Piezoelectric Crystal Research Articles

Optical Control of Bulk Phonon Modes in Crystalline Solids

AbstractLong‐lived phonons within crystalline bulk acoustic wave (BAW) resonators have become coherent carriers of information, which can be utilized for a variety of scientific and technological applications. Herein, a brief introduction to the field of phonon control is given with an emphasis on bulk phonons at high frequencies within crystalline solids. In cavity optomechanics, the photons and phonons can be confined by material boundaries, yielding large optomechanical coupling rates at gigahertz (GHz) frequencies, but the spurious heating is detrimental to robust operation. Although electromechanical techniques can be used to access long‐lived phonons in piezoelectric crystals, they are not suitable for the study of non‐piezoelectric crystals. The phase‐matched Brillouin interactions enable efficient optical access GHz frequency mechanical modes within macroscopic crystalline solids. Combining with the well‐established framework of cavity optomechanics, efficient optical control of BAWs can be obtained. For optical phonons, strong spontaneous Raman cooling and heating based on the interaction between excitons and phonons are considered. In addition, the application of optical phonons in quantum memory at room temperature is introduced. The review finishes with a discussion of the research direction for bulk optomechanical systems and exciton–phonon coupling systems in the future.

High-temperature behavior of housed piezoelectric resonators based on CTGS

Abstract. A temperature sensor based on piezoelectric single crystals allowing stable operation in harsh environments such as extreme temperatures and highly reducing or oxidizing atmospheres is presented. The temperature dependence of the mechanical stiffness of thickness shear mode resonators is used to determine temperature changes. The sensor is based on catangasite (Ca3TaGa3Si2O14 – CTGS), a member of a langasite crystal family. CTGS exhibits an ordered crystal structure and low acoustic losses, even at 1000 ∘C. The resonance frequency and quality factor of unhoused and of housed CTGS resonators are measured up to about 1030 ∘C. A temperature coefficient of the resonance frequency of about 200 Hz K−1 for a 5 MHz device is found and enables determination of temperature changes as small as 0.04 K. Housed CTGS resonators do not show any significant change in the resonance behavior during a 30 d, long-term test at 711 ∘C.

Synthesis of (K, Na)NbO3 piezoelectric crystals with tunable K/Na ratios

(K, Na)NbO3 (KNN) lead-free piezoelectric crystals with different K/Na molar ratios were synthesized through a hydrothermal method using isopropanol/deionized water as the reaction medium. It is shown that cube-like KNN crystals were synthesized at a relatively low [OH–] concentration. The structure of the as-synthesized KNN crystals transfers from a NaNbO3-type orthorhombic phase to a KNbO3-type tetragonal phase with the increase of the K/Na ratio. This principle is also instructive in a finer range of K/Na ratio (0.71:0.29–0.73:0.27), indicating a facile synthesis route and recommended conditions for the synthesis of KNN materials with a morphotropic phase boundary (MPB) between NaNbO3 and KNbO3.

Relationship Between the Electrical Resistivity and the Band Gap for High-Temperature Piezoelectric Crystals

Aspects in Mining & Mineral Science Relationship Between the Electrical Resistivity and the Band Gap for High-Temperature Piezoelectric Crystals Shiwei Tian, Fapeng Yu* and Xian Zhao Institute of Crystal Materials, Center for Optics Research and Engineering, Shandong University, P.R. China *Corresponding author: Fapeng Yu, Institute of Crystal Materials, Center for Optics Research and Engineering, Shandong University, Jinan 250100, P.R. China Submission: December 30, 2019;Published: November 10, 2021 DOI: 10.31031/AMMS.2021.07.000673 ISSN 2578-0255Volume7 Issue5

A Method and Analysis to Enable Efficient Piezoelectric Transducer-Based Ultrasonic Power and Data Links for Miniaturized Implantable Medical Devices.

Acoustic links for implantable medical devices (implants) have gained attention primarily because they provide a route to wireless deep-tissue systems. The miniaturization of the implants is a key research goal in these efforts, nominally because smaller implants result in less acute tissue damage. Implant size in most acoustic systems is limited by the piezoelectric bulk crystal used for power harvesting and data communication. Further miniaturization of the piezocrystal can degrade system power transfer efficiency and data transfer reliability. Here, we present a new method for packaging the implant piezocrystal; the method maximizes power transfer efficiency ( η ) from the acoustic power at the piezo surface to the power delivered to the electrical load and information transfer across the acoustic link. Our method relies on placing piezo-to-substrate anchors to the piezo regions where the vibrational displacement of the mode of interest is zero. To evaluate our method, we investigated packaged 1×1×1 mm3 piezocrystals assembled with different sized anchors. Our results show that reducing the anchor size decreases anchor loss and thus improves piezo quality factor (Q). We also demonstrate that this method improves system electromechanical coupling. A strongly coupled, high-Q piezo with properly sized and located anchors is demonstrated to achieve significantly higher η and superior data transfer capability at resonance. Overall, this work provides an analysis and generic method for packaging the implant piezocrystal that enables the design of efficient acoustic power and data links, which provides a path toward the further miniaturization of ultrasonic implants to submillimeter scales.

Flexoelectric effect on thickness-shear vibration of a rectangular piezoelectric crystal plate

Thickness-shear (TSh) vibration of a rectangular piezoelectric crystal plate is studied with the consideration of flexoelectric effect in this paper. The developed theoretical model is based on the assumed displacement function which includes the anti-symmetric mode through thickness and symmetric mode in length. The constitutive equation with flexoelectricity, governing equations and boundary conditions are derived from the Gibbs energy density function and variational principle. For the effect of flexoelectricity, we only consider the shear strain gradient in the thickness direction so as to simply the mathematical model. Thus, two flexoelectric coefficients are used in the present model. The electric potential functions are also obtained for different electric boundary conditions. The present results clearly show that the flexoelectric effect has significant effect on vibration frequencies of thickness-shear modes of thin piezoelectric crystal plate. It is also found that the flexoelectric coefficients and length to thickness ratio have influence on the thickness-shear modes. The results tell that flexoelectricity cannot be neglected for design of small size piezoelectric resonators.

Piezo-modulated active grating for selecting X-ray pulses separated by one nanosecond.

We present a novel method of temporal modulation of X-ray radiation for time resolved experiments. To control the intensity of the X-ray beam, the Bragg reflection of a piezoelectric crystal is modified using comb-shaped electrodes deposited on the crystal surface. Voltage applied to the electrodes induces a periodic deformation of the crystal that acts as a diffraction grating, splitting the original Bragg reflection into several satellites. A pulse of X-rays can be created by rapidly switching the voltage on and off. In our prototype device the duty cycle was limited to ∼1 ns by the driving electronics. The prototype can be used to generate X-ray pulses from a continuous source. It can also be electrically correlated to a synchrotron light source and be activated to transmit only selected synchrotron pulses. Since the device operates in a non-resonant mode, different activation patterns and pulse durations can be achieved.

Drop-On-Demand Lubrication of Gears: A Feasibility Study

Different lubrication methods such as oil dip or injection lubrication are used in gearboxes to lubricate tribological contacts and to dissipate frictional heat. To improve resource and energy efficiency, novel needs-based lubrication methods like the drop-on-demand lubrication are being developed. It includes an ink-jet nozzle driven by a piezo element to generate picoliter droplets injected to tribological contacts. This study evaluates the feasibility of drop-on-demand lubrication of gears. Friction measurements in rolling-sliding contacts indicate the formation of typical elastohydrodynamic contacts. Power loss measurements of gears show a similar behavior compared to continuous minimum quantity lubrication. Hence, the study confirms that the operation of gears with drop-on-demand lubrication is possible. It introduces the possibility of dynamic and flexible oil supply on a contact needs-based level.

“Generation III” Piezoelectric Single Crystals Developed by Solid-State Single Crystal Growth Method

Crystallographically engineered Relaxor-PT single crystals, specifically PMN-PT (Generation I) and PIN-PMN-PT/PMN-PZT (Generation II), offer much higher piezoelectric and electromechanical coupling coefficients (d33>1,500 pC/N, k33>0.9), when compared to polycrystalline PZT-5H ceramics (d33>600 pC/N, k33>0.75). Recently Ceracomp Co., Ltd. (www.ceracomp.com) has developed the solid-state single crystal growth (SSCG) technique and successfully fabricated Gen III PMN-PZT single crystals modified with acceptors or donors. The piezoelectric constants (d33) of (001) Gen III PMN-PZT single crystals were measured to be higher than 4,000 pC/N and thus about two times higher than those of PMN-PT/PZN-PT (Gen I) and PIN-PMN-PT/PMN-PZT (Gen II) single crystals. The Gen III PMN-PZT single crystals have been firstly applied to single crystal-epoxy composites, ultrasonic transducers, piezoelectric sensors, and piezoelectric actuators. In this paper we introduce the development of Gen III PMN-PZT single crystals, piezoelectric composites and multilayer single crystal actuators.

An advanced boundary integral equation method for wave propagation analysis in a layered piezoelectric phononic crystal with a crack or an electrode

The paper presents an extended and advanced boundary integral equation method (BIEM) for simulating the elastic wave excitation and propagation in a layered piezoelectric phononic crystal with a strip-like crack or electrode. The method is based on the integral representation in terms of the Fourier transform of the Green's matrix for the whole piezoelectric laminate. A novel algorithm for constructing the Green's matrix, which allows taking into account the periodicity of the structure, is proposed. The obtained boundary integral equations are solved numerically using the Bubnov-Galerkin method with Chebyshev polynomials of the first and the second kind for a crack and an electrode respectively. The present method is compared with the standard finite element method (FEM), and the efficiency and convergence of the present method are also demonstrated by several representative numerical examples. The main advantages of the present extended and advanced BIEM lie in its strong capability of simulating unbounded piezoelectric laminates with a large number of layers (periodically or non-periodically arranged) as well as its high accuracy and efficiency compared with the FEM. The latter allows us to apply the method for a comprehensive parametric analysis and for the complex cases of multiple cracks and/or electrodes as well as for periodic arrays of cracks and/or electrodes.

Autonomous recombination and self-healing of fracture in piezoelectric organic crystals: scopes in crystal engineering

Autonomous recombination and self-healing of fracture in piezoelectric organic crystals: scopes in crystal engineering

Feasibility of Molten Salt Reactor Heat Exchanger Online Monitoring

Abstract Online structural health corrosion monitoring in advanced molten salt reactor heat exchangers is desirable for detecting tube degradation prior to leaks that would either cause mixing of heat exchanger fluids or release of radiologically contaminated fluids beyond the design containment boundary. This program seeks to demonstrate the feasibility for a torsional wave mode sensor to attach to the outside of a long (30-m) heat exchanger tube in the stagnant flow area where the tube joins the heat exchanger plenum and where it is possible to protect a sensor cable from high-force flow connecting through a heat exchanger shell to a monitoring instrument. The envisioned sensor and cable management approach will be impractical to implement on existing heat exchangers; rather, sensors must be installed in conjunction with the heat exchanger fabrication. Initially, flaw surrogates of interest (50% notch and 50% flat-bottom hole) have been detected in a 3-m tube using low-temperature PZT piezoelectric crystals. The transducer consisted of multiple shear elements placed circumferentially around a tube. The program will continue to investigate higher temperature piezoelectric ceramics, long-term performance of high-temperature adhesives, and flaw sensitivity on long (30-m +) tubes.

Influence of Phase Transitions on Electrostrictive and Piezoelectric Characteristics in PMN-30PT Single Crystals.

The ultrahigh electrostrain and piezoelectric constant (d33) in relaxor piezoelectric PMN-30PT single crystals are closely related to the coexistence and transition of multiple phases at the morphotropic phase boundary (MPB). However, the key mechanisms underlying the stability of the phases and their transitions are yet to be fully understood. In this work, we undertake a systematic study of the influences of phase transitions on the electrostrictive and piezoelectric behaviors in ⟨001⟩-, ⟨011⟩-, and ⟨111⟩-oriented PMN-30PT single crystals. We first classify the various phase transitions within the quasi-MPB in electric field-temperature phase diagrams as either dominated by the electric field or by temperature. We find that the electrostrain reaches a maximum at each phase transition, especially in the electric-field-dominated transitions, whereas d33 only peaks at specific phase transitions. In particular, the electrostrain in the ⟨001⟩ crystal reaches a maximum of S = 0.52% at 55 °C under an external electric field with E = 15 kV/cm, primarily due to a joint contribution of the electric field-dominated rhombohedral-monoclinic and monoclinic-tetragonal phase transitions at the quasi-MPB. An ultrahigh d33 (∼2460 pC/N) only occurs at the rhombohedral-monoclinic phase transition in the ⟨001⟩ crystal and at the rhombohedral-orthorhombic transition in the ⟨011⟩ crystal (d33 ∼ 1500 pC/N) due to the lower energy barriers. The temperature-dominated phase transitions also contribute toward minor peaks in electrostrain and/or d33. This work provides a deeper and quantitative understanding of the microscopic mechanisms underlying electrostrictive and piezoelectric behaviors relevant for the design of high-performance materials.

High-Level Software Interface to the LLRF System Developed for the European Spallation Source Facility

The European Spallation Source (ESS) accelerator is composed of superconducting elliptical cavities. When the facility is running, the cavities are fed with an electric field from klystrons. Parameters of this field are monitored and controlled by the low-level radio frequency (LLRF) system. Its main goal is to keep the amplitude and phase at a given set point. The LLRF system is also responsible for the reference clock distribution. During operation, the cavities are periodically experiencing strain caused by the Lorentz force, while the high gradient of the electric field is generated for the beam acceleration. Even small changes in the physical dimensions of a cavity shift its resonance frequency. This phenomenon, called detuning, causes significant power losses. It is actively compensated by the LLRF control system, which can physically tune lengths of the accelerating cavities with stepper motors (slow, coarse-grained control) and piezo elements (active compensation during operation). This article describes the implementation and tests of the software supporting various aspects of the LLRF system and cavities management. The Piezo Driver management and monitoring tool is dedicated to a piezo controller device. The LO distribution application is responsible for configuration of the local oscillator. The cavity simulator tool was designed to provide access to properties of the hardware device, emulating behavior of the elliptical cavities. IPMI Manager Software was implemented to monitor the state of MicroTCA.4 crates, which are a major part of the LLRF system architecture. All applications have been created using the experimental physics and industrial control system (EPICS) framework and built in the ESS EPICS Environment (E3).

Excitation Features of Surface Acoustic Waves by Interdigital Transducer in Piezoelectric Crystals

Excitation Features of Surface Acoustic Waves by Interdigital Transducer in Piezoelectric Crystals

Electro-mechanical coupling diode of elastic wave in nonlinear piezoelectric metamaterials.

In this investigation, the bandgaps and nonreciprocal transmission of the nonlinear piezoelectric phononic crystal and elastic wave metamaterial are studied. Analytical solutions for the wave motion equations with the electro-mechanical coupling are obtained. According to the continuous conditions, the stop bands and transmission coefficients of both fundamental wave and second harmonic are derived by the stiffness matrix method. Some particular examples are presented to show the nonreciprocal transmission of the nonlinear elastic waves. Additionally, nonlinear ultrasonic experiments are applied to verify the theoretical analyses and numerical simulations. This work is intended to be helpful in the design and fabrication of devices of the elastic wave diode with piezoelectric materials.

Dispersion relations of anti-plane elastic waves in micro-scale one dimensional piezoelectric semiconductor phononic crystals with the consideration of interface effect

In this paper, the propagation properties of anti-plane elastic waves in a piezoelectric semiconductor (PS) layered periodic composites are theoretically investigated. The periodic layered composites consist of periodically repeated two micro-scale geometrical thickness PS slabs with different elasticity, piezoelectricity and charge carriers. Following consideration of the coupling mechanical anti-plane displacement, electric potential and perturbation of charge carriers, the influences of interface effects resulted from homo- and hetero-junctions on the dispersion relations of anti-plane elastic waves are systematically discussed. It is found that homo- and hetero-junctions can be approximately treated as rigid imperfect interfaces, which can enhance the width of band-gaps of anti-plane elastic waves, especially for high-frequency short-wavelength anti-plane elastic waves. The establishment of mathematical models and the revelation of physical mechanisms are all fundamental to the analysis and optimization of micro-scale energy harvesters based on the propagation of anti-plane elastic waves.

Furcated droplet motility on crystalline surfaces.

Directed liquid motion has been conventionally mediated by functionalizing chemical inhomogeneity or texturing topological anisotropy on target surfaces. Here we show the self-propulsion of droplets that furcated in well-defined directions on piezoelectric single crystals in the absence of any apparent asymmetry or external force. By selecting the crystal plane to interface with the droplets, the thermoelastic-piezoelectric interplay yields intricate electric potential profiles, enabling various forms of self-propulsion including unidirectional, bifurcated and trifurcated. This effect originates from an anisotropic crystalline structure that generates contrasting macroscopic liquid behaviours and is observed with cold/hot and volatile droplets. Intrinsically oriented liquid motions have broad applicability in processes ranging from soft matter engineering, autonomous material delivery and thermal management to biochemical analysis.

Autonomous self-repair in piezoelectric molecular crystals.

Living tissue uses stress-accumulated electrical charge to close wounds. Self-repairing synthetic materials, which are typically soft and amorphous, usually require external stimuli, prolonged physical contact, and long healing times. We overcome many of these limitations in piezoelectric bipyrazole organic crystals, which recombine following mechanical fracture without any external direction, autonomously self-healing in milliseconds with crystallographic precision. Kelvin probe force microscopy, birefringence experiments, and atomic-resolution structural studies reveal that these noncentrosymmetric crystals, with a combination of hydrogen bonds and dispersive interactions, develop large stress-induced opposite electrical charges on fracture surfaces, prompting an electrostatically driven precise recombination of the pieces via diffusionless self-healing.

Autonomous self-healing

Materials Science The ability to autonomously restore shape or self-heal are useful properties that have been incorporated into a range of materials, including metals and polymers. Bhunia et al. found that both of these abilities could be achieved in piezoelectric molecular crystals, specifically bipyrazole organic crystals. When the crystals are fractured, they develop charged surfaces that attract each other, drawing the two faces together to enable self-repair as long as they remain within a critical distance of each other. The effect can also be seen in other noncentrosymmetric piezoelectric crystals. Science , abg3886, this issue p. [321][1] [1]: /lookup/doi/10.1126/science.abg3886