Lead Magnesium Niobate-lead Titanate Research Articles

Investigations of high-Performance Ultrasonic Transducers based on PMN-PT Single Crystals

Ultrasonic transducers for NDE applications are commonly based on Lead Zirconate Titanate or PZT, an inorganic compound and ceramic perovskite material. Until now the advantages of PMN-PT are used in medical applications, but are not implemented in NDE. Lead Magnesium Niobate-Lead Titanate (PMN-PT) is well known for its high sensitivity and broad frequency spectrum. While conventional PZT materials have an electromechanical coupling factor K33 (a measure of the conversion between electrical and acoustic energy) of about 0.72, PMN-PT materials reach peak values of more than 0.93. For applications with low signal amplitudes, high electronic noise and small transducer elements, the performance of ultrasonic probes can be significantly enhanced by using Lead Magnesium Niobate-Lead Titanate (PMN-PT) instead of PZT. This single-crystal material offers significantly better piezo parameters and leads to a higher sensitivity and larger bandwidth. There is a better depth resolution possible with this transducers as practical tests have shown. Similar to PZT it can also be fabricated in 1-3 piezo- composite technology. In a cooperation between Fraunhofer IKTS, iBULe Photonics, and IFU Diagnostic Systems, PMN-PT ultrasonic transducers are developed and optimized. The performance of phased array probes and single element transducers was measured by a so called PCUS® pro electronic front end from Fraunhofer and compared with equivalent PZT-based probes. As a result various single element and phased array transducers with im-proved performances are available for NDT of typical aerospace materials and applications. These test setups were used to weigh up the advantages and disadvantages, such as achievable precision or costs, for the implementation of a PMN-PT-based UT matrix probe. Based on this, a wiring variant adapted to the PMN-PT was developed and optimised for the matrix setups by pre- assembling the matching layers. The most favourable setup turned out to be bonding the PMN- PT composites to the prefabricated matching layers together with a rigid-flexible PCB frame. This enabled direct wire bonding of 64 matrix elements to the matching PCB pads on the rigid frame.

High-powered superhydrophobic pyroelectric generator via droplet impact

Recent studies on water-based pyroelectric generators (PEGs), which convert thermal energy to electrical energy, have focused on different operational modes like water evaporation, water stream, and droplet sliding. However, the development of sustainable, high-powered generators and comprehensive theoretical models has been limited. In response, our research introduces a droplet-based superhydrophobic pyroelectric generator (S-DPEG), exploiting the characteristics of lead magnesium niobate-lead titanate (PMN-0.3PT) coated with titanium dioxide nanoparticles. We analyzed power density by considering the phase transient temperature that maximizes the pyroelectric coefficient of PMN-0.3PT, testing various Weber numbers and droplet diameters within a moderate operating temperature range of 40°C to 80°C. Considering the dynamic characteristics of water droplet on superhydrophobic surfaces, we suggest a peak current model that can accurately predict the peak current within ∼15% of error. Also, the maximum power density of 54.5 μW/cm2 at a droplet diameter of 3.6 mm and a temperature of 80°C, a noteworthy improvement over 3 times higher than previous water-based PEGs. Our results enhance the understanding of the pyroelectric effect coupled with drop impact dynamics and outline novel strategies for designing high-performance water-based PEGs.

Parallel differential evolution paradigm for multilayer electromechanical device optimization

Design optimization of multilayer piezoelectric transducers is intended for efficient and practical usage of wideband transducers for fault diagnosis, biomedical, and underwater applications through adjusting layer thicknesses and volume fraction of piezoelectric material in each layer. In this context, we propose a parallel differential evolution (PDE) algorithm to mitigate the complexities of multivariate optimization as well as the computation time to achieve an optimized wideband transducer for the particular application. For lead magnesium niobate-lead titanate (PMN PT)- and PZT5h-based piezoelectric materials, the fitness function is formulated based on uniformity of mechanical pressure at the first three harmonics to achieve wide bandwidth in the required functional frequency range. It is carried out using a one-dimensional model (ODM), while input layer thicknesses and volume fractions of active material are evaluated using PDE. The simulation is performed on a parallel computing platform utilizing three different host machines to reduce computational time. Results of the proposed methodology for PDE are statistically represented in the form of minimum, maximum, mean, and standard deviation of fitness value, while graphically represented in terms of speedup and time. It can be observed that the execution time for parallel DE decreases with the increasing number of cores.

High Entropy Nonlinear Dielectrics with Superior Thermally Stable Performance.

A high configurational entropy, achieved through a proper design of compositions, can minimize the Gibbs free energy and stabilize the quasi-equilibrium phases in a solid-solution form. This leads to the development of high-entropy materials with unique structural characteristics and excellent performance, which otherwise couldnot be achieved through conventional pathways. This work develops a high-entropy nonlinear dielectric system, based on the expansion of lead magnesium niobate-lead titanate. A dense and uniform distribution of nano-polar regions isobserved in the samples owing to the addition of Ba, Hf, and Zr ions, which lead to enhanced performance of nonlinear dielectrics. The fact that no structural phase transformation isdetected up to 250°C, and no noticeable change or a steep drop in structural and electrical characteristics isobserved at high temperatures suggests a robust thermal stability of the dielectric systems developed. With these advantages, these materials hold vast potential for applications such as dielectric energy storage, dielectric tunability, and electrocaloric effect. Thus, this work offers a new high-entropy configuration with elemental modulation, with enhanced dielectric material features.

Samarium-Doped Lead Magnesium Niobate-Lead Titanate Ceramics Fabricated by Sintering the Mixture of Two Different Crystalline Phases.

The fabrication method plays a key role in the performance of lead magnesium niobate-lead titanate-based ceramics. (1 - w)[Pb(Mg1/3Nb2/3)0.67Ti0.33O3]-w[Pb1-1.5xSmx(Mg1/3Nb2/3)yTi1-yO3] piezoelectric ceramics were prepared by sintering the mixture of two different crystalline phases in which two pre-sintered precursor powders were mixed and co-fired at designated ratios (w = 0.3, 0.4, 0.5, 0.6). The X-ray diffraction results show that all the ceramics presented a pure perovskite structure. The grains were closely packed and the average size was ~5.18 μm based on observations from scanning electron microscopy images, making the ceramics have a high density that is 97.8% of the theoretical one. The piezoelectric, dielectric, and ferroelectric properties of the ceramics were investigated systematically. It was found that the properties of the ceramics were significantly enhanced when compared to the ceramics fabricated using the conventional one-step approach. An outstanding piezoelectric coefficient d33 of 1103 pC/N and relative dielectric permittivity ε33/ε0 of 9154 was achieved for the ceramics with w = 0.5.

Effective electromechanical properties and energy harvesting response in PMN-0.3PT/PDMS flexible piezoelectric composites: a combined experimental and theoretical study

In this work, lead magnesium niobate-lead titanate (PMN-0.3PT) and polydimethylsiloxane (PDMS)-based flexible piezoelectric-polymer composites are designd and developd for efficient mechanical energy harvesting through a combined experimental-theoretical approach. A solid-state reaction method was employed to synthesize PMN-0.3PT piezo-ceramic, which was subsequently used for the fabrication of -PMN-0.3PT/PDMS piezoelectric-polymer 0–3 composite with different volume fractions, = 0.03, 0.25, and 0.50 of PMN-0.3PT reinforcement. Uniformly distributed PMN-0.3PT particles were found to retain their structural symmetry across the volume fractions and are well adhered to the PDMS matrix. The effective electromechanical properties of the composites were measured and compared with model predictions employing the finite element method and Eshelby–Mori–Tanaka-based micromechanical models. Considering that flexibility is a critical design parameter, we propose a new figure-of-merit term that would consider both electromechanical conversion as well as the mechanical flexibility of the material. We show that at = 0.5, PMN-0.3PT/PDMS 0–3 composite yields an optimum combination of energy harvesting performance and flexibility. Our study further demonstrates that the orientation of the PMN-0.3PT particles does not significantly influence the effective elastic and dielectric properties at low and moderate PMN-PT content, attributed to the lower aspect ratio of the reinforcement particles. The piezoelectric charge coefficient showed small yet finite change with increasing reinforcement content. A maximum current density, 35 nA cm−2, and electric field, 90 V cm−1, was obtained with a cyclic compressive stress of 0.22 MPa (force, 50 N) at 5 Hz, in a piezoelectric generator, based on = 0.5.

Revisiting lead magnesium niobate-lead titanate piezoceramics for low-frequency mechanical vibration-based energy harvesting

Revisiting lead magnesium niobate-lead titanate piezoceramics for low-frequency mechanical vibration-based energy harvesting

Investigation on ferroelectric, dielectric and pressure sensing properties of samarium substituted lead magnesium niobate-lead titanate oxide

In the last several decades, researchers have been developing hydraulic pressure sensors suitable in harsh oil mediums with high figures of merit. A well-known columbite method is used to prepare a series of phase pure electroceramics Pb(1-1.5y)Smy[(Mg1/3Nb2/3)1-xTix]O3 (Sm(y)-PMN(x)PT) with x = 0.20, 0.30; and y = 0.010, 0.025 for possible applications as hydraulic pressure sensors. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out to study the crystal structure, microstructure, and morphology of the sintered ceramics. The frequency and temperature-dependent dielectric and ac conductivity analyses were performed over a temperature range of 300–480 K to understand the phase stability and phase transition temperatures. Room temperature (297 K) polarization-electric field and PUND analysis confirmed the large polarization (∼30–40 μC/cm2) in the investigated compositions. The hydrostatic pressure-dependent relative capacitance change was examined using a lab-made setup for different compositions for the pressure varying from 0 to 50 MPa. The percentage sensitivity varies with samarium and titanium compositions that range from 0.078 MPa−1 to 0.197 MPa−1. The highest relative change in capacitance was obtained for Pb0.963Sm0.025[(Mg1/3Nb2/3)0.80Ti0.20]O3 (Sm0.025-PMN0.20PT) ceramic with percentage sensitivity 0.197 MPa−1, nearly double to our earlier report on Pb[(Mg1/3Nb2/3)0.7Ti0.3]O3 composition. The improvement in sensitivity may be due to inherent properties, such as slim hysteresis, low tangent loss (∼0.002–0.1), large change in phase transition temperature (∼25 K) due to dielectric dispersion and relaxor-like nature compared to other investigated systems.

Development of Single-Channel Dual-Element Custom-Made Ultrasound Scanner with Miniature Optical Position Tracker for Freehand Imaging.

Handheld ultrasound has great potential in resource-limited areas, and can improve healthcare for rural populations. Single-channel ultrasound has been widely used in many clinical ultrasound applications, and optical tracking is considered accurate and reliable. In this study, we developed a 10 MHz lead magnesium niobate-lead titanate (PMN-PT) dual-element ultrasound transducer combined with a miniature optical position tracker, and then measured the rectus femoris of the thigh, upper arm, and cheek muscles. Compared to single-element transducers, dual-element transducers improve the contrast of near-field signals, effectively reduce noise, and are suitable for measuring curved surfaces. The purpose of position tracking is to calculate the location of the ultrasound transducer during the measurement process. By utilizing positioning information, 2D ultrasound imaging can be achieved while maintaining structural integrity. The dual-element ultrasound scanner presented in this study can enable continuous scanning over a large area without a scanning width limitation. The custom-made dual-element ultrasound scanner has the advantage of being a portable, reliable, and low-cost ultrasound device, and is helpful in popularizing medical care for remote villages.

Fabrication and Characterization of High Performance PVDF-based flexible piezoelectric nanogenerators using PMN-xPT (x:30, 32.5, and 35) particles

Flexible piezoelectric nanogenerators based on polyvinylidene difluoride (PVDF) and lead magnesium niobate-lead titanate Pb(Mg1/3Nb2/3)O3–PbTiO3(PMN-xPT compositions for x between 30 and 35) particles with various filler ratios from 10 to 30 vol% were fabricated through the electrospinning method. The phase and microstructural characterizations revealed that the homogenous and continuous fiber-shaped composite structure with good interfacial interaction between the PMN-PT particles and the PVDF matrix was achieved. It was found that the diameter of the neat PVDF fibers was approximately 354 nm, whereas the PVDF/PMN-35PT fibers with ceramic particle concentrations of 10, 20, and 30 vol% had average diameters of 317, 249, and 163 nm, respectively. The piezoelectric performance tests indicated that the 30 vol%PVDF/PMN-35PT nanogenerator had a 3 times greater electrical power efficiency (10.59 μW) at 20 Hz compared to that of the pure PVDF nanogenerator (3.56 μW) at 15 Hz under the same resistance load of 1 MΩ. All in all, the incorporation of PMNT-PT particles into the PVDF appears to be a good approach for the fabrication of high-performance flexible piezoelectric nanogenerator applications for biomechanical energy harvesting of devices converting the mechanical movements of organs such as cardiac and lung into electrical energy.

Graphene enhanced flexible piezoelectric transducers for dynamic strain measurement: from material preparation to application

In this study, graphene particles are introduced to the lead magnesium niobate-lead titanate and polyvinylidene fluoride (PVDF) to form a flexible ternary composite. The graphene concentration is rigorously designed and morphologically optimized, warranting good piezoelectric and dielectric properties. The piezoelectric and dielectric performances are greatly increased compared with the pure PVDF films. Then a theoretical model is formulated to quantitatively interpret the graphene effect on the permittivity performance and to provide guidelines for the optimization of graphene volume fraction. Moreover, a simple and cost-effective technique is designed to package the composite film as a large-area, lightweight and flexible transducer. Several confirmatory experiments and a proof-of-concept test are performed based on the proposed flexible piezoelectric transducer to validate the capability of the dynamic strain sensing. By comparing with the results from conventional strain gauges and ceramic piezoelectric wafers, it is verified that the proposed flexible transducer has proven responsivity and precision in responding to quasi-static strain, medium-frequency vibration, and ultrasound. The great potential of the developed transducer for a wide range of applications including structural health monitoring and human motion detection has been demonstrated.

Manipulation of magnetic anisotropy by voltage induced strain in Co2MnAl/PMN-PT heterostructure

We have investigated the effect of an external electric field on the magnetic properties of Co2MnAl thin films deposited on a lead magnesium niobate-lead titanate (PMN-PT) (011) substrate. Stain-induced magnetoelectric coupling affects the magnetic properties of the Co2MnAl/PMN-PT system. The piezo-strain induced by applying an external field normal to the surface induces only in-plane strain, which leads to the rotation of easy-axis orientation of Co2MnAl from [100] to [011¯] direction. The remanent magnetization states and coercivity of the Co2MnAl film vary significantly and asymmetrically with the applied voltage due to anisotropic strain originating from PMN-PT. Electrical control of magnetic anisotropy in a Co2MnAl Heusler compound at room temperature will be of interest for realizing next-generation magnetoelectric random access memory devices.

Boosting the lifespan of magneto-mechano-electric generator via vertical installation for sustainable powering of Internet of Things sensor

Sustainability is essential for magneto-mechano-electric (MME) energy harvesters that convert low-frequency magnetic noise into useful electrical energy to be considered a practical power source for implementing real-life Internet of Things (IoT) sensor networks. In this study, we propose a vertically installed MME energy harvester based on a piezoelectric lead magnesium niobate-lead zirconate titanate (Pb(Mn1/3Nb2/3)O3-Pb(Zr,Ti)O3, PMN-PZT) single-crystal macro fiber composite cantilever. The MME harvester generates 12.2 mW output power from a low-amplitude stray magnetic field of 2.5 Oe and exhibits a long-term usable lifetime of 2.5 × 109 cycles while maintaining over 90 % of its output. An accelerated life test method is employed to predict the usable lifetime of the MME harvester using an inverse power law-Weibull model with accelerating stress of magneto-mechanical vibration-induced strain. In addition, a standalone wireless environmental monitoring system is demonstrated to operate for 10 weeks by exploiting the harvested power from stray magnetic fields (~2.2 Oe) near the power cables of home appliances. This study paves the way for lifetime assessment and prediction of sustainable MME harvesters to increase the practicability of self-powered IoT devices in smart infrastructures.

Generation of selective single-mode guided waves by d36 type piezoelectric wafer

In general, mixed modes and dispersion of guided wave occur at any excitation frequency, while single modes are needed for effective nondestructive evaluation of structures. In this work, we present an approach to generate a selective single-mode guided wave in plate-like structures by exploiting the unique directionality of the d36 type piezoelectric wafer and the symmetry of fundamental guided wave modes. Specifically, we devise a unified fundamental shear horizontal (SH0) wave/fundamental antisymmetric mode (A0) wave directional transducer pair by attaching the d36 type piezoelectric wafers back to back on the opposite sides of the plate to provide selective, directional single-mode guided waves for actuation and sensing. Originally, the d36-type piezoelectric wafer, poled and cut from the lead magnesium niobate-lead titanate crystal, produces a mixture of the in-plane SH0 (symmetric) mode and out-of-plane A0 (asymmetric) and S0 (symmetric) modes. By applying the in-phase or out-of-phase applied electrical field to the coupled d36-type piezoelectric wafer pair, our devised approach generates selective single modes, SH0 or A0, respectively, to propagate in the structure. We describe the theoretical development of our approach and conduct both numerical simulations and laboratory experiments for validations.

Design and Micro-Fabrication of Focused High-Frequency Needle Transducers for Medical Imaging.

In this study, we report an advanced fabrication technique to develop a miniature focused needle transducer. Two different types of high-frequency (100 MHz) transducers were fabricated using the lead magnesium niobate-lead titanate (PMN-0.3PT) and lithium niobate (LiNbO3) single crystals. In order to enhance the transducer’s performance, a unique mass–spring matching layer technique was adopted, in which gold and parylene play the roles of the mass layer and spring layer, respectively. The PMN-0.3PT transducer had a 103 MHz center frequency with a −6 dB bandwidth of 52%, and a signal-to-noise ratio (SNR) of 42 dB. The center frequency, −6 dB bandwidth, and SNR of the LiNbO3 transducer were 105 MHz, 66%, and 44 dB, respectively. In order to compare and evaluate the transducers’ performances, an ultrasonic biomicroscopy (UBM) imaging on the fish eye was performed. The results showed that the LiNbO3 transducer had a better contrast resolution compared to the PMN-0.3PT transducer. The fabricated transducer showed an excellent performance with high-resolution corneal epithelium imaging of the experimental fish eye. These interesting findings are useful for the future biomedical implementation of the fabricated transducers in the field of high-resolution ultrasound imaging and diagnosis purpose.

Design, fabrication, and characterization of piezoelectric single crystal stack actuators based on PMN-PT

A piezoelectric stack actuator (PSA) consisting of 28 lead magnesium niobate-lead titanate (PMN-PT) piezoelectric single crystal layers is developed. The free stroke and blocking force, which are the figures of merit of a PSA, are simulated through finite element analysis. The free stroke of the PSA samples measured using a laser displacement sensor was in the range of 6.4–8.0 µm at 200 V. In addition, the blocking force of the PSA samples measured using a custom-made system, consisting of a strain gauge, a motor and a load cell, was in the range of 191–226 N at 200 V. An analysis of seven samples exhibited that a large free stroke resulted in a blocking force of the PSA.

Effects of Composition Segregation in PMN-PT Crystals on Ultrasound Transducer Performance.

This study investigates the relationship between the composition segregation in lead magnesium niobate-lead titanate (PMN-PT; PMN-29%PT, PMN-29.5%PT, PMN-30%PT, PMN-30.5%PT, and PMN-31%PT) single crystals within morphotropic phase boundary (MPB) and the corresponding ultrasonic transducer performance through PiezoCAD modeling and real transducer testing. For five crystals with compositions distributed across the main body of a crystal ingot, the piezoelectric coefficient and free relative permittivity values were measured to vary by over 30%, whereas the transducer bandwidth and center frequency values were modeled to change by less than 10%. For the single-element ultrasonic transducers fabricated using those crystals without matching layers, the variations of -6-dB bandwidth, insertion loss, receiver-free field voltage response, and center frequency were measured to be 9.61%, -15.23%, 9.76%, and 1.41%, respectively, confirming the modeling results. Using the Mason and Krimholtz, Leedom, and Matthaei (KLM) models, it is found that the relatively stable transducer performance can be attributed to the relatively consistent electromechanical coupling coefficient, acoustic impedance, and clamped relative permittivity originated from the stable elastic compliance properties among the crystals of various compositions. It is expected that the relatively stable performance could be extended to multielement transducers with matching layers for the same contributing mechanisms. Our results suggest that it is possible to use crystal plates of different compositions within the MPB region, obtained from one and the same ingot, to fabricate a batch of ultrasonic transducers that will exhibit a similar performance, significantly reducing the cost of materials.

Electric-field tunable rotation of optical mode ferromagnetic resonance in FeCoB/Ru/FeCoB/PMN-PT multilayers

FeCoB/Ru/FeCoB trilayers with a uniaxial magnetic anisotropy were deposited on (011)-cut lead magnesium niobate-lead titanate (PMN-PT) single crystal ferroelectric substrates using a compositional gradient sputtering (CGS) method. Ultrahigh optical mode resonance frequencies from 11.76 to 18.96 GHz at zero magnetic field were achieved due to the strong interlayer exchange coupling between FeCoB films through Ru spacer. In this study, two orthogonal magnetic anisotropic fields (one is CGS induced anisotropy field HKCGS and the other is the piezoelectric stress-induced anisotropy field HKME) were set to realize electric-field (E-field) controlled switch of magnetic moment configuration through their competition. As a result, the optical mode resonance intensity can make reversible 90° rotation under applied E-field, while the advantages of ultrahigh frequency optical mode resonance in trilayers are still maintained because the interlayer exchange coupling is not destroyed by magnetoelectric coupling. The ultrahigh resonance frequency and E-field tunable and reversible FMR rotation in these trilayers provide a potential route to guide microwave flow in multifunctional microwave and spintronic devices.

Traceable Nanoscale Measurements of High Dielectric Constant by Scanning Microwave Microscopy.

The importance of high dielectric constant materials in the development of high frequency nano-electronic devices is undeniable. Their polarization properties are directly dependent on the value of their relative permittivity. We report here on the nanoscale metrological quantification of the dielectric constants of two high-κ materials, lead zirconate titanate (PZT) and lead magnesium niobate-lead titanate (PMN-PT), in the GHz range using scanning microwave microscopy (SMM). We demonstrate the importance of the capacitance calibration procedure and dimensional measurements on the weight of the combined relative uncertainties. A novel approach is proposed to correct lateral dimension measurements of micro-capacitive structures using the microwave electrical signatures, especially for rough surfaces of high-κ materials. A new analytical expression is also given for the capacitance calculations, taking into account the contribution of fringing electric fields. We determine the dielectric constant values εPZT = 445 and εPMN-PT = 641 at the frequency around 3.6 GHz, with combined relative uncertainties of 3.5% and 6.9% for PZT and PMN-PT, respectively. This work provides a general description of the metrological path for a quantified measurement of high dielectric constants with well-controlled low uncertainty levels.

A High Sensitivity Transparent Ultrasound Transducer based on PMN-PT for Ultrasound and Photoacoustic Imaging.

We recently introduced piezoelectric lithium niobate (LN) based transparent ultrasound transducers (TUT) as a new platform for developing multimodal optical, ultrasound and photoacoustic imaging systems. However, LN based TUT is limited in its signal-to-noise ratio due to material's low piezoelectricity (d 33). In this paper, we report, for the first time, a 0.2 mm thick transparent lead magnesium niobate-lead titanate (PMN-PT) based TUT (PMN-PT-TUT) for ultrasound and photoacoustic applications and compared its performance with a 0.25 mm thick transparent LN based TUT (LN-TUT). To improve the ultrasound energy transmission efficiency, TUTs were fabricated with a two-matching-layer design. This resulted in a dual frequency response with center frequencies of 7.8 MHz/13.2 MHz and corresponding bandwidths of 28.2%/66.67% for PMN-PT-TUT, and center frequencies of 7.2 MHz/11.8 MHz and bandwidths of 36.1%/62.7% for LN-TUT. The optical transmission rate of PMN-PT-TUTs and LN-TUTs are measured as ~73% and ~91% respectively at 532 nm optical wavelength. The PMN-PT-TUT exhibited higher sensitivity compared to LN-TUT with a nearly three-fold higher pulse echo amplitude and more than two-fold higher photoacoustic amplitude. Furthermore, optical resolution photoacoustic microscopy (ORPAM) experiments on phantom targets demonstrated lateral resolutions of 7 μm and 5.1 μm, and axial resolutions of 285.6 μm and 375.9 μm for PMN-PT-TUT and LN-TUT respectively. These results indicated that PMN-PT is a viable alternative to LN for developing TUT based multimodal ultrasound and photoacoustic imaging systems.