Poling Process Research Articles

Flexible Composites with Rare-Earth Element Doped Polycrystalline Particles for Piezoelectric Nanogenerators

Energy harvesting plays an important role in advancing personalized wearables by enabling continuous monitoring, enhancing wearable functionality and facilitating sustainable solutions. We aimed to develop a flexible piezoelectric energy harvesting system based on inorganic piezoelectric materials that convert mechanical energy into electricity to power a wide range of mobile and portable electronic devices. There is significant interest in flexible piezoelectric energy harvesting systems that use inorganic piezoelectric materials due to their exceptional physical features and prospective applications. Herein, we successfully demonstrated a flexible piezoelectric nanogenerator (PENG) designed by the co-doped rare-earth element ceramics (RE-PMN-PT) embedded in PVDF and PDMS composite film and attained a significant output performance while avoiding electrical poling process. The impact of dielectric characteristics on the electrical output of nanogenerators was investigated, together with the structure of the composites. The Sm/La-PMN-PT particles effectively amplify both the voltage and current output, showcasing their potential to power portable and wearable devices, as demonstrated by their capacity to illuminate LEDs. The maximal output power of 2 mW was correlated with the high voltage (220 V) and current (90 µA) of Sm/La-PMN-PT/PVDF, which demonstrated that the device has the potential for energy harvesting in biomedical applications.

Self-healable and stretchable perovskite-elastomer gas-solid triboelectric nanogenerator for gesture recognition and gripper sensing

Gas-solid triboelectric nanogenerators (GS-TENGs) based on porous elastomers provide a promising avenue for the design of self-powered sensors. However, the intrinsic limitation of low electric output in GS-TENGs could affect the accuracy and sensitivity of sensing systems. Here, we develop a porous composite by integrating an adhesive poly(siloxane-diphenylglyoxime-urethane) (PSDU) elastomer with ferroelectric (3,3-difluorocyclobutylammonium) 2 CuCl 4 [(DF-CBA) 2 CuCl 4 ] fillers. PSDU, an intrinsically triboelectric negative material with alternating hard-soft segments and supramolecular bonds, imparts excellent compressibility, adhesion, and self-healing properties to the composite. Simultaneously, the incorporation of (DF-CBA) 2 CuCl 4 as functional fillers leverages the formation of a hydrogen bonding network to enhance charge transfer processes. These fillers facilitate charge accumulation through an electric poling process, resulting in a power output improvement that surpasses 1400 times higher than that of a dense PSDU-based GS-TENG. Tapping onto the versatile properties of porous poly(siloxane-diphenylglyoxime-urethane)-perovskite (PSDU-PK) GS-TENGs, applications such as hand gesture/food recognition and dual-mode sensing system have been demonstrated, suggesting their promising potential in wearable electronics and smart agriculture.

Spatial inequality in sub-national human development index: A case study of West Bengal districts

Human Development and its regional disparity is an area of topical interest. In this paper, we consider space as an instrumental variable in understanding this disparity and explore spatial interdependence in human development across districts of West Bengal using alternate indicators of human development. This study uses both the standard United Nations Development Programme (UNDP) technique and an alternative methodology to construct a sub-national human development index. Spatial interdependence is measured using Moran's I coefficient and Local Indicators of Spatial Autocorrelation (LISA) cluster maps. Spatial regression is used to evaluate the spatial association between the Human Development Index as the dependent variable and a few independent variables. A high degree of clustering in all three dimensions of human development is observed among the southern districts of West Bengal. The pattern of cluster maps indicates the presence of both the growth pole process and the metropole-periphery process in the state. Spatial regression results indicate that the share of socially backward class population and urbanization rate are important variables affecting regional human development patterns. The findings of this study suggest policies targeted to promote social inclusion and urbanization linked with better access to economic opportunities in the lagging areas can help reduce regional imbalances.

Optimizing the polar phase transformation in PVDF-HFP/BaTiO3-activated carbon composite films with the mixture design of experiments

ABSTRACT A salient bottleneck to driving the wider use of polyvinylidene fluoride (PVDF) and its copolymers in smart applications is the requirement for a high-voltage poling process required to activate their β -phase crystal structure before the realisation of the piezoelectricity response. In pursuit of enhancing the β-phase content of PVDF-based films, various approaches have been employed in recent years. Yet, a perfect solution to the challenge remains elusive. Here, we report a preliminary investigation into the production of unpoled poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) films reinforced with barium titanate (BaTiO3) and activated carbon (AC) to improve the piezoelectric property. Employing the mixture design of experiments (MDOE) method, various formulations of the composite’s constituents weight fractions were determined. Afterwards, series of composite films were produced via a toxic-free solution casting method and characterised by Fourier Transform Infrared Spectrum (FTIR) to determine the β-phase content. A non-linear polynomial regression model was established from the experimental FTIR data, and the adequacy of the model was confirmed using ANOVA. Subsequently, an MDOE-enabled optimisation was undertaken, generating a formulation of the composite to obtain the highest β-phase content to be 15 wt.% BaTiO3 and 0.74 wt.% AC. This combination produces a theoretically predicted β-phase content of 72.7 %. A further experimental test employing the optimal formulation produced a β-phase content of 71.90 %, achieved with neither mechanical stretching, thermal annealing, nor electrical poling.

The impact of anodic mesh density and halogen anions on the optical characteristics of gradient refractive index microlens arrays fabricated in chalcohalide glass via microthermal poling

Gradient refractive index microlens arrays (GRIN MLAs), covering the visible to mid-infrared wavelength range, are imprinted in GeS2-Ga2S3-CsX (X = Cl, Br, and I) chalcohalide glasses by an efficient and economical microthermal poling process. This study investigates the impact of anodic mesh number (ranging from 400 to 2000 mesh) and halogen anions on the optical properties, including focal length, resolution, and aberration. Findings reveal that as the mesh number decreases, the focal length and aberration of GRIN MLAs increase. Optimal resolution is achieved with the 500 mesh sample, which also shows the best phase difference performance. The migration depth of Cs+ ions, influenced by halogen anions (from Cl to I), results in contrasting optical properties between lower mesh (400–750) and higher mesh (1000–2000) samples. Notably, the Cl-500 GRIN MLAs demonstrate a focal length of 615.0 μm, a maximum resolution of 6.35 lp/mm, and minimal aberration of −0.0591. These changes are attributed to the predominant transverse and longitudinal migration of Cs+ ions in mesh square areas. This research highlights the relationship between microthermal poling conditions, ion migration, and optical performance, providing valuable insights for the application of GRIN MLAs in advanced optical systems.

Enhanced piezoelectrical properties of Pb(Zn1/3Nb2/3)O3 - PbTiO3 single crystals by AC poling

We investigated the effectiveness of AC poling (ACP) processes for [001] direction oriented Pb(Zn1/3Nb2/3)O3-0.055PbTiO3 (PZN-PT) single crystals (SCs) and obtained a dielectric constant ε 33 T/ε 0 of 6680 and piezoelectric strain constant d 33 of 2760 pC/N, a piezoelectric charge constant g 33 of 46.7 × 10−3 Vm/N, and a figure of merit (FOM) (d 33 × g 33) of 129 × 10−12 m2/N. These values were 19%, 31%, 10%, and 45% higher than those of DC poling PZN-PT SC, respectively. The phase change temperature T pc, Curie temperature T c, and acoustic impedance (Z 33) of the ACP PZN-PT SC were 121 °C, 165 °C, and 30.5 MRayls, respectively. Compared with Pb(Mg1/3Nb2/3)O3−0.3PbTiO3 SCs, the higher T pc, T c, and FOM and lower Z 33 of the PZN-PT SCs enable the applications in high temperature with superior Z 33 matching to water and human body than conventional Pb(Mg1/3Nb2/3)O3−0.3PbTiO3 SCs , and these findings are vital for a wide range of ultrasonic transducer applications.

Advancing large-scale thin-film PPLN nonlinear photonics with segmented tunable micro-heaters

Thin-film periodically poled lithium niobate (TF-PPLN) devices have recently gained prominence for efficient wavelength conversion processes in both classical and quantum applications. However, the patterning and poling of TF-PPLN devices today are mostly performed at chip scales, presenting a significant bottleneck for future large-scale nonlinear photonic systems that require the integration of multiple nonlinear components with consistent performance and low cost. Here, we take a pivotal step towards this goal by developing a wafer-scale TF-PPLN nonlinear photonic platform, leveraging ultraviolet stepper lithography and an automated poling process. To address the inhomogeneous broadening of the quasi-phase matching (QPM) spectrum induced by film thickness variations across the wafer, we propose and demonstrate segmented thermal optic tuning modules that can precisely adjust and align the QPM peak wavelengths in each section. Using the segmented micro-heaters, we show the successful realignment of inhomogeneously broadened multi-peak QPM spectra with up to 57% enhancement of conversion efficiency. We achieve a high normalized conversion efficiency of 3802% W−1 cm−2 in a 6 mm long PPLN waveguide, recovering 84% of the theoretically predicted efficiency in this device. The advanced fabrication techniques and segmented tuning architectures presented herein pave the way for wafer-scale integration of complex functional nonlinear photonic circuits with applications in quantum information processing, precision sensing and metrology, and low-noise-figure optical signal amplification.

Efficient Poling‐Free Wavelength Conversion in Thin Film Lithium Niobate Harnessing Bound States in the Continuum

AbstractOver the past two decades, there has been a surge of interest in photonic integrated circuits (PICs) to enable low‐cost industrial mass manufacture of miniaturized optical systems while simultaneously improving performance and energy efficiency following the trajectory of electronics and large‐scale integration. An essential characteristic of any PIC lies in the ability of waveguides to efficiently confine light. The phenomenon of bound states in the continuum (BIC) shows promise in achieving confinement of light for modes that otherwise would suffer from high leakage losses, which can occur in many PIC platforms. In this contribution, the usefulness of operating near a BIC to achieve efficient second harmonic generation of ≈300% W−1 cm−2 in Silicon Nitride (SiN) loaded lithium niobate on insulator (LNOI) waveguides without needing to either pole or etch the lithium niobate is experimentally demonstrated. The guided fundamental mode is phase matched at the telecom wavelength to a higher order mode at the second harmonic wavelength that is engineered as a bound state in the continuum to mitigate leakage losses. This demonstrates the promise of using BIC in weakly confining waveguides for nonlinear optical applications all while avoiding the poling process by engineering waveguide geometry.

Generation of second harmonic at wide conversion band in GRIN multimode fibers

Optical poling of multimode graded-index fibers (GRIN) has emerged as a promising technique for creating periodic inscriptions of the second-order nonlinear optical susceptibility χ(2), enabling the generation of a second harmonic in silica fibers. In this work, we investigate the generation of multiple spectral peaks using a continuous broadband source in the infrared domain, generated in the same fiber by a femtosecond laser with a central wavelength different from the one used for the poling process. Building upon theoretical foundations, this work contributes at explaining how second and third-order nonlinear processes participate to the broad generation of the second harmonic in GRIN fibers.

Promoting Periodical Poling in Lithium Niobate Crystal Through Surface Acoustic Wave‐Induced Local Lattice Activation

AbstractAchieving precise construction of ferroelectric domain structure in lithium niobate (LN) crystals holds significance for expanding the applications of periodically poled lithium niobate (PPLN), especially in nonlinear frequency conversion. However, challenges exist during the application of electric field for poling, especially for small‐period PPLN crystals, where ferroelectric domains in LN crystals tend to unevenly expand laterally, making it hard to precisely control the domain structures. LN, as a piezoelectric crystal, has the capability to generate energy‐carrying surface acoustic waves (SAW). Herein, an method is presented to optimize the periodic poling process by integrating SAW and poling on a LN chip, which remarkably reduces the poling electric field by 10%, attributed to the enhanced local lattice vibrations during SAW propagation. The integrated SAW and poling chip achieves a 9 µm‐period PPLN crystal. Through second harmonic generation, a nonlinear light conversion from 1158 to 579 nm is realized, exhibiting a nonlinear optical efficiency up to 17.4%. This efficiency aligns with the theoretical prediction, validating the high‐quality domain structure. This integrated chip provides a unique opportunity for manipulating ferroelectric domain with high‐precision, benefiting a wide range of applications in nonlinear‐optics, ferroelectrics, and integrated optics.

Bi compensation and poling process to enhance piezoelectric properties of BiFeO3-BaTiO3 lead-free piezoceramics

BiFeO3-BaTiO3 (BF-BT) ceramics are an excellent choice for high-temperature lead-free piezoelectric ceramic due to their high Curie temperature and good piezoelectric properties, but the volatilization of Bi leads to the formation of A-site cationic vacancies and oxygen vacancies, culminating in heightened leakage currents and detrimental effects on piezoelectric properties. In this study, a chemical composition of 0.70Bi(1+x)Fe0·97Al0·03O3-0.30BaTiO3 ceramics, abbreviated as B1+xFA-BT, where 0 ≤ x ≤ 0.05, were synthesized, with special attention on the effects of Bi compensation and poling process on their insulation and piezoelectric properties. Due to the coexistence of R-PC phases and low leakage current, B1+xFA-BT ceramics exhibit excellent piezoelectric properties and high Curie temperature, among which the B1.02FA-BT ceramic boasts optimal overall properties: d33 = 196 pC N−1, TC = 480 °C, kp = 34%, θmax = 49.5° and Qm = 32, under optimal poling parameters Ep = 50 kV cm−1 and Tp = 100 °C. The poling process is directly linked to the reorientation of domains, the redistribution of positive/negative space charge and the aggregation or injection of holes, which is achieved by tuning the poling field and temperature in a ceramic with optimal integrated piezoelectric properties. The poling process of BF-BT ceramics is significantly influenced by their leakage characteristics, which can have a significant impact on their overall performance. Optimizing electrical poling conditions and minimizing leakage current is crucial to achieving favorable piezoelectric properties in BF-BT ceramics with R-PC coexisting structures.

Topology optimization for the design of manufacturable piezoelectric energy harvesters using dual-MMC method

Abstract This paper presents a new topology optimization scheme for the manufacturable piezoelectric energy harvesters (PEHs). Most of the existing topology optimization schemes for the design for PEHs are difficult to cope with manufacturing constraints producing design results that pose serious challenges for the local poling of the piezoelectric materials. In this work, dual-Moving Morphable Component (dual-MMC) scheme for explicit topology optimization for the design of PEHs is presented. In dual-MMC scheme, two independent sets of MMC are employed to describe the structural topology of the PEH and polarization profile in piezoelectric material in an explicit manner. With the use of the scheme, the shape of electrodes and the opposite polarization directions in the local poling process can be effectively treated as a constraint making the realization of the PEH an easy task. Several examples for the design of cantilever-type PEH are provided to demonstrate the effectiveness of the proposed approach. Furthermore, a designed PEH actually manufactured for demonstration of the production process.

Textured CsPbI3 nanorods composite fibers for stable high output piezoelectric energy harvester

The utilization of piezoelectric nanogenerator (PENG) based on halide perovskite materials has demonstrated significant promise for energy harvesting applications. However, the challenge of synthesizing halide perovskite materials with both high output performance and stability using a straightforward process persists as a substantial obstacle. Herein, we present the fabrication of CsPbI3 nanorods (NRs) exhibiting highly uniform orientation within polyvinylidene fluoride (PVDF) fibers through a simple texture engineering approach, marking the instance of enhancing PENG performance in this manner. The resultant composite fibers showcase a short-circuit current density (Isc) of 0.78 ​μA ​cm−2 and an open-circuit voltage (Voc) of 81 ​V, representing a 2.5 fold increase compared to the previously reported highest value achieved without the electric poling process. This outstanding output performance is ascribed to the orientation of CsPbI3 NRs facilitated by texture engineering and dipole poling via the self-polarization effect. Additionally, the PENG exhibits exceptional thermal and water stability, rendering it suitable for deployment in diverse and challenging environmental conditions. Our findings underscore the significant potential of textured CsPbI3 NRs composite fibers for powering low-power consumer electronics, including commercial LEDs and electronic watches.

Wafer-Scale Periodic Poling of Thin-Film Lithium Niobate.

Periodically poled lithium niobate on insulator (PPLNOI) offers an admirably promising platform for the advancement of nonlinear photonic integrated circuits (PICs). In this context, domain inversion engineering emerges as a key process to achieve efficient nonlinear conversion. However, periodic poling processing of thin-film lithium niobate has only been realized on the chip level, which significantly limits its applications in large-scale nonlinear photonic systems that necessitate the integration of multiple nonlinear components on a single chip with uniform performances. Here, we demonstrate a wafer-scale periodic poling technique on a 4-inch LNOI wafer with high fidelity. The reversal lengths span from 0.5 to 10.17 mm, encompassing an area of ~1 cm2 with periods ranging from 4.38 to 5.51 μm. Efficient poling was achieved with a single manipulation, benefiting from the targeted grouped electrode pads and adaptable comb line widths in our experiment. As a result, domain inversion is ultimately implemented across the entire wafer with a 100% success rate and 98% high-quality rate on average, showcasing high throughput and stability, which is fundamentally scalable and highly cost-effective in contrast to traditional size-restricted chiplet-level poling. Our study holds significant promise to dramatically promote ultra-high performance to a broad spectrum of applications, including optical communications, photonic neural networks, and quantum photonics.

Comparison of field-cooling DC poling and AC poling for lead perovskite relaxor-PbTiO3 single crystals grown by a continuous feeding Bridgman process

We investigated the effectiveness of poling processes for Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals (SCs) produced using a continuous feeding Bridgman method, which is known to produce a high property uniformity. The four studied poling processes are: (I) standard direct current poling (STD-DCP); (II) low-voltage field-cooling DCP (LV-FCP); (III) high-voltage field-cooling DCP (HV-FCP); and (IV) mid-temperature alternating current poling (MT-ACP). The highest free dielectric constant (ε 33 T/ε 0) and piezoelectric constant (d 33) were obtained by MT-ACP (ε 33 T/ε 0 = 11 000, d 33 = 3000 pC/N), followed by LV-FCP (ε 33 T/ε 0 = 7500, d 33 = 2400 pC/N), HV-FCP (ε 33 T/ε 0 = 6250, d 33 = 1850 pC/N), and STD-DCP (ε 33 T/ε 0 = 6200, d 33 = 1800 pC/N). The LV-FCP SC showed a 21% and 33% increase in ε 33 T/ε 0 and d 33 compared to that of the STD-DCP SC; however, this was not as much as the 77% and 67% improvement of the MT-ACP SC. These results provide guidance for SC transducers.

Self-poling and DC poling of Mn doped Pb(Mg1/3Nb2/3)O3-Pb(ZrTi)O3 single crystals grown by a solid state crystal growth process

Acceptor Mn-doped Pb(Mg1/3Nb2/3)O3-Pb(ZrTi)O3 (PMN-PZT) single crystals (SCs) grown by a solid state crystal growth (SSCG) process electrode with Ag at 650 °C showed a high piezoelectric coefficient (d 33) of 520 pC N−1 at 25 °C by self-poling, i.e. without any additional poling process. Upon heating above the Curie temperature (T c), the impedance characteristics’ oscillation peak due to piezoelectricity disappears. However, as the temperature falls below T c, these oscillation peaks reemerge around T c. And when the temperature is further lowered to around RT, the impedance characteristics return to almost the original state. The d 33 values of the non-poled SCs, initially 520 pC N−1, increased to 910 pC N−1 after DC poling (DCP) and to 1170 pC N−1 after field cooling (FC)-DCP. These values surpass those of commercially available high-Qm PZT ceramics. These high-Qm PMN-PZT single crystals developed using the SSCG method demonstrate huge potential for future transducer applications.

3D Printing of Anisotropic Piezoresistive Pressure Sensors for Directional Force Perception.

Anisotropic pressure sensors are gaining increasing attention for next-generation wearable electronics and intelligent infrastructure owing to their sensitivity in identifying different directional forces. 3D printing technologies have unparalleled advantages in the design of anisotropic pressure sensors with customized 3D structures for realizing tunable anisotropy. 3D printing has demonstrated few successes in utilizing piezoelectric nanocomposites for anisotropic recognition. However, 3D-printed anisotropic piezoresistive pressure sensors (PPSs) remain unexplored despite their convenience in saving the poling process. This study pioneers the development of an aqueous printable ink containing waterborne polyurethane elastomer. An anisotropic PPS featuring tailorable flexibility in macroscopic 3D structures and microscopic pore morphologies is created by adopting direct ink writing 3D printing technology. Consequently, the desired directional force perception is achieved by programming the printing schemes. Notably, the printed PPS demonstrated excellent deformability, with a relative sensitivity of 1.22 (kPa*wt. %)-1 over a substantial pressure range (2.8 to 8.1kPa), approximately fivefold than that of a state-of-the-art carbon-based PPS. This study underscores the versatility of 3D printing in customizing highly sensitive anisotropic pressure sensors for advanced sensing applications that are difficult to achieve using conventional measures.

The Franz–Keldysh effect in the optical absorption spectrum of a TlGaSe2 layered semiconductor caused by charged native defects

The Franz–Keldysh effect in the optical absorption edge of a bulk TlGaSe2 layered semiconductor poled under an external electric field was investigated in the present work. The Franz–Keldysh shift below the optical bandgap absorption region, as well as the quasi-periodic oscillations above the fundamental bandgap of TlGaSe2, were observed. The measured changes in optical light absorption of the TlGaSe2 sample were revealed after poling processing. The poling technique is used to produce the built-in internal electric field within the TlGaSe2 semiconductor. The frozen-in internal electric field in TlGaSe2 was experimentally monitored through changes in the lineshape of the absorption spectra at the fundamental band edge. The observed results are accurately fitted with the theoretical lineshape function of the Franz–Keldysh absorption tail below the bandgap of TlGaSe2 and quasi-periodic oscillations above the bandgap. A good agreement between the theoretical and experimental results was observed. The present study demonstrated that the Franz–Keldysh effect can be used to identify and characterize the localized internal electric fields originating from electrically active native imperfections in the TlGaSe2 crystals.

Self-poled piezoelectric polymer composites via melt-state energy implantation

Lightweight flexible piezoelectric polymers are demanded for various applications. However, the low instinctively piezoelectric coefficient (i.e. d33) and complex poling process greatly resist their applications. Herein, we show that introducing dynamic pressure during fabrication is capable for poling polyvinylidene difluoride/barium titanate (PVDF/BTO) composites with d33 of ~51.20 pC/N at low density of ~0.64 g/cm3. The melt-state dynamic pressure driven energy implantation induces structure evolutions of both PVDF and BTO are demonstrated as reasons for self-poling. Then, the porous material is employed as pressure sensor with a high output of ~20.0 V and sensitivity of ~132.87 mV/kPa. Besides, the energy harvesting experiment suggests power density of ~58.7 mW/m2 can be achieved for 10 N pressure with a long-term durability. In summary, we not only provide a high performance lightweight, flexible piezoelectric polymer composite towards sustainable self-powered sensing and energy harvesting, but also pave an avenue for electrical-free fabrication of piezoelectric polymers.

Topography and Nonlinear Optical Properties of Thin Films Containing Iodide-Based Hybrid Perovskites.

This article covers selected properties of organic-inorganic thin films of hybrid perovskites with the summary formulas CH3NH3MI3, where M = Pb, Cd, Ge, Sn, Zn. The paper discusses not only the history, general structure, applications of perovskites and the basics of the theory of nonlinear optics, but also the results of experimental research on their structural, spectroscopic, and nonlinear optical properties. The samples used in all presented studies were prepared in the physical vapor deposition process by using co-deposition from two independent thermal sources containing the organic and inorganic parts of individual perovskites. Ultimately, thin layers with a thickness of the order of nanometers were obtained on glass and crystalline substrates. Their structural properties were characterized by atomic force microscopy imaging. Spectroscopic tests were used to confirm the tested films' transmission quality and determine previously unknown physical parameters, such as the absorption coefficient and refractive index. Experimental results of the nonlinear optical properties were obtained by studying the second and third harmonic generation processes and using initial sample polarization in the so-called Corona poling process. The obtained experimental results allowed us to determine the second- and third-order nonlinear optical susceptibility of the tested materials.