Dielectric Relaxation Behavior Research Articles

Influence of processing parameter on structural, morphological, optical, and dielectric properties of LaPO4 ceramics

LaPO4 ceramics has been synthesized using Auto Combustion. The prepared ceramics sintered at 1100 ˚C, 1200 ˚C & 1300 ˚C to study crystal phase and diffractograms from x-ray diffraction confirmed that sample crystallizes in monoclinic crystal phase at 1200 ˚C & 1300 ˚C. The SEM micrographs show that grain size as well as grain growth increases continuously with increasing sintering temperature whereas EDS spectra confirms the presence of elements. The UV–Visible spectra show that band gap of prepared ceramics remains almost constant with increasing sintering temperature. The dielectric relaxation behaviour of prepared ceramics was studied from Cole-Cole fitting of experimentally collected data.

Relaxation behavior at high temperature associated with oxygen vacancy in the Sr1-x(LiCe)x/2.5Bi2Nb2O9 ceramics

Dielectric relaxation behavior and conductiviy of Sr1-x(LiCe)x/2.5Bi2Nb2O9 ceramics prepared by conventional solid-sate reaction method were investigated. With the introduction of the (LiCe), the conductivity was improved significantly and the large conductivity at high temperature (∼10−4 S·cm−1 at 530 °C) could be obtained. Phase transition from normal ferroelectric to relaxor-like ferroelectric was detected in the Sr1-x(LiCe)x/2.5Bi2Nb2O9 ceramics. Results of the complex impedance analysis indicated that the concentration of charge carriers increased gradually with the increase in (LiCe). Oxygen vacancy was confirmed to be responsible for the conductivity at high temperature by calculating activation energy of the carriers in the corresponding range of high temperature. Dielectric relaxation behavior at high temperature was attributed to the short-range conductivity of oxygen vacancies under thermal stimulation.

The Effect of Blending Natural Rubber‐graft‐poly(methyl methacrylate) on the Dielectric Relaxation of Poly(ethylene oxide)

AbstractThis study focuses on the dielectric relaxation of the immiscible PEO/NR‐g‐PMMA blends. Due to the heterogeneous morphologies of the blends, the molecular mobility in the polymer chains displays various relaxation responses. The dielectric relaxation of the blends is analyzed in terms of complex impedance, complex permittivity, tangent loss spectra, and complex modulus. The molten neat PEO promotes a long‐range conduction mechanism. On the other hand, NR‐g‐PMMA displays the relaxation of short‐range motion only at temperatures above the glass transition temperature of PMMA‐graft. As for the blends, the relaxation of the dipoles proceeds slower and broader dispersion of relaxation times occurs when NR‐g‐PMMA is added to PEO. In the molten state, only blends with an excess of PEO display the dominance of the long‐range motion of the dipolar entities. The short‐range motion of the dipolar entities becomes dominant when NR‐g‐PMMA is in excess. This suggests that the high restriction of dipole motions in NR‐g‐PMMA affects the dielectric relaxation behavior of PEO/NR‐g‐PMMA blends.

Dielectric Relaxation Behavior of Halobenzene Confined in the δ‐Phase of Syndiotactic Polystyrene

AbstractSyndiotactic polystyrene (sPS) incorporates low‐mass guest molecules to form a co‐crystalline structure, the δ‐phase, in which the guest molecules are confined within a nanosized space. Under such spatial constraints, what factors determine the dynamics of the guest molecules? This is an interesting question and needs to be clarified toward the functionalization of sPS/functional guest systems. In this study, the size effect of the guest molecules and use monosubstituted halobenzenes (fluorobenzene, chlorobenzene, bromobenzene, and iodobenzene) to systematically change the molecular size is focussed. Since halobenzene has a large electric dipole moment, dielectric relaxation measurements can effectively detect its molecular motion. This study aims to identify the guest dynamics in the δ‐phase by dielectric relaxation measurement and examines the molecular length dependence of the rotational relaxation times and their activation energies.

Electrical characterization of AgNPs-PVA nanocomposites thin film-based heterojunction diode

The purpose of this work is to study the results of electrical measurements carried out of nano metal-semiconductor heterojunctions based on Poly Vinyl Alcohol (PVA)to examine the possibilities of either an Ohmic contacts or rectifying behavior like a Schottky junction. The PVA doped silver nanoparticles (AgNPs-PVA)were confirmed and characterized by using x-ray Diffraction (XRD),Fourier-Transform Infrared Spectroscopy (FT-IR), Thermogravimetric analysis (TG) and Differential Scanning Calorimeter (DSC). A thorough investigation of the predominant conduction mechanism, dielectric relaxation, and current-voltage behavior of a polyvinyl alcohol (PVA)–Silver nanoparticles (AgNPs) nanocomposite film has been presented. With two activation energies, Ag nanoparticles have been demonstrated to improve the conductivity and dielectric permittivity of films. In the sample, a non-Debye type asymmetric behavior has been found, which may be analyzed using a modified Cole-Cole model. The temperature dependence of the a.c. conductivity σ ac and power law exponent s is reasonably interpreted by the Correlated Barrier Hopping (CBH) and Small Polaron Tunnelling (SPT) models at low and high frequency ranges, respectively. The junctions were created by spin coating and characterized of evaluated according to their I-V characteristics. Non-Ohmic electrical behavior was observed. The phenomenon supposed to be partly responsible for such nonlinearity is existence of thin barrier layer on the surface of dried polymer nanocomposites, through which charge carriers could pass by tunneling. This Schottky diode manufactured of an AgNPs-PVA nanocomposite was electrically characterized and investigated. However, deeper discussion will be necessary to illuminate all the circumstances leading to understand this behavior.

Thermal and dielectric properties of PVDF/PEO/SiO2 nanodielectrics for flexible radioelectronic device technologies

Hybrid polymer nanocomposites (HPNCs) are innovative multifunctional materials, which are developed and intensively studied for their uses in the rapid evolution of flexible and lightweight device technologies. Accordingly, to contribute in this area, thermal properties of the crystal phases and the broadband radio frequencies dielectric dispersion and relaxation behaviour of the HPNC films based on poly(vinylidene fluoride) (PVDF)/poly(ethylene oxide) (PEO)/silica (SiO2) are formulated and studied by employing differential scanning calorimeter (DSC) and impedance/material analyzer (IMA). DSC thermograms of these semicrystalline HPNCs explained the wide range alteration in the crystals melting temperature of PVDF (153–167 ​°C) and PEO (59–72 ​°C) and the total degree of crystallinity (4–87%) with varying compositional ratio over the entire range of the PVDF/PEO blend host matrix and the dispersed amount of amorphous SiO2 nanomaterial up to 15 ​wt%. The dielectric dispersion behaviour of these HPNCs, at 20 ​°C, confirmed a non-linear decrease in permittivity with the increase of applied radio wave electric field frequency from 1 ​MHz to 1 ​GHz, which lies in the range of 6 to 2. At a fixed frequency, dielectric permittivity values exhibited an uneven variation with the increase of SiO2 amount and also the modification in the composition of polymer blend matrix in these composites. The analysis of dielectric loss spectra and relaxation processes revealed that these are low loss dielectrics and the presence of SiO2 nanoparticles in the polymer blend matrix impedes the chain segmental dynamics and the dipole reorientation. The electrical conductivity of these HPNCs enhanced in the range of 10−8 to 10−4 ​S/cm with the increase in frequency but it changed anomalously when the constituent amounts of the formulated composites are varied. The polymer crystals thermal properties and the dielectric and electrical conductivity dispersion behaviour of these materials are demonstrated with the consideration of polymer-polymer and polymer-nanoparticle hybrid interfaces and interactions. The experimental results evidenced the behaviour of PVDF/PEO/SiO2 films as tunable nanodielectrics with their compositions and could be used as insulator and dielectric substrate materials in the advances of flexible radioelectronics and energy storage devices.

High Temperature Dielectric Relaxation Properties of SrTiO3-Zn2SnO4 Composite Ceramics

ST-xZS ceramics were prepared by solid-state sintering and have high temperature dielectric relaxation behavior at the temperature ranges of 300 °C–500 °C. We explore the origin of high temperature dielectric relaxation behavior of samples by activation energy calculation, XPS energy spectrum analysis and oxygen treatment experiment. We get a conclusion that the dielectric relaxation of pure ST ceramics comes from the migration of Vo. However, with the increase of ZS content, the dielectric relaxation related to Vo migration is gradually transformed into the influence of Ti4+ ion polarization, and the possible causes of relaxation behavior dependence are analyzed in detail.

Influence of Samarium on Structural, Morphological, and Electrical Properties of Lithium Manganese Oxide

Research and developments on preparing electrode material for lithium-ion batteries are burgeoning nowadays widely. In this study, we used the high energy ball-milling method to prepare pure and samarium-doped lithium manganese oxide (Li4Mn5O12) and investigated its structural, morphological, and electrical properties. The XRD spectrum for the produced materials confirmed the phase purity and crystallinity of the material. The fourier transform infrared spectrum was used to determine the different sorts of vibrations between molecules. The particle size with the presence of polyhedral-shaped morphology was certified by using SEM and TEM analysis. EDS mapping was used to assess the elemental composition and purity of the samples. Complex impedance spectroscopy analysis was used to investigate the temperature dependency of the materials’ electrical properties, and high conductivity (1.15 × 10−7 S cm−1) was reported for samarium-doped lithium manganese oxide at 100°C, and its dielectric relaxation behavior was examined.

Interpretation of dielectric behavior and polaron hopping in lead-free antimony-based double perovskite.

Lately, double perovskite materials have become well-known in the commercialization area owing to their potential use in optoelectronic applications. Here, double perovskite Cs2AgSbCl6 single crystals (SCs) with cubic crystal structure and Fm3̄m space group were successfully synthesized via the slow cooling technique. This paper investigates the dielectric relaxation and charge transfer mechanism within Cs2AgSbCl6 using electrochemical impedance spectroscopy (EIS) in the 273-393 K temperature range under light. The dielectric response in Cs2AgSbCl6 has been explained by the space charge polarization and the ionic motion. The ε'(ω) study at different temperatures shows a remarkable frequency transition at which dε'/dT changes from a positive to a negative coefficient. Based on Stevels approach, the density of traps diminishes with the temperature increase, which improved conduction. However, this approach proves the polaronic conduction in Cs2AgSbCl6. 0.42 and 0.21 eV are the binding (Ep) and polaron hopping (WH) energy values, respectively. Contrary to free-charge carrier motion, polaron hopping was proposed as the principal conduction process since the ambient-temperature thermal energy was lower than Ep. Moreover, the analysis of M''(ω) and -Z''(ω) as a function of temperature shows the thermally-activated relaxation from the non-Debye to Debye type model in Cs2AgSbCl6. This scientific research offers an essential understanding of the dielectric relaxation behavior, which is required for improving dielectric switches. Also, this paper provides a deep insight into the conduction mechanism within double perovskite materials.

The origin of dielectric relaxation behavior in TiO2 based ceramics co-doped with Zn2+, W6+ ions under a N2/O2 sintering atmosphere.

Dense (Zn0.5W0.5)xTi1-xO2 (ZWTOx) ceramics were fabricated using a conventional solid state reaction method with sintering under a nitrogen atmosphere (ZWTOx-N2) and an oxygen atmosphere (ZWTOx-O2), respectively. Colossal permittivity (ε > 104) and low loss (tan δ < 0.1) were simultaneously achieved in ZWTOx-N2 ceramics, and two types of dielectric relaxation behaviors observed were interpreted to be due to interface polarization and disassociation between oxygen vacancies and trivalent titanium ions, respectively. The impedance plots suggested that the ZWTOx-N2 ceramics are electrical heterostructures composed of semiconductor and insulator grain boundaries, which proved that the CP performance of ZWTOx-N2 ceramics almost originates from the internal barrier layer capacitance (IBLC) effect. In addition, a series of anomalous dielectric behaviors such as low permittivity and low frequency dispersion were observed for ZWTOx-O2 ceramics; polarization (P)-electric field (E) hysteresis loop curves were obtained for ZWTOx-O2 ceramics, and that impedance plots have shown that the ZWTOx-O2 ceramics display higher insulation resistivity. Density functional theory (DFT) calculations illustrated that the Zn2+-W6+ ion pairs are easy to form in ZWTOx-O2 ceramics, which causes destruction of the local lattice and thus leads to abnormal dielectric behavior. This work will provide a new strategy for defect engineering in TiO2 and other CP materials.

Dielectric relaxation, dipole moment, electronic characterization and non-covalent interaction behavior of valeramide and halo-phenol in non-polar liquid: A density functional theory-based approach

In the present work, DFT has been used to explore the structural, electronic, charge transfer and molecular interactions between valeramide and halogenated phenol in solvent benzene and Dielectric relaxation studies have also been used. The optimized geometrical parameters, wavefunctional characteristics like a reduced density gradient, chemical bonds and the electron localization function are reported. It has been discovered that the HOMO and LUMO computed energies accurately depict the characteristics of electron excitation. MEP analysis is used to identify electrophilic and nucleophilic sites. The analysis of the UV–visible spectrum using the TD-DFT method with solutions and the computational investigation of spectroscopic wavenumbers (IR, Raman). The study of natural bond orbitals is carried out to provide an explanation for the charge transfer and stabilization energy resulting from current intra- or intermolecular interactions. Dipole moments of the pure liquids are calculated from the dielectric data using Higasi’s method and compared with the literature results. Various dielectric parameters are given, including the dielectric constant ε′, the dielectric loss ε′′ at microwave frequency, the static dielectric constant ε0 and the dielectric constant ε∞ at optical frequency. The different parameters of dielectric, relaxation time (τ0) and the dipole moment (μ) has been evaluated using the single-frequency concentration Higasi’s method. The fact that the relaxation time of the 1:1 M ratio are greater than those of other higher molar ratios (i.e. 3:1, 2:1, 1:2, 1:3) confirms the presence of a 1:1 complex structure between the studied systems, as well as a complex formation between the free hydroxyl group of phenols and the carbonyl group of amide.

High temperature stability and low dielectric loss in colossal permittivity TiO2 based ceramics co-doped with Ag+ and Mo6+

In this work, dense (Ag2/5Mo3/5)xTi1-xO2 ceramics (AMTOx) were successfully prepared by a conventional solid state method. The dielectric properties of AMTOx ceramics were systematically investigated. Good dielectric properties with superior temperature stability were realized in AMTOx ceramics. Encouragingly, the AMTO0.0125 ceramics obtained a giant permittivity of ∼20604 and a dielectric loss of ∼0.045 at 1 kHz, while being able to satisfy with the requirement of application temperature of Z9R capacitor. Moreover, two kinds of dielectric relaxation behavior in low and high temperature region can be interpreted by the interface polarization, and ionization or displacement of oxygen vacancies, respectively. The data of complex impedance combined with XPS results further proved that internal barrier layer capacitor (IBLC) effect is the dominant mechanism of colossal permittivity in AMTOx ceramics.

Dielectric Relaxation and Dielectric Switching Behaviors in (N,N-Diisopropylethylamine) Tetrachloroantimonate(III).

Dielectric switches have drawn renewed attention to the study of their many potential applications with the adjustable switch temperatures (Ts ). Herein, a novel antimony-based halide semiconductor, (N,N-diisopropylethylamine) tetrachloroantimonate ((DIPEA)SbCl4 , DIPEA+ =N,N-diisopropylethylamine), with dielectric relaxation behavior and dielectric switches has been successfully synthesized. This compound, consisting of coordinated anion chains and isolated DIPEA+ cations, undergoes an isostructural order-disorder phase transition and shows a step-like dielectric anomaly, which can function as a frequency-tuned dielectric switch with highly adjustable switch temperature (Ts ). Variable-temperature single-crystal structure analyses and first-principles molecular dynamics simulations give information about the general mechanisms of molecular dynamics. This work enriches the dielectric switch family and proves that hybrid metal halides are promising candidates for switchable physical or chemical properties.

Enhanced dielectric properties of the ZnO nanoparticles dispersed PU/PANI blend nanocomposites

Dielectric systems composed of conductive polymers and metal oxide nanoparticles become the most frontier hybrid materials to be used in various electronics for their superior dielectric characteristics and easy processibility. In the present study, the effects of conducting polyaniline (PANI) and Zinc Oxide (ZnO) nanoparticles on the dielectric characteristics like dielectric constant (ε′), loss factor (ε″), current permitting ability (σac), both real and imaginary impedance (Z′ and Z″), Nyquist plots, etc., have been explored. The prime objective is to explore the effect of ultra-low loading levels of ZnO nanoparticles on the significant improvement in the dielectric relaxation behavior. Prior to the dielectric analysis, the dispersion pattern of ZnO nanoparticles in the bulk of TPU/PANI phases has been analyzed from the microphotographs obtained from the field emission scanning electron microscopy (FESEM) as well as high-resolution transmission electron microscopy (HRTEM) analysis. The analysis of the frequency of the applied electric field's effects (1 to 106 Hz) on the dielectric characteristics shows that the produced hybrid materials may be used in a variety of applications. The variation of the aforesaid parameters with change in temperature is also explored which informs the suitability of the hybrid system in the manufacturing of high-temperature sensing applications. Significant improvement in the dielectric properties at 0.1 wt% loading level of ZnO is the novelty of this present analysis. The predominance of ε′ over ε′′ after a certain frequency of the applied field ensures the electric energy storing ability of the systems rather than energy loss. The reduced area under the Nyquist plot informs the approach of the system from an insulator to a perfect dielectric material that can be used in a capacitor for electric energy storage purposes.

The dielectric properties and relaxor behavior of gadolinium oxide modified barium zirconate titanate ceramics for Y5V capacitor applications

The dielectric properties and relaxor behavior of gadolinium oxide modified barium zirconate titanate ceramics for Y5V capacitor applications

Anomalous Phase Transition, Polarization Switching, and Relaxation in a Novel Composite Consisting of Dimethylammonium Aluminum Sulfate Hexahydrate and Oxidized Multiwalled Carbon Nanotubes

A novel ferroelectric composite consisting of dimethylammonium aluminum sulfate hexahydrate (CH3)2NH2Al(SO4)2·6H2O and oxidized multiwalled carbon nanotubes was developed to investigate its dielectric relaxation, phase transition, and ferroelectric switching behaviors. Experimental methods combined with theoretical analyses were employed. The results showed that the filler of oxidized multiwalled carbon nanotubes caused the freezing of domain-wall motion in (CH3)2NH2Al(SO4)2·6H2O at 98.2 K, leading to a decrease in dielectric constant, dielectric loss, and the polarization. In addition, an increase in dielectric permittivity and dielectric loss was found at higher temperatures. The role of hydroxyl groups incorporated in the carbon nanotubes after its oxidation was responsible for the obtained anomalies.

Optical, rheological, dielectric, and electrical properties of multiple oxides nanosuspended glycerol based semiconductor hybrid nanofluids

Semiconductor hybrid nanofluids (SHNFs) of multiple hybrid nano oxides (TiO2 + ZnO, TiO2 + Al2O3, TiO2 + SiO2, ZnO + Al2O3, and ZnO + SiO2) dispersed at fixed concentration (0.01 wt/wt%) in glycerol (Gly) fluid were prepared through solution mixing and probe ultrasonic cavitation process. These formulated SHNFs (i.e., TiO2 + ZnO/Gly, TiO2 + Al2O3/Gly, TiO2 + SiO2/Gly, ZnO + Al2O3/Gly, and ZnO + SiO2/Gly) were characterized by employing an ultraviolet–visible (UV–vis) spectrophotometer (wavelength range 200 – 800 nm), rheometer (shear rate range 1.32 – 5.28 s−1), and precision inductance–capacitance–resistance (LCR) meter (frequency range 50 Hz – 1 MHz). The dependency of UV–vis absorbance on the equal weight amount combinations of semiconductive and insulating nanosuspended hybrid oxides for these SHNFs was explored and analyzed for energy band gaps which showed strongly ruled by the wide band gap semiconductor TiO2 and ZnO materials. Dielectric permittivity, electrical conductivity, impedance, and electric modulus spectra of these SHNF materials were reported at 298.15 K and confirmed the influence of nanosuspended hybrids on the dielectric polarizations and relaxation behaviour. Dynamic viscosity and shear stress study with the shear rate explained the Newtonian behaviour of these SHNF materials. The multi-functionality of these novel SHNFs for the advances in soft condensed matter device/system technologies including optoelectronic, photovoltaic, UV-blocking, sensing, wavelength filtering, nanodielectric, electrical insulator, and thermal energy and mass transporter were demonstrated.

Anomalous Ca Content Dependence of Dielectric Properties of Charge-Ordered Pr1−xCaxMnO3 as a Signature of Charge-Ordered Phase Modulation

Low-temperature dielectric properties of charge/orbital-ordered manganite, Pr1−xCaxMnO3 for 0.40 ≤ x ≤ 0.50, was investigated systematically as a function of Ca content, x. The Ca content dependence of dielectric permittivity and dissipation factor exhibited distinct maxima near x~0.45. The overall dielectric response of charge-ordered Pr1−xCaxMnO3 was dominated by dielectric polarization induced by polaron hopping and exhibited thermally activated relaxation behaviour. The thermally activated dielectric relaxation behaviour over the investigated temperature range was further analysed with the help of two models: the small polaron hopping model and the Mott three-dimensional variable range hopping model. The estimated polaron transport parameters also displayed non-monotonic variation with x and exhibited a broad minima between x = 0.425 and 0.45. Considering the previous work reported so far, the charge order pattern of Pr1−xCaxMnO3 below x = 0.425 was most likely to be of Zener-polaron type, while near x = 0.50 was checker-board type and for in-between compositions; neither pure checker-board type nor pure Zener-polaron type can be considered a ground state. The observed results suggest that a modulation of the checkerboard-type charge/orbital ordering pattern in Pr1−xCaxMnO3 possibly takes place in the Ca content range of investigation, 0.40 ≤ x ≤ 0.50.

Influence of melt stretching process on POK dielectric properties and relaxation behavior

The dielectric properties and relaxation behaviors of POK films with different melt draw ratios were investigated. The dielectric constant of the sample increases to 11.1 (1 kHz) after melt stretching. The molecular chain orientation induced by melt stretching reduces the thermodynamic relaxation temperature, but the well-aligned lamellae restrict the movement of amorphous chains. The dielectric relaxation of the crystalline region and the amorphous region is inconsistent, and the dipole relaxation in crystalline region is obviously weaker than that of the amorphous region. After melt stretching, the activation energy of dipole motion perpendicular to the oriented molecular chains decreases, resulting in an increase in the dielectric constant of POK films with increasing melt stretching ratio.

High temperature dielectric relaxation and energy storage properties achieved in the CaZrO3–SrTiO3composite ceramics

We synthesized lead-free ([Formula: see text]CaZrO3–[Formula: see text]SrTiO3solid-solution ceramics and studied their structure, dielectric and energy storage properties. X-ray diffraction and scanning electron microscope reveal the microstructure of the samples. A high temperature dielectric relaxation behavior at the temperature ranges of 200[Formula: see text]C–550[Formula: see text]C is found for [Formula: see text], 0.5 and 0.7 samples. We explore that the origin of high temperature dielectric relaxation behavior is related to the migration of oxygen vacancies by Arrhenius law and oxygen treatment experiment. Moreover, with the increase of SrTiO3content, the 0.3CaZrO3–0.7SrTiO3exhibits high dielectric constant ([Formula: see text] at 1 kHz), low dielectric loss ([Formula: see text] at 1 kHz), good energy density ([Formula: see text] J/cm[Formula: see text] and high efficiency ([Formula: see text]%) simultaneously, and the possible causes of energy storage behavior dependence are analyzed in detail.