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Abstract Polymer dielectrics with excellent thermal resistance and superior energy storage behaviour are extensively demanded with the increasing development of film capacitors applied in hostile environments. In this study, novel diamine with sulfonyl‐containing side chain was designed and synthesised. The corresponding polyimide (PI) dielectrics derived from the sulfonyl‐containing diamine were prepared, so were the polyimides possessing the same backbone but without side chains. Consequently, superior thermal resistance of glass transition temperature ranged from 162–208°C was obtained. Moreover, the polyimides presented permittivity of 3.34–5.89 at 1 kHz, Weibull breakdown strength of 377–538 MV/m and discharged energy density of 3.82–5.85 J/cm3. In particular, sulfonyl‐containing polyimide of SPI‐2 with flexible backbone and sulfonyl side chain indicates the highest discharged energy density and charge‐discharge efficiency simultaneously. The introduction of the strong polar sulfonyl group in the side chain enhances dielectric and energy storage properties effectively. In addition, it is found that the dipolar moment density (μ/Vvdw) calculated from molecular simulation is closely correlated to permittivity measured from experiments. The combined method of molecular simulation and experiments would offer an effective approach to assist in molecular design of high‐performance polymer dielectrics.

Abstract Dielectric capacitors play an important role in advanced electronic and power systems such as portable electronic devices, hybrid electric vehicles and electronic weapon systems, and the improvement of energy storage density will have a positive effect on reducing the volume and weight of equipment. Here, a series of single‐layer dielectrics with boron nitride nanosheets (BNNSs) uniformly dispersed and multilayer dielectrics with BNNSs showing a positive gradient distribution (PGD) and inverse gradient distribution (IGD) in the poly(vinylidene fluoride‐trifluoroethylene‐chlorotrifluoroethylene) (P[VDF‐TrFE‐CTFE]) matrix were prepared by high‐speed electrospinning and hot press technology. It is found that the best performance is observed inthe lowest interlayer gradient component in both PGD and IGD composite dielectrics. However, the performance of PGD is better than that of IGD, and the 3‐5‐3 multilayer dielectric in the positive gradient structure has the best electrical performance. Its maximum energy storage density of the 3‐5‐3 composite dielectrics is 12.93 J/cm3 at the applied electric field of 380 kV/mm. The above research results show that the gradient structure design plays an important role in optimising the breakdown strength and energy storage characteristics of composite dielectrics.

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Poly(vinylidenefluoride-trifluoroethylene)-based (P(VDF-TrFE)-based) terpolymers represent a new class of electroactive polymer materials that are relaxor-ferroelectric (RF) polymers and that offer unique and attractive property combinations in comparison with conventional ferroelectric polymers. The RF state is achieved by introducing a fluorine-containing termonomer as a "defect" into the ferroelectric P(VDF-TrFE) copolymer, which reduces the interaction between the VDF/TrFE dipoles. The resulting terpolymer exhibits a low Curie transition temperature and small remanent and coercive fields yielding a slim hysteresis loop that is typical for RF materials. Though the macroscopic behavior is similar to RF ceramics, the mechanisms of relaxor ferroelectricity in semi-crystalline polymers are different and not fully understood yet. Structure-property relationships play an important role in RF terpolymers, as they govern the final RF properties. Hence, a review of important characteristics, previous studies and relevant developments of P(VDF-TrFE)-based terfluoropolymers with either chlorofluoroethylene (CFE) or chlorotrifluoroethylene (CTFE) as the termonomer is deemed useful. The role of the termonomer and of its composition, as well as the effects of the processing conditions on the semi-crystalline structure which in turn affects the final RF properties are discussed in detail. In addition, the presence of noteworthy transition(s) in the mid-temperature range and the influence of preparation conditions on those transitions are reviewed. A better understanding of the fundamental aspects affecting the semi-crystalline structures will help to elucidate the nature of RF activity in VDF-based terpolymers and also help to further improve their applications-relevant electroactive properties. [ABSTRACT FROM AUTHOR]

Temperature-dependent dielectric relaxations of (1-x)BiFeO3-x(Bi1/2K1/2)TiO3 (BF-BKT) lead-free piezoceramics (0.4≤x≤0.8) were investigated via impedance spectroscopic techniques. Regardless of the compositions, the dielectric maximum temperatures exhibit a frequency-dependent dispersion, originating from a Debye relaxation due to the presence of oxygen vacancies. It was also observed that there exist local dielectric maxima due to the relaxation of polar nanoregions as a shoulder on the lower temperature side. The onset temperature for the Debye-type relaxation decreased with decreasing BKT content, gradually overlapping with the low-temperature dielectric dispersion from the relaxation of polar nanoregions. It is proposed that the role of BKT in the BF-BKT system is to enhance the random fields that favor a relaxor state and to suppress the Debye-type relaxation of oxygen vacancy related dipoles. [ABSTRACT FROM AUTHOR]

Non-linear dielectric spectroscopy (NLDS) is employed as an effective tool to study relaxation processes and phase transitions of a poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) relaxor-ferroelectric (R-F) terpolymer in detail. Measurements of the non-linear dielectric permittivity ε 2 ′ reveal peaks at 30 and 80 ∘ C that cannot be identified in conventional dielectric spectroscopy. By combining the results from NLDS experiments with those from other techniques such as thermally stimulated depolarization and dielectric-hysteresis studies, it is possible to explain the processes behind the additional peaks. The former peak, which is associated with the mid-temperature transition, is found in all other vinylidene fluoride-based polymers and may help to understand the non-zero ε 2 ′ values that are detected on the paraelectric phase of the terpolymer. The latter peak can also be observed during cooling of P(VDF-TrFE) copolymer samples at 100 ∘ C and is due to conduction and space-charge polarization as a result of the accumulation of real charges at the electrode–sample interface. [ABSTRACT FROM AUTHOR]

During the breaking process of a vacuum interrupter, there is a time interval between current zero and generation of recovery voltage. This time interval is variable and matters to the calculation of continuous transition model, but always simplified as a constant. In this article, we put forward the concept of preparatory stage of sheath, analyze the production mechanism and influence on breaking ability, and give the computation method for the duration of this stage. In order to verify the rationality of the theoretical analysis and calculation method proposed in this article, experimental measurement is conducted. The experimental results are in good agreement with the values of duration calculated by the theoretical formula in this article in terms of magnitude and variation law. [ABSTRACT FROM AUTHOR]

We performed self-consistent modelling of nonlinear electrotransport and electromechanical response of thin films of mixed ionic-electronic conductors (MIEC) allowing for steric effects of mobile charged defects (ions, protons, or vacancies), electron degeneration, and Vegard stresses. We establish correlations between the features of the nonlinear space-charge dynamics, current-voltage, and bending-voltage curves for different types of the film electrodes. A pronounced ferroelectric-like hysteresis of the bending-voltage loops and current maxima on the double hysteresis current-voltage loops appear for the electron-transport electrodes. The double hysteresis loop with pronounced humps indicates a memristor-type resistive switching. The switching occurs due to the strong nonlinear coupling between the electronic and ionic subsystems. A sharp meta-stable maximum of the electron density appears near one open electrode and moves to another one during the periodic change of applied voltage. Our results can explain the nonlinear nature and correlation of electrical and mechanical memory effects in thin MIEC films. The analytical expression proving that the electrically induced bending of MIEC films can be detected by interferometric methods is derived. [ABSTRACT FROM AUTHOR]

With the use of the modified Sawyer-Tower scheme and Merz technique, studies were conducted on the repolarization characteristics of ferroelectric (BaZrO3/BaTiO3) superlattices on monocrystalline MgO substrate. Studies of temperature changes in the dielectric hysteresis loops indicated a sufficiently smooth decrease in spontaneous polarization compared with homogeneous barium titanate near the phase transition temperature of the superlattice. Experimental studies of switched currents have shown that the switching processes in the synthesized superlattices are implemented in two stages: activation motion ("creep" mode) and non-activation motion (slip mode). The presence of the activation switching stage and the numerical estimates show that with high probability, the movement of domain boundaries accomplishes the processes of switching in the studied superlattice. The threshold field separating the stated stages decreases with increasing temperature up to the Curie point of the superlattice, similar to the coercive field. Detection of the non-strictly exponential dependence of the switching current on the reverse field strength in the activation stage was modulated by the dependence with the power-law exponent for the applied electric field. Both techniques indicate that the studied superlattices have a small internal displacement field directed from the superlattice to the substrate. [ABSTRACT FROM AUTHOR]

Lead-free (1–x)(0.4BiScO(3)–0.6BaTiO(3))-x(Bi(0.5)Na(0.5))TiO(3) (BSBT–xBNT) ceramics were prepared by traditional ceramics preparation method. The energy storage characteristics, as well as dielectric spectrum curves of BSBT–xBNT ceramics, were systematically used in research. The ternary system formed perovskite solid solution with dense and homogenous microstructure. BSBT–xBNT ceramics exhibited slimmer and slanted hysteresis loops followed by higher saturation polarisation (P(max)) and lower remnant polarisation (P(r)), which induced high-energy storage density of 1.39 J/cm^3 (E = 180 kV/cm). Ranging from 200 to 400°C, BSBT–xBNT ceramics had high permittivities, and a matching dielectric loss, which exhibited flat temperature coefficients of permittivity (TCɛ). The impedance spectroscopy analysis indicated that the non-Debye relaxation mechanism existed in BSBT–xBNT ceramics. BSBT–xBNT ceramics may have potential application value for the high-temperature capacitor.

Polymer dielectrics with high energy density and low dielectric loss are highly desired due to the rapid development of electric devices. Among known polymers, poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorofluoroethylene) P(VDF-TrFE-CFE) is one of the promising materials for energy storage capacitor applications because of its high dielectric constant. Nevertheless, it suffers from high dielectric loss especially at the high electric field, which suppresses its breakdown strength and energy storage density. Herein, sandwiched structure dielectric films were fabricated by employing polymethyl methacrylate (PMMA) as the outer layer and P(VDF-TrFE-CFE) as the central layer. By modulating the thickness of the central layer, an enhanced discharged energy density of 7.03 J/cm^3 is achieved at a high electric field of 480 MV/m, which is 132% more than that of P(VDF-TrFE-CFE) at its maximum electric field 300 MV/m. Meanwhile, this sandwiched structure film also retains a high discharge efficiency of 78% at 480 MV/m, which is never been seen in polyvinylidene fluoride-based polymers. Results show that PMMA acts as charge barrier and simultaneously enhance the breakdown strength and suppress the dielectric loss of P(VDF-TrFE-CFE).

Single-crystalline Z-cut lithium niobate (LiNbO3, LN) thin film with a thickness of ~ 878 nm situated between top and bottom electrodes is fabricated depending on crystal-ion-slicing (CIS) technique and SiO2 bonding method. Microstructure characteristics indicate that the LN thin film has a good crystalline quality and there is no obvious defects on the surface. Moreover, ferroelectric performances are intensively analyzed by the ferroelectric hysteresis loop measurements, which express a glorious rectangularity in spite of shifting to the forward electric field under the effect of internal polarization field. And when external electric field increases the polarization intensity approximates saturation at 900 kV/cm and the value is around 58 μC/cm2. The great ferroelectric performances make it potential for the tunable filters based on the CIS-fabricated LN thin film in other cut directions. The leakage current is also measured in different direction bias and the conduction mechanism is further analyzed, which is dominated by Schottky emission mechanism and has no effect of bulk defects. [ABSTRACT FROM AUTHOR]

Polymer composite films with high energy density as well as high efficiency are promising dielectric materials in pulsed power systems. In improving the energy discharged efficiency, poly vinylidene fluoride-hexafluoropropylene [P(VDF-HFP)] film blended with 20 vol.% poly(methylmethacrylate) (PMMA), which has a much slimmer ferroelectric hysteresis loop, is employed as the polymer matrix. Highly dispersive Ba(0.6)Sr(0.4)TiO(3) (BST) nanoparticles with an average particle size of 12.1 nm are utilised to improve the polarisation of the blend film without sacrificing the dielectric strength. Uniform nanocomposite films with high flexibility and excellent energy-storage performance are obtained. Especially, due to the optimisation of both polymer matrix and fillers, the BST modified P(VDF-HFP)/PMMA blend films show improved breakdown strength and depressed energy loss, which leads to an enhanced energy density of 10.3 J/cm^3 at 378 kV/mm.

Ferroelectric tunnel junctions have recently attracted a lot of research interest, not only for memory operation but also for e.g. neuromorphic computing. Retention characteristics of these devices are of utmost importance in many applications. The authors have recently demonstrated the feasibility of double‐layered ferroelectric tunnel junctions where the ferroelectric hafnium zirconium oxide acts as the memory layer and the dielectric aluminium oxide as the tunnelling barrier. The depolarisation field from the unscreened polarisation charges that is introduced by this structure causes serious limitations on the retention behaviour due to the unintentional back‐switching of ferroelectric domains. This leads to a diminishing memory window over time. By using a built‐in bias field from different work function metal electrodes, in this case platinum and titanium nitride with 0.85 eV difference, one can shift the polarisation hysteresis curve and counteract the electric depolarisation field. This leads to a more stable on‐current over time while only marginally increasing the off‐current degradation. Extrapolation to ten years shows a much larger memory window compared to the symmetric metal electrode structure. [ABSTRACT FROM AUTHOR]

Homologous series of DTA + nBA (where n varies from 2 to 8) comprises of seven homologues, out of which DTA+4BA alone exhibits a new smectic ordering labelled as smectic X*. Hence DTA+4BA is chosen to investigate various chemical, thermal optical and electrical studies. DSC thermograms reveal the transition temperature and enthalpy values of smectic X* phase. FTIR spectroscopy confirms the formation of hydrogen bonding. Variation of tilt angle with temperature is studied and fitted to a power law confirming the Mean field theory predicted value. An interesting feature of this work is the observation of memory effect in smectic X* phase. When an external field is applied to the mesogen in smectic X* phase, the texture undergoes a change and remains invariant even after the field is removed, further the texture of the phase can be erased only by taking it to isotropic temperature. Another proof for memory effect is the dielectric hysteresis in smectic X* recorded with field. Helix in smectic X* is reported. Yet another interesting observation is the identification of parachromatism in smectic X* phase namely the textures remain the same while the colour of the textures changes completely with decrement in the temperature of the mesogen. Dielectric relaxations in Goldstone mode are studied and analyzed with Cole-Cole plots. The relaxation is suppressed on application of field indicative of Arrhenius in nature. [ABSTRACT FROM AUTHOR]

35 Bi(Mg1/2Ti1/2)O3-65 PbTiO3 (35 BiMT-65 PT) thin films with varying levels of A-site deficiency were investigated as a potential candidate for high-temperature nonvolatile ferroelectric memories. PbTiO3 seed layers utilized to nucleate the perovskite phase in A-site deficient films induced a thickness dependence to the ferroelectric hysteresis and dielectric permittivity. Adjusting for this, the dielectric response of the 35 BiMT-65 PT films is $\approx 960$. The maximum dielectric permittivity was 430 °C at 1 MHz for A-site deficient films. The transition temperature is independent of film thickness to 85 nm. Tan($\delta$) remains less than 15% at 1 MHz regardless of film thickness and temperature up to 585 °C. High-temperature polarization–electric field hysteresis measurements show charge injection with increasing temperature, while positive-up-negative-down measurements show little temperature dependence of $P_{r}$ up to temperatures of 200 °C. Poole–Frenkel emission dominated the high field leakage behavior. The refractive index measured by ellipsometry is 2.58 at 633 nm. All samples show significant retention loss. As the stoichiometry improves, retention improves such that >40% of the initial $\Delta P$ is retained over $\approx 280$ min. [ABSTRACT FROM AUTHOR]

35 Bi(Mg1/2Ti1/2)O3 - 65 PbTiO3 (35 BiMT-65 PT) is a potential candidate material for a high-temperature nonvolatile ferroelectric memory. For pulsed-laser deposited 35 BiMT-65 PT films with the perovskite structure, it was found that as the chamber pressure during deposition decreased, the Mg and Pb contents in as-deposited films drop, while the concentration of Bi increases. Concurrently with the change in composition, the remanent polarization $P_{r}$ increases 64% to $\approx 21~\mu \text{C}$ /cm2 and the polarization–electric field loops rotated counterclockwise as the deposition pressure increases. Decreasing the seed layer thickness from 36 to 16 nm led to a decrease in $P_{r}$ to $\approx 14~\mu \text{C}$ /cm2. Adjusting the target composition allowed the deposition of films which had near-stoichiometric Bi and Mg concentrations, but in all cases, the grown films were lead deficient. These films had remanent polarizations of 18– $20~\mu \text{C}$ /cm2. If the lead content of the target was increased too far, the remanent polarization decreased, possibly due to the need to evolve more PbO from defective growth layers. Finally, the deposition rate showed no substantial effect on the film composition, but did have a significant impact on the ferroelectric properties. As the deposition rate decreased, the $P_{r}$ increased to $\approx 22~\mu \text{C}$ /cm2 due to enhanced crystalline quality. At laser frequencies of 5 Hz, a Mg-rich pyrochlore phase begins to form and films showed a maximum $P_{r} \approx 22~\mu \text{C}$ /cm2. The processing-composition behavior is explained via preferential adsorption of Bi on the A-site, which results in lead vacancies. [ABSTRACT FROM AUTHOR]

Macroscopic properties measurements, such as dielectric permittivity and ferroelectric hysteresis, differential scanning calorimetry, and average structure information are combined with complementary techniques sensitive to the local structure, i.e. Pair Distribution Function (PDF) and Raman spectroscopy, to gain comprehensive insight into the structure-property relationships and origin of relaxor behaviour in BaCe x Ti 1-x O 3 ceramics over a broad composition ( x  = 0.02–0.30) and temperature (100–450 K) range. The resulting phase diagram displays sequential phase transitions with a tricritical point (TCP) at x  = 0.09 and a ferroelectric to relaxor crossover (FRC) at x  ≈ 0.20. In contrast, the local structure is rhombohedral irrespective of x and the PDF reveals the existence of a high level of disorder and significant local strains determined by the ionic size mismatch (Ce 4+ : 0.87 Å, Ti 4+ : 0.605 Å). The diffuse character of the phase transitions observed when x  ≥ 0.05 is most likely originated by these deformations. Parallel of BaM x Ti 1-x O 3 phase diagrams (M = Sn, Hf, Zr, Ce) shows that the compositions corresponding to TCP and FRC are nearly independent of M. This suggests that, irrespective of the ionic radius of M 4+ , in homovalent-substituted BaTiO 3 a critical number of Ti-O-Ti bonds has to be broken before a new “state” is established, whereas local electric and strain fields seem to have a marginal effect. [ABSTRACT FROM AUTHOR]

An optical method is proposed to extract the displacement vector of domain wall (DW) sidewise motion from ferroelectric domain configuration pattern on a tetragonal Mn:Fe:KTN crystal. The ferroelectric domain configuration evolution under an external electric field is observed in situ using optical microscope imaging system, and the relative displacement of DW sideways motion between two adjacent electric fields is extracted. By the combination of the new domain length vector extracted, the ferroelectric domain displacement vector as a function of field strength can be obtained; what is more, the hysteresis loop can be achieved during field cycling. The method provides an access to directly manipulating DW motion and exploring the properties of ferroelectric materials from ferroelectric domain configuration pattern. [ABSTRACT FROM AUTHOR]

Samples of lead–free Ba(Zr x Ti 1-x )O 3 bulk and thick film were fabricated using solid state reaction and tape – casting technique, respectively. A comprehensive investigation of dielectric, ferroelectric, and electrocaloric properties of these samples has been carried out. The results show that there is a dielectric relaxation behavior in the thick film Meantime, the “re–entrant relaxor behavior” and thermal hysteresis are observed in the bulk. Moreover, the electrocaloric effects are observed in the thick film and the bulk. The peak values of Δ T E C of the bulk and the thick film are 2.78 K and 0.37 K, respectively. This work is beneficial for realizing high efficiency and environmentally friendly cooling technology. [ABSTRACT FROM AUTHOR]

Eco-friendly lead-free relaxor ferroelectrics, Ba 1-x (Bi 0.5 Li 0.5 ) x TiO 3 (BBLT) with x = 0.3, 0.4 and 0.5, have been synthesized by using the conventional solid-state reaction route. The crystal structure and phase purity were verified by x-ray diffraction (XRD) patterns using Rietveld refinement which revealed the presence of tetragonal (95–80%) and orthorhombic phases (5–20%) in the matrix. The temperature dependent dielectric constant and tangent loss dispersion spectra, slim ferroelectric-hysteresis, and nano-scale microstructures suggest the presence of short-range ordering (SRO)/polar nano-regions (PNRs) in the matrix. The dielectric spectra suggest that the dielectric dispersion increases with increase in Bi/Li concentrations which may be due to compositional fluctuations, ordering of cations at nano-scale and presence of metastable states of SRO and long-range ordering (LRO) regions. The nonlinear Vogel-Fulcher relationship is fitted for maximum dielectric constant temperatures ( T m ) which provides activation energy and freezing temperature of all compositions. The current density (J) versus electric field (E) (J-E) data obey bulk-limited current conduction mechanisms that may be due to a diffusive displacement of Ti 4+ at octahedral center, the creation of random fields due to in-homogeneity at A-site, and trap-assisted hoping of charge carriers under high E-fields. [ABSTRACT FROM AUTHOR]

Electric field driven in-situ high-temperature polarization (P) vs. electric field (E) and switching current (I) vs. E measurements performed on Na 0.5 Bi 0.5 TiO 3 (NBT) ceramics gave a direct evidence for the exact nature of polar ordering and witnessed a new ferroelectric phase transition sequence viz., R .T → FE 180 ° C → FE + FE 2 200 ° C → ≥ 200 ° C FE + AFE . In-situ high-temperature Raman scattering studies performed on poled NBT revealed the local structural origins of the aforementioned electric field driven ferroelectric (FE) phase transition sequence. The origin of observed two ferroelectric phase co-existence in a narrow temperature range between 180 °C–200 °C is due to the local structural distortion in the Ti O bond coupled through TiO 6 octahedral tilt transition. The observed antiferroelectric (AFE) phase coexistence above 200 °C is strongly driven by the A-O phonon vibrations as a consequence of a change in A-site symmetry i.e., antiparallel A-site cation displacements. [ABSTRACT FROM AUTHOR]

In this paper, we have used the effective field theory (EFT) based on the probability distribution method (PDM) to study the hysteresis behavior of a ferroelectric nanowire with core/shell morphology (FN(C/S)M) in a random electric field (REF). This system is studied by using the transverse Ising model (TIM). We have studied the effects of the temperature, the random transverse field (RTF), the surface shell coupling, and the concentration on the hysteresis loops, the coercive field, and the remanent polarization of the nanowire. A number of characteristic behaviors have been found, such as the existence of the relaxor character for appropriate values of the system parameters. The remanent polarization and the coercive field, as a function of the temperature, are examined. [ABSTRACT FROM AUTHOR]

Here we report our investigations on a pseudo-cubic 0.5BiFeO 3 –0.5BaTiO 3 ceramic (0.5BF–0.5BT) in which ferroelectric relaxor and antiferromagnetic and magnetic relaxor orders coexist. The temperature dependence of ferroelectric hysteresis loops and dielectric data confirms the existence of the ferroelectric relaxor state. The temperature of the maximum dielectric constant (T m ) at 1 MHz and electric freezing temperature (T f ) are 584 K and ~250 K, respectively. The magnetic data imply that a Neel transition occurs below 174 K. Most importantly, a magnetic relaxor order appears below ~6 K. The magnetic states of 0.5BF–0.5BT are rather different from those of BF–BT ceramics with the low BT concentration. [ABSTRACT FROM AUTHOR]

Dielectric hysteresis loops of pure and lanthanum doped TlInS 2 ferroelectric-semiconductors were studied at the frequency 50 Hz for different temperatures below the Curie temperature ( T c ). It has been revealed that, without any poling procedure, pure TlInS 2 exhibits normal single hysteresis loops at T < T c . After electric field-cooled treatment of TlInS 2 the shape of hysteresis loops was strongly affected by corresponding charged deep level defects which were previously activated during the poling process. As a result, an additional defect polarization state from space charges accumulated on the intrinsic deep level defects has been revealed in pure TlInS 2 at the temperatures below T c . Besides, unusual multiple hysteresis loops were observed in La doped TlInS 2 at T < T c after application of different external perturbations (electric field, exposition and memory effect) to the sample. Measurements of the hysteresis loops in TlInS 2 :La revealed the slim single, double and even triple polarization–electric field ( P–E ) hysteresis loops. This intriguing phenomenon is attributed to the domain pinning by photo- and electrically active La-impurity centers. The temperature variation of double-hysteresis loop was also investigated. Due to the heat elimination of the random local defect polar moments, the double-hysteresis loops were transformed into a normal single hysteresis loops on increasing the temperature. [ABSTRACT FROM AUTHOR]

A pair of novel enantiomerically chiral clusters, R/S-[Zn 4 (HL) 2 (L) 2 ·(CH 3 OH) 2 ]·(NO 3 ) 2 , have been obtained via the self-assembly of R/S-H 2 L Schiff base ligands with divalent zinc nitrate (H 2 L = 2-[(1-benzyl-2-hydroxy-ethylimino)-methyl]-6-methoxy-phenol). The compounds were characterized by single-crystal X-ray diffraction, elemental analysis and infrared spectroscopy. Their structures reveal that the enantiomers are not only in a chiral space group but also have a non-centrosymmetric polar packing arrangement. Both clusters display ferroelectric behavior at room temperature. Impressively, the clusters show well-defined ferroelectric hysteresis loops with high Ps values at a relatively high frequency of 100 Hz, which is very rarely in the field of molecule-based ferroelectrics. [ABSTRACT FROM AUTHOR]

We report on the heat treatment to stabilize 0.65[Pb(Mg 1/3 Nb 2/3 )O 3 ]-0.35[PbTiO 3 ] ceramics and its effect on the functional response. The stabilization heat treatment at 1050 °C for 4 h was effective in removing un-reacted PbO from the ceramics, which was confirmed through the measurements of dielectric and ferroelectric properties for a series of samples with different PbO contents. We also found that the stage of the stabilization heat treatment affected the sample properties. When this treatment was administrated to the sample during calcination, it exhibited excellent ferroelectric behavior. On the other hand, the same stabilization heat treatment given to the compacted pellet prior to sintering resulted in excellent dielectric properties with comparatively low ferroelectric hysteresis. [ABSTRACT FROM AUTHOR]

(100-x) BaTiO3(BT)-(x) CoFe2O4(CFO) (X = 10, 20 and 30 wt%) composites were prepared through conventional solid state reaction method by mixing two individual phases by weight. Structure and surface morphology of the composites were observed using X-ray diffraction and Scanning electron microscopy respectively. Polarization study of the BT-CFO composites was done by measuring the polarization (P) against the electric field (E) up to 30 KV/cm, pattern observed showed good ferroelectric behaviour with Pmax= 4.10 µC/cm2for BT-CFO/90-10. In order to estimate the effect of magnetic phase on ferroelectric nature of BT, dielectric and magnetoelectric measurements were also done on the composites and are presented here. [ABSTRACT FROM PUBLISHER]

This paper explains the extraction from the measurement of the parameters necessary in time domain to identify the hysteretic behavior of the coupling capacitance of through silicon vias (TSVs). The algorithm was developed in such a way that the equivalent capacitance model can be implemented into standard circuit simulators. A comparison with a known procedure based on the genetic algorithm approach is offered as validation. Results showing the robustness of the algorithm and the effects of the hysteresis on the crosstalk among TSV and integrated circuit active devices are reported and discussed. [ABSTRACT FROM AUTHOR]

In this brief, we reported a ferroelectric versatile memory with strained-gate engineering. The versatile memory with high-strain-gate showed a >40% improvement on ferroelectric hysteresis window, compared to low-strain case. The high compressive stress induced from high nitrogen-content TaN enhances monoclinic-to-orthorhombic phase transition to reach stronger ferrolectric polarization and lower depolarization field. The versatile memory featuring ferroelectric negative capacitance exhibited excellent transfer characteristics of the sub-60-mVdec subthreshold swing, ultralow off-state leakage of <1fA/ \mu \textm and > 10^\mathsf 8 on/off current ratio. Furthermore, the ferroelectric versatile memory can be switched by ±5 V under 20-ns speed for a long endurance cycling (~1012 cycles). The low-power operation can be ascribed to the amplification of the surface potential to reach the strong inversion and fast domain polarization at the correspondingly low program/erase voltages. [ABSTRACT FROM PUBLISHER]

In order to understand the effect of polarization frequency and temperature on polarization rule of tourmaline, the ferroelectric hysteresis loops of three kinds of tourmaline samples are measured in different polarization conditions. It is demonstrated that the spontaneous polarization alongc-axis of tourmaline is larger than that perpendicular toc-axis. Furthermore, the polarization frequency and temperature have great influences on the ferroelectric hysteresis loop of tourmaline, inferring that the polarization forms of tourmaline may be composed of turning-direction polarization of electric dipole and thermionic relaxation polarization. [ABSTRACT FROM AUTHOR]

Zigzag FeO 2 nanoribbon defected by the removal of oxygen atoms is simulated using Monte Carlo simulations. All possible arrangements of positions and number of oxygen vacancy are investigated. Temperature dependence of polarization, dielectric susceptibility, internal energy, specific heat and dielectric hysteresis loops are all studied. Results show the presence of second order phase transition and Q − type behavior. Dielectric properties dependence on ribbon's edge, positions and number of oxygen vacancy are discussed in detail. Moreover, single and square hysteresis loops are observed whatever the number of oxygen vacancy in the system. [ABSTRACT FROM AUTHOR]

Novel multiferroic materials have attracted increasing attention in recent years. Aurivillius bismuth‐layer structured Bi4Ti3O12·nBiFeO3 (BTFO: n = 1–3, 5) compounds with potential multiferroic properties are such a compound. However, the data on these BTFOs are ambigious, inconsistent, and incomplete. Therefore BTFOs were grown into single crystals for a systematic evaluation. Their crystal structures and microstructures show that intergrowth of layer structure occurs easily in this class of material. Their ferroelectric measurements show strong anisotropy and dielectric peaks at high temperature, accompanied by an abnormal loss that corresponds to their polar phase transition. At room temperature, ferroelectric hysteresis loops were successfully measured; the loops show a strong dependence in their polarization and coercive field on different values of n and anisotropy. Magnetic measurement shows that all the single crystals display magnetic transitions at high temperatures and weak ferromagnetism at room temperature. Electron spin resonance (ESR) results show the coexistence of ferromagnetic and paramagnetic signal components in all the compounds. Scanning probe microscope measurements show magnetic domains switched together with electric domains by use of an electric field. Therefore we conclude that overall spin disorder with localized order is the character of this class of material, with observed magnetoelectric (ME) coupling. This work could also point the way to novel multiferroic materials in locally magnetic ordered systems. [ABSTRACT FROM AUTHOR]

This article presents the effect of processing parameters on the ferroelectric hysteresis behavior of Ba0.85Sr0.15Zr0.1Ti0.9O3(BSZT) ceramics. The ferroelectric hysteresis scaling relations for coercive field (Ec) and remnant polarization (Pr) as a function of temperature have been proposed. The power law temperature exponents based on scaling were systematically established for all the hysteresis parameters. The temperature dependent scaling of Ecand Prat sintering temperature of 1400, 1425, 1450 and 1475°C yields EcαT0.43, EcαT0.84, EcαT0.50, EcαT0.37and PrαT−1.73, PrαT−1.55, PrαT−1.73, PrαT−1.69respectively. Additionally, the scaling relations for the samples sintered at 1450°C at different time intervals of 3, 4, 5 and 6 hrs were also established. Finally, to understand the domain dynamics, back switching polarization (Pbc) as a function of temperature (T) was also estimated by Arrhenius law and the average activation energy was evaluated. [ABSTRACT FROM PUBLISHER]

A methodology based on computer simulations and aiming to estimate the lifespan of transformer windings after the occurrence of short circuits is presented in this paper. The Von Mises and fatigue criteria are employed to determine the failure proximity of the windings. The obtained results contribute to the evaluation of the influence of electromechanical effects in transformer windings and to the determination of the number of short circuits that a transformer winding can support. The simulation results may also be employed in the design of transformers and failure diagnosis, to increase the security margin against mechanical failures. [ABSTRACT FROM PUBLISHER]

A solid solution of multiferroic BiFeO and ferroelectric BaTiO in equal molar ratio (i.e., (BiBa) (FeTi) O (BF-BT)) was synthesized by using solid state reaction route. By adding BaTiO in BiFeO, the crystalline structure and ferroelectric properties of the system was improved. The significantly reduced leakage current results to get regular ferroelectric hysteresis loop of the parent compound. The dielectric relaxation observed at 365 °C may be related to the anti-ferromagnetism transition suggesting the coupling between the ferroelectric and magnetic orders essential for the multiferroic materials. Moreover, the remnant magnetization (2M) of 0.00014 emu/g and coercive field (2H) of 6.94 kOe were observed in the system. The ac conductivity study confirmed transport phenomena in the material are due to hopping of polarons. [ABSTRACT FROM AUTHOR]

We present the first devoted theoretical and experimental study of the hysteresis phenomenon in relation to frequency tunability of gyrotrons. In addition, we generalize the theory describing electron tuning of frequency in gyrotrons developed earlier to arbitrary harmonics. It is found that theoretical magnetic and voltage hysteresis loops are about two times larger than experimental loops. In gyrotrons whose cavities have high quality factors, hysteresis allows one only little to broaden the frequency tunability range. [ABSTRACT FROM AUTHOR]

PIN–PMN–PT single crystals near the morphotropic phase boundary with low level of In 3+ doping were grown through slow cooling their high temperature solution. Temperature-dependent dielectric constants and pyroelectric coefficients indicated two phase transitions, i.e. orthorhombic (O)–tetragonal (T)–cubic (C), took place in 19PIN–45PMN–36PT single crystals upon heating from 35 °C to 250 °C. The dielectric constant of O phase was higher than that of T phase, which was related to the polarization rotation. When the temperature approached to the depolarization temperature, tetragonal macrodomains converted to microdomains. The polarization change led to the analogous observed in the plots of temperature-dependent pyroelectric coefficients and dielectric constants. However, the temperature-dependent remanent polarization indicated a lower O–T phase transition temperature. Such a discrepancy in T ot could be ascribed to the decline of ferroelectric phase transition energy caused by the superposition of the AC field at each temperature test point when perform bipolar ferroelectric hysteresis loops measuring. The domain structure variation upon heating an unpoled [0 0 1] c -oriented 19PIN–45PMN–36PT single crystal was observed with a polarized light microscopy, further indicating the occurrence of the two phase transitions. [ABSTRACT FROM AUTHOR]

1-3 type piezocomposites are very attractive materials for transducers and biomedical application, due to its high electromechanical coupling effects. Reliability study on 1-3 piezocomposites subjected to cyclic loading condition in transducer application is one of the primary concern. Hence, this study focuses on 1-3 piezocomposites for various PZT5A1 fiber volume fraction subjected to electrical fatigue loading up-to 106 cycles and at various elevated temperature. Initially experiments are performed on 1-3 piezocomposites, in order to understand the degradation phenomena due to various range in amplitude of electric fields (unipolar & bipolar), frequency of applied electric field and for various ambient temperature. Performing experiments for high cycle fatigue and for different fiber volume fraction of PZT5A1 is a time consuming process. Hence, a simplified macroscopic uni-axial model based on physical mechanisms of domain switching and continuum damage mechanics has been developed to predict the non-linear fatigue behaviour of 1-3 piezocomposites for temperature dependent electrical fatigue loading conditions. In this model, damage effects namely domain pinning, frozen domains and micro cracks, are considered as a damage variable (ω). Remnant variables and material properties are considered as a function of internal damage variable and the growth of the damage is derived empirically based on the experimental observation to predict the macroscopic changes in the properties. The measured material properties and dielectric hysteresis (electric displacement vs. electric field) as well as butterfly curves (longitudinal strain vs. electric field) are compared with the simulated results. It is observed that variation in amplitude of bipolar electric field and temperature has a strong influence on the response of 1-3 piezocomposites. [ABSTRACT FROM AUTHOR]

A hybrid nanocomposite comprising 5CB liquid crystal (LC) and block copolymer (BCP) functionalized barium titanate ferroelectric nanoparticles was prepared. This hybrid system exhibits a giant soft-memory effect that was detected by dielectric hysteresis. Spontaneous polarization of ferroelectric nanoparticles couples synergistically with the radially aligned BCP chains to create nanoscopic domains where LC mesogens can align directionally. Such domains can be rotated electromechanically and locked in space even after the removal of the applied electric field. The resulting non-volatile memory is several times larger than the non-functionalized sample and provides an insight into the role of non-covalent polymer functionalization on enhancing the size of the nanoscopic domains. [ABSTRACT FROM AUTHOR]

Effect of active layer thickness, influenced by the hydrophobic dielectric surface, on the performance of copper phthalocyanine based organic field effect transistors (OFETs) was studied. While charge carrier mobility was found to be highest for an optimum thickness of 30 nm, hysteresis and threshold voltage shift were found to be minimum for 15 nm thick film which is attributed to the excess availability of photogenerated carriers, especially close to the dielectric/semiconductor interface, as this thickness is within the exciton quenching length in organic semiconductors. But prolonged bias stress resulted in larger decay in drain current for higher thickness indicating the dominant role played by the larger grain boundary density in the increased volume. These results were found to be different from that on unmodified SiO 2 dielectric with higher surface energy and were suggested to be caused by the 3D growth mode of CuPc films on the hydrophobic surface. Mobility degradation at higher gate voltages also exhibited a dependence on the active layer thickness which was tuned by the hydrophobic surface induced growth mode at the dielectric/semiconductor interface. [ABSTRACT FROM AUTHOR]

In this paper, a study is presented on the microstructure, dielectric and piezoelectric properties of 0–3 connectivity barium titanate-Portland cement composite with 40% barium titanate content at this composition has an acoustic impedance that match with concrete structure. The results show that both of dielectric constant (ϵr) and dielectric loss (tanδ) of composite were found to decrease with increasing frequency. The ϵrvalue of composite was 239 at a frequency of 1 kHz. In addition, the ferroelectric hysteresis loops of composite indicate that the “apparent”remnant polarization increases as an applied external electrical field increases. Furthermore, the piezoelectric coefficient was 7 pC/N under a low poling field of 1 kV/mm. [ABSTRACT FROM PUBLISHER]

This paper proposes a numerical solution of the nonlinear equations that describes the hysteretic behavior of the coupling capacitance among through silicon vias in three-dimensional integrated circuits. Behavioral ordinary differential equations are formulated and solved by an equivalent circuit described in SPICE syntax. These results are then compared with those obtained by measurements. [ABSTRACT FROM AUTHOR]

Asymmetric ferroelectric hysteresis ( P- E) loops and strain hysteresis ( S- E) curves are detected in poled-aged Li doped (BiNaK)CeTiO ceramics at room temperature. Temperature dependence of electrical and structural analysis is used to study the stability of electrically induced long-range ferroelectric order. Interestingly, this asymmetric characteristic can sustain at 80 °C ≤ T ≤ 90 °C, where the ferroelectric and non-ergodic relaxor phase coexist. Our results suggest that the preferentially reoriented defect dipoles have the pinning effect on temperature- and electric field- induced phase transition between long-range ferroelectric and relaxor. [ABSTRACT FROM AUTHOR]

Dielectric properties, ferroelectric hysteresis loops, and leakage current characteristics of an epitaxial BaTiO (BTO) film were investigated with LaSrCoO as bottom electrode and the different noble metal as top electrodes (Au, Ag and Pt, which were deposited on the same surface of a BTO film). The dielectric constants, dielectric loss, leakage currents and ferroelectric loops all exhibited the top-electrode-dependent behavior, which can be attributed to the different interface state. The J- V characteristics were analyzed with various transportation mechanisms in detail. Regardless of the top electrode materials, the leakage current characteristics were described by a modified Schottky contact model for all BTO film capacitors. It was proved that large space charge densities were the main contribution to the slim hysteresis loops. The potential of these interface charge dominated BTO film heterostructures in the application of high energy density storage capacitors was also demonstrated. [ABSTRACT FROM AUTHOR]