of the thermoelastic coupling parameter on the initial deformation. For the case of a piezoelectric method of detecting the mechanical vibrations in a uniformly deformed sample, an analytical expression is obtained for the electrical signal taken off from the piezoelement. The behavior of the piezoelectric signal under various conditions is investigated, and the results are compared with the available experimental data and found to be in qualitative agreement. Zh. Tekh. Fiz. 69, 59–63 (July 1999)     

Large piezoelectric effects in charged, heterogeneous fluoropolymer electrets

Large piezoelectric d₃₃ coefficients around 600 pC/N are found in corona-charged non-uniform electrets consisting of elastically “soft” (microporous polytetrafluoroethylene PTFE) and “stiff” (perfluorinated cyclobutene PFCB) polymer layers. The piezoelectric activity of the two-layer fluoropolymer stack exceeds the d₃₃ coefficient of the ferroelectric ceramic lead zirconate titanate (PZT) by more than a factor of two and that of the ferroelectric polymer polyvinylidene fluoride (PVDF) by a factor of 20. Soft piezoelectric materials may become interesting for a large number of sensor and transducer applications, in areas such as security systems, medical diagnostics, and nondestructive testing. Accepted: 9 November 1999 / Published online: 3 December 1999     

Application of piezoelectric transient response in transducer acoustic power measurement

To explore a more convenient method for measuring the focused ultrasound power,a piezoelectric ceramic plate was used to receive ultrasonic signal directly.Due to an acoustic force acts on the surface of piezoelectric ceramic plate,the piezoelectric response was obtained by means of electromechanical analogy,which was composed of voltage response caused by forced vibration and high frequency attenuation response caused by natural vibration.The conversion relationship between output signal of piezoelectric ceramic plate and acoustic power of transducer was analyzed.The envelope of output piezoelectric signal was extracted in twice,and a voltage amplitude curve with sinusoidal distribution that could describe the changes of acoustic power was obtained.Under different drive voltage of transducer,the maximum peak voltage of envelope curve was found respectively.Their squared values were made a linear fitting with acoustic power measured by acoustic power meter,and then the proportional coefficient of theoretical relational expression was calibrated.The experimental results are in good agreement with the theory.The relative error between calibrated theoretical acoustic power and that measured by acoustic power meter was less than 8.7%.The paper can provide a guideline for measuring acoustic power of transducer by using piezoelectric signal.     

Piezoelectric properties of oriented Z′ cuts of PZT-type ferroelectric ceramics

The piezoelectric and dielectric properties of oriented β°Z′ cuts (β=0, 15, 30, 45, 60°) of piezoelectric crystals of TsTS-83G (lead zirconate titanate) composite are studied. A static model is proposed for the case of a maximally polarized ceramic based on the conditions of complete and partial stability of the polar axes c with allowance for their nonuniform distribution for 180° and 90° domain reorientations. It is found that the TsTS-83G piezoelectric composite does not exhibit anisotropy in the piezoelectric coefficient d ₃₃ ^′ when the axis of the Z′ cut is rotated in the ZY plane relative to the XYZ coordinate system. Zh. Tekh. Fiz. 68, 75–79 (July 1998) Deceased.     

压电瞬态响应在换能器声功率测量中的应用

探索一种简便的聚焦超声功率测量方法,利用压电陶瓷片直接接收超声信号,通过机电类比得到压电瞬态响应由压电片在声波作用力下引起受迫振动产生的电压响应与固有振动产生的高频衰减响应叠加而成,分析输出压电信号与换能器声功率之间的换算关系。对输出压电信号进行二次包络提取,获得表征声功率变化的电压幅度曲线,分别找出不同换能器驱动电压下包络曲线的最大峰值电压,将其平方值与声功率计所测声功率进行线性拟合,并对理论关系式中的比例系数进行标定。实验结果所得线性拟合度较高,且标定后所得声功率与声功率计所测值相对误差低于8.7%,证明了通过压电瞬态响应测量换能器声功率具有可行性。      

Excitation of bulk elastic waves at the surfaces of piezoelectric crystals with 422,622 symmetry

The problem of exciting bulk elastic waves at the surface of a piezoelectric with symmetries 422,622 has been solved by a successive approximation method. In the approximation of a fixed electric field, created at the surface of the piezoelectric crystal by a two-electrode transducer, the distributions are found for the shear wave stress and the energy flux density in the far zone. The equivalent circuit parameters for a two-electrode radiator are determined taking account of the dynamic piezoelectric correction obtained in the second approximation. The equivalent circuit parameters and the transducer loss are treated for TeO₂ crystals. A realistic possibility of using surface transducers in the development of acousto-optic modulators in the s.h.f. region is shown. Tomsk State Academy of Control Systems and Radio Electronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 8–15, January, 1997.     

Experimental test of the nonlinearity of the characteristics of the piezoelectric transducer of the phase modulator of a fiber ring interferometer at small sinusoidal deformations

We show that the level of the second harmonic of sinusoidal modulation resulting from the non-linearity of the characteristics of piezoelectric transducer does not exceed0.005–0.0005% for deformations ranging from10−8 to10−6. The influence of the nonlinearity of the characteristics of a piezoelectric transducer used as a modulator of the optical length of the loop of a fiber ring interferometer on the accuracy parameters of the latter is analyzed. It is shown that the given level of the second harmonic does not lead to a significant shift of the zero of the interference of counterpropagating waves at the interferometer output. Institute of Applied Physics, Russian Academy of Sciences; Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 2, pp. 198–200, February 1999.     

Nonstationary radiation mode of a thin-walled piezoceramic sphere with a correcting electric circuit

A transducer in the form of a water-loaded thin-walled piezoceramic sphere is considered. On the electric side, the transducer is connected to an RL circuit. The pulsed radiation mode of the transducer is studied using the theory of equivalent schemes of piezoelectric transducers and the spectral Fourier transform. For the system under study, the parameters that provide the minimal emitted signal duration are determined for different values of the relative wall thickness of the sphere. The durations and amplitudes of acoustic pulses emitted by the transducer in the presence and absence of the electric circuit are compared.     

0.90(Bi1/2Na1/2)TiO3–0.05(Bi1/2K1/2)TiO3– 0.05BaTiO3 transducer for ultrasonic wirebonding applications

Lead-free piezoelectric ceramic 0.90(Bi_1/2Na_1/2)TiO₃–0.05(Bi_1/2K_1/2)TiO₃–0.05BaTiO₃ (BNKBT-5) rings (OD=12.7 mm, ID=5.1 mm and 2.3-mm thick) were fabricated and characterized. Four ceramic rings were used as the driving element in an ultrasonic wirebonding transducer and the performance of the transducer was characterized. The lead-free transducer was found to have comparable voltage rise and fall times as a lead-based PZT transducer and has a relatively large vibration amplitude, thus showing that BNKBT-5 has the potential to be used in fabricating lead-free ultrasonic wirebonding transducers. PACS 77.22.Ej; 77.84.-s; 85.50.-n     

Photothermoacoustic oscillations in a solid-piezoelectric layered structure

Photothermoacoustic oscillations in a thin plane-layered structure consisting of an isotropic solid and a piezoelectric crystal of class 6mm (or piezoelectric ceramics) are studied theoretically and experimentally. Expressions for the potential difference across an arbitrary layer of the piezoelectric transducer are derived. For the case of a two-layer transducer, the amplitude-frequency and phase-frequency dependences of the signal are analyzed. It is shown that, from these experimental dependences, one can determine certain elastic and thermal parameters of a solid. An experiment is performed with samples of Cu, Zn, and TsTS-19 piezoceramics in the frequency range within 9–1000 Hz. The experimental data are used to determine the values of the reduced Young’s modulus and the thermal diffusivity of the materials under study.     

Simulation of elastic wave propagation in cylindrical structures including excitation by piezoelectric transducers

The development and optimization of non-destructive testing procedures usually needs experimental data. As experiments are time-consuming and expensive to conduct, we would like to use numerical data instead. This is admissible, if the simulation describes the physical experiments accurately. A three-dimensional displacement-stress finite-difference model is presented for a piezoelectric transducer coupled to an anisotropic tube. The allocation of the displacement and stress components on a staggered grid leads to a stable scheme. A full piezoelectric model of the transducer is used, including transverse isotropy in the elastic, dielectric, and piezoelectric constants. Similar to an experiment, elastic waves are excited in the corresponding simulation by applying a voltage signal to the electrodes of the piezoelectric transducer. Predictions of the simulation model for a piezoelectric ring transducer coupled to a carbon-fibre-reinforced shell are compared to experimental results to test the validity of the numerical data.     

Theoretical analysis of a quartz-enhanced photoacoustic spectroscopy sensor

Quartz-enhanced photoacoustic spectroscopy (QEPAS) sensors are based on a recent approach to photoacoustic detection which employs a quartz tuning fork as an acoustic transducer. These sensors enable detection of trace gases for air quality monitoring, industrial process control, and medical diagnostics. To detect a trace gas, modulated laser radiation is directed between the tines of a tuning fork. The optical energy absorbed by the gas results in a periodic thermal expansion which gives rise to a weak acoustic pressure wave. This pressure wave excites a resonant vibration of the tuning fork thereby generating an electrical signal via the piezoelectric effect. This paper describes a theoretical model of a QEPAS sensor. By deriving analytical solutions for the partial differential equations in the model, we obtain a formula for the piezoelectric current in terms of the optical, mechanical, and electrical parameters of the system. We use the model to calculate the optimal position of the laser beam with respect to the tuning fork and the phase of the piezoelectric current. We also show that a QEPAS transducer with a particular 32.8 kHz tuning fork is 2–3 times as sensitive as one with a 4.25 kHz tuning fork. These simulation results closely match experimental data.     

Interaction of light with acoustic waves excited by an inphase multielement transducer in the 1.0–2.5 GHz range

Interaction between a weakly divergent optical beam and an acoustic wave generated in the range 1.0–2.5 GHz by an inphase multielement electroacoustic piezoelectric transducer is analyzed. A piezoelectric (Y + 36°)-cut LiNbO₃ plate is fixed on the surface of an X-cut LiNbO₃ acoustic duct with the help of metallic sublayers (Cr, Cu, In, Cu, or Cr). The inphase structure of the transducer is formed by the upper electrodes inter-connected by short conductors. The signal is applied through a coaxial Chebyshev transformer. The efficiencies of electroacoustic conversion and acoustooptic interaction are calculated as functions of frequency. The experimental setup, method, and results are described.     

铌酸钾钠基无铅压电陶瓷纵振换能器*

高性能环境友好型无铅压电陶瓷及其应用是当前压电材料研究的热点之一,为了探究其在水声换能器领域的应用潜力,该文对铌酸钾钠基无铅压电陶瓷和锆钛酸铅压电陶瓷纵振式换能器进行了对比研究。依据仿真结果优化结构尺寸,制作了两种换能器样机并测试了其在空气中和水中的电声性能。测试结果表明,铌酸钾钠基无铅压电陶瓷换能器的谐振频率为35kHz,最大发送电压响应为 151dB,声源级可达 190dB,在 26kHz~67kHz 的频率范围内发送电压响应的起伏不超过±4.5dB,谐振频率处-3dB 的指向性开角约为 76°。该无铅压电陶瓷换能器具有和锆钛酸铅压电陶瓷换能器相当的发射性能,有望推动无铅压电材料在水声换能器领域的应用进程。     

Orientational contribution to the piezoelectric constants of BaTiO3 ceramic in ferroelectric phases with various symmetries

A self-consistent method based on the interaction of a piezoelectric sphere with a piezoelectric medium that has anisotropic elastic and dielectric properties is used to calculate the components of the tensor piezoelectric modulus of BaTiO₃ ceramic in all three ferroelectric modifications. A comparison of the calculated and measured piezoelectric moduli shows that at least 60–70% of the piezoelectric effect in BaTiO₃ ceramic is caused by domain boundary movement throughout the entire ferroelectric region. Fiz. Tverd. Tela (St. Petersburg) 41, 1080–1083 (June 1999)     

Modeling of circular piezoelectric micro ultrasonic transducer using CuAl<Subscript>10</Subscript>Ni<Subscript>5</Subscript>Fe<Subscript>4</Subscript> on ZnO film for sonar applications

Modeling and theoretical characterization of piezoelectric micro ultrasonic transducer (pMUT) using ZnO film sandwiched between nickel aluminum bronze (CuAl₁₀Ni₅Fe₄) electrodes was reported in this paper. The transducer is targeted to be utilized in sonar applications. Analyses on the model were carried out using finite element method. Model’s dimensional parameters were optimized for desired performance. Simplified technique was proposed to determine transmit and receive sensitivities of the model. As the result, micro ultrasonic transducer model with resonance frequency of 40 kHz was proposed with estimated receive and transmit sensitivities of −93 dB re 1 V/μPa and 137 dB re 1 μPa/V, respectively. Further model validations require actual device fabrication and this will be included in our future works.     

Determination of displacement with a piezoelectric transducer using phase-shift algorithms

This investigation accurately measures the relationship between applied voltage and the displacement of a piezoelectric transducer device both by analyzing phase shifting interferometry algorithms and using a Twyman-Green interferometer. Simulations are performed to calculate unknown phase shifts, especially around π/2 and 3π/2. It is indicated that the Hariharan algorithm is indeed an effective phase shifting interferometry algorithm.     

厚度模压电超声换能器无源声学材料研究进展*

厚度模压电超声换能器作为超声波发射、接收以及电信号间转换的载体,是超声成像与检测系统的核心器件,一般由压电层、匹配层和背衬层3部分组成。超声换能器的性能一定程度上决定着整体超声设备的性能,影响了其在工业、医学、军事等领域的应用。该换能器的关键性能指标(带宽、灵敏度)除了受到压电层的影响,还与匹配层、背衬层等无源声学材料的设计密切相关。该文综述了近年来厚度模压电超声换能器无源声学材料(匹配层、背衬层和声透镜)的研究进展,提出了当前该类材料面临的难题和解决途径,并对其未来发展方向进行了展望。