Electric Polarization Effects Research Articles

Advantageous Effects of Phase Transition-Modulated Electric Polarization of Hollow CuSx for Enhanced Electromagnetic Wave Absorption.

Scrutinizing the electromagnetic wave absorption mechanism of sulfides remains a challenge due to the variability of the modulation of the crystal structure of the sulfides. To take advantage of this variability, nanosheet-assembled Cu9S5/CN composites with sulfur vacancies were prepared in this study by self-assembly synthesis and subsequent high-temperature heat treatment. Systematic studies show the phase transition-dependent induced decrease in the conductivity, the defect site-induced difference in the charge density, the weakened vacancy formation of defect polarization loss, and the influence of valence state on electric dipole polarization loss and interfacial polarization loss, making the optimization of the dielectric constant a significant positive effect on the improvement of impedance matching. This work provides a reliable example and theoretical guidance for the crystal structure design for the preparation of a new generation of efficient sulfide-based wave-absorbing materials.

Electro-responsive OCNT/PPy membrane for efficient irreversible-fouling control through electroregulation of electrostatic and fluid interaction forces

Membrane-based separation process has been proven to be a powerful strategy for low-energy-consumption and high-efficiency water purification. However, the practical application is still subjected to serious membrane fouling. In this study, an impressive approach to alleviate membrane fouling is proposed using an electro-conductive oxygenated carbon nanotube/polypyrrole (OCNT/PPy) membrane combining electrically-regulated electrostatic and fluid forces. Benefiting from the negative potential (−1.18 V vs. SCE) applied on the membrane, the electric polarization effects significantly enhance the repulsive electrostatic force on contaminant. The transmembrane pressure increases at an ignorable rate during the filtration process. Meanwhile, for accumulated irreversible membrane fouling after multi-cycle filtrations, the positive potential (+1.19 V vs. SCE) exerted on OCNT/PPy membrane can decrease the fluid resistances of backwash flow. As a result, the electrically-regulated hydraulic backwash achieves a thorough recovery rate of permeance at 99.1 %. The numerical analysis of the antifouling mechanism reveals that the mitigation of irreversible membrane fouling is mainly attributed to rapid formation of a loose cake layer under electrical assistance. Moreover, the computational fluid dynamics verifies that the reduction of water-channel resistance enhances the elimination of foulants in membrane pores. This work motivates a new thought for membrane fouling control through electroregulation of electrostatic and fluid forces at the membrane-water interface.

Entangling imidazolium-based ionic liquids and melanins: A crossover study on chemical vs electronic properties and carrier transport mechanisms

Melanins (mel) are a class of pigments that are nearly ubiquitous and among the oldest compounds found in nature. However, their practical application has been limited due to their low solubility in water and in most organic solvents. Recent research on polydopamine has revealed that ionic liquids (ILs) not only enhance melanin’s dissolution but also fine-tune its redox properties through specific dipolar interactions. In this study, we expand upon previous investigations by customizing new suspensions on a broader range of melanins. Concerning ILs, we focus on imidazolium based ILs, tailoring their chemical properties (pKa) and structural characteristics (cation radius, anion radius).The melanins under consideration include synthetic polymers derived from the oxidative polymerization of 5,6-dihydroxyindole (DHI) and its 2-carboxylic acid counterpart (DHICA), as well as the natural pigment Sepiomelanin (Sepiomel), which is isolated from the ink sack of cuttlefish. Our comparative analysis between neat ILs and ILs-mel responses reveals several key findings: the increase in solubility, the tuning of the redox ability, the decrease of the ionic charge resistance (from MΩ τo kΩ); the partial removal of the electrical polarization effects and the delocalized ionic charge hopping mechanisms in conductivity; the increase of the free ionic diffusion mobility and Debye lengths. Notably, electrical transport is influenced by both the chemical features and the steric hindrance in the ILs as well as the specific type of melanin employed. These factors contribute to the high order correlation between free ionic charge densities and their corresponding Debye lengths. Consequently, our findings suggest that for these complex systems, an improved model extending beyond a simplified electrostatic interaction mechanism is required.

A New Numerical Simulation Framework to Model the Electric Interfacial Polarization Effects and Corresponding Impacts on Complex Dielectric Permittivity Measurements in Sedimentary Rocks

A New Numerical Simulation Framework to Model the Electric Interfacial Polarization Effects and Corresponding Impacts on Complex Dielectric Permittivity Measurements in Sedimentary Rocks

Effects of electric polarization and defect energy levels induced by ion irradiation on the electrical behavior of 4H-SiC Schottky barrier diodes

The effects of electric polarization and defect energy levels induced by C4+ irradiation on the electrical behavior of 4H-SiC Schottky barrier diodes (SBDs) are discussed. The parameters of the SBDs were extracted from capacitance–voltage (C–V) and current–voltage (I–V) measurements, the deep level transient spectroscopy (DLTS) was used to identify defect energy levels. In addition, the dielectric function and energy band structure of 4H-SiC were calculated using a first-principles approach to verify the enhancement of polarization and the origin of the defect energy levels. The results show that the net (donor) carrier concentration (N d) increases with the increase of irradiation fluence, which is caused by the competition between irradiation-induced defects and the polarization effect. On the one hand, Z 1/2 is determined by DLTS. It is related to the doubly negatively (2-|0) charged state of V c (carbon vacancy), which is a double acceptor. The intensity of the Z 1/2 peak increases with increasing irradiation fluence, which means that the defects caused by irradiation should reduce the N d. On the other hand, the polarization effect does exist and it becomes stronger with the increase in the irradiation fluence, which makes the N d increase. Obviously, the polarization effect induced by the irradiation is dominant for N d when the depth of ion penetration is in the shallow layer behind the metal–semiconductor (M–S) interface. Irradiation induced electron traps and an uneven distribution of positively charged centers, which can cause ln(I)-V to exhibit a non-linear component before reaching the turn-on voltage. The series resistance (R s), reverse current (I R) increase and the forward current decreases with the increase in irradiation fluence. All these show that the irradiation causes degradation of Ni/4H-SiC SBD performance.

External electric field-assisted electronic restructuring of transition metal oxides derived from spent lithium-ion batteries to enhance persulfate activation

Discarded lithium-ion batteries contain abundant transition metal oxides, which benefit to persulfate activation. Inspired by electrocatalysis and the structural properties of the ternary lithium-ion battery cathode, we investigate the effect of external electric field polarization on the electronic structure reorganization behavior of NCM and the catalytic performance of peroxymonosulfate (PMS). Firstly, external electric field polarization promotes the gathering of Co and Ni. Secondly, the electric field modified waste NCM (E-PD@NCM) has 1.61 times higher degradation rate of SMX than the non-electric field modified waste NCM (PD@NCM). Meanwhile, electric field polarization increased the oxygen vacancy content in the spent NCM, and the abundant oxygen vacancies effectively restructured the electronic structure of E-PDNCM, further accelerating charge transfer and significantly improving the PMS activation efficiency. The catalytic mechanism analysis indicates that SO4•− and 1O2 play a dominant role in the degradation of pollutants. This study demonstrates the high catalytic performance of TMO through reorganization of the electronic structure and provides a new strategy to guide the design of other metal oxide nano-catalysts.

Exact first-principles calculation reveals universal moiré potential in twisted two-dimensional materials

Recently, twisted moir\'e systems have attracted intense attention, where the emergence of the moir\'e potential is experimentally observed as an effective way to regulate the electron and exploit novel properties. Various theoretical models have been proposed and attributed the moir\'e potential as a result from interlayer electrical polarization or atomic relaxation effects. To date, the moir\'e potential is not yet directly calculated via an exact first-principles method and the universal mechanism in different systems is still unclear. Here, we obtain and analyze the surface superlattice potential by directly using first-principles calculations. We demonstrate that the moir\'e potential is a widely existing phenomenon in twisted systems with or without interlayer electrical polarization and is generally determined by the local work function. Specifically, the surface moir\'e potential is positively proportional to the local work function in single-atom-thick materials and negatively in multi-atom-thick ones due to a compensation effect. Interestingly, the surface potential amplitude of an unpolarized phosphorene system ($\ensuremath{\sim}430$ meV) is much larger than that of the polarized $h$-BN system ($\ensuremath{\sim}170$ meV). Our work directly reveals the universal moir\'e potential via fully first-principles calculations and provides a different angle in the study of moir\'e systems and twistronics.

Quantum magnetic phenomena in engineered heterointerface of low-dimensional van der Waals and non-van der Waals materials.

Investigating magnetic phenomena at the microscopic level has emerged as an indispensable research domain in the field of low-dimensional magnetic materials. Understanding quantum phenomena that mediate the magnetic interactions in dimensionally confined materials is crucial from the perspective of designing cheaper, compact, and energy-efficient next-generation spintronic devices. The infrequent occurrence of intrinsic long-range magnetic order in dimensionally confined materials hinders the advancement of this domain. Hence, introducing and controlling the ferromagnetic character in two-dimensional materials is important for further prospective studies. The interface in a heterostructure significantly contributes to modulating its collective magnetic properties. Quantum phenomena occurring at the interface of engineered heterostructures can enhance or suppress magnetization of the system and introduce magnetic character to a native non-magnetic system. Considering most 2D magnetic materials are used as stacks with other materials in nanoscale devices, the methods to control the magnetism in a heterostructure and understanding the corresponding mechanism are crucial for promising spintronic and other functional applications. This review highlights the effect of electric polarization of the adjacent layer, changed structural configuration at the vicinity of the interface, natural strain induced by lattice mismatch, and exchange interaction in the interfacial region in modulating the magnetism of heterostructures of van der Waals and non-van der Waals materials. Further, prospects of interface-engineered magnetism in spin-dependent device applications are also discussed.

A Survey – Wearable Antenna Techniques and its Applications

Smart Antenna is an array of antennas which uses the smart signal processing algorithms to track and locate the client device using the direction of arrival of a signal. Smart Wearable Antennas are designed to function while being worn. Wearable antennas are used within the context of Wireless Body Area Networks. The wearable antenna is high in efficiency, miniature in size, and simple in structure, and is implemented with electrical performance and polarization effects, which helps in healthcare, medical and military applications, smart glasses, sensor devices in sports, etc. This research study reviews different wearable antenna technologies such as wearable textile antenna, microstrip antenna and wearable antenna array. Furthermore, the integrated different next generation antennas are also discussed.

A Survey – Wearable Antenna Techniques and its Applications

Smart Antenna is an array of antennas which uses the smart signal processing algorithms to track and locate the client device using the direction of arrival of a signal. Smart Wearable Antennas are designed to function while being worn. Wearable antennas are used within the context of Wireless Body Area Networks. The wearable antenna is high in efficiency, miniature in size, and simple in structure, and is implemented with electrical performance and polarization effects, which helps in healthcare, medical and military applications, smart glasses, sensor devices in sports, etc. This research study reviews different wearable antenna technologies such as wearable textile antenna, microstrip antenna and wearable antenna array. Furthermore, the integrated different next generation antennas are also discussed.

Frequency-Dependent Dielectric Spectroscopy of Insulating Nanofluids Based on GTL Oil during Accelerated Thermal Aging

Improving the dielectric properties of liquid-insulating materials is a current problem in research into the insulation system of a power transformer. Modern optimization of insulating liquids involves the potential use of unique synthetic esters enriched with nanoparticles. This study presents the results of the dielectric response of liquefied gas-based (GTL) insulating liquids during accelerated thermal aging. The dielectric relaxation spectroscopy method was used in the frequency domain to point out power losses as an imaginary part of a complex electric modulus. The relaxation spectra express the validity of applying this complex dielectric parameter. The polarization processes of the base oil alternately change position in the low-frequency band during thermal aging. Fullerene nanofluid undergoes three phases of dielectric loss changes during thermal aging. In the case of magnetic nanofluid, the effect of electric double-layer polarization disappeared after 500 h of thermal aging. It was found that with the gradual increase in the thermal aging time, there is no gradual increase in the dielectric losses investigated in the measured frequency spectrum. This study shows that the concentration of the two types of nanoparticles independently causes a different dielectric response to an applied AC electric field in the GTL base fluid.

Dipole moment background measurement and suppression for levitated charge sensors.

Optically levitated macroscopic objects are a powerful tool in the field of force sensing, owing to high sensitivity, absolute force calibration, environmental isolation, and the advanced degree of control over their dynamics that have been achieved. However, limitations arise from the spurious forces caused by electrical polarization effects that, even for nominally neutral objects, affect the force sensing because of the interaction of dipole moments with gradients of external electric fields. Here, we introduce a technique to measure, model, and eliminate dipole moment interactions, limiting the performance of sensors using levitated objects. This process leads to a noise-limited measurement with a sensitivity of 3.3 × 10−5 e. As a demonstration, this is applied to the search for unknown charges of a magnitude much below that of an electron or for exceedingly small unbalances between electron and proton charges.

Laser-induced dynamic alignment of the HD molecule without the Born-Oppenheimer approximation.

Laser-induced molecular alignment is well understood within the framework of the Born-Oppenheimer (BO) approximation. Without the BO approximation, however, the concept of molecular structure is lost, making it hard to precisely define alignment. In this work, we demonstrate the emergence of alignment from the first-ever non-BO quantum dynamics simulations, using the HD molecule exposed to ultrashort laser pulses as a few-body test case. We extract the degree of alignment from the non-BO wave function by means of an operator expressed in terms of pseudo-proton coordinates that mimics the BO-based definition of alignment. The only essential approximation, in addition to the semiclassical electric-dipole approximation for the matter-field interaction, is the choice of time-independent explicitly correlated Gaussian basis functions. We use a variational, electric-field-dependent basis-set construction procedure, which allows us to keep the basis-set dimension low while capturing the main effects of electric polarization on the nuclear and electronic degrees of freedom. The basis-set construction procedure is validated by comparing with virtually exact grid-based simulations for two one-dimensional model systems: laser-driven electron dynamics in a soft attractive Coulomb potential and nuclear rovibrational dynamics in a Morse potential.

Multiple polarization phases and strong magnetoelectric coupling in the layered transition metal phosphorus chalcogenides TMP2X6(T=Cu,Ag;M=Cr,V;X=S,Se) by controlling the interlayer interaction and dimension

Magnetoelectric multiferroic materials are the potential candidates for the high-density nonvolatile data storage devices. However, up to now, multiferroic materials with strong magnetoelectric coupling are still rare. Here, based on the first-principles calculations and theoretical model, we predict a different class of single phase multiferroic materials, transition metal phosphorus chalcogenides $TM{\mathrm{P}}_{2}{X}_{6}(T=\mathrm{Cu},\phantom{\rule{0.16em}{0ex}}\mathrm{Ag};\phantom{\rule{0.16em}{0ex}}M=\mathrm{Cr},\phantom{\rule{0.16em}{0ex}}\mathrm{V};\phantom{\rule{0.16em}{0ex}}X=\mathrm{S},\phantom{\rule{0.16em}{0ex}}\mathrm{Se})$ with multiple polarization phases and strong magnetoelectric coupling. The ferroelectric polarization originates from the movement of Cu/Ag atoms breaking the symmetry of spatial inversion and the magnetism arises from partially filled $d$ orbitals of the V/Cr atoms. It is predicted that the different ferroelectric phases of $TM{\mathrm{P}}_{2}{X}_{6}$ bulk have different band gaps, providing a way to control electronic and transport properties by the external electric field. Most prominently, for $\mathrm{CuV}{\mathrm{P}}_{2}{\mathrm{S}}_{6}$ bilayer and few layers, one of the ferroelectric phases has ferromagnetic ground state and the other has antiferromagnetic states, realizing the electric-field control of magnetism. We reveal that the physical mechanism of the strong magnetoelectric coupling is from the reduced dimension and symmetry by constructing a theoretical model including the crystal field splitting, electric polarization effect, and exchange interaction. This work not only predicts a different class of magnetoelectric multiferroic materials, but also proposes a strategy to design them by controlling the interlayer interaction in van der Waals layered materials.

Electric Field Polarized Fe−N Functionalized Graphene Oxide Nanosheet Catalyst for Efficient Oxygen Reduction Reaction

AbstractLow‐cost noble‐metal‐free electrocatalysts for oxygen reduction reaction (ORR) are useful for future energy storage and conversion devices, and other technologies. In this work, iron (Fe)‐nitrogen (N) functionalized graphene oxide (Fe−N−GO) nanosheets have been synthesized and studied for ORR properties in alkaline solution. We utilized a multi‐layer/multi‐polarization method to study the DC electric field polarization effect on the electrocatalytic properties of the Fe−N−GO catalyst. The poling effect with DC electric field was created on the catalyst ink drop‐casted on a polished glassy carbon working electrode, resulting in more compact electrocatalyst electrode. Compared to the commercial Pt/C catalyst, the polarized Fe−N−GO catalyst exhibited similar ORR catalytic activity along with superior stability in alkaline media.

Sensitive electric field control of first-order phase transition in epitaxial multiferroic heterostructures

Strongly correlated electron materials that exhibit rich phase transition and multiple phase separation have shown many fascinating properties. Using these properties in the electronic device will require the ability to control their phase transition and phase separation behaviours. In this work, we report a sensitive electric field control of first-order phase transition in epitaxial (011)-Nd0.5Sr0.5MnO3/0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 (PMN-PT) heterostructure. The pristine film shows phase separation character with the penetration of the ferromagnetic metallic phase into the charge and orbital ordered antiferromagnetic insulating phase, and this was revealed by the XMCD and XLD investigation. The (011)-oriented PMN-PT piezoelectric single crystal adopted can exert anisotropic in-plane tensile strains on the epitaxial Nd0.5Sr0.5MnO3 film when applying the electric field. The coaction of the electric field-induced strain and polarization effects of the PMN-PT piezoelectrics enable the efficient manipulation of orbital ordering and the coupled electronic and magnetic phase transitions. Accordingly, a small +1.6 kV cm−1 electric field can recover the first-order metal-insulator transition which was inhibited in the pristine heterostructure, increase the transition temperature by 56 K and the maximum resistance change reaches 7033%. Furthermore, the electric field demonstrated non-volatile control of magnetization, and the magnetoelectric coefficient reaches 1.89 × 10−7 s m−1 at 200 K. This work indicates that choosing the piezoelectric substrate with appropriate electric-field-induced strain opens a route to designing functional electronic devices where the tunable macroscopic properties derive from strongly interacting degrees of freedom present in the manganite.

Plasma assisted micro poling of glassy surfaces: a new tool to achieve liquid crystal multi-domain alignments [Invited

We propose an innovative approach to program the alignment of liquid crystal (LC) assemblies allowing for the formation of multi-domain alignments whose orientation axis and sizes are controlled at the micrometer scale by an electrically patterned glass surface. The glass surface preparation is based on a thermo-electrical imprinting process to induce localized space charge implantations in the glass matrix just below its anode surface. To demonstrate this new approach, a commercial soda-lime glass slide has been polarized using as anode a simple micrometric nickel grid. Characterizing the polarized glass surface by second harmonic generation polarized microscopy; we show an accurate control of both location and spatial components of frozen static fields embedded in the glass as a function of the electrode patterns. The polarized glassy surface is then used in the conception of a LC cell in which homeotropic or planar alignments can be controlled following the electrical pattern induced on the glass surface. This study also points out the importance of plasma discharges spatially controlled along the electrode pattern during the process in order to promote the in-plane electrical polarization effects, which are essential for the programming of the in-plane LC alignment on the polarized glass surface.

Role of crystal structure and electrical polarization of an electrocatalyst in enhancing oxygen evolution performance: Bi-Fe-O system as a case study

This work aims to give an insight into the influence of crystal structure (for a system containing same elements but crystallizing in different structures) and the effect of electrical polarization on these oxides on the performance of oxygen evolution reaction (OER). We have tried to highlight this influence by taking the Bi-Fe-O system for the study. Herein, we have synthesized three structures of the Bi-Fe-O system viz. BiFeO3 (perovskite structure), Bi2Fe4O9 (mullite structure), and Bi25FeO40 (sillenite structure) as an example to establish the relation. These oxides were characterized by Rietveld refinement for structure and scanning electron microscopy (SEM) for morphology. Their optical and magnetic properties were also investigated. Systematic studies were carried out with both as-synthesized and electrically polarized oxides for their performance towards OER. We observed that the order for OER activity (using non-polarized catalyst) of the three stable structures synthesized was Bi2Fe4O9 > BiFeO3> Bi25FeO40, which was attributed to the presence of Fe(oct)-O-Fe(td) linkages in Bi2Fe4O9. While the current density of Bi2Fe4O9 and BiFeO3 remained unchanged after poling, that of Bi25FeO40 increased by four-fold. From the study, we have demonstrated that proper choice of the crystal structure and utilization of electrical polarization can be effective strategies to manipulate the surfaces of an electrocatalytic material.

Molecular dynamics simulation of typical molecular ferroelectrics based on polarized crystal charge model

Molecular ferroelectrics are a promising class of ferro-electrics, with environmental friendliness, flexibility and low cost. In this work, a set of characteristic molecular ferroelectrics are simulated by molecular dynamics (MD) with polarized crystal charge (PCC). From the simulated results, their ferroelectric switching mechanisms are elucidated, with their ferroelectric hysteresis loops. The PCC charge model, recently developed by our group, containing the quantum electric polarization effect, is suitable in nature for studying molecular ferroelectrics. The simulated systems include the typical molecular ionic ferroelectrics, di-isopropyl-ammonium halide (DIPAX, X=C (Cl), B (Br), and I), as well as a pair of newly validated organic molecular ferroelectrics, salicylideneaniline and (-)-camphanic acid. In total, there are five systems under investigation. Results demonstrate that the PCC MD method is efficient and reliable. It not only elucidates the ferroelectric switching mechanism of the studied molecular ferroelectrics, but also extends the application range of the PCC MD. In conclusion, PCC MD provides an efficient protocol for extensive computer simulations of molecular ferroelectrics, with reliable ferroelectric properties and associated mechanisms, and would promote further exploration of novel molecular ferroelectrics.

Surface Electric Fields Increase Human Osteoclast Resorption through Improved Wettability on Carbonate-Incorporated Apatite.

Osteoclast-mediated bioresorption can be an efficient means of incorporating the dissolution of biomaterials in the bone remodeling process. Because of the compositionally and structurally close resemblance of biomaterials with the natural mineral phases of the bone matrix, synthetic carbonate-substituted apatite (CA) is considered as an ideal biomaterial for clinical use. The present study therefore investigated the effects of electrical polarization on the surface characteristics and interactions with human osteoclasts of hydroxyapatite (HA) and CA. Electrical polarization was found to improve the surface wettability of these materials by increasing the surface free energy, and this effect was maintained for 1 month. Analyses of human osteoclast cultures established that CA subjected to a polarization treatment enhanced osteoclast resorption but did not affect the early differentiation phase or the adherent morphology of the osteoclasts as evaluated by staining. These data suggest that the surface characteristics of the CA promoted osteoclast resorption. The results of this work are expected to contribute to the future design of cell-mediated bioresorbable biomaterials capable of resorption by osteoclasts and of serving as a scaffold for bone regeneration.