Poling Process Research Articles

Enhanced Output Performance of a Flexible Piezoelectric Nanogenerator Realized by Lithium-Doped Zinc Oxide Nanowires Decorated on MXene.

A flexible piezoelectric composite is composed of a polymer matrix and piezoelectric ceramic fillers to achieve good mechanical flexibility and processability. The overall piezoelectric performance of a composite is largely determined by the piezoelectric filler inside. Thus, different dispersion methods and additives that can promote the dispersion of piezoelectric ceramics and optimal composite structures have been actively investigated. However, relatively few attempts have been made to develop a filler that can effectively contribute to the performance enhancement of piezoelectric devices. In the present work, we introduce the fabrication and performance of the composite piezoelectric devices composed of Li-doped ZnO nanowires (Li: ZnO NWs) grown on the surface of MXene (Ti3C2) via the hydrothermal process. Through this approach, a semiconductor-metal hybrid structure is formed, increasing the overall permittivity. Moreover, the Ti3C2 layer can serve as a local ground in the composite so that the ferroelectric phase-transformed Li: ZnO NWs grown on its surface can be more effectively polarized during the poling process. In addition, the NW-covered surface of Ti3C2 prevents the aggregation of metallic Ti3C2 particles, promoting a more uniform electric field distribution during the poling process. As a result, the output performance of the piezoelectric nanogenerator (PENG) fabricated with a Li: ZnO NW/Ti3C2 composite was greatly improved compared to that of the devices fabricated with Li: ZnO NWs without the Ti3C2 platform. Specifically, the Li: ZnO NW/Ti3C2 composite piezoelectric nanogenerator (PENG) demonstrated a twofold higher output power density (∼9 μW/cm2) compared with the values obtained from the PENG devices based on Li: ZnO NWs. The approach introduced in this work can be easily adopted for an effective ferroelectric filler design to improve the output performance of the piezoelectric composite.

Second harmonic generation by quasi-phase matching in a lithium niobate thin film

Lithium niobate thin film becomes a promising material platform for integrated nonlinear optics. Quasi-phase matching is an important way to realize optical frequency conversion. Due to the strong dispersion of the high-refractive-index-contrast lithium niobate thin film waveguides, a small poling period (several micrometers) is needed, which becomes a challenge for the poling process. In this paper, a periodic reversed domain with a period of 3.8 µm was realized by poling with an external electric field in the x-cut lithium niobate thin film. The reversed domains were characterized by piezoresponse force microscopy and the confocal Raman spectroscopy. The second harmonic generation was realized in the ridge waveguides, and the normalized conversion efficiency was 684%W−1cm−2. The waveguide loss, the irregularity of the reversed domain, and the inhomogeneities effective index along the waveguide were analyzed to be the main sources of the conversion efficiency decrease. The simulations showed that the phase matching was very sensitive to waveguide geometry. This work provided useful information for studying second harmonic generation in the lithium niobate on insulator.

Nanoscale Activation Energy Mapping and Leveraging for Accelerating Ferroelectric Domain Nucleation and Growth

AbstractThe dynamics of ferroelectric domain switching are directly mapped in a PbZr0.2Ti0.8O3 thin film using piezoresponse force microscopy. Employing the rastering tip as a poling electrode to locally apply a fixed bias near the coercive field, while simultaneously monitoring the evolving domain pattern during continuous imaging, the effectively independent switching dynamics for numerous domains are directly investigated. While areal poling follows the anticipated S‐curve, this is shown to be the collective outcome of linear terminal radial growth for an ensemble of independently nucleating domains. By repeating such spatially resolved measurements in the same region, but with progressively greater fields, nucleation sites and growth patterns are shown to clearly repeat. This reveals apparent defects which comparatively promote switching, and nucleation times and growth rates that accelerate exponentially. After analyzing and mapping the ratio of activation energies for nucleation to growth, a high density of nucleation sites can possibly be activated with higher poling fields—even if only at the start of a poling process—enabling faster and more efficient switching to be engineered as directly demonstrated.

Composition and poling process dependence of phase and piezoelectric activity of Er:PMN-PT crystals

Composition and poling process dependence of phase and piezoelectric activity of Er:PMN-PT crystals

Dendronized Hyperbranched Polymer: A New Architecture for Second-Order Nonlinear Optics

Organic/polymeric second-order nonlinear optical (NLO) materials, which rely on the poling-induced non-centrosymmetric arrangement of NLO chromophores, have played a very important role in laser technology and optical fiber communication, due to their ultra-fast response speed, excellent machining performance and low dielectric constant. However, the NLO chromophores have the large dipole moments with strong intramolecular charge transfer, which lead to the intermolecular electrostatic interactions to tend to the centrosymmetric arrangement and decrease the poling efficiency. Since the special three-dimensional spatial separation can minimize these strong intermolecular electrostatic interactions during poling process, dendrimers and hyperbranched polymers have been considered as better topology for the next generation of highly efficient NLO materials. In 2013, by the attachment of low generation dendrimers to the hyperbranched backbone, a new dendritic architecture of dendronized hyperbranched polymer (DHP) was proposed for improving the comprehensive performance of NLO materials. Recent results showed many advantages of DHPs in NLO field, such as easy syntheses, large NLO coefficients and high orientation stability, etc. In this review, the latest advancement of DHPs, including the design principle, synthesis, as well as their application as NLO materials is summarized. The new opportunities arising from DHPs are also summarized in the future perspective.

Low‐Harmonic Generation in Cascaded Thin‐Film Lithium Niobate Waveguides

Herein, frequency conversion to the third‐ and fourth‐order harmonics are demonstrated in ultracompact cascaded periodically poled thin‐film lithium niobate (LN) waveguides on silicon substrates. Pumped at 1550 nm wavelength, the tightly confined waveguides produce strong third‐ (523 nm) and fourth‐harmonic (386 nm) signals. Actively monitoring the periodic poling process on the LN devices renders these efficient frequency conversions. Measurements with a femtosecond pulsed laser source result in comparable power levels across the generated harmonics. A model that simulates harmonic generation from the pulsed source is presented and discussed. The model's results are in general agreement with the experimentally observed processes.

Enhanced photocatalytic activity in ferroelectric BiFeO3 nanoparticles treated by a corona poling method

BiFeO3 particles of about 50 nm were prepared by the sol-gel method with the calcination temperature of 450°C. The corona poling treatment was carried out on BiFeO3 nanoparticles for different electric fields and duration time. XRD analysis reveals that the BiFeO3 nanoparticles maintain the stable perovskite structure before and after the poling treatment. Raman and XRD analysis respectively show that the Bi–O bonds stretched and the lattice distorted for BiFeO3 nanoparticles with corona poling treatment. The poled BiFeO3 nanoparticles exhibit better photocatalytic kinetics in degradation of methyl orange (MO) dyes under the visible light irradiation for 3 h, which is about 5.1 times better relative to the BiFeO3 nanoparticles without the poling treatment. We conjecture that the enhanced internal electric fields produced by the corona poling process may be beneficial to the reduction of the combination of photogenerated electron-hole pairs resulting in the enhanced photocatalytic activity of BiFeO3 nanoparticles.

Synthesis of KNN nanoblocks through surfactant-assisted hot injection method and fabrication of flexible piezoelectric nanogenerator based on KNN-PVDF nanocomposite

With the tremendous growth of flexible piezoelectric nanogenerators, alkali niobates have gained considerable attention and are perceived to be the eco-friendly substitute for the unsustainable lead based piezoelectric systems. However, successful realization of potassium sodium niobate (KNN) based devices with appreciable piezoelectricity requires tailored molecular level organization. Herein, we have developed a lead-free flexible piezoelectric nanogenerator based on KNN-PVDF nanocomposite, in which the KNN nanoblocks were synthesized using a novel non-aqueous surfactant-assisted hot injection method. Also, the synthesis of KNN employed non-toxic surface stabilizer, oleic acid and reaction catalyst, oleyl amine respectively, making the preparation environmental benign. The KNN nanoblocks homogeneously dispersed in the PVDF matrix up to 10 wt% filler loading, enhanced the piezoelectric and dielectric properties of the composite. Further, the fabricated flexible piezoelectric nanogenerator without any external poling process exhibits an output open circuit voltage of ∼ 2.1 V and a short circuit current of ~ 42 nA on a gentle finger tapping force (~3 N). The results demonstrate the potential of chemically engineered KNN nanoblocks dispersed in PVDF for large-scale sustainable piezoelectric nanogenerator applications.

Enhanced electrocaloric effect, energy storage density and pyroelectric response from a domain-engineered lead-free BaTi0.91Sn0.08Zr0.01O3 ferroelectric ceramic.

A BaTi0.91Sn0.08Zr0.01O3 (BTSZ) ceramic was prepared by a conventional solid-state reaction method. Its structural, dielectric, ferroelectric, and pyroelectric properties were carefully studied. The Rietveld refinement was used to characterize the structural proprieties of the synthesized ceramic. The microstructure was observed by scanning electron microscopy. Phase transitions observed in the temperature dependent dielectric permittivity (ε r-T and tan δ-T) showed a transition close to room temperature, resulting in improved piezoelectric, pyroelectric and electrocaloric performance. In addition, it was found that an electric field poling process changed the character of ε r-T and tan δ-T plots. Resonance modes in the polarized state, where maximum power transmission was achieved, were observed in the impedance spectrum. The extra-slim hysteresis loops revealed a relatively low coercive field and hysteresis loss related to the diffuse phase transition, which can significantly improve energy storage efficiency up to 75% at 100 °C. To characterize the electrocaloric effect (ECE), indirect and direct methods based on the thermodynamic approach were used. Both methods results showed good consistency and revealed a large ECE peak evolving along the phase diagram. Furthermore, pyroelectric figures of merit (FOMs) for voltage responsivity (F v), current responsivity (F i), energy harvesting (F E), new energy harvesting and detectivity (F d) were calculated. Finally, thermal energy harvesting (N D) was determined by using the Olsen cycle. The obtained maximum N D was 233.7 kJ m-3 when the Olsen cycle operated at 25-100 °C and 0-30 kV cm-1. This study introduces not only a technique to produce a high performance ceramic for refrigeration devices, but also broadens the range of applications for BT-based lead-free ferroelectrics beyond actuators, sensors, and energy harvesting to solid-state cooling.

The mechanism of a PVDF/CsPbBr3 perovskite composite fiber as a self-polarization piezoelectric nanogenerator with ultra-high output voltage

The piezoelectric properties of conventional piezoelectric materials are generally obtained through the rearrangement of dipoles by an electric poling process.

Identification of Gold Mineralization Zones Using Magnetic Data at Gunung Gupit Area, Magelang, Central Java

Indonesia is one of the biggest gold producing countries in the world. the discovery of new gold reserves makes the passion of the gold mining industry increase. The Gunung Gupit area of Magelang Regency in Central Java has discovered new gold potential, but has not been thoroughly explored. The magnetic method is applied to identify and determine the distribution of the presence of gold mineralized zones based on the magnetic properties of rocks. A total of 1001 points on 41 magnetic line were acquired using Proton Precession Magnetometer (PPM) Geometrics model G-856 in an area of 2.5 km2. Field data is obtained as Magnetic Field Anomaly. Reduction to pole (RTP) and low-pass filter process is applied to the magnetic anomaly. The results showed the Gunung Gupit area was divided into 4 zones based on magnetic anomaly responses, i.e strong, medium, weak anomaly and igneous rock zones. The 2.5 D modeling result shows the presence of northwest-southeast normal fault and strike slip fault that is perpendicular to the normal fault. These faults control the hydrothermal alteration in Gunung Gupit and its surroundings. A strong mineralization zone lies between these two faults. The presence of gold and other metal minerals lies in this strong mineralization zone, and moderate alteration. The coverage area is quite wide and distributed along the two faults.

Dielectric and piezoelectric behavior of PVDF-modified 3-3 type cement-based piezoelectric composites

In this research, 3–3 type cement-based piezoelectric composites were prepared by casting Portland cement paste in porous lead zirconate titanate (PZT) ceramics, then the polyvinylidene fluoride (PVDF) of N-methylpyrrolidone solvent with concentration of 50–200 mg ml−1 was utilized to modify the lead zirconate titanate-Potland cement (PZT-PC) composites. The effects of PVDF concentration on the density, microstructure, dielectric, piezoelectric and electromechanical properties were studied. The results indicate that the density of PZT-PC composites increased gradually with PVDF concentration for the increasing combined weight of PVDF with the composites. The introduction of PVDF has also contributed to the reduction of leakage current during the poling and testing process, which led to increased relative permittivity ϵ r and longitudinal piezoelectric strain coefficient d 33, while the dielectric loss tanδ and longitudinal piezoelectric voltage coefficient g 33 demonstrated an opposite changing trend. The thickness electromechanical coupling factor K t of composites increased with the concentration of PVDF solution. The acoustic impedance (Z) of PVDF modified PZT-PC composites ranged from 6.89 to 7.65 MRayls, making it suitable for applications in the health monitoring of civil engineering.

Dominant frequency component tracking of noisy time‐varying signals using the linear predictive coding pole processing method

The linear predictive coding pole processing (LPCPP) method proposed in our previous work overcomes the shortcomings of the LPC method, especially its sensitivity to noise and the filter order. The LPCPP method is a parameterised method that involves processing the LPC poles to produce a series of reduced-order filter transfer functions to estimate the dominant frequency components of a signal. This paper analyses the ability of the LPCPP method to track the frequency changes of noisy, time-varying signals in real-time. Linear chirped frequency modulation signals are used in a series of experiments to simulate signals with different rates of frequency change. The results show that the LPCPP method can achieve real-time tracking of the dominant frequency in the signal and outperforms the LPC method under different frequency change rates and different noise levels. Specifically, the valid estimate percentage of LPCPP is up to 41.3% higher than that of LPC which indicates that the LPCPP method significantly improves the validity of frequency estimates.

Fast 3D Digital Light Process Printing of PVDF‐HFP Composite with Electric In Situ Poling System for Piezoelectric Applications

Inside Front Cover: In article number 2100266 by Sooman Lim and co-workers, a digitial light processing system with in situ poling process is first used to fabricate piezoelectric devices, which can greatly shorten poling times while improving the piezoelectric properties of the resulting materials. Furthermore, assembling 3D printed sensors with special structures together can effectively monitor human movement, which has promising potential for wearable devices or other large-area applications.

Improving fatigue resistance of PIMNT single crystal via two-step poling process

The fatigue resistance of pseudo-ternary single crystal 0.22Pb(In1/2Nb1/2)O3-0.53Pb(Mg1/3Nb2/3)O3-0.25PbTiO3 (PIMNT) is tested by a “two-step poling process” – alternate current poling (ACP) with different cycles followed by direct current poling (DCP). The remnant polarization of the hysteresis loop decreases significantly and then does not change, and the coercive field raises with increasing polarization cycles. However, the two-step poling process contributes to the optimization and stability of fatigue resistance. Before 700 cycles, the piezoelectric constant d33 of the crystal is obviously promoted compared with the conventional DCP sample of d33 = 2200 pC/N, which increases by 40.9%–3100 pC/N, while the average thickness mode electromechanical coupling coefficient Kt remains at 0.518. With the increase in number of polarization cycles, the d33 and Kt are larger and more stable than for the ACP only sample. This improvement is due to nanoscale denser and smaller domains induced by the two-step poling process.

Hybrid printing of wearable piezoelectric sensors

Piezoelectricity provides an ideal electromechanical mechanism with emerging applications in wearable devices due to its simplicity and self-powered nature. However, the 3D printing of piezoelectric devices still faces many challenges, including material printability, high energy poling process, and low dimensional accuracy. This study demonstrates, for the first time, a tellurium nanowire-based piezoelectric device fabricated by a hybrid printing method integrating highly complementary aerosol jet printing and extrusion printing in a single printing platform. The aerosol-jet-printed tellurium nanowire demonstrates piezoelectric properties without the need for any poling processing due to the unique properties of the tellurium nanowires. The silver nanowire electrodes printed by aerosol jet printing demonstrate excellent conductivity and stretchability without the need for sintering. An extrusion method is employed to print the silicone films, which serve as the stretchable substrate and the electrical insulation layers between the printed tellurium and silver. The printed wearable piezoelectric devices were attached to a human wrist to detect different hand gestures and to a human neck to detect heartbeat without using an external power source. The fully printed, sintering-free and poling-free, and stretchable piezoelectric device opens enormous opportunities for facile integration with a broad range of printed electronics and wearable devices.

Electromechanical simulation and analysis of perovskite piezoelectric ‎unimorph cantilever nanogenerator with interdigitated electrodes in ‎vibration energy harvesting application

This paper addresses a unimorph cantilevered piezoelectric nanogenerator having high ‎output power through vibrational energy harvesting that is simulated using finite element ‎method (FEM). The simulations are done for three types of perovskite piezoelectric ‎materials including PZT, PMN-PT and MAPbI3. The interdigitated electrodes were ‎exploited‏ ‏to obtain longitudinal vibration mode using d33 mode of piezoelectric layer during ‎the bending of nanogenerator structure. The presented structure consists of a piezoelectric ‎nanolayer with gold interdigitated electrodes on it, which is placed on a flexible PET ‎polymeric substrate. To encapsulate the piezoelectric layer, an SU-8 epoxy is placed over ‎the surface. The poling process is also simulated by applying high voltage through IDs to ‎piezoelectric layer. Generally, the electric potential distribution of the piezoelectric layer ‎must be performed by applying mechanical loadings. Then the output voltage, ‎power for free vibrations and base excitation (0.25-2g) of the nanogenerator at resonance ‎frequency are investigated. The resonance frequency of the PZT, PMN-PT, and MAPbI3 were ‎calculated to be 549 Hz, 560.5 Hz and 631 Hz, respectively. We found that PZT ‎piezoelectric materials yields maximum output voltage and electrical power values of 91.69 ‎V and 350 mW which shows better performance in vibrational energy harvesting ‎application. In comparison, the results of the simulation implied a good agreement with ‎other experimental studies. The unimorph piezoelectric energy harvester system generates ‎high voltage and output power in response to sub-kilohertz ambient vibration‎.‎‎

Progressive Poling of Large Area, High r33 Electro-Optic Polymer SEO100c

SEO100c, an EO-polymer, has been reported of having an r33 in excess of 100 pm/V. Experimental poling research was performed on rib waveguide modulator for device design and development. Reported is the determination of the impact that temperature and voltage have on the poling of a SEO100c waveguide device in order to maximize the r33 while avoiding damage to the device structure ensuring high yield in manufacture. The poling process is shown to have a nonlinear relationship between r33 and poling field aiding in the selection of achievable poling voltages for required r33 values. Device thermal stability is quantified and reported for the complete poling process and the impacts upon r33. Investigation into the possible relaxation of device r33 is measured over an extended period demonstrating desirable use within deployable devices.

Influences of poling temperature and elongation ratio on PVDF-HFP piezoelectric films

Abstract Poly(vinylidene fluoride) (PVDF) and its copolymers exhibit excellent piezoelectric properties and are potential materials for high efficiency energy harvesting devices. In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films are prepared by the solution casting method. The prepared film is then subjected to mechanical stretching and poling process. By adjusting the temperature of the poling process and the elongation ratio of the mechanical stretching process, the relative content of β-phase F(β) increases significantly, leading to high piezoelectric performance. The maximum output voltage of the PVDF-HFP films poled at 40°C reaches 3.67 V, 71% higher than that of the films poled at room temperature. Fourier transform infrared spectroscopy analysis (FTIR), XRD (X-ray diffraction), and differential scanning calorimetry are used to investigate the influences of mechanical stretching and poling process on the crystal structure to discover the enhancement mechanism. This work provides a straightforward and low-cost route to prepare high piezoelectric PVDF-HFP-based materials.

Bimodal Nanocomposite Platform with Antibiofilm and Self-Powering Functionalities for Biomedical Applications.

Advances in microelectronics and nanofabrication have led to the development of various implantable biomaterials. However, biofilm-associated infection on medical devices still remains a major hurdle that substantially undermines the clinical applicability and advancement of biomaterial systems. Given their attractive piezoelectric behavior, barium titanate (BTO)-based materials have also been used in biological applications. Despite its versatility, the feasibility of BTO-embedded biomaterials as anti-infectious implantable medical devices in the human body has not been explored yet. Here, the first demonstration of clinically viable BTO-nanocomposites is presented. It demonstrates potent antibiofilm properties against Streptococcus mutans without bactericidal effect while retaining their piezoelectric and mechanical behaviors. This antiadhesive effect led to ∼10-fold reduction in colony-forming units in vitro. To elucidate the underlying mechanism for this effect, data depicting unfavorable interaction energy profiles between BTO-nanocomposites and S. mutans using the classical and extended Derjaguin, Landau, Verwey, and Overbeek theories is presented. Direct cell-to-surface binding force data using atomic force microscopy also corroborate reduced adhesion between BTO-nanocomposites and S. mutans. Interestingly, the poling process on BTO-nanocomposites resulted in asymmetrical surface charge density on each side, which may help tackle two major issues in prosthetics-bacterial contamination and tissue integration. Finally, BTO-nanocomposites exhibit superior biocompatibility toward human gingival fibroblasts and keratinocytes. Overall, BTO-embedded composites exhibit broad-scale potential to be used in biological settings as energy-harvestable antibiofilm surfaces.