Piezoelectric Transducer Applications Research Articles

Frequency tuning and automatic frequency tracking of shunted piezoelectric transducers

Piezoelectric ultrasonic transducers, vital in medical devices and aerospace, often face challenges like resonant frequency shifts and impedance variations affecting their operational efficiency. This paper introduces a shunted piezoelectric transducer which could tune itself by digitally programmable inductance. A transformer and inductance-capacitance matching network ensures enhanced compatibility and impedance management. Proposing a fuzzy PI-based phase control method achieves resonant frequency tracking, synchronizing operational frequency with the transducer. In contrast to traditional methods, our approach enables faster and more precise fine-tuning, detecting and rectifying real-world deviations for optimal performance. A comprehensive experimental validation, based on fundamental knowledge analysis, confirms the feasibility and superiority of our proposed method, and the commonly encountered issues of resonance frequency deviation and impedance variation in high-power piezoelectric transducer applications can be effectively mitigated.

Push-Pull Inverter Using Amplitude Control and Frequency Tracking for Piezoelectric Transducers.

Frequency tracking and amplitude control are essential for piezoelectric transducers. Frequency tracking ensures the piezoelectric transducer operates at the resonant frequency for maximum power output, and amplitude control regulates the mechanical motion of the output. This paper presents a novel driver based on a push-pull inverter for piezoelectric transducers. The proposed driver realizes the frequency tracking and amplitude control scheme by a voltage sensing bridge in the case of transformer secondary matching, guaranteeing automatic frequency tracking and precise mechanical functions regardless of environmental and load variations. The proposed scheme is verified by the ultrasonic scalpel and the ultrasonic motor (USM). The experimental results show that this scheme reduces the build-up time from 10 ms to 3 ms and loaded frequency variations from 250 Hz to 200 Hz. In addition, the amplitude control performance was further observed on USM for various loads. The overshoot is less than 5.4% under different load torques. Therefore, the proposed scheme improves the load adaptability and stability of piezoelectric transducers and promotes the application of piezoelectric transducers under various conditions.

Acceptor doping and actuation mechanisms in Sr-doped BiFeO3[sbnd]BaTiO3 ceramics

BiFeO3-BaTiO3 (BF-BT) ceramics are important multiferroic materials, which are attracting significant attention for potential applications in high temperature lead-free piezoelectric transducers. In the present study, the effects of Sr2+ as an acceptor dopant for Bi3+, in the range from 0 to 1.0% (in mole), on the structure and ferroelectric/piezoelectric properties of 0.7BiFeO3-0.3BaTiO3 ceramics were evaluated. The use of a post-sintering Ar annealing process was found to be an effective approach to reduce electrical conductivity induced by the presence of electron holes associated with reoxidation during cooling. A low Sr dopant concentration (0.3%, in mole) yielded enhanced ferroelectric (Pmax ∼ 0.37 C/m2, Pr ∼ 0.30 C/m2) and piezoelectric (d33 ∼ 178 pC/N, kp ∼ 0.27) properties, whereas higher levels led to chemically heterogeneous core-shell structures and secondary phases with an associated decline in performance. The electric field-induced strain of the Sr-doped BF-BT ceramics was investigated using a combination of digital image correlation macroscopic strain measurements and in-situ synchrotron X-ray diffraction. Quantification of the intrinsic (lattice strain) and extrinsic (domain switching) contributions to the electric field induced strain indicated that the intrinsic contribution dominated during the poling process.

Achieving High Piezoelectricity and Excellent Temperature Stability in Pb(Zr,Ti)O3-Based Ceramics via Low-Temperature Sintering.

Developing piezoelectric ceramics with high piezoelectric properties and broad temperature usage ranges via low-temperature sintering is one of decisive importance for flourishing developments for emerging electromechanical applications. However, these properties are usually mutually exclusive, such as low-temperature sintering and high piezoelectricity as well as high piezoelectricity and temperature stability. Here, we report high piezoelectricity (i.e., piezoelectric constant d33 ≈ 744 pC/N, electromechanical coupling factor kp ≈ 75%, and Curie temperature TC ≈ 201 °C) and superior temperature stability (d33 varies less than 10% within 25-160 °C) in Pb0.905Ba0.095(Zr0.54Ti0.46)O3 + 1 mol % Nb2O5 + 1 wt % Bi2O3 + x wt % CdCO3 (PBZTNB-xCd) ceramics that are fabricated at a sintering temperature of as low as 960 °C, superior to those of other reported random and textured ceramics. Good piezoelectricity is attributed to the remaining rhombohedral-tetragonal (R-T) phase coexistence and the high ceramic density. Excellent temperature stability is related to the stable crystal structure and domain structure. These properties confer to the produced materials attractive characteristics for further consideration in several advanced applications, especially for piezoelectric transducer applications requiring constant structures over a broad temperature range.

Temperature Stable Piezoelectric Imprint of Epitaxial Grown PZT for Zero-Bias Driving MEMS Actuator Operation.

In piezoelectric transducer applications, it is common to use a unipolar operation signal to avoid switching of the polarisation and the resulting nonlinearities of micro-electromechanical systems. However, semi-bipolar or bipolar operation signals have the advantages of less leakage current, lower power consumption and no additional need of a DC−DC converter for low AC driving voltages. This study investigates the potential of using piezoelectric layers with an imprint for stable bipolar operation on the basis of epitaxially grown lead zirconate titanate cantilevers with electrodes made of a metal and metal oxide stack. Due to the manufacturing process, the samples exhibit high crystallinity, rectangular shaped hysteresis and a high piezoelectric response. Furthermore, the piezoelectric layers have an imprint, indicating a strong built-in field, which shifts the polarisation versus electric field hysteresis. To obtain the stability of the imprint, laser doppler vibrometry and switching current measurements were performed at different temperatures, yielding a stable imprinted electric field of −1.83 MV/m up to at least 100 °C. The deflection of the cantilevers was measured with a constant AC driving voltage while varying the DC bias voltage to examine the influence of the imprint under operation, revealing that the same high deflection and low nonlinearities, quantified by the total harmonic distortion, can be maintained down to low bias voltages compared to unipolar operation. These findings demonstrate that a piezoelectric layer with a strong imprint makes it possible to operate with low DC or even zero DC bias, while still providing strong piezoelectric response and linear behaviour.

Al0.7Sc0.3N butterfly-shaped laterally vibrating resonator with a figure-of-merit (kt2·Qm) over 146

This work presents the laterally vibrating Lamb wave resonators (LVRs) based on a 30% aluminum scandium nitride (Al0.7Sc0.3N) thin film with three interdigited transducer pairs operating in the S0 mode. In order to reduce the anchor loss, perfect matched layer-based finite element analysis simulations are utilized to design and optimize the device. Thanks to the high quality AlScN using magnetron sputtering with a single alloy target, vertical etching profile, and designed device structure, 1-μm-thick Al0.7Sc0.3N-based LVRs with high performance are fabricated. The resonator equivalent electric parameters are extracted utilizing the modified Butterworth–Van Dyke model. The best Al0.7Sc0.3N LVR achieves an electromechanical coupling coefficient (kt2) of 9.7% and a loaded quality factor (Qr) of 1141.5 operating at approximately 305 MHz. The same resonator shows a motional quality factor (Qm) of 1507.2, resulting in a high figure-of-merit (FoM = kt2 · Qm) of 146.2. A 1.8 MHz tuning range is measured for an Al0.7Sc0.3N LVR by applying DC voltage in the range of −40 to 40 V due to the ferroelectric property of high Sc doping in Al0.7Sc0.3N. With the high FoM, Qr, Qm, and low motional resistance (Rm), the Al0.7Sc0.3N-based LVRs show strong potential in applications of radio frequency communications and piezoelectric transducers.

Enhancement of Nonlinear Dielectric Properties in BiFeO3-BaTiO3 Ceramics by Nb-Doping.

BiFeO3–BaTiO3 (BF–BT) ceramics exhibit great potential for diverse applications in high temperature piezoelectric transducers, temperature-stable dielectrics and pulsed-power capacitors. Further optimization of functional properties for different types of applications can be achieved by modification of processing parameters or chemical composition. In the present work, the influence of pentavalent niobium substitution for trivalent ferric ions on the structure, microstructure and dielectric properties of 0.7BF–0.3BT ceramics was investigated systematically. Doping with niobium led to incremental reductions in grain size (from 7.0 to 1.3 µm) and suppression of long-range ferroelectric ordering. It was found that core-shell type microstructural features became more prominent as the Nb concentration increased, which were correlated with the formation of distinct peaks in the dielectric permittivity–temperature relationship, at ~470 and 600 °C, which were attributed to the BT-rich shell and BF-rich core regions, respectively. Nb-doping of BF–BT ceramics yielded reduced electronic conductivity and dielectric loss, improved electrical breakdown strength and enhanced dielectric energy storage characteristics. These effects are attributed to the charge compensation of pentavalent Nb donor defects by bismuth vacancies, which suppresses the formation of oxygen vacancies and the associated electron hole conduction mechanism. The relatively high recoverable energy density (Wrec = 2.01 J cm−3) and energy storage efficiency (η = 68%) of the 0.7BiFeO3–0.3BaTiO3 binary system were achieved at 75 °C under an electric field of 15 kV mm−1. This material demonstrates the greatest potential for applications in energy storage capacitors and temperature-stable dielectrics.

Twelve modified figures of merit of 2–2-type composites based on relaxor-ferroelectric single crystals

Twelve modified figures of merit are studied for the first time for 2–2-type composites based on relaxor-ferroelectric single crystals such as [001]-poled (1 – x)Pb(A1/3Nb2/3)O3 – xPbTiO3, where A = Mg or Zn. These modified figures of merit are related to the piezoelectric coefficients d3j* of the composite (j = 1, 2 and 3) and characterise the effectiveness of energy harvesting and transduction along the three co-ordinate axes OXj of a piezoelectric composite under a constant mechanical stress or strain. The volume-fraction dependencies of the modified figures of merit are analysed for parallel-connected 2–2 and 2–2–0 composites, and the effect of porosity (i.e. the volume fraction and shape of air pores in each polymer layer) on these figures of merit is considered for 2–2–0 composites. Linkages between the modified figures of merit and traditional energy-harvesting figures of merit d3j*g3j* are discussed for the studied 2–2-type composites. New diagrams are developed to indicate important volume-fraction ranges that correspond to a large anisotropy of exemplar modified figures of merit. Due to the large effective parameters and large anisotropy of specific figures of merit, the studied composites are of interest in piezoelectric sensor, transducer and energy-harvesting applications.

Low temperature sintering of Li2CO3 added Pb(Ni1/3Nb2/3)-Pb(Zr,Ti)O3 ceramics with high piezoelectric properties

Multilayer structure is an effective approach for reducing driving voltages or increasing output electric signal for piezoelectric devices. However, it is a challenge to achieve high piezoelectric coefficient at low sintering temperature. In this work, we fabricated Li2CO3 (LC) doped Pb(Ni1/3Nb2/3)-Pb(Zr,Ti)O3 (PNN-PZT) ceramics via solid state reaction method. Piezoelectric coefficient at low quasi-static signal d33 and effective piezoelectric coefficient under high electric field d33* are 692 pC/N, 1114 pm/V for PNN-PZT+0.2 wt% LC sintered at 950 °C, which is comparable to high temperature sintered commercial Pb(Zr,Ti)O3 (PZT) based ceramics. Detailed piezoelectric, ferroelectric, dielectric properties, temperature stability and material structure were investigated. The planar electromechanical coupling factor Kp, relative dielectric constant εr and dielectric loss tan δ at 1 kHz, Curie temperature Tc, coercive electric field Ec are measured to be 0.557, 4280, 0.025, 113 °C, 4.34 kV/cm. It shows great potential for applications in multilayer structured cofired piezoelectric actuators and transducers.

Application of piezoelectric transducers in photoacoustic spectroscopy for trace gas analysis

AbstractPhotoacoustic spectroscopy (PAS) is a boomingly developed spectroscopic method for trace gas analysis in the past decades. Unlike traditional laser absorption spectroscopy, an acoustic transducer is employed to detect the acoustic waves instead of optical waves. Microphone is a commonly used transducer to convert the acoustic signal into electrical signal, which is related to the gas concentration. In recent years, piezoelectric materials are playing important roles in the acoustic‐to‐electrical conversion process of photoacoustic system. In this article, recently used transducers in PAS such as quartz tuning fork, polyvinylidene fluoride, lead zirconate titanate, electromechanical film and LiNbO3, BiB3O6, NbCOB crystals are summarized and discussed in detail. The different spectrophone configuration, schematic diagram, and experimental system are reported. Side by side comparison is carried out to show the gas sensing performance of these piezoelectric transducers.

Comparison of effective parameters of lead-free 1–3-type composites based on ferroelectric single crystals

The article reports results of the comparative study on the performance of lead-free 1–3-type composites based on domain-engineered lead-free ferroelectric single crystals. Of interest are the 1–3–0 ferroelectric single crystal/porous polymer and 1–0–3 ferroelectric single crystal/piezoelectric single crystal/polymer composites with heterogeneous matrices. In the 1–3–0 composite this matrix is a polymer medium with the system of spheroidal air pores. In the 1–0–3 composite the polymer matrix contains a system of spheroidal piezoelectric single crystal inclusions, and the arrangement of these inclusions is similar to that of the pores in the matrix of the related 1–3–0 composite. Volume-fraction and aspect-ratio dependences of the piezoelectric properties, squared figure of merit and electromechanical coupling factors of the 1–3-type composites are analysed, and comparison of the effective parameters of the composites is made. The role of the composite microgeometry in forming the piezoelectric anisotropy and squared figures of merit is discussed. Due to large electromechanical coupling factors, squared figures of merit and anisotropy factors, the studied lead-free 1–3-type composites are of interest as advanced materials suitable for piezoelectric transducer, sensor and energy-harvesting applications.

Post-Voltage-Boost Circuit-Supported Single-Ended Class-B Amplifier for Piezoelectric Transducer Applications.

Piezoelectric transducers are important devices that are triggered by amplifier circuits in mobile ultrasound systems. Therefore, amplifier performance is vital because it determines the acoustic piezoelectric transducer performances. Particularly, mobile ultrasound applications have strict battery performance and current consumption requirements; hence, amplifier devices should exhibit good efficiency because the direct current (DC) voltage in the battery are provided to the supply voltages of the amplifier, thus limiting the maximum DC drain voltages of the main transistors in the amplifier. The maximum DC drain voltages are related with maximum output power if the choke inductor in the amplifier is used. Therefore, a need to improve the amplifier performance of piezoelectric transducers exists for mobile ultrasound applications. In this study, a post-voltage-boost circuit-supported class-B amplifier used for mobile ultrasound applications was developed to increase the acoustic performance of piezoelectric transducers. The measured voltage of the post-voltage-boost circuit-supported class-B amplifier (62 VP-P) is higher than that of only a class-B amplifier (50 VP-P) at 15 MHz and 100 mVP-P input. By performing the pulse-echo measurement test, the echo signal with the post-voltage-boost circuit-supported class-B amplifier (10.39 mVP-P) was also noted to be higher than that with only a class-B amplifier (6.15 mVP-P). Therefore, this designed post-voltage-boost circuit can help improve the acoustic amplitude of piezoelectric transducers used for mobile ultrasound applications.

The Effect of Mixed Doping on the Microstructure and Electrophysical Parameters of the Multicomponent PZT-Type Ceramics.

This work shows the influence of admixture on the basic properties of the multicomponent PbZr1−xTixO3 (PZT)-type ceramics. It presents the results of four compositions of PZT-type material with the general chemical formula, Pb0.99M0.01((Zr0.49Ti0.51)0.95Mn0.021Sb0.016W0.013)0.9975O3, where, in the M position, a donor admixture was introduced, i.e., samarium (Sm3+), gadolinium (Gd3+), dysprosium (Dy3+) or lanthanum (La3+). The compositions of the PZT-type ceramics were obtained through the classic ceramic method, as a result of the synthesis of simple oxides. The X-ray diffraction (XRD) pattern studies showed that the obtained multicomponent PZT materials have a tetragonal structure with a P4mm point group. The microstructure of the obtained compositions is characterized by a well crystallized grain, with clearly visible grain boundaries. The composition with the admixture of lanthanum has the highest uniformity of fine grain microstructure, which positively affects its final dielectric and piezoelectric properties. In the multicomponent PZT-type ceramic, materials utilize the mixed (acceptor and donor) doping of the main compound. This dopiong method has a positive effect on the set of the electrophysical parameters of ceramic materials. Donor dopants W6+ (at positions B) and M3+ = Sm3+, Gd3+, Dy3+, and La3+ (at positions A) increase the dielectric and piezoelectric properties, while the acceptor dopant Sb3+ (at positions B) increases the time and temperature stability of the electrophysical parameters. In addition, the suitable selection of the set of admixtures improved the sinterability of the ceramic samples, as well as resulted in obtaining the required material with good piezoelectric parameters for the poling process. This research confirms that all ceramic compositions have a set of parameters suitable for applications in micromechatronics, for example, as actuators, piezoelectric transducers, and precision microswitches.

PZT ceramic particles/polyurethane composites formalism for mechanical energy harvesting

More recently, the ferroelectric ceramic/polymer composites have been progressively replacing ferroelectric ceramics and polymers as they combine their interesting properties. Such as high compliance of polymers and high electromechanical coupling of ferroelectric ceramics those are required for piezoelectric transducer applications. At the same time, the ferroelectric ceramic/polymer composites formalism for predicting their energy-conversion capabilities is of both academic and industrial interest. The novelty of this paper is that the electrical power harvested by the PZT/PU polarized composite has been expressed in terms of the effective longitudinal piezoelectric coefficient (d33) of the composite via a parameter p related to the poling ratio. Besides, the parameter p, that is characterizing the PZT/PU composites with different longitudinal piezoelectric coefficients (d33), was evaluated. The other parameters of the electrical power expression were calculated using the Yamada model for the dielectric, piezoelectric and elastic constants. Finally, a good agreement was found between experience and model.

Evaluation of Mössbauer spectra linearization methods

Mossbauer spectra linearity is a critical parameter for Mossbauer spectrometer accuracy determination. This paper deals with comparison of various Mossbauer spectra linearizing methods. First method uses sine velocity waveform followed by linearization process. Next method introduces additional modulation based on the velocity error signal measured by laser vibrometer. Last evaluated method combines both. It uses the velocity error signal measured by laser vibrometer as linearization function. Custom Mossbauer spectrometer was constructed for the linearization evaluation. The spectrometer velocity driving system is based on the digital PID controller concept deployed in the FPGA chip of CompactRIO real-time hardware device. The obtained data demonstrate that all evaluated methods increases the linearity of spectra in a wider frequency and amplitude range of a drive signal in comparison with those measured using a traditional measurement method. Highest linearization effect has the method using sine velocity waveform, as generally harmonic movement is natural for used double loudspeaker type velocity transducers. Results show the possibility to use proposed linearization methods for higher velocity ranges using standard transducers and shows potential to be applied in the simple control of transducers without PID regulation or in piezoelectric transducer applications.

Piezoelectric performance of PZT-based materials with aligned porosity: experiment and modelling

A new micromechanical model is proposed to analyse the piezoelectric properties of freeze-cast porous composite materials based on a ferroelectric lead zirconate titanate-type (PZT) ceramics. The important influence of the composite microgeometry and the porous ceramic matrix on the piezoelectric coefficients and and the piezoelectric anisotropy factor in the porosity range of mp = 0.2–0.6 is evaluated and discussed. The resulting piezoelectric parameters of parallel-connected freeze-cast composites with highly aligned pore channels are then compared to those of PZT-based porous materials with randomly distributed porosity. Due to the relatively large piezoelectric coefficients ∼ 102 pC N−1, ≈ 40–100 mV m N−1, anisotropy factor ≈ 3–5 and the presence of aligned porous channels, the parallel-connected freeze-cast composite has advantages over conventional monolithic PZT-type ceramics (e.g. g33 = 24.2 mV m N−1 and d33/∣d31∣ = 2.2 in the PZT-5 ceramic) and is suitable for piezoelectric transducer, sensor, acoustic, and energy-harvesting applications.

Applications of piezoelectric MFC type transducers in mechatronic measurement systems - the impact of a mechanical subsystem damage on a system operation

The work include a report of research works concerning applications of non-classical piezoelectric transducers in mechatronic measuring systems. Composite piezoelectric transducers called Macro Fiber Composite (MFC) are considered. Characteristics of considered transducers were made, indicating their advantages and disadvantages, as well as the results of carried out laboratory tests are presented, in which MFC transducers were used as sensors for mechatronic measurement systems. A series of laboratory tests was carried out on the created laboratory stand to determine the impact on the measured values of damage of the mechanical subsystem on which the MFC-type piezoelectric transducer was glued. Results of measurements are presented and analysed in relation to different applications of the piezoelectric MFC sensors.

A Guided Wave Transducer with Sprayed Magnetostrictive Powder Coating for Monitoring of Aluminum Conductor Steel-Reinforced Cables.

Aluminum conductor steel-reinforced (ACSR) cables are typically used in overhead transmission lines, requiring stringent non-destructive testing owing to the severe conditions they face. Ultrasonic guided wave inspection provides promising online monitoring of the wire breakage of cables with the advantages of high sensitivity, long-range inspection, and full cross-sectional coverage. It is a very popular method to generate and receive guided waves using magnetostrictive and piezoelectric transducers. However, uniformly coupling the acoustic energy excited by transducers into multi-wire structures is always a challenge in the field application of guided waves. Long-term field application of piezoelectric transducers is limited due to the small coupling surface area, localized excitation, and couplant required. Conventional magnetostrictive transducers for steel strand inspection are based on the magnetostrictive effect of the material itself. Two factors affect the transducing performance of the transducers on ACSR cables. On one hand, there is a non-magnetostrictive effect in aluminum wires. On the other hand, the magnetostriction of the innermost steel wires is too weak to generate guided waves. The bias magnetic field is attenuated by the outer layers of aluminum wires. In this paper, an alternative sprayed magnetostrictive powder coating (SMPC) transducer was developed for guided wave generation and detection in ACSR cables. The Fe83Ga17 alloy powder with large magnetostriction was sprayed uniformly on the surfaces of certain sections of the outermost aluminum wires where the transducer would be installed. Experimental investigations were carried out to generate and receive the most commonly used L(0,1) guided waves for wire breakage detection at frequencies of 50 and 100 kHz. The results demonstrate that the discernable reflected waves of the cable end and an artificial defect of three-wire breakage (5.5% reduction in the cable’s cross-sectional area) were received by the transducer with SMPC, which was impossible for the transducer without SMPC. This method makes long-term and online monitoring of ACSR cables feasible due to the high coupling efficiency and good structural surface adaptability.

Dielectric relaxation and electrical properties of Bi2.5Nd0.5Nb1.5Fe0.5O9 ceramics

Abstract Aurivillius single-phase Bi2.5Nd0.5Nb1.5Fe0.5O9 (BNNF) ceramics was synthesized via solid state mixed oxide sintering method. Electrical properties of the samples were intensely studied in a wide range of temperature (25 °C–650 °C). Dielectric behaviors were investigated by dielectric and impedance spectroscopies in the range (40 Hz−10 MHz) of frequency. Single dielectric relaxation was observed due to the grains contribution. The phase transition temperature (TC) was noticed at ∼270 °C. Kinetic analysis of dielectric data was used to understand the possible relaxation-conduction behaviors in the ceramics. Above ∼250 °C, relaxation and conduction of the ceramics was assigned to the motion of ionized oxygen vacancies. The Aurivillius ceramics has promising industrial applications in dielectric capacitors and piezoelectric transducers due to low leakage below ∼200 °C. The results could be valuable for designing and/or modifying properties of BNNF related materials.

The high piezoelectric properties and high temperature stability in Mn doped Pb(Mg0.5W0.5)O3-Pb(Zr,Ti)O3 ceramics

Mn doped Pb(Mg0.5W0.5)O3-Pb(Zr,Ti)O3 (PMW-PZT) ceramics were prepared by solid state reaction method and their crystal structures and electrical properties were investigated systematically. All Mn doped PMW-PZT compositions were located within the morphotropic phase boundary region and Mn doping slightly increased the volume fraction of rhombohedral phase. The results showed that Mn doping enhanced the ferroelectric and piezoelectric properties of PMW-PZT ceramics markedly, which was different from other Mn doped piezoelectric ceramics. It's very interesting that there was a dielectric anomaly below the Curie temperature for poled Mn doped PMW-PZT ceramics. The dielectric anomaly disappeared and temperature stability of piezoelectric properties improved after aging treatment. With high d33 (~562 pC/N), high kp (0.69), medium Qm (~139), low loss (~0.6%) and good temperature stability, 0.5 at% Mn doped PMW-PZT ceramics could be a potential candidate for piezoelectric actuator and transducer application.