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In this study, using a solution casting process, thermoplastic polyurethane elastomer (TPU) composites containing different contents of lead zirconate titanate (PZT) ferroelectric particles were produced. The damping treatment of composites at high volume of fillers was investigated. SEM micrographs showed that PZT particles had a proper distribution in the PU matrix. Differential scanning calorimetry (DSC) thermograms indicates that melting enthalpy decreases by raising PZT filler content. The results of the dynamic mechanical thermal analysis (DMTA) proved that the magnitude of loss factor (tan δ) strongly depends on PZT content, and it decreased from 0.51 to 0.27 as PZT content increased. The value of E0 increases to 0.32 GPa in the composite reinforced with 50 v% of PZT. The role of PZT on the acoustic behavior of TPU was measured using the acoustic absorption coefficient (a). The results showed that as PZT content increased from 0 to 50%, the acoustic absorption coefficient reached 0.25 at 6000 Hz frequency. The composites of PZT/PU with 0–3 connectivity were poled, and the optimal poling conditions that could be applied without sample breakdown were studied. Moreover, we prepared composites containing 70 vol% PZT particles by modifying the particles. Modification of PZT particles caused a decrease in both d33 and g33 constants of the PZT/PU composites.

This study demonstrates enhancement of in-device electro-optic activity via a series of theory-inspired organic electro-optic (OEO) chromophores based on strong (diarylamino)phenyl electron donating moieties. These chromophores are tuned to minimize trade-offs between molecular hyperpolarizability and optical loss. Hyper-Rayleigh scattering (HRS) measurements demonstrate that these chromophores, herein described as BAH, show >2-fold improvement in β versus standard chromophores such as JRD1, and approach that of the recent BTP and BAY chromophore families. Electric field poled bulk devices of neat and binary BAH chromophores exhibited significantly enhanced EO coefficients (r33) and poling efficiencies (r33/Ep) compared with state-of-the-art chromophores such as JRD1. The neat BAH13 devices with charge blocking layers produced very large poling efficiencies of 11.6 ± 0.7 nm2 V−2 and maximum r33 value of 1100 ± 100 pm V−1 at 1310 nm on hafnium dioxide (HfO2). These results were comparable to that of our recently reported BAY1 but with much lower loss (extinction coefficient, k), and greatly exceeding that of other previously reported OEO compounds. 3 : 1 BAH-FD : BAH13 blends showed a poling efficiency of 6.7 ± 0.3 nm2 V−2 and an even greater reduction in k. 1 : 1 BAH-BB : BAH13 showed a higher poling efficiency of 8.4 ± 0.3 nm2 V−2, which is approximately a 2.5-fold enhancement in poling efficiency vs. JRD1. Neat BAH13 was evaluated in plasmonic–organic hybrid (POH) Mach–Zehnder modulators with a phase shifter length of 10 μm and slot widths of 80 and 105 nm. In-device BAH13 achieved a maximum r33 of 208 pm V−1 at 1550 nm, which is ∼1.7 times higher than JRD1 under equivalent conditions. ISSN:2051-6347 ISSN:2051-6355

Ferroelectric Polyvinylidene fluoride (PVDF) and its copolymers are used in a wide range of devices due to their excellent mechanical properties, high thermal and chemical stability, piezoelectric and pyroelectric responses. In the present investigation, Praseodymium oxide (Pr2O3) nanoparticles were synthesized hydrothermally and embedded in PVDF and films were fabricated by solution casting method. Enhancement of technologically important β-phase is observed in nanocomposite films. Electro active β and γ phase fractions are increased tremendously without poling and annealing is the highlight of the present work. Increased dielectric properties with low loss and enhanced photoluminescence on addition of nanoparticles are attributed to the enrichment of electro active phases.

Lithium niobate LiNbO3 (LN) on insulator wafers (LNOI) representing a submicron-thick LN film bonded to a SiO2 layer deposited on a thick LN substrate have been manufactured recently by ion slicing. Today, LNOI is one of the most promising materials for fabrication of various integrated optical devices, including waveguides, electro-optical modulators, and wavelength convertors, due to their high drop in refractive index at the interface between the film and the SiO2 layer. Creation of the stable domain structures with submicron periods in LNOI will improve the properties of nonlinear optical devices. Periodically poled LN with periods below 300 nm can be used to implement an optical parametric oscillator in the backward configuration. We have studied experimentally the ways to create the stripe domains and periodical domain structures in LNOI with a dielectric layer under the film by local switching. The identified scenarios of the domain evolution were attributed to the ineffective screening of depolarization field. We have shown that stripe domains and periodic domain structures can be produced by scanning with a biased tip only at temperatures above 80 °C. Periodical stable domain structures with periods down to 300 nm have been created.

Piezoelectric materials are an indispensable part of modern life. Yet the existing environmental issues with conventional lead-based piezoelectrics has motivated scientist to develop novel substitutes including lead-free piezoelectric polymer composites. Following this path, the present research has focused on the fabrication of ternary composites of Polyvinylidene fluoride (PVDF)/Potassium Sodium Niobate (KNN)/nano-Silicon carbide (SiC) via hot compression molding and studying the effect of additives on the PVDF structure and the electrical properties of the composite. The obtained scanning electron micrographs and density measurements showed that the fabrication method provided dense samples. The activated polarization phenomena in the prepared samples enhanced dielectric permittivity and dielectric loss at a constant frequency with increasing KNN and SiC contents. Besides the expected dipole polarization, the presence of interfaces in the composites gave rise to the Maxwell–Wagner–Sillars effect and its corresponding polarization phenomenon. The semiconductive nature of SiC also promoted space charge polarization. However, these properties were frequency-dependent because the first two polarization mechanisms are deactivated at high frequencies. XRD patterns showed that SiC addition can alter the primary crystalline structure of PVDF and promote β-phase formation in the poled samples. Piezoelectric measurements confirmed the significant role of SiC addition to PVDF-KNN composites. The most significant increase in the piezoelectric properties was observed in PVDF-60KNN-1SiC, with a 183% increase in d33 value. The PVDF-80KNN-1SiC had the highest d33 value of 30.5 pC/N. It also had the best piezoelectric voltage coefficient and hence the highest figure of merit. Higher SiC contents restrict the efficiency of poling by forming a conductive path across the sample which would deteriorate the piezoelectric performance of the material. The present findings show that PVDF-KNN-SiC composites can be considered as a potential flexible piezoelectric material for future applications.

The rapid development of flexible micropower electronics has aided the opportunity for the broader application of flexible piezoelectric composites (PCs) but has also led to higher requirements for their power generation. Among them, 0-3 PCs with embedded zero-dimension piezoparticle fillers, although low cost and easy to prepare, suffer from suboptimal output performance because of inherent structural defects. In this work, the voltage output was increased from 3.4 to 12.7 V under a force of 7 N, through first-step regulation by aligning the KNbO3 (KN) particles in the polydimethylsiloxane (PDMS) matrix; then, a significantly enhanced current output (from 0.7 to 4.5 μA) through second-step regulation by introducing copper nanorods (Cu NRs) interspersed in the gaps between the KN chains. Consequently, the proposed PC exhibits much higher power density, 37.3 μW/cm2, than that of random KN/PDMS and thus shows good potential for high-performance, flexible piezoelectric energy harvesters.

The additive manufacturing of piezoelectric ceramic Lead Zirconate Titanate (PZT) through paste extrusion 3D printing was demonstrated. Different paste compositions with varied water weight content were studied to find a composition suitable for printing. The pastes were evaluated in terms of their viscosities, yield stresses, and stability when aged. Furthermore, the material properties of the ceramics produced through paste extrusion were characterized and compared with those of ceramics fabricated through a conventional die pressing method. Paste extruded PZT with achieved densities as high as 94.9% of the theoretical density after sintering, which nearly matched the 95% density attained by the pressed samples. Upon poling, the paste extruded PZT piezoelectric ceramics attained piezoelectric coefficients and dielectric constants that were close to the values of die pressed samples. As near full density PZT ceramics were successfully fabricated through paste extrusion, this work paves the way for piezoelectric ceramics with application-driven geometry designs for sensors, actuators, and energy harvesters.

Three-dimensional (3D) printing of polymer smart materials offers great potential in terms of design of applications either requiring inherent electromechanical sensing or vibration-based energy production capabilities. Currently, the piezoelectric response of homopolymer 3D printed polyvinylidene fluoride (PVDF) lags the properties offered using the costly alternative feedstock PVDF-TrFE or the geometrically limited sheets of homopolymer PVDF produced commercially via mechanical stretching. This work focuses on the influences of using post-printing processing techniques for producing material extrusion additive manufactured (MEAM) PVDF components with mechanical and electromechanical properties comparable to their more expensive counterparts. In particular, this research describes the effects of using post-fabrication thermal cycles and electrical poling on the development of microstructures favorable to piezoelectricity and on the mechanical properties. The dynamic electromechanical response is demonstrated for the highest beta-phase case of each in a simplistic energy harvesting application. Results from characterization tests showed that higher beta-phase content and greater Young’s modulus and ultimate tensile strength were affiliated with longer annealing process times. Structures annealed at temperature 85 °C for 5 h exhibited greater beta-phase crystallinity than other annealing conditions. In addition, applying electrical field was led to increasing the piezoelectric response within the 3D printed PVDF parts.

Intensive research has been conducted to develop flexible piezoelectric pressure sensors, since selfpowering devices are advantageous for wearable electronic applications. Recently, two types of piezoelectric devices, ceramic-PDMS composite film and PVDF nanofiber mats, have drawn attention in the research community. Piezoelectric ceramics such as BaTiO3 (BTO) and PZT exhibit outstanding piezoelectric coefficients, while PDMS provides flexibility. In contrast, a PVDF nanofiber mat simultaneously exhibits piezoelectricity and flexibility. In the present study, a comparative analysis of BTO-PDMS composite film and a PVDF nanofiber mat for application to flexible pressure sensors was carried out. First, step-wise electric poling was conducted on these two types of pressure sensors, after which the open-circuit voltage (Voc) was measured under compressive force. The 1.8 V peak-to-peak Voc was measured in a BTO-PDMS composite with a 30 wt.% BTO content that was poled by 10 kV/mm electric field for 15 min. This peak-to-peak Voc of the BTOPDMS composite increased further to ~ 4 V when it was poled for 24 hr. Unlike the BTO-PDMS composite films, the maximum Voc (1.1 V) was measured in a PVDF nanofiber mat that did not undergo subsequent electric poling. A BTO-PDMS composite film and a PVDF nanofiber mat were fabricated, and the compressive force and strain-rate dependencies of Voc and the short-circuit current (Isc) were investigated. Overall, the Voc and Isc of the BTO-PDMS composite film exceeded those of the PVDF nanofiber mat in a force range of 1 - 25 N and frequency range of 0.5 - 2.0 Hz. However, the Voc and Isc signals from the PVDF nanofiber mat were more stable than those from the BTO-PDMS composite film due to the longer lifetime of the signals. (Received March 19, 2021; Accepted April 9, 2021)

The creation of the stripe domain structures with submicron periods by local switching using a biased tip of a scanning probe microscope was studied on Z-cut of lithium niobate on insulator (LNOI)....

This work highlights improved photosensing performance in ITO/ ( Bi 0.93 Sm 0.07 ) FeO 3 /Au heterostructure through a prior electric field poling. Maximal responsivity (R) of 2.0 × 10 − 2 A / W and specific detectivity (D*) of 2.2 × 10 11 Jones were obtained under 405-nm irradiation. The mechanism behind the observed photosensing performance is linked to the combined effects of the polarization-induced electric field and built-in electric fields at the interfaces (i.e., p–n junction and Schottky barrier). The net internal electric field established in the device serves as the driving force for the separation and transport of the photo-generated electron–hole pairs. The reduced direct optical bandgap (Eg) of 2.13 eV, the well-defined ferroelectric polarization hysteresis loops, and the conduction pathways formed by the electric field-stimulated interconnection of domain walls and grain boundaries play significant roles in the remarkable photosensitivity of ( Bi 0.93 Sm 0.07 ) FeO 3 ceramics, thus providing insight into optimizing BiFeO3-based materials for near-UV photodetector.

Lithium niobate and lithium tantalate are among the most important and most widely used materials in acousto-optics and acoustoelectronics. These materials have high values of piezoelectric constants, which makes it possible to use these materials as actuators; however, their use is limited by the thermal instability of a lithium niobate crystal and the low Curie temperature (TC) of a lithium tantalate crystal. LiNb(1-x)TaxO3 crystals have to overcome the aforementioned limitations of individual compounds.Crystals LiNb0.5Ta0.5O3 were grown by the Czochralski method, of good quality. Comparative studies of the features of high-temperature single domainization of LiNb0.5Ta0.5O3 crystals have been carried out. The main differences in the technological regimes for single-domainization of congruent LiNb0.5Ta0.5O3 crystals from congruent LiNbO3 crystals are demonstrated. The parameters of high-temperature electrodiffusion processing LiNb0.5Ta0.5O3 crystals are presented, which make it possible to obtain single-domain crystals for further study of their physical properties.

This paper reports the first fabrication of high-entropy Ba(Ti,Hf,Zr,Fe,Sn)O3 films on fluorine-doped tin oxide substrates through spin coating and hydrothermal synthesis. A homogeneous distribution of all constituent elements was observed through energy-dispersive x-ray spectroscopy mapping. High distortion (approximately 1.7%) of the lattice structure was caused by the underlying substrate and partial substitution of Ti with other larger elements of Hf, Zr, Fe, and Sn on B sites. Two types of Ba(Ti,Hf,Zr,Fe,Sn)O3 films were studied: high-density and slightly textured polycrystalline particles (Sample A), and randomly distributed [110]-oriented nanorods with marginal crystallinity (Sample B). In the piezoelectric experiment, Samples A and B substantially outperformed the medium-entropy oxide (MEO) samples and single-crystal ZnO bulk. Sample A also exhibited the highest piezoelectric coefficient (d33 ∼ 60 pm/V) among all studied samples. Its superior performance was attributable to a combination of high crystallinity, strong out-of-plane distortion, slightly textured polycrystalline structures, and cocktail effects. Furthermore, enhanced piezoelectricity was achieved after poling for the high-entropy oxide (HEO) and MEO samples, indicating their ferroelectric effect. The d33 of Sample A more than doubled (≈126.7 pm∙V−1), and the increase was substantially higher than that of Sample B. Our HEO samples have promise for use in piezoelectric- and ferroelectric-related applications.

Developing a mild and efficient method to simultaneously enhance poling efficiency and temporal stability is meaningful and challenging for organic second-order nonlinear optical materials. In this paper, a new poly (aryl ether ketone) and chromophores functionalized with anthracene groups have been designed and prepared. Poling and crosslinking process could be separated by the mild and photo-initiated cycloaddition of anthracene group. As the UV–Vis spectrum, DSC and TGA curves, the networks had formed by 30-min irradiation of the Lower-power UV light which led little decomposition of dipolar chromophores. The maximum electro-optic coefficient (r33) of these polymers is 28.5 pm V−1 (at 1.3 μm), and the order parameter reaches 0.22. Moreover, the depolarization temperature of α peak, related to the dipole relaxation, has been increased to 129 °C after crosslinking, which is 17 °C higher than uncrosslinked ones. All these results indicated that the photo-crosslinking of anthracene exhibited promising potential for improving alignment stability and NLO activity at the same time.

A series of nonlinear optical chromophores A–D based on the diethylaminophenyl donor and tricyanofuran or phenyl-trifluoromethyl-tricyanofuran acceptors coupled through a tetraene bridge was synthesized and investigated. In particular, the donor and bridge sections of chromophores B and D were functionalized with a small chromophore alkylaniline cyanoacetate (B1) and dialkylaminobenzylidene malononitrile (D1) group, respectively, compared to the pentafluorobenzene group of chromophores A and C. Before poling, two small chromophores B1 and D1 with large dipole moment will greatly weaken the electrostatic interaction between chromophores by steric effect and electrostatic screening effect, thus increasing the poling efficiency. Although density functional theory calculations suggested that they have similar first-order hyperpolarizability, polymeric thin films doped with chromophores A–D exhibited the different r33 values of 115, 166, 213 and 276 pm V−1 at 1310 nm, respectively. The normalized r33 value of chromphores B and D was up to 7.72 × 10−19 and 17.25 × 10−19 pm cc per (V molecules), which is much higher than that of chromophores A and C. All these prove that introducing a small chromophore into the main chromophore can greatly improve the electro-optic coefficient of the chromophore by a rational molecular design.

Free standing thin composite films of PVDF (polyvinylidene fluoride) with Cadmium sulphide (CdS/PVDF) were synthesised using sol gel method. The as-prepared samples were subjected to vacuum poling under high voltage. As prepared films as well as poled films were studied using XRD, FTIR, XPS and FESEM techniques. Effect of CdS loading on the elctroactive phases has been studied using XRD and FTIR techniques. Amount of electroactive (EA) phase content in the films was calculated. Chemical composition and modulation the bonding environment was studied using XPS. Modification of surface morphology is also discussed.

Controlling the thermal expansion coefficient can effectively reduce the thermal stress and enhance the reliability of materials or structures. In this work, based on the fact that the thermal expansion coefficient of ferroelectric ceramics is negative along the poling direction and positive along the transversal direction, we tailored the domain structure of Lead Zirconate Titanate (PZT) ceramics by two-dimensional periodically orthogonal poling. The in-plane thermal expansion coefficient can be controlled in a wide range ( α = − 8.2 × 10 − 6 ∘ C − 1 ∼ 2.5 × 10 − 6 ∘ C − 1 ) which may find wide applications in the fields of thin film fabrication, electronic packaging, etc.

The development of electro-optic materials with both large electro-optic coefficients and stability has always been the most challenging topic in this field. A series of chromophores C1–C3 based on the same bis(N,N-diethyl)aniline donor and tricyanethyldihydrofuran acceptor with isophorone-derived bridges were developed. Two-arm dendrimer C2 and three-arm dendrimer C3 were synthesised and evaluated compared to one-chromophore-containing dendritic material C1. This is the first time that a bis(N,N-diethyl)aniline-based donor has been used in CLD-type chromophores and a multichromophore system. Compared to chromophore C1, multichromophores C2 and C3 show much higher electro optic coefficients and glass transition temperatures. A large r33 (180 pm V−1) and poling efficiency (1.94 ± 0.08 nm2 V−2) at 1310 nm have been achieved for neat films containing chromophore C2. Moreover, the glass transition temperature of dendrimer C2 was as high as 122 °C. The large electro-optic coefficient and strong stability make this material very promising in commercial applications.

Self-poling poly(vinylidene fluoride) (PVDF) featuring uniformly aligned dipoles can convert mechanical vibrations into electrical energy without post-poling treatment, which is a topic of intense ...

This study reports the facile synthesis, characterization and quantitative structure-property relationship analysis of molecular and material properties of tricyanofuran-based (TCF) dipolar heptamethines with different electron donors of indoline ( F1 ), benzo[ e ]- indoline ( F2 ), benz[ cd ]indoline ( F3 ), and Michler’s base derivatives ( M1 and M2 ). The linear and nonlinear optical (NLO) properties of these chromophores have been thoroughly investigated, and the relationship between molecular and bulk response has been analyzed and compared with dipolar tetraene AJLZ53 as one of the best chromophores for electro-optic (EO) devices. In particular, we provide responsible data collection and analysis of optical and EO properties for poled thin films using a widely-recognized and accredited methodology of prism coupling system with the help of rigid oriented gas model. We found that these push-pull heptamethines with synthetic efficacy exhibit high near-infrared absorption, excellent chemical stability and large hyperpolarizabilities ( β ) varied from 1,023×10−30 esu for F1 , 3,047×10−30 esu for M1 , and 3,547×10−30 esu for F3 at 1,304 nm in poled films, respectively. The β values of these molecules are among the highest ones for TCF-based dipolar chromophores, and also agree well with reported analytical results in the solutions. In poled polymers with a modest chromophoric loading density of 1.3× 1020 cm−3, M1 and M2 give a high poled-induced noncentrosymmetric order and relatively large r 33 values around 40 pm V−1 at 1,304 nm, indicative of large μβ values and suitable structural modification for high poling efficiency. Furthermore, a binary EO polymer based on the co-loading of M1 and AJLZ53 achieve a large r 33 value of 143.3 pm V−1 at 1,304 nm. Our studies suggest that concise synthesis and molecular design of push-pull polymethines can be well guided by the tabulation of their linear and NLO properties in bulk materials, and streamline future development of high performance organic EO materials for photonic applications.

We present an EO Q-switched Tm:YAP laser constructed with a periodically poled Mg-doped congruent lithium niobate (PPMgCLN) Bragg modulator. A 2-mm-thick PPMgCLN modulator was adopted, and the internal stress generated in the electric poling process was released by annealing. The peak stress-induced refractive index variance for e-wave was deduced to be 2.29 × 10-5 at 1064 nm. When the absorbed pump power and repetition rate were 13.4 W and 1 kHz, respectively, the laser had a Q-switched pulse energy of 2 mJ, a pulse duration of 60 ns, and a peak power of 33.3 kW. By varying the reflection of the output coupler, output wavelengths of between approximately 1985 and approximately 1940 nm can be selected, making this laser a potential tool for pumping mid-IR sources and biomedical applications.

A watt-level continuous wave (CW) orange-red laser with wavelength tunable properties is experimentally implemented based on sum-frequency generation (SFG) in a composite cavity. The cavity is composed of an 880 nm laser diode (LD) side-pumped Nd: GdVO4 p-polarized 1062.9 nm cavity and a single-resonant optical parametric oscillator (SRO) of signal light using a magnesium oxide-doped periodically-poled LiNbO3 (MgO: PPLN) crystal with a poling period of 29.1 μm. In the overlap region of the two cavities, orange-red laser is generated by using a type-II critical phase-matched potassium titanyl phosphate crystal (KTP) crystal. In the temperature tuning range of the MgO: PPLN crystal (from 30 °C to 200 °C), the CW orange-red laser beams are generated in a tunable waveband from 612.24 nm to 620.72 nm (Δλ = 8.48 nm), corresponding to the mid-infrared idler light is also obtained with tunable wavelength from 4027.5 nm to 3708.2 nm (Δλ = 319.3 nm). At the lowest tuning temperature of 30 °C, the maximum CW output power of the orange-red laser at 612.24 nm and the idler light at 4027.5 nm are obtained, which are 1.145 W and 2.83 W, respectively.

Polyvinylidene fluoride (PVDF) has been applied in various industries due to its excellent piezoelectric property. In this study, the optimization of various processing conditions such as poling st...

Smart composites, which are composed of piezoelectric ceramics and cement-based materials, have been developed for sensing and health monitoring of concrete infrastructure. Barium titanate (BT)-Portland cement (PC)-polyvinylidene fluoride (PVDF) composites with 40-60 vol.% BT particles (with a median size of ~ 425 µm) and 0-7 vol.% PVDF were fabricated by the pressing and curing method. The effects of the PVDF content on the acoustic impedance (Zc), dielectric constant (er), piezoelectric charge coefficient (d33) and piezoelectric voltage coefficient (g33) of the BT-PC-PVDF composites were investigated. Increasing the PVDF content in the composites led to a decrease in the Zc value so that it approached that of concrete. The PC phase was replaced by the PVDF phase in the BT-cement-based composites to reduce the leakage current in these composites. As a result, the piezoelectric properties of the BT-PC-PVDF composites improved noticeably. BT contents of 50 and 60 vol.% and a PVDF of 5 vol.% had the highest d33~24-25 pC/N. Moreover, the composite with 50 vol.% BT and 5 vol.% PVDF had the highest piezoelectric voltage coefficient herein (g33=14.6 × 10-3 V∙m/N).

Ferroelectric domain structure in BaTiO3 ceramics was studied with nanoscale spatial resolution before and after poling by application of the uniform electric field. Complimentary vector piezorespo...

The vinylidene fluoride copolymer with tetrafluoroethylene P(VDF-TFE) is a typical ferroelectric polymer that has not been sufficiently studied so far in comparison with pure polyvinylidene fluoride (PVDF) and its copolymer with trifluoroethylene. The purpose of this work was to reveal the features of forming ferroelectric polarization and its switching in thin films of P(VDF-TFE) under various conditions, such as the level of the applied electric field and the duration of its action within 8 orders of magnitude from 10 μs to 100 s. The sequence of voltage pulses applied during poling and polarization reversal allowed to reveal the characteristics of the polarization switching dynamics. To increase the resolution of the measurements, two complementary methods of recording electrical induction were used. The features of polarization and space charge relaxation over time have been studied by thermally stimulated depolarization method. A new phenomenon of gradual separation of the relaxation processes associated with polarization and space charge was observed. Both components were accompanied by trapped charges that compensated the depolarizing field. Several practical recommendations have been formulated regarding the desirable values of poling parameters and additional processing to increase the ferroelectric polarization stability.

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based composite nanofibers containing different barium titanate (BaTiO3) nanoparticle contents of 10–60 wt% were fabricated by an efficient electrospinning. The piezoelectric performance of PVDF-HFP/BaTiO3 composite nanofibers under a periodic compressional pressure of ∼20 kPa was investigated by considering the BaTiO3 content and the electric poling. The X-ray diffraction patterns revealed the presence of piezoelectric tetragonal BaTiO3 nanoparticles in the composite nanofibers with PVDF β-form crystals. The SEM images demonstrated that the BaTiO3 nanoparticles were dispersed uniformly in the composite nanofibers at relatively low loadings of 10–20 wt%, but they formed aggregates at high loadings of 30–60 wt%. The piezoelectric performance of the composite nanofibers increased with the BaTiO3 content up to 20 wt% and decreased at higher BaTiO3 contents of 30–60 wt%, which results from the trade-off effect between the piezoelectric performance and the dispersibility of BaTiO3 nanoparticles in the composite nanofibers. Accordingly, the composite nanofibers with 20 wt% BaTiO3 exhibited maximum piezoelectric outputs such as voltage of ~9.63 V, current ~0.52 µA, and electric power of ~7892.2 nW. After the electric poling, the piezoelectric performance was further enhanced to ~11.69 V, ~20.56 µA, and ~1115.2 nW, which was high enough to light up a small LED bulb after rectification.

In this article, two AB2-type second-order nonlinear optical monomers (DN-SH and DS-SH) containing two double bonds and one thiol group, respectively, were synthesized successfully. These two monomers could be in situ photo-crosslinked via a thiol–ene click reaction under 365 nm UV light without a photoinitiator after poling. Thanks to the photo-crosslinking process of thin films, the thermostability of the second-order nonlinear optical property was much enhanced. DS-SH exhibited a larger NLO effect and better NLO thermostability than DN-SH, because of the introduction of sulfonyl-based chromophores which can decrease the electrostatic interaction between nitro-based chromophore moieties. T80% of the photo-crosslinked DS-SH films increased to 112.5 °C, much higher than that of uncrosslinked ones (75 °C), while T80% of DN-SH films increased from 58 to 95 °C. More excitedly, the doped thin films of DN-SH and DS-SH at different molar ratios (1 : 1, 2 : 1, and 1 : 2) showed better NLO properties (123, 122, and 114 pm V−1, respectively) after photo-crosslinking than single DN-SH (89 pm V−1) and DS-SH (108 pm V−1) respectively.

Hybrid organo-metal halide perovskites (OMHPs) have been extensively explored for photo or photo-enhanced applications, which are time, location or light-limited. Unlike in other works, herein, methylammonium lead iodide (MAPbI3) perovskite was employed as a small area (

Organic nonlinear optical (NLO) materials are very important for high-speed information processing in addressing the challenges of reduced energy consumption and enhanced speed and bandwidth. In particular, organic second-order NLO materials are very promising for meeting the combined requirements of ultra-low energy and ultra-high bandwidth in electro-optic (EO) modulation, while organic third-order NLO materials have good potential for applications in ultra-speed all-optical signal processing (AOSP). This review highlights the recent significant progress made in organic second- and third-order NLO materials. For second-order NLO materials, the recent advances in the efficient and cost-effective synthesis of dipolar polyene chromophores and thin-film engineering for efficient electric field poling are summarized. The applications and prospects of these high-performance EO materials are also discussed. For third-order NLO materials, we discuss the molecular design strategies of cyanine dyes for AOSP applications, particularly focusing on anionic tricyanofuran (TCF)-based cyanines. We aim to provide a better understanding of the structure–property relationships for cyanine-based AOSP materials. Finally, a summary and outlook for advancing high-performance organic NLO materials are provided.

Poly(vinylidene difluoride) (PVDF) and its copolymers as the polymers with the highest piezoelectric coefficient have been widely used as sensors and generators. However, their relatively low performances limit their applications in some harsh environments. In this work, piezoelectric poly(vinylidene-trifluoroethylene) P(VDF-TrFE) matrices with different amounts of polyhedral oligomeric silsesquioxane (POSS) were prepared by a low temperature solvent evaporation method and thermal poling. The morphology, surface performance, crystalline phase, and piezoelectric and ferroelectric properties of the nanocomposites were investigated and the influence of POSS on these performances was studied. POSS had good compatibility with P(VDF-TrFE) and did not affect the crystalline phase formation of the matrix. The composites presented good piezoelectric properties. Piezo- and triboelectric nanogenerators were designed and fabricated. The voltage and current outputs were analyzed and the polarization effect was evaluated. The average output voltage and the current density of the matrix were 3 V and 0.5 μA cm−2 when subjected to a force of 38 N on an area of 1 cm2. The mechanical properties of P(VDF-TrFE)/POSS nanocomposites were also studied by the nanoindentation test. The hardness and modulus of samples increased 20% and 17% with a low addition of POSS. Atomic oxygen erosion properties of the composites were numerically simulated by the Monte Carlo method. The erosion cavity shape and depth were compared and studied. The influence of POSS addition on the P(VDF-TrFE) matrix and the associated reinforcing mechanism were analyzed.

Piezoelectric Poly (vinylidene fluoride) (PVDF) films with high flexibility are a suitable and promising replacement for rigid ceramic piezoelectric materials. However, for this purpose, enhancing piezoelectric properties and adopting an industrial fabrication method are of great importance. In this study, 5–9 µm thick PVDF films were fabricated by a nozzle-less ultrasonic spray coating (USC) system, followed by an annealing process at 100 °C. By applying proper spraying parameters, we could obtain highly uniform films with large d33 values (48 pm/V) and 56% crystallinity. Results show that the uniformity of the films plays an important role in the final piezoelectric properties. Thus, ultrasonic spray coating method can be used for fabrication of large-scale piezoelectric films with no need for poling or stretching processes.

More than one century ago, piezoelectricity and ferroelectricity were discovered using Rochelle salt crystals. Today, modern societies are invited to switch to a resilient and circular economic model. In this context, this work proposes a method to manufacture piezoelectric devices made from agro-resources such as tartaric acid and polylactide, thereby significantly reducing the energy budget without requiring any sophisticated equipment. These piezoelectric devices are manufactured by liquid-phase epitaxy-grown Rochelle salt (RS) crystals in a 3D-printed poly(Lactic acid) (PLA) matrix, which is an artificial squared mesh which mimics anatomy of natural wood. This composite material can easily be produced in any fablab with renewable materials and at low processing temperatures, which reduces the total energy consumed. Manufactured biodegradable samples are fully recyclable and have good piezoelectric properties without any poling step. The measured piezoelectric coefficients of manufactured samples are higher than many piezoelectric polymers such as PVDF-TrFE.

Potassium titanyl phosphate (KTP) is a nonlinear optical material with applications in high-power frequency conversion or quasi-phase matching in submicron period domain grids. A prerequisite for these applications is a precise control and understanding of the poling mechanisms to enable the fabrication of high-grade domain grids. In contrast to the widely used material lithium niobate, the domain growth in KTP is less studied, because many standard methods, such as selective etching or polarization microscopy, provides less insight or are not applicable on non-polar surfaces, respectively. In this work, we present results of confocal Raman-spectroscopy of the ferroelectric domain structure in KTP. This analytical method allows for the visualization of domain grids of the non-polar KTP y-face and therefore more insight into the domain-growth and -structure in KTP, which can be used for improved domain fabrication.

We experimentally measure percent-level optical-to-multi-cycle terahertz conversion efficiencies by injecting a home-made wavelength- and duration-tunable two-line laser into periodically poled lithium niobate. We study the efficiency vs. the input laser peak fluence, pulse duration, crystal length and poling period at cryogenic temperature. Our work is a significant step towards high energy terahertz pulses for linear electron acceleration.

Piezocatalysis is a promising area of research that would enable new advances in environmental catalytic processes independent of energy sources such as light or electricity. To shed more light on this field, theoretical and experimental studies were conducted using poled and unpoled BF-KBT-PT ceramics as catalysts in order to investigate the effect that piezocatalyst size, piezocatalyst poling/unpoling and agitation mode have on the degradation of a dye, Rhodamine B (RhB), in water. While an apparently contradictory trend in the theoretical and experimental results was observed in relation to piezocatalyst size, poling indeed had a significant effect on the degradation of RhB, indicating that a complex combination of different phenomena such as ‘top-to-bottom’ electric potential difference due to ‘bulk’ piezoelectric polarisation, nanoscale piezoelectric response and sonocatalysis may result in the overall catalytic degradation of RhB. However, the greatest contribution to the degradation of the dye would come from sonochemistry, as ultrasound in absence of a catalyst already achieved a remarkable degradation of RhB. This study therefore demonstrates the complexity of piezocatalysis, and why other phenomena besides bulk piezoelectric polarisation of catalysts must be taken into account in piezocatalysis research.

One century ago, ferroelectricity and then piezoelectricity were discovered using Rochelle salt crystals. Today, modern societies are invited to switch towards a resilient and circular economy model. In this context, this work proposes a method to manufacture piezoelectric devices made from agro-resources such as tartric acid and polylactide significantly reducing the energy budget without requiring any sophisticated equipement. These piezoelectric devices are manufactured by liquid phase epitaxy grown Rochelle salt (RS) crystals into a 3D printed poly(Lactic acid) (PLA) matrix being the artificial squared meshes which mimic the natural wood anatomy. This composite material can easily be produced in any fablab with renewable materials and at low processsing temperatures, reducing then the total energy consumed. Manufactured biodegradable samples are fully recyclable and have good piezoelectric properties without any pooling step. The measured piezoelectric coefficients of manufactured samples are higher than many piezoelectric polymers such as PVDF-TrFE.

Piezoelectric catalysis is the catalytic action driven by the force-electrical conversion of piezoelectric materials. In this paper, the piezoelectric activity of K0.5Na0.5NbO3 (KNN) was thoroughly investigated by annealing KNN at a series of temperatures and poling KNN under different electric-fields. With the application of an ultrasonification, the degradation activity for the Rhodamine B (RhB) dye molecules of the poled KNN was 253% higher than that of unpoled samples. The piezocatalytic activity of the poled KNN was significantly improved, which stemmed from the orderly ferroelectric domain to effectively reduce the recombination rate of the carriers by the built-in electric field. In addition, the superior piezocatalytic activity was achieved at KNN materials with the average grain size of ~0.29 μm, and after 160 min of mechanical vibration, the degradation rate of RhB (~5 mg/L) was as high as 95.7%. The high mechanical catalytic degradation rate of KNN materials reveals a bright application prospects in vibration catalytic degradation of organic pollutants.

Seven Indian copper coins of the Kushan Period (1st–3rd centuries C.E.) were studied by multi-analytical techniques like WD-XRF, XRD, and FESEM-EDX to understand coin composition and the metallurgical process of fabrication. Analytical results reveal a compositional gradient in the distribution of elements between the external surface and the inner core of the coins, and the coins show isolated patches of surface mineralization leading to the formation of copper oxides, magnesium silicate, and silica. The analysis also showed the probable use of sulfide ore of copper for smelting and poor workmanship for this hoard. The impurities like sulfur, iron, silica, etc. could not be removed due to low firing temperature and improper poling during smelting. Striations have formed in the coin interior, with grain boundaries showing micro-cracks due to stress like punching or hammering with the die. The coins under study are a single-phase copper with associated impurities of Si, Al, P, and Mg in all coins and black spots of copper sulfide in coin inner core.

Above-bandgap photovoltages in lead-free perovskite BiFeO 3 have been substantially studied for energy harvesting and photocatalytic applications. However, most reported photocurrents and conversion efficiencies are still too small due to wide bandgaps. Remarkably large and durable field-modulated external quantum efficiency (EQE) ∼11% and power conversion efficiency (PCE) ∼1% have been achieved under 405 nm irradiation in polycrystalline Nd-doped BiFeO 3 (BNFO) ceramic with a bandgap E g ∼2.12-2.24 eV. The photovoltaic voltage and current density can reach ∼0.9 V and ∼8.0 A/m 2 after poling ( E =1 kV/cm) at irradiation intensity 10 3 W/m 2 . The p-n-junction layer between indium tin oxide (ITO) thin film and BNFO ceramic is the primary mechanism for the field-modulated photovoltaic responses in conjunction with the polarization-induced Schottky-barrier modulation. The field-induced domain nucleation within the grains and nanodomains play important roles for the enhanced photocurrent and conversion efficiencies.

This paper represents a polymeric piezoelectric manufacturing process for sensing and actuation applications. The electric poling-assisted additive manufacturing (EPAM) process combining additive manufacturing (AM) with polymeric poling process has been recently introduced. This process keeps piezoelectric polymer dipoles well-aligned and uniform over a large area in a single-step direct printing process. Here, the EPAM process was employed to directly print polyvinylidene fluoride (PVDF) polymer; sensing and actuation performance was tested with dynamometer, a baseline comparison measuring instrument. Also, the plasma-assisted poling process that potentially increases piezoelectricity was briefly introduced and discussed with a preliminary result. As a result, this study promises new multi-functional materials, novel designs, and approaches in a single AM and fabrication step by combining AM with piezoelectric polymer poling methods in convenient, fast, and precise manner.

Eco-friendly nanocellulose-based composite films including different barium titanate (BaTiO3) nanoparticle contents were fabricated by an efficient aqueous suspension casting and following electric poling. The microstructures, dielectric/electrical property, and piezoelectric performance of the nanocellulose composite films were investigated as a function of the BaTiO3 content. The electron microscopic images demonstrated that the BaTiO3 nanoparticles were uniformly dispersed in the nanocellulose-based composite films. The X-ray diffraction results confirmed the presence of piezoelectric tetragonal BaTiO3 nanoparticles in the nanocellulose matrix with cellulose II phase. The dielectric constant and loss tangent of the composite films were found to increase and decrease with increasing the BaTiO3 content, respectively, which is favorable to achieve high piezoelectric outputs. On the other hand, the piezoelectric performance of the composite films increased with the BaTiO3 content up to 40 wt% and it decreased for the composites with 50–60 wt% BaTiO3, which results from the trade-off effect between the piezoelectric performance and the mechanical stiffness of BaTiO3 nanoparticle. Accordingly, the nanocellulose composite film with 40 wt% BaTiO3 was found to attain maximum piezoelectric outputs of voltage of ∼2.86 V, current of ∼262.4 nA, and electric power of ∼378.2 nW under a relatively low compressional stress of 5 kPa, which was high enough to charge microcapacitors after rectification.

Piezoelectric and electroactive composites are being investigated as a generation of self-powered energy harvesting devices for a wide range of applications. More specifically, three-phase piezoelectric composites are capable of maintaining high reliability, durability, and sensitivity, all while being economically feasible and nontoxic. In addition, three-phase composites can be tailored towards multifunctional applications depending on which material is incorporated as the third phase. The criteria that govern the applicability of these composites depend upon their electromechanical properties such as their impedance, resistivity, conductivity, and dielectric constant. Therefore, the present work involved fabrication of barium titanate–epoxy–zinc oxide (BT–Ep–ZnO) multifunctional composites, and study of the variation of their electron transport properties. The volume fraction of BT was held constant at 0.40, while the volume fraction of ZnO was varied from 0.01 to 0.10. The dipoles of the electroactive phases were aligned using a contactless corona plasma discharge poling technique. The impedance, resistance, conductance, and capacitance were measured over the frequency range from 20 Hz to 10 MHz. The geometry of the composites was measured and used to normalize the data by calculating the resistivity, conductivity, and dielectric constant. The piezoelectric strain coefficients, d33 and d31, were measured using a piezometer at frequency of 110 Hz. The fractured surface morphology and distribution of the particles were observed by scanning electron microscopy.

Piezoelectric thin-film-based cantilevers have been investigated for higher energy-harvesting performance with simplified processing steps. Here, a simple in situ film deposition process of heavily Nb-doped lead zirconate titanate (PZT) films, which does not require annealing and poling, has been demonstrated to verify the possibility of use of the resultant films as energy-harvesters specifically for low frequency vibrating sources. The in situ domain formation of the films during the deposition was demonstrated from the apparent shifts of the capacitance-electric field curves, indicating the presence of internal electric fields. The so-called imprint behavior was found to be directly related to the performance of piezoelectric energy harvesting. As an optimal example, 12 mol% Nb-doped cantilever harvesters that showed the largest imprint behavior exhibited the best values of ∼19.1 GPa figure-of-merit and ∼1436 μWcm−3g−2 power density, which are competitive compared to other reported values.

We herein report the preparation of a soluble polyimide from a photoreactive diamine and a phenolic diamine, to which electro-optic (EO) properties were imparted by the introduction of an EO chromophore (Disperse Red 1) into the phenolic group of the polyimide. Following poling at 1 MV/cm and 210 °C, the polyimide was irradiated with UV light (280–310 nm) to form a photo-crosslinking network. The EO coefficient of the polyimide-containing EO device was 27.7 p.m./V at 1.3 μm, and this value was maintained at ≥90%, even after annealing at 150 °C for 500 h. Our results indicated that the thermal and chemical stabilities of the EO polyamide were remarkably increased due to the photo-crosslinking reaction.

Poly(vinylidene fluoride) (PVDF) is one of the most studied polymers that exhibits piezoelectric and ferroelectric properties. PVDF crystallizes into four different forms, namely α, β, γ, and δ phases. Generally, the nonpolar α phase, as a replacement for the polar β phase with the most superior ferroelectric and piezoelectric properties, is formed from the precursor melt and solution. Here, we report a method for the preparation of β-phase-dominant PVDF thin films by doping PVDF solution with a metal hydrated salt, such as Co(NO₃)₂·6H₂O, without any stretching procedure. The crystal structure of the film was analyzed using X-ray diffraction -2 scanning and Fourier transform infrared spectroscopy. The morphology of the film was observed using a field emission-scanning electron microscope. To determine the frequency dependence of dielectric properties, an LCR meter was used in the range of 50 Hz to 1 MHz. The crystalline phase and morphology of the electrostatic spray-deposited PVDF films depended on the chemical additive. Our results show that the addition of a metal hydrated salt can induce an in situ poling effect, consequently facilitating the preferred dipole orientation in the electrostatically sprayed PVDF films.

Flexible piezoelectric generators (PEGs) present a unique opportunity for renewable and sustainable energy harvesting. Here, we present a low-temperature and low-energy deposition method using solvent evaporation-assisted three-dimensional printing to deposit electroactive poly(vinylidene fluoride) (PVDF)-trifluoroethylene (TrFE) up to 19 structured layers. Visible-wavelength transmittance was above 92%, while ATR-FTIR spectroscopy showed little change in the electroactive phase fraction between layer depositions. Electroactivity from the fabricated PVDF-TrFE PEGs showed that a single structured layer gave the greatest output at 289.3 mV peak-to-peak voltage. This was proposed to be due to shear-induced polarization affording the alignment of the fluoropolymer dipoles without an electric field or high temperature.

Pyroelectric energy harvesting has been attracting increasing attention due to its abundance and potential applications. In this work, we comparably investigated the pyroelectric properties of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 bulk ceramics without (PNZT95/5) and with Mn doping (PNMZT95/5). Compared to PNZT95/5, PNMZT95/5 demonstrated a lower dielectric constant and low rhombohedral - high rhombohedral ferroelectric phase transition temperature (TLH from 37 °C to 27 °C). Moreover, the poling time displayed significant effects on the dielectric and pyroelectric properties of the ceramics. A giant pyroelectric response was obtained for the PNMZT95/5 ceramics, of which the maximum pyroelectric figure of merit FE was 16017 J/(m3K2) after 180 min of poling, which increased 62% compared with the FE for PNZT95/5 (9890 J/(m3K2), far higher than those of other pyroelectric materials as well. PNMZT95/5 ceramics is suggested to be a promising candidate for the thermal energy harvesting applications.

The development of piezoelectric materials has been an important topic within the ever-growing field of energy harvesting technologies. With recent advances, nanostructured piezoelectric nanogenerators have become a state-of-the-art technology for energy scavenging applications. A large variety of devices have been developed in recent decades. The performance of these electromechanical energy transformation devices has been radically increased with the use of nanostructured and novel materials. Metal oxides with perovskite structures and polyvinylidene fluoride (PVDF) are two important substrates paving the way towards enhanced piezoelectric devices in the modern era. Previously, only ferroelectric materials with strong dipole moment had the upper hand in term of electromechanical response. Further, advanced studies have shown that surface activation could lead to an increase of the organized dipole, and thus allow for avoidance of poling. This review summarizes recent advanced techniques and improvements of energy generation through this electromechanical piezoelectric system. Classification of multi-dimensional piezoelectric material based nanogenerators has also been briefly addressed.

PVDF-TrFE-based wearable nanogenerators were designed and fabricated with enhanced performances via reduced graphene oxides (rGO) and in situ electric polarization. Our laboratory-made polarization system may complete the in situ poling of PVDF-TrFE films in 5 min without heating, which has the advantages of high production efficiency, excellent piezoelectric performances, and favorable uniformity, compared to traditional poling approaches. The addition of rGO into PVDF-TrFE significantly improved the crystallinity of the β-phase PVDF-TrFE and enhanced the formation of hydrogen bonds via interaction of dipoles between rGO and PVDF-TrFE. This further improved the energy-harvesting performances of these piezoelectric nanogenerators with 1.6 times of the open-circuit voltage and 2 times of the power density than that of pure PVDF-TrFE-based devices. The high production efficiency and excellent piezoelectric performances of in situ polarized rGO/PVDF-TrFE make them of great potential for self-powered, wearable/portable devices.