Ferroelectric Relaxation Research Articles

Voltage-assisted 3D printing of polymer composite dielectric films with low energy loss and high energy storage density

PVDF-based polymers have garnered significant attention in the field of high-power density electrostatic capacitors due to their exceptional dielectric strength. However, their practical applications are constrained by low charge-discharge efficiency (η) and energy storage density (Ue), which stem from high ferroelectric relaxation and low breakdown strength (Eb). Here, a hydrogenated glassy polymer poly(styrene-methyl methacrylate-methylallyl alcohol) (PSMA) is designed and synthesized to be homogeneously distributed in PVDF through voltage-assisted 3D printing-hot pressing, resulting in a flexible composite film. The findings demonstrate that PSMA, rich in hydrogen bonds and high modulus strength, effectively mitigates the ferroelectric phase transition of PVDF to enhance η. Additionally, the voltage-assisted 3D printing process induces an entropy gain mechanism, facilitating the uniform distribution of the two phases and enhancing the interfacial properties for enhancing Eb. Remarkably, the study achieves prominent growth in energy storage performance, with Ue and η reaching 18.1 J/cm3 and 80 % at 525 MV/m, respectively. These remarkable results highlight the potential of 3D printing technology in enhancing the energy storage performance of PVDF-based dielectrics.

Oxygen vacancy redistribution and ferroelectric polarization relaxation on epitaxial perovskite films during an electrocatalytic process

Ferroelectric catalysis BaTiO3 films show negative ferroelectric polarization drives the oxygen vacancies redistribution to the surface accelerating the adsorption of reactants and charge transfer, resulting in an enhanced OER performance.

Ultrasonic methods for the study of relaxation phenomena in dissipative media

In this work, a new method for study of the process of domain orientations and space charge relaxation in ferroelectrics using the surface acoustic waves (SAW) has been developed. The results of an experimental study of the dc electric field influence on the parameters of SAW propagation in piezoceramics with different ferroelectric "hardness" are presented.

Research on Improving Energy Storage Density and Efficiency of Dielectric Ceramic Ferroelectric Materials Based on BaTiO3 Doping with Multiple Elements

In order to promote the research of green energy in the situation of increasingly serious environmental pollution, dielectric ceramic energy storage materials, which have the advantages of an extremely fast charge and discharge cycle, high durability, and have a broad use in new energy vehicles and pulse power, are being studied. However, the energy storage density of ordinary dielectric ceramic ferroelectric materials is low, so, in this paper, we have divided eight components based on BaTiO3 (BT). Through the traditional solid phase sintering method, AB positions were replaced with various elements of different proportions to improve their energy storage density and the energy storage efficiency of BT-based ferroelectric materials. In this paper, we studied the results of XRD, Raman, ferroelectric, dielectric, and impedance tests of doped samples, and the best components were determined. The (1−x)BT−xBi(Mg1/3Zn1/3Ta1/6Nb1/6)O3 series of ceramics are made by the incorporation of five elements, Bi3+, Mg2+, Zn2+, Ta5+, and Nb5+. With the rising electric hysteresis loop of the doping amount x thin, the saturation polarization strength and residual polarization strength decrease, and the energy storage density rises first and then decreases. The dielectric characteristic after x = 0.08 showed a flat dielectric peak, indicating that the ferroelectric relaxation had been formed. The energy storage density and efficiency of the best component x = 0.12 reached 1.75 J/cm3 and 75%, respectively, and the Curie temperature was about −20 °C, so it has the potential to be used at room temperature.

Lead-free KNN-based ceramics incorporated with Bi(Zn2/3Nb1/3)O3 possessing excellent optical transmittance and superior energy storage density

The application of lead-free dielectric ceramics for energy storage has received extensive attention because of their remarkable potential as pulse capacitors in power electronic devices. The current study developed a strategy for improving the energy storage performance of (K0.5Na0.5)NbO3 (KNN)-based ceramics by incorporating Bi(Zn2/3Nb1/3)O3 to reduce grain size, increase dielectric breakdown strength, and enhance ferroelectric relaxation degree. The resulting 0.87KNN–0.13BZN ceramics exhibited a high energy density (7.4 J/cm3) and moderate energy efficiency (74%) at an ultrahigh electric field (750 kV/cm) as well as excellent optical properties. Therefore, the 0.87KNN–0.13BZN ceramic is a promising candidate for pulse capacitors, providing a feasible approach for the development of new lead-free energy storage materials.

Optimisation of electrical conductivity and dielectric properties of Sn4+-doped (Na0.5Bi0.5)TiO3 perovskite

The structural, microstructural, dielectric, and conductivity properties of Tin modified Sodium Bismuth Titanate (Na0.5Bi0.5)(Ti1-xSnx)O3, where x (mol%) = 0%, 1%, 3% (labeled as NBT, NBTS1, and NBTS3, respectively) were experimentally investigated in this paper. In this regard, the solid-state reaction process was used to prepare polycrystalline materials, where sintering was performed at 1100 °C for 3 h under atmospheric air. As a result, X-ray diffraction confirms, as it seems, the presence of a rhombohedral phase (R3c) in all compositions at room temperature. The electrical properties of the compositions are also studied using complex impedance spectroscopy (CIS). Subsequently, at room-temperature, doping 1% of Sn4+ in the NBT perovskite reduces the dielectric loss from 4.4 × 10−2 to 3.43 × 10−2 at 1 MHz. Moreover, it is around 3.05 × 10−2 at 93.6 °C and 1 MHz for NBTS3. Sn4+ significantly doping improved electrical conductivity. Therefore, at 10 Hz and 450 °C, the electrical conductivity of NBTS3 (σac = 8.76 × 10−3 S.m−1) is 61.26 times that of pure NBT (σac = 1.43 × 10−4 S.m−1). Joncher's power law investigates the conduction mechanism's nature; (i) the decreasing variation of the exponent s1 with temperature suggests that the NBT compound is characterized by the CBH (Correlated Barrier Hopping) model. On the other hand, for NBTS1 and NBTS3 (ii), the increase in s1 and s2 parameters under temperature indicates that the NSPT (non-overlapping small polaron tunneling) model is the most dominant. In this work, all tested compounds exhibit a sort of ferroelectric relaxation behavior. Our results demonstrate that doped materials can be applied to solid oxide fuel cells.

Phase formation and performance of high Curie temperature Bi(Ni0.5Ti0.5)O3–BiFeO3–PbTiO3 ceramics

0.55 Bi(Ni0.5Ti0.5)O3–0.05BiFeO3–0.4PbTiO3 ((0.55BNT–0.05BF–0.4PT)) ceramics were prepared by low-temperature solid-phase sintering method due to adding sintering additives. The 800 °C calcined powders present relatively pure perovskite structure. The 990 °C–1030 °C sintered ceramics exhibit pure perovskite structure, and the density is increased significantly as compared with the undoped ones due to the addition of 0.5 wt% LiBO2. The “0.55BNT–0.05BF–0.4PT” samples sintered at 1010 °C have large density, compact microstructural morphology, high Curie temperature and excellent electrical properties. The ceramics show apparent relaxor ferroelectric behavior and dielectric relaxation characteristic. Grains conduction contributes mainly to the high-temperature conduction, which can be attributed to the migration of oxygen vacancies produced due to the evaporation of ions during sintering.

Enhanced ferroelectric relaxation behaviors of KSr2Nb5O15-based ceramics by A-site entropy-engineering

• A novel tetragonal tungsten bronze structured ferroelectric ceramic was prepared. • The A-site entropy-engineering aggravated the distortion of NbO 6 octahedrons. • Distortion of NbO 6 octahedrons and grain size effects enhanced the relaxation features. A novel tetragonal tungsten bronze (TTB) structured K(Ca 0.25 Sr 0.25 Ba 0.25 La 0.25 ) 1.96 Sm 0.04 Nb 5 O 15 ferroelectric ceramic was prepared by an A-site entropy-engineering design. The results of Rietveld refinements of X-ray diffraction patterns showed that the A-site entropy-engineering aggravated the distortion of NbO 6 octahedrons, especially along the single polarization axis direction. The aggravated distortion of NbO 6 octahedrons and reducing of grain sizes further enhanced the ferroelectric relaxation feature, slightly strengthened the diffuseness degree, and caused the obvious frequency dependence of the dielectric phase transition around room temperature. This work provides a valuable strategy for tailoring the electric properties of tungsten bronze structured ferroelectric ceramics.

Relaxation Induced by Imprint Phenomena in Low-Temperature (400 °C) Processed Hf0.5Zr0.5O2-Based Metal-Ferroelectric-Metal Capacitors

Ferroelectricity in Hf0.5Zr0.5O2 (HZO) has garnered increasing interest due to its potential applications in neuromorphic and nonvolatile memory devices. However, with time, the adverse shift in the coercive voltage (Vc) observed in a prepoled HZO ferroelectric capacitor can lead to insufficient polarization switching from one polarity owing to the development of a built-in voltage, causing reliability concerns. Another consequence of developed built-in voltage is polarization relaxation, that is, the rapid loss of stored polarization with time (t < 6 s). In this work, the correlation between the data retention issues in ferroelectric films, namely, imprint (Vc shift with time) and polarization relaxation, is studied carefully by pulse measurement techniques in HZO-based metal-ferroelectric-metal capacitors. In a nonaged ferroelectric, there are no significant relaxation effects for a switching time delay up to 6 s, even at higher measurement temperatures until 125 °C. After a baking process was performed at higher temperatures (25–125 °C) to a prepoled ferroelectric capacitor, an apparent systematic imprint was observed with increasing baking time (up to 200 h). Conjunctively, we also see that the imprinted ferroelectric capacitor shows a strong polarization relaxation effect even for short time periods due to the generated built-in voltages. For the 2.0 V operation, based on the delay time between the re-WRITE pulse and READ pulses, the lifetime extracted for a 65 °C bake can show a stable 10-year lifetime using a 10 μs delay time compared to a 0.5 year lifetime when using a delay time of 6 s. This work explores the drastic relaxation effects due to imprint in ferroelectric HZO films and the need to mitigate defects/space charges causing these issues.

Effect of synthesis method on structural, ferroelectric and conduction relaxation in Pb1-xLaxTiO3, where x = 0.25 ceramics

The structural, ferroelectric, dielectric and conduction mechanism of Pb0.75La0.25TiO3 ceramics synthesized using solid state reaction route & Auto Combustion method have been reported. X-ray diffraction data reveals that prepared ceramics using both the methods crystallizes into tetragonal phase whereas ferroelectric loop confirms the presence ferroelectric ordering. Frequency dependent ε′ and ε″ at different temperature shows the Cole-Cole relaxation behaviour. The Jonscher’s power law fitted parameter ‘n’ vs. temperature explains the conduction mechanism in prepared ceramics.

A unique and discrete Ce(iii) macrocyclic complex exhibits ferroelectric, dielectric, and slow relaxation of magnetization properties

A [Ce(L1)(NO3)3] (1) was found to exhibit ferroelectric and magnetic bistability simultaneously. The ferroelectric to paraelectric transition was observed at 303 K and a small external electric field was required to switch the spontaneous polarization in 1.

Tailoring ferroelectric polarization and relaxation of BNT-based lead-free relaxors for superior energy storage properties

Dielectric energy storage materials have attracted much attention because of their wide applications in the electronics industry. However, low energy storage density and poor thermostability limit their application. In this work, a strategy was proposed to prepare lead-free relaxor ferroelectric ceramics with ultra-high energy storage properties and superior temperature stability by precisely adjusting the relaxation and ferroelectricity states and increasing the electric field intensity. An ultra-high recoverable energy storage density (Wr) of 4.97 J/cm3 and an efficiency (η) of 84.4% are simultaneously obtained for the 0.95(0.9Bi0.5Na0.5TiO3-0.1Ba0.85Ca0.15Zr0.1Ti0.9O3)-0.05BaSnO3 ceramic. Moreover, a high Wr of 2.73 J/cm3 with brilliant η of 80.6% are obtained in the ceramic at 140 ℃ and there is almost no thermal degradation of energy storage properties from 25 ℃ to 140 ℃. The Wr and η have decreased by 2.2% and 1.9% after 105 cycles under 200 kV/cm, respectively, which demonstrates the good cycle stability of the sample. A discharge power density of up to 99.0 MW/cm3 is obtained in the 0.95(0.9Bi0.5Na0.5TiO3-0.1Ba0.85Ca0.15Zr0.1Ti0.9O3)-0.05BaSnO3 ceramic and the good charge and discharge performance of this sample is important for practical applications.

Ferroelectric columnar assemblies from the bowl-to-bowl inversion of aromatic cores

Organic ferroelectrics, in which the constituent molecules retain remanent polarization, represent an important topic in condensed-matter science, and their attractive properties, which include lightness, flexibility, and non-toxicity, are of potential use in state-of-the-art ferroelectric devices. However, the mechanisms for the generation of ferroelectricity in such organic compounds remain limited to a few representative concepts, which has hitherto severely hampered progress in this area. Here, we demonstrate that a bowl-to-bowl inversion of a relatively small organic molecule with a bowl-shaped π-aromatic core generates ferroelectric dipole relaxation. The present results thus reveal an unprecedented concept to produce ferroelectricity in small organic molecules, which can be expected to strongly impact materials science.

Atomistic studies of temporal characteristics of polarization relaxation in ferroelectrics

Polarization relaxation fundamentally determines the speed, energy consumption, and functionality of ferroelectric materials and devices, which is considered as the core aspect of ferroelectric-based applications and attracts considerable attention. The relaxation time, describing the temporal characteristics of polarization relaxation, has been reported to vary from subpicoseconds to hundreds of nanoseconds in ferroelectrics, and the microscopic picture is still an open question. In this paper, starting from atomistic models for ferroelectrics, a generalized Langevin equation is proposed to describe the dynamical behaviors of polarization at the mesoscale or macroscale. On one hand, through the artificial construction of adiabatic processes, it is derived that the relaxation time is connected with the lifetimes of the phonon modes involved in a many-body ferroelectric system, bridging the thermodynamics of polarization with the dissipation behavior of the phonon modes at the microscale. On the other hand, the relaxation time is then linked to the kinetic coefficient used in the time-dependent Ginzburg-Landau equation, for the polarization evolution on the meso- or macroscale. Furthermore, based on driven Brownian motion, we propose a theoretical model of the dependence of the polarization switching time with an applied external electric field on a ferroelectric monodomain system. The prediction of the switching time is found to agree well with the dynamical simulation data, which verifies the applicability and reliability of the physical picture of the relaxation time clarified in the current work. Our discussion of the physical picture of the polarization relaxation time provides useful ideas for the development of multiscale modeling method for ferroelectrics.

Structural, dielectric and electrical characteristics of manganese modified (Bi0.5Ba0.25Sr0.25) (Ti0.5Fe0.5)O3 relaxor

In this communication, detailed studies of the structural, microstructural, dielectric, and electrical properties of polycrystalline materials, (Bi0.5Ba0.25Sr0.25) (Ti0.5Fe0.5)O3 and (Bi0.5Ba0.25Sr0.25) (Ti0.25Mn0.25Fe0.5)O3, synthesized by using a high–temperature solid-state-reaction method, have been reported. X-ray structural and scanning electron micrograph studies exhibit phase pure tetragonal system and surface morphology (size and distribution of grains and grain boundaries) of the samples respectively. Analysis of the temperature and frequency dependence of dielectric and electrical (impedance, modulus, and conductivity) data reveals the ferroelectric relaxor behavior, relaxation mechanism, and semiconductor (negative temperature coefficient of resistance) properties of the bulk BFBST and Mn modified BFBST electro-ceramics. The relaxation time and activation energy (Ea) were calculated from the above data. The characteristics of Mn modified BFBST have been compared to that of it’s parent (BFBST) compound. The different inherent conduction mechanisms, such as Ohmic, hopping, space charge limited (SCLC) have been analyzed. The bulk- and interface-limited conduction processes were evidently found in the materials by the Poole–Frenkel (PF) and Schottky (SEmen modified BFBST have been compared to that of its parent (BFBST) compound) emission fitting of the J ∼ E characteristic data. The leakage data of BFBST-Mn (Mn modified Mn) quantified the average energy gap (Eg) in the range of 0.83–0. 87 eV for different applied voltages and in a wide range of temperature (25 °C–300 °C). With the increase in voltage, Eg decreases. This work suggests that Mn-substitution (Mn4+) at B (Ti4+) site keeping the stoichiometry undisturbed enhances structural, dielectric response (higher dielectric constant) and reduce the leakage behavior especially at low temperature and high-frequency range.

The ultrahigh discharge efficiency and energy density of P(VDF-HFP)viaelectrospinning-hot press with St-MMA copolymer

Flory–Huggins theory combined with experimental tests and phase-field simulation proves that electrospinning improves the homogeneity andEbin composite films, and MS can limit the ferroelectric relaxation of PVDF and significantly increaseUeandη.

Enhanced dielectric, piezoelectric properties and strengthened relaxor behavior in K-modified Na0·5Bi0·5TiO3 lead-free ceramics

The effect of K+ modification on the phase composition, micro structure and electrical properties of Na0·5Bi0·5TiO3 ceramics prepared via solid phase reaction was investigated. The samples (Na1-xKx)0.5Bi0·5TiO3 still present pure perovskite structure. The doping K+ can increase grain size and relative density, and improve the electrical properties of BNT samples. The dielectric constant of (Na1-xKx)0.5Bi0·5TiO3 samples increased from 800 to 1844, the piezoelectric constant from 61 pC/N to 172 pC/N, and the dielectric constant at Curie temperature increased from 1950 to 7182. The samples modified by K+ exhibit strong relaxation performance and excellent dielectric-temperature stability at high temperatures. The mechanism of K+ modification was explained and analyzed in detail using domain theory, lattice theory and ferroelectric relaxation theory.

High recoverable energy storage density and large energy efficiency simultaneously achieved in BaTiO3–Bi(Zn1/2Zr1/2)O3 relaxor ferroelectrics

Relaxor ferroelectrics have attracted much attention as electric energy storage materials for intermittent energy storage because of their high saturated polarization, near-zero remnant polarizations, and considerable dielectric breakdown strength (BDS). Despite the numerous efforts, the dielectric energy storage performance of relaxor ferroelectric ceramics is incomplete or unsatisfactory. The enhancement of recoverable energy storage density Wrec usually accompanies with the sacrifice of discharge-to-charge energy efficiency η; therefore, it is an important issue to achieve high recoverable Wrec and large efficiency η simultaneously. In this work, the (1-x)BaTiO3-xBi(Zn1/2Zr1/2)O3 (abbreviated as BT-100xBZZ, 0 ≤ x ≤ 0.20) ferroelectric ceramics were prepared using the conventional solid-state reaction method. The phase structure, microstructural morphology, dielectric and ferroelectric properties, relaxation behaviors, and energy storage properties of BT-BZZ ceramics were investigated in detail. X-ray powder diffraction, dielectric spectra, and ferroelectric properties confirm the transformation of tetragonal phase for normal ferroelectrics (BT) to pseudo-cubic phase for relaxor ferroelectrics (BT-8BZZ). A high recoverable energy storage density Wrec of 2.47 J/cm3 and a large energy efficiency η of 94.4% are simultaneously achieved in the composition of BT-12BZZ, which presents typical weakly coupled relaxor ferroelectric characteristics, with an activation energy Ea of 0.21 eV and a freezing temperature Tf of 139.7 K. Such excellent energy storage performance suggests that relaxor ferroelectric BT-12BZZ ceramics are promising dielectric energy storage materials for high-power pulsed capacitors.

Alternative, Direct Synthesis Method of the Ceramic Solid Solutions Based on BaTiO3 Through a High Energy Ball Milling

Polycrystalline samples BaTiO3 and the solid solutions Ba0.9Sr0.1TiO3, Ba0.9Sr0.1Ti0.9Sn0.1O3, Ba0.9Sr0.1Ti0.8Sn0.2O3 were obtained by means of a mechanochemical treatment based on the high-energy ball milling technique and next a high temperature solid state reaction method. The influence of synthesis condition on microstructural, dielectric and ferroelectric properties of obtained solid solutions were investigated. The structure and morphology of the investigated samples were characterized by an X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterization of electrical properties of the ceramics within the temperature range from –130°C to 250°C were performed by means of a dielectric spectroscopy method at the frequency ranging from 0.1 Hz to 10 MHz. The diffusion of the paraelectric – ferroelectric phase transition and dielectric relaxation for ceramic samples are described.

Dynamic relaxation process of a 3D super crystal structure in a Cu:KTN crystal

In this Letter, we report the existence and relaxation properties of a critical phenomenon on called a 3D super crystal that emerges at T = TC − 3.5°C, that is, in the proximity of the Curie temperature of a Cu:KTN sample. The dynamics processes of a 3D super crystal manifest in its formation containing polarized nanometric regions and/or polarized clusters. However, with strong coupling and interaction of microcomponents, the characteristic relaxation time measured by dynamic light scattering demonstrates a fully new relaxation mechanism with a much longer relaxation time. As the relaxation mechanism of a relaxator is so-far undetermined, this research provides a novel perspective. These results can help structure a fundamental theory of ferroelectric relaxation.