Piezoelectric Crystal Research Articles

Stretchable nanofibers of polyvinylidenefluoride (PVDF)/thermoplastic polyurethane (TPU) nanocomposite to support piezoelectric response via mechanical elasticity

Interest in piezoelectric nanocomposites has been vastly growing in the energy harvesting field. They are applied in wearable electronics, mechanical actuators, and electromechanical membranes. In this research work, nanocomposite membranes of different blend ratios from PVDF and TPU have been synthesized. The PVDF is responsible for piezoelectric performance where it is one of the promising polymeric organic materials containing β-sheets, to convert applied mechanical stress into electric voltage. In addition, the TPU is widely used in the plastic industry due to its superior elasticity. Our work investigates the piezoresponse analysis for different blending ratios of PVDF/TPU. It has been found that TPU blending ratios of 15–17.5% give higher output voltage at different stresses conditions along with higher piezosensitivity. Then, TPU addition with its superior mechanical elasticity can partially compensate PVDF to enhance the piezoelectric response of the PVDF/TPU nanocomposite mats. This work can help reducing the amount of added PVDF in piezoelectric membranes with enhanced piezo sensitivity and mechanical elasticity.

Modeling, analysis and design optimizations of an axial-type piezoelectric energy generator for optimal output

This paper presents the optimal design of axial-based piezoelectric generators. The optimization problem is solved for the combination of the two different types of poling piezo elements used and the total cumulative voltage output. The task is to optimize the design in such a way as to obtain the optimal output voltage for a given mechanical excitation. The Piezoelectric Energy Generators (PEGs) have two domains—active and passive domains. The optimization process is divided into several steps, which significantly reduces the number of calculations. This paper is focused on the optimization process in the passive domain, that increases the output voltage for given mechanical excitation. In the optimization, the process can be developed for specific operating conditions, various lengths of duralumin base plate, the various position of proof mass, and different applied acceleration. It has been modeled and analyzed for axial-based piezoelectric generators. The maximum voltage and power are observed 11.64 V and 1355 µw at 633 Hz, respectively, when the length of the duralumin base plate is 150 mm and 5 m s−2 acceleration. The analysis of this study can guide the passive domain optimization of PEGs to meet desired purposes of energy harvesting.

Switchability of a single port SAW resonator using the electrical Bragg band gap

A proof of concept of a new solution for achieving tunable SAW components based on the electrical Bragg band gap concept developed for piezoelectric phononic crystals is presented on a SAW resonator on a LiNbO3 substrate. In this work, it is shown that for a fixed geometry, it is possible to shift the main resonance frequency by modifying the electrical condition on the electrodes that constitute the cavity's mirrors. The concept was validated by both numerical simulations and experimental characterization of single port resonators fabricated on LiNbO3.

Edge states in a non-Hermitian chiral lattice

Non-Hermiticity can alter the topological properties of energy bands and drive topologically trivial systems with Hermitian limits to generate nontrivial topological edge states. Nevertheless, most efforts were devoted to the study of isotropic systems containing multiple pairs of non-Hermitian components, while the influence of distribution of non-Hermitian components was seldom explored. Here, we first investigated a two-dimensional square-lattice non-Hermitian model in which the losses increase in either clockwise or counterclockwise direction, leading to distinct non-Hermitian chiral structures. The effective Hamiltonian satisfied non-Hermitian particle-hole symmetry, which can induce non-Hermitian zero modes. By combing two chiral structures, various edge states emerged from the interface, whose bands strongly depend on the distribution of non-Hermitian components. And the band properties of edge states were analyzed and predicted basing on the non-Hermitian particle-hole symmetry and hypothetical parity-time symmetry. Furthermore, to validate our theory, we proposed a piezoelectric phononic crystal with an external circuit. The band structures were coincident with our theoretical results. And robust wave propagation was also identified. Our study may provide an alternative method to actively engineer propagating waves in non-Hermitian systems.

High-Frequency Vibration Analysis of Piezoelectric Array Sensor under Lateral-Field-Excitation Based on Crystals with 3 m Point Group.

Based on Mindlin’s first-order plate theory, the high-frequency vibrations of piezoelectric bulk acoustic wave array sensors under lateral-field-excitation based on crystals with 3 m point group are analyzed, and the spectral-frequency relationships are solved, based on which, the optimal length–thickness ratio of the piezoelectric crystal plate is determined. Then, the dynamic capacitance diagram is obtained by a forced vibration analysis of the piezoelectric crystal plate. The resonant mode conforming to good energy trapping is further obtained. The frequency interferences between different resonator units are calculated, and the influences of the spacing between two resonant units on the frequency interference with different electrode widths and spacings are analyzed. Finally, the safe spacings between resonator units are obtained. As the electrode spacing value of the left unit increases, the safe spacing d0 between the two resonator units decreases, and the frequency interference curve tends to zero faster. When the electrode spacings of two resonator units are equal, the safe distance is largest, and the frequency interference curve tends to zero slowest. The theoretical results are verified further by finite element method. The analysis model of high frequency vibrations of strongly coupled piezoelectric bulk acoustic array device based on LiTaO3 crystals with 3 m point group proposed in this paper can provide reliable theoretical guidance for size optimization designs of strongly coupled piezoelectric array sensors under lateral-field-excitation.

Sintering Aid‐Assisted Growth of 0.95(K0.5Na0.5)NbO3–0.05(Bi0.5Na0.5)(Zr0.85Sn0.15)O3 Single Crystals by the Solid‐State Crystal Growth Method and Their Characterization

In this work, 0.95(K0.5Na0.5)NbO3–0.05(Bi0.5Na0.5)(Zr0.85Sn0.15)O3 (KNN–BNZS) lead‐free piezoelectric single crystals are grown by the solid‐state crystal growth (SSCG) method and their phase transitions and properties characterized. Addition of an appropriate amount of Li2CO3 and Bi2O3 sintering aids considerably promotes single‐crystal growth. Chemical composition of the single crystal is similar to the nominal composition with a slight deficiency in Na and K as evaluated by electron probe microanalysis (EPMA). X‐Ray diffraction (XRD), electrical property measurements, and temperature‐controlled Raman scattering reveal that the phase transition near room temperature is from a rhombohedral to an orthorhombic or tetragonal phase. Wide temperature range Raman scattering and dielectric properties consistently indicate transitions associated with the phase transformations or boundaries of a phase coexistence region and further details. Nontrivial frequency dependence of dielectric properties is successfully parameterized by capacitance relaxations described by Debye and Cole–Cole responses with special constant phase elements with fixed exponents of 0.5 (Warburg elements). High‐frequency dielectric constants and additional dielectric relaxations and dc relaxations are deconvoluted. The modeling parameters indicate the phase transition temperatures (or boundaries of the phase coexistence region) unambiguously. Polarization–electric field and bipolar strain–electric field hysteresis loops show that the single crystal is a classic lossy ferroelectric material.

Conceptual Design: High-Voltage Transformer

This paper shown and describe this behaviour an original conceptual design of an electrical transformer. The device it is constituted by an electrodynamic actuator and piezoelectric crystals.The input AC voltage generates an axial vibration in the electrodynamic actuator. The axial vibration is transmitted to a piezoelectric crystal which is polarized in the axial direction and generates the output voltage. In a reduced volumes and a single step, it would be possible to reach voltages of tens of MV and great transformation ratios-achieving these voltages is impossible with conventional systems-The transformer works at axial resonance of the piezoelectric crystal. This device operates to the frequency of order kHz; therefore could be used to generate electromagnetic waves. The capacitive and inductive at its output negligible respect conventional transformer. This transformer could be used in countless devices, such as gamma‐ray machines, electron microscope, solid-state propulsion system, Ion thruster, small particle accelerator etc.

A Strategy for Extracting Full Material Coefficients of AlN Thin Film Based on Resonance Method.

AlN thin film is widely used in piezoelectric MEMS devices, and the accurate characterizations of its material coefficients are critical for the optimization of the AlN thin film process and the design of AlN thin-film-based devices. However, it is difficult to extract the material coefficients of AlN in the form of thin film. This paper reports a strategy for systematically extracting full elastic coefficients, piezoelectric coefficients and dielectric constants of c-axis-oriented AlN thin film based on the resonance method outlined in IEEE Standard on Piezoelectricity Std 176-1987. In this strategy, four self-suspended resonators with length thickness extension (LTE), thickness extension (TE), radial extension (RE), lateral electric field excited thickness shear (LEF-TS) modes together with a lamb wave resonator (LWR) are specifically adopted, and the material coefficients of AlN thin film are extracted by measuring the impedance spectra of these resonators. In addition, the effects of the pad and electrodes on the resonators were systematically studied, and the corresponding procedures to eliminate their influences on the extraction accuracy of material coefficients were proposed. Finally, a complete extraction process based on the above strategy was established. The simulation results show that the strategy can achieve high accuracy for AlN thin film with different thicknesses and electrode configurations, and it can also be applied to other materials belonging to the 6 mm piezoelectric crystal class such as ZnO, ScAlN, etc.

Assembly and interconnection technology for high-temperature bulk acoustic wave resonators

Abstract. A sensor based on a piezoelectric single crystal enables operation even under harsh environmental conditions. In addition to the sensor element, the packaging technology is crucial for sensor performance. In this paper, a suitable assembly and interconnection technology concept of Ca3TaGa3Si2O14 (CTGS) resonators for high-temperature applications is presented as a platform for future sensor assemblies. The concept described here has already been functionally tested as a temperature sensor (Schulz et al., 2021). The concept includes a sapphire base plate, a housing lid, and a spacer made from aluminium oxide (Al2O3). The substrate is metallised with platinum manufactured into thin film and thick film technology. The ceramic components are fused with glass solder. The connection of the resonator to the conductive tracks is realised by thermosonic bonding with 25 µm platinum wire. Initially, the stability of the metallisation must be investigated before subsequent electrical testing under high temperature. Diffusion processes play a major role in this temperature range, and the stability of the layer is a necessary condition for subsequent investigations. A suitable set of bonding parameters and the strength of the platinum bonds prior to and after thermal load is analysed. Shear tests are used to evaluate the quality of the ceramic materials fused with glass solder after thermal ageing. The dielectrical properties of sapphire and glass solder such as the isolation resistance, the relative permittivity, and the loss factor at high temperatures are evaluated using interdigital structures. The loss factor is measured on both bare interdigital structures and the samples coated with glass solder to make an estimation about the conductive behaviour up to 1000 ∘C. A ceramic lid for the sensor housing is attached by a high-temperature stable glass solder. Since platinum conductors are fed through this glass solder connection, the electrical conductivity of the glass solder is characterised at high temperature. Furthermore, the hermeticity of the assemblies is verified by means of helium leakage tests. These investigations are the basis for the implementation of an assembly and interconnection technology that is suitable for reliable operation under extreme temperature conditions. The packaging technology also offers further possibilities for pressure or chemical sensors that can withstand high-temperature loads.

SH type guided wave transducer based on Ca2Al2SiO7 piezoelectric crystal for high-temperature structure health monitoring

The development of high-temperature guided wave transducers for high-temperature structure health monitoring is of great interest in many aspects of industrial engineering. In this work, the zero-order shear horizontal (SH0) guided wave transducer was designed and analyzed based on the X-plate from Ca2Al2SiO7 (CAS) crystals. Furthermore, the excitation and reception performances were evaluated. It is determined from the finite element simulation that the CAS-based guided wave transducer can excite pure SH0 waves in a specific direction. Experimental results confirmed that pure SH0 waves could be achieved and received by the designed CAS-based transducer, which is in good agreement with the theoretical study. Strong SH0 wave signals were chosen at elevated temperatures, and a moderate signal-to-noise ratio >12 dB was realized at the high temperature of 600 °C, showing the advantages of a CAS-based transducer for high-temperature sensing application.

Smart piezoelectric phononic crystals and metamaterials:State-of-the-art review and outlook

机械振动的有效控制与弹性波的精准调控多年来一直是力学工作者和工程界十分关注与高度重视的研究领域。近年来，随着高端装备、精密仪器、在线监测、以及孵能技术的迅猛发展，人们对该研究领域提出了诸多新颖的研究课题、赋予更高的期望。声子晶体与超构材料作为一种人工设计的新型复合材料，具有许多独特和超常的弹性波传播特性，为上述研究领域提供了一个崭新的研究途径与良好的应用前景。然而传统的声子晶体与超构材料在加工制备之后不易根据实际需求重新调整其几何参数和材料属性，这大大限制了声子晶体和超构材料的实际应用。压电材料隶属智能或机敏材料，具有力-电耦合效应，能够将机械能和电能进行相互转换。因此，将压电材料与声子晶体/超构材料有机的融为一体，即可形成智能压电声子晶体与超构材料。通过调节电场可以调控结构的振动或波动特性，实现预期的目标。这大大拓宽了传统声子晶体与超构材料的应用范围。本文首先依据压电材料与弹性材料或结构不同的融合形式，对智能压电声子晶体与超构材料进行了分类。在此基础上，依据声子晶体/超构材料的周期维度，对不同维度、不同形式的智能压电声子晶体/超构材料的研究现状及其应用进行了阐述，主要内容涉及到力-电耦合效应和外接电路的影响、带隙调控、弹性波导、单向传输、弹性波拓扑绝缘体、时空调制、弹性波隐身、弹性波聚焦等等。最后，对该领域未来研究工作的需求与期待进行了展望。

A Review on High Temperature Piezoelectric Crystal La3Ga5SiO14 for Sensor Applications.

In this review article, we have investigated the credibility and suitability of the lanthanum gallium silicate (La3Ga5SiO14, LGS) crystals in the application of high-temperature sensing. All the basic properties of the langasite family piezoelectric crystals, such as elastic properties, are taken into consideration and discussed. The crosstalk effects between different vibration modes of LGS crystal are investigated to optimize the crystal cuts. Thereafter, dependences of properties, such as electroelastic properties, resistivity, and electromechanical coupling coefficients of langasite family crystals on higher temperatures, are discussed. Finally, thermal-related properties of langasite family crystals, such as specific heat as well as thermal expansion coefficients, are studied for higher temperature ranges and a comparison with other piezoelectric crystals has also been presented.

Nonlinear piezoelectric surface acoustic waves.

The theory for nonlinear surface acoustic waves in crystals developed using Hamiltonian mechanics [Hamilton, Il'inskii, and Zabolotskaya, J. Acoust. Soc. Am. 105, 639 (1999)] is modified to account for piezoelectric material properties. The derived spectral evolution equations permit analysis of nonlinear surface wave propagation along a cut surface of any orientation with respect to the crystallographic axes and for piezoelectric crystals with any symmetry. Numerical simulations of waveform distortion in the particle velocity and electric field components are presented for surface wave propagation in Y-cut lithium niobate along the X- and Z-crystallographic axes. The influence of piezoelectricity is illustrated by comparing the nonlinear evolution of waveforms along a surface bounded by a vacuum (free space) and an ideal conductor (short circuit). Contributions to the nonlinearity from elasticity, piezoelectricity, electrostriction, and dielectricity are quantified separately for the two boundary conditions.

A New Analytical Method to Quantify Ammonia in Freshwater with a Bulk Acoustic Wave Sensor.

A new method to analyse ammonia in freshwater, based on a piezoelectric quartz crystal coated with the metalloporphyrin chloro[5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato] manganese(III) is presented. A 9 MHz quartz crystal coated on both faces with an amount of porphyrin produced a frequency decrease of 21.4 kHz, which allowed ammonia in a 10.00 mL sample to be quantified in concentrations between 5 and 70 µg L−1, with a sensitivity of 0.60 Hz L µg−1, over a period of at least eight months. The proposed method has several advantages over the officially recommended indophenol spectrophotometric method: sample volume was reduced by a factor of 2.5, toxic reagents (phenol and sodium nitroprusside) were eliminated, analysing turbid samples presented no difficulty, and there was not only a significant time saving in solution preparation, but also in sample analysis time, which was reduced from 1 h to 2 min. No statistically significant differences (α = 0.05) were found both in the mean and precision of the results obtained for ammonia in water samples collected from domestic wells, analysed by this new method and by the indophenol spectrophotometric method. Furthermore, the proposed method would allow the individual quantification, with similar sensitivity, of amines and ammonia within a single analytical run.

High-Performance Curved Piezoelectric Single-Crystal Composites via 3D-Printing-Assisted Dice and Insert Technology for Underwater Acoustic Transducer Applications.

Piezoelectric single-crystal composites (PSCCs) have been studied and applied because of their improved resolution and power source level performance in underwater acoustic transducer applications relative to traditional piezoelectric ceramic composites (PCCs). Currently, the methods to fabricate curved PSCCs are mostly derived from PCCs, including molding with flexible backing, molding with heating, and molding with the casting rubber method. Unfortunately, the methods mentioned above are not suitable for preparing curved PSCCs for underwater acoustic transducer applications because of their brittleness, the large anisotropy of piezoelectric single crystals, and the high thickness (>2 mm) of PSCCs for achieving the low operating frequency (<700 kHz). In the present work, we proposed a preparation method, 3D-printing-assisted dice and insert technology, and successfully prepared curved PSCCs with high performance. Although the PSCCs have a low volume fraction of single crystals in this work (∼33%), a high thickness electromechanical factor kt of 86% and a large piezoelectric coefficient d33 of 1550 pC/N were achieved in the curved 1-3 PSCCs, which are superior to other reported PSCCs and PCCs with nearly the same volume fraction of single crystals and piezoelectric ceramics. This work presents a paradigm for fabricating curved PSCCs for underwater acoustic transducers, and this method shows the potential for large-area, special-shaped PSCCs, which are key materials for next-generation underwater acoustic transducers.

Development of Cardiac Phased Array With Large-Size PZN-5.5 %PT Single Crystals.

In recent years, the manufacturing process of lead zinc niobate-lead titanate [Pb(Zn1/3Nb2/3)O3-PbTiO3, also called PZN-PT], has been enhanced with improvements in size, consistency, and a suitable compromise between piezoelectric properties and phase transition temperature, which means that it is possible to obtain PZN-PT single crystals in sufficient size for performance characterization studies and batch manufacturing to produce high-performance medical ultrasonic transducers. This article mainly focuses on the development of the 64-element phased array ultrasonic transducer based on novel large-size PZN-PT piezoelectric single crystals. The composition of the single crystal was chosen as PZN-5.5 %PT. The designed center frequency of the phased array is 3.0 MHz, which is suitable for cardiac ultrasound imaging. The array elements were spaced at a 0.254-mm pitch, and interconnected through a custom-designed flexible circuit. Double matching layers with a light backing structure were applied in the transducer fabrication process to improve the performance of the array. The test results of the developed phased array showed a center frequency of 3.0 MHz, and an average -6 dB fractional bandwidth of 72%. In the vicinity of the center frequency, the two-way insertion loss (IL) was about -46 dB, while a crosstalk between the adjacent elements was less than -31 dB. The wire phantom can be distinctly imaged with the phased array, and the axial and lateral resolutions were measured to be 660 and [Formula: see text], respectively. The image of a standard phantom was acquired to present the imaging performance of the transducer. The final results indicate that the transducer arrays based on novel large-size PZN-PT single crystals are quite promising for use in medical ultrasound imaging applications.

Self-powered energy-harvesting magnetic field sensor

Driven largely by the recent growth in the Internet of Things, there is a rapid surge in the demand for low-powered or self-powered sensors and devices. Here, we report a fully self-powered magnetic sensor system based on the magnetoelectric (ME) effect. This device consists of both a field-detection element and a power-generation element, which are designed using magnetostrictive Metglas amorphous ribbons and piezoelectric PMN-PT single crystal plates, respectively. The ME laminates for energy harvesting exhibit a giant resonance magnetic responsivity of 350 nC/Oe at 15 kHz. The magnetic-field sensing element shows a linear response with a high resolution up to 32 nT, and the magnetic-harvest element can reach a power of 48.68 mW/Oe at an optimum load resistance of 5 kΩ. The self-powered sensor system has shown excellent capability to convert magnetic energy into electrical energy, as demonstrated in powering a small electronic screen. The high sensitivity and power generation of our system suggest potential applications in sustainable intelligent sensor networks.

Surface Acoustic Wave (SAW) Sensors: Physics, Materials, and Applications.

Surface acoustic waves (SAWs) are the guided waves that propagate along the top surface of a material with wave vectors orthogonal to the normal direction to the surface. Based on these waves, SAW sensors are conceptualized by employing piezoelectric crystals where the guided elastodynamic waves are generated through an electromechanical coupling. Electromechanical coupling in both active and passive modes is achieved by integrating interdigitated electrode transducers (IDT) with the piezoelectric crystals. Innovative meta-designs of the periodic IDTs define the functionality and application of SAW sensors. This review article presents the physics of guided surface acoustic waves and the piezoelectric materials used for designing SAW sensors. Then, how the piezoelectric materials and cuts could alter the functionality of the sensors is explained. The article summarizes a few key configurations of the electrodes and respective guidelines for generating different guided wave patterns such that new applications can be foreseen. Finally, the article explores the applications of SAW sensors and their progress in the fields of biomedical, microfluidics, chemical, and mechano-biological applications along with their crucial roles and potential plans for improvements in the long-term future in the field of science and technology.

Piezoelectric lattice vibrations in GaN at optical frequencies

At optical frequency range, lattice vibrations in piezoelectric crystal are associated with ionic polarizations. A relationship is formulated, based on classical dispersion theory, involving the dielectric constant (εjj) and the piezoelectric coefficient (djj) of wurtzite GaN. The relation is utilized to investigate the piezoelectric lattice vibrations in GaN at optical frequency, and a close agreement between the computed and the experimental value of djj is found. The study reveals that applications of piezoelectric nature of GaN could be extended to optical frequencies to generate phase coherent acoustic phonons to modulate thermal conduction. At optical frequencies there are no direct experimental methods exist at present for measurement of djj; however, the proposed relation can help to determine djj from infrared reflection measurements.

Band structure of love wave in a one-dimensional piezoelectric layered phononic crystal with imperfect interface

The propagation of Love wave in a phononic crystal consisting of superlattice lithium niobate substrate carrying a piezoelectric waveguide layer is analyzed. The interface between the waveguide layer and the substrate is imperfectly bonded, which is described by means of a shear spring model. Numerical results show that the bandgap shifts to a lower frequency range and the bandwidth decreases as the interface imperfection increases. Moreover, the transmission coefficient calculations using finite element simulation revealed that a perfect interface results in more effective bandgap attenuation.