Complex Electric Modulus Research Articles

Correlated barrier charge hopping and non-Debye relaxation in columbite MnNb2O6

A comprehensive study on the mechanism of ac-charge transport and dielectric relaxation in the MnNb2O6 columbite system has been reported. Thermally driven, Arrhenius-like behaviour of the ac-conductivity is predominant at temperatures above 300 K in the frequency range 50 Hz–5 MHz with activation energies lying between 0.45 and 0.38 eV. Besides, a quadratically decreasing trend in the activation energy is evident as given by: = A + Bf + Cf 2 with the constants A (0.413 eV), B (0.023 eV Hz−1) and C (−0.004 eV Hz−2). The measured data is analysed using the Double power law to explain the dispersive behaviour of electrical conductivity. These studies also provide evidence for the correlated-barrier hopping (CBH) conduction mechanism of charge carriers for temperatures in the range 173–473 K. Further, the temperature dependence of frequency exponent, s(T) displays two distinct regions both of which are associated with the CBH mechanism with slopes K−1 and K−1 in Region-I (173–300 K) and the slope K−1 with non-linear variation of s 2 in Region-II (300–473 K). However, the second region is more dominated by thermally activated Arrhenius-like behaviour. The dynamical response of complex electric modulus spectra and the corresponding analysis using Kohlrausch-Williams-Watts method reveals the presence of a non-Debye type relaxation process with decay function exponent β lying between 0.794 and 0.840. This inference of the non-Debye type relaxation process is further supported by depressed semicircles in Nyquist plots and the higher magnitude of full width half maximum (FWHM) (≈1.44 decades) of the normalized master cusp vs compared to the FWHM ( = 1.14 decades) for ideal Debye behaviour. Both short-range and long-range conductivity regions are ubiquitous in with a pronounced distribution of relaxation times (s) with temperature. This study further leads to the estimation of activation energy of charge carriers, E M = 0.44 eV which is in consonance with .

Synthesis, structure, and improved frequency-dependent transport properties of copper doped zinc oxide nanoparticles at high temperatures

The nanostructures of ZnO are studied in this research utilizing a simple, eco-friendly, and cost-effective co-precipitation have a formula Zn 1 − x Cu ( x ) O with (x = 0.0, 0.03, 0.06, and 0.10). The effects of copper (Cu) doping on structure, morphology, impedance, dielectric, and electrical conductivity were investigated using an XRD, SEM, and LCR meter, respectively. All prepared samples have a hexagonal wurtzite structure, and the average crystalline size varies between 46 and 56 nm, according to the XRD spectra. Impedance measured data analyzes that a capacitance phase element perfectly modulates the fabricated samples with the equivalent circuits. Depending on the temperature, the examination of complex impedance and complex electrical modulus revealed a non-Debye types relaxation process. The Arrhenius plots for the conduction mechanism were used to investigate single activation energy. A correlated barrier hopping (CBH) model dominated the conduction process in un-doped and Cu-doped ZnO nanoparticles. The dielectric measurements in low-frequency at high temperatures regions exhibited high dielectric constant values for the prepared samples. Compared to undoped ZnO, the dielectric constant values increase with Cu concentration, also improving the ac conductivity of all Cu-doped ZnO nanoparticles, making them a suitable choice for energy storage applications. The electrical modulus displays a dual nature of relaxation times for all synthesized samples with lower values. • Pure ZnO and Cu-doped ZnO nanostructures have been fabricated using a Co-precipitation method. • The average crystalline size of ZnO and Cu-doped ZnO nanostructures lies at 46 nm to 56 nm. • The samples of pure and Cu-doped ZnO nanostructures showed negative temperature coefficient resistance (NTCR). • Dielectric and ac conductivity properties improved with the addition of Cu concentrations. • The Cu-doped ZnO nanostructures shall be beneficial for optoelectronics applications.

Electrical, Microstructural and Physical Characteristics of Talc-based Cordierite Ceramics

The aim of this work is to study the effect of various talc rocks for the preparation of talc-based cordierite ceramics. Raw talc and sintered cordierite-based ceramic samples (1000-1375ºC for 2 h) were characterized using XRD, XRF, TGA-DTG, laser PSDs, Archimedes method, SEM-EDAX and dielectric relaxation spectrometer (DRS). Results show that impurity oxide contents, particle size and mineralogical changes of green batches influenced the microstructure densification and crystallization of orthorhombic and hexagonal cordierite. The complex electric modulus plot shows the existence of two relaxation processes associated with the capacitive contribution grain boundaries and grain at low and high frequencies, respectively. The dielectric loss reached much lower values (0.0004–0.0007) for the ceramics composed of higher cordierite phase composition (87.00 to 92.00wt.%) that sintered at 1350 and 1375ºC. Such ceramics could be promising in electronic applications like capacitors, microwave devices and wireless communication.

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

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

Onset of vacancy-mediated high activation energy leads to large ionic conductivity in two-dimensional layered Cs2PbI2Cl2 Ruddlesden-Popper halide perovskite

We report the dielectric properties of a two-dimensional layered Ruddlesden-Popper halide perovskite ${\mathrm{Cs}}_{2}{\mathrm{PbI}}_{2}{\mathrm{Cl}}_{2}$ synthesized via a simple mechanochemical process to explore fundamental aspects of ionic conduction and relaxation mechanism over a wide temperature and frequency range. Several experimental techniques, such as complex impedance spectroscopy, alternating current (AC) conductivity spectroscopy, and complex electric modulus spectroscopy, have been employed to investigate the nuances of ionic conduction and relaxation mechanisms, and the results have been corroborated using different theoretical models, such as the Maxwell-Wagner equivalent circuit model, the modified Jonscher power law, the Havrilliak-Negami (HN), and the Kohlrausch-Williams-Watts (KWW) model. The contribution of the grains and grain boundaries to the total impedance in the system is estimated by the analysis of the Nyquist plots. In temperature-dependent AC conductivity spectra, a critical temperature (413 K) is observed, beyond which the conductivity increases abruptly. This critical temperature also defines two distinct temperature ranges: the low-temperature (303--413 K) and the high-temperature (423--463 K) regimes, where the ionic transport mechanism switches from the normal ionic transport to a vacancy-mediated ionic transport mechanism. A substantially high activation energy $\ensuremath{\sim}1.82\phantom{\rule{0.16em}{0ex}}(\ifmmode\pm\else\textpm\fi{}0.02)\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ is calculated from the Arrhenius plot of the ionic conductivity in the high-temperature region, while at the low-temperature region, the activation energy is found to be $\ensuremath{\sim}0.48\phantom{\rule{0.28em}{0ex}}(\ifmmode\pm\else\textpm\fi{}0.02)\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$. The abrupt jump in the ionic conductivity beyond the critical temperature is attributed to the onset of the anionic vacancy-mediated enhanced ionic conductivity. Polaronic models have been used to interpret the AC conductivity and its power-law exponent. The activation energy obtained from ionic conductivity measurements is consistent with those calculated from relaxation time using the HN and KWW models. The presence of two master curves in time-temperature superposition scaling of AC conductivity and modulus loss spectra specifies the validity of two different conduction mechanisms.

Investigation of the dielectric and optic properties of rosehip seed extract loaded hydrogels

Rosehip seed (RS) extract-loaded hydrogel samples RS1 (poly(AMPS-co-MBAAm), RS2 (poly(AMPS- co - CrA- co - MBAAm)), RS3 (poly(AMPS - co - MAA - co - MBAAm)) and RS4 (poly(AMPS -co - IA - co- MBAAm)) were prepared to examine their structural and optical properties. Furthermore, frequency and bias voltage evolution of dielectric and electrical parameters were analyzed using impedance spectroscopy (IS) for all samples at room temperature (RT). Fluctuating and self-consistent results were obtained in the Ultraviolet–visible (UV) spectrum of the samples. The conductivity mechanisms were determined by calculating the s parameters of all samples for different regions. The complex impedance, capacitance, phase angles, dielectric constant, tangent factor, electric modulus, and frequency variation of ionic conductivity for the rosehip seed loaded hydrogel were successfully analyzed in detail using IS in the broadband frequency range. The increase in ionic conductivity of the RS-doped hydrogel with increasing frequency was attributed to its ability to exhibit the Langevin equivalent of Brownian motion in viscoelastic fluids, surface/bulk Maxwellian stress relaxation behavior, and the validity of the Stokes-Einstein relationship in biological fluids. In particular, the capacitive effect observed as a result of the Cole-Cole diagrams of the dielectric constant adapting to Smith Chat and the equivalent RC circuit allowed the material to be used as a capacitor.

Pechini citrate-gel synthesised In3+ substituted X-type barium zinc hexaferrites: An investigation on structural, optical, magnetic and dielectric properties

Indium substituted X-type Ba2Zn2InxFe28-xO46 (0.0≤x≤2.0) ferrites were synthesised by a citrate-gel aqueous combustion technique, and heated at 1300 °C. XRD, FTIR, SEM with EDX, magnetic hysteresis, Mössbauer spectroscopy, UV–visible spectroscopy, and dielectric measurements up to 20 GHz have been carried out to study the modification of the structural, morphological, magnetic, optical and frequency dependant dielectric properties when indium is introduced, replacing iron in the lattice of X-type hexaferrites. XRD analysis reveals formation of a major X-type phase in all compositions. The systematic rise in lattice constants (a, c) along with cell volume (V) confirm the replacement of iron by indium. Magnetic hysteresis loops reveal a soft ferrite nature with low Mr/MS values, suggesting a multidomain structure in all samples. The HC values decrease from 22.22 kA m-1 to 12.18 kA m−1 (279 Oe to 153 Oe) with increasing indium, while magnetisation remained high between 56 A m2 /kg and 62 A m2/kg for all samples. Room temperature Mӧssbauer spectra of all samples were fitted with six Zeeman sextets of five different magnetic sublattices. It was ascertained that In-substitution reduces the Fe population in the k (spin up) sublattice, resulting in a reduction in magnetisation. The average hyperfine magnetic field <Hf> is also reported to decrease with Indium substitution for all samples. The value of the isomer shift (δ) confirmed that the iron-ions are in high spin Fe3+ state. The complex impedance and electric modulus plots reveal non-Debye type relaxation in all samples at 100 Hz to 2 MHz.

Ag-Doped Cu2Se: Tunability of Structural, Optical, and Electrical Properties

A successful synthesis of high-purity Cu2−xAgxSe nanopowders (x = 0.03, 0.06, and 0.0.9 mole) was realized through a direct fusion approach. The XRD measurements uncovered the existence of two phases in the Cu2−xAgxSe nanopowders with dominant orientation along the(101) plane.The (101) reflection displayed a monotonical shift towards 2θ angles due to small disfigurement of unit cell originating from the replacement of Cu with Ag. The optical parameters such as absorption coefficient (α), energy band gaps (Eg), extinction coefficients (k), and the refractive index (n) were thoroughly investigated. The values of the energy band gap were found to be 0.78 to 1.5 eV. The increase in the band gap may be due to the decrease in grain size, or the increase in strains. Scanning and transmission electron microscope (SEM) and TEM were used to investigate the morphology of the samples. Cu0.97Ag0.03Se exhibits distinguishable particles and a clear grain boundary, while Cu0.91Ag0.09Se exhibits particles with tetragonal and monoclinic shapes, which supported the presence of two phases-tetragonal CuAgSe and monoclinic −Cu2Se-found in the XRD data. The presence of Ag, Cu, and Se was confirmed by the energy-dispersive X-ray analysis (EDAX). The dielectric characteristics, ac conductivity, and the complex electric modulus were investigated in the frequency range from 0.1 Hz to 10 MHz at temperatures 30 °C and 150 °C.

Microstructure, electrical, optical and electrochemical characteristics of silver phosphate glasses cathode for magnesium battery applications

The realization of a practical magnesium battery is combined with the development of a high kinetic cathode and compatible electrolyte to facilitate the redox process. For this reason, silver phosphate glasses in the binary system (Fe2O3–AgPO3) are prepared using the conventional quenching method. The glasses were defined in the form [Fe2O3] x [AgPO3](100−x) and the composition with 0 ⩽ x ⩽ 40 wt. %. The molar volumes and densities were measured. These glass systems were characterized using x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV–Vis–NIR spectrophotometer, electrochemical procedures and impedance spectroscopy. X-ray diffraction revealed that pristine AgPO3 sample was formed in a glassy state, whereas two crystalline phases (AgFeP2O7 and Fe2O3) were formed after the incorporation of Fe2O3 by different concentrations. Bond assignments associated with different functional groups were investigated by an FT-IR spectroscopy. The values of the band gap were decreased with the increase of Fe2O3 content. The effect of grains and grain boundaries in a heterostructure made up of Fe2O3 and AgFeP2O7 crystallites grown in silver phosphate glasses was studied using impedance spectroscopy. The complex impedance, electrical conductivity, and complex electric modulus were measured in terms of frequency and temperature dependency in [Fe2O3] x –[AgPO3](1−x). In the studied glass systems, non-Debye relaxation was observed. Under a variable regime, σ ac conductivity follows a modified Jonscher’s law Arrhenius fitting of multiple relaxation processes in the material yielded activation energy of (0.12 eV–0.271 eV) which support a Maxwell–Wagner relaxation model in the heterostructure glasses at high temperatures and low frequencies. The dc conductivity decreases with iron rate and follows the Arrhenius law with very low activation energy (0.12–0.27 eV. Mg//electrolyte//Glass coin cells are assembled and show an initial discharge capacity of up to ∼564 mAh g−1. These materials are attractive for application in modernistic electrochemical devices because of their great compositional and preparation variety which enables tuning the types and techniques of electrical conduction in the material.

Enhanced the structural, optical, electrical and magnetic properties of PEO/CMC blend filled with cupper nanoparticles for energy storage and magneto-optical devices

Nanocomposite samples of polyethylene oxide (PEO) and carboxymethyl cellulose (CMC) blend filled with different concentrations of cupper nanoparticles (Cu NPs) were prepared via the casting route. The components of the blend were miscible as shown by the X-ray diffraction (XRD) and FTIR measurements. Transmission electron microscope (TEM) image showed that the Cu NPs have diameters in the range from 4.09 to 19.65 nm. Fourier transform infrared (FTIR) spectra showed the complexation between polymeric matrix and Cu NPs through the formation of hydrogen and coordination bonds. Ultraviolet/visible (UV/vis.) spectra showed an improvement in the optical features for the filled samples. The scanning electron microscope (SEM) micrographs indicted the smooth and homogeneous surface of nanocomposite samples, reflecting the homogeneity of this blend that was affected after the filling process. The differential scanning calorimetry (DSC) curve displayed that the pure blend had a single glass transition temperature (Tg), indicating that the blend components were miscible. Also, DSC exhibited an improvement in the thermal stability of the polymeric matrix after the addition of Cu NPs. The AC conductivity was increased with increasing content of Cu NPs. The highest value of AC conductivity for the pristine sample was 4.57 × 10−8 S/cm at 20 MHz that was increased to 3.71 × 10-6 S/cm for nanocomposite (1.60 wt % Cu NPs) at room temperature due to the increase of charge carrier number. The complex permittivity (ε*) and electric modulus spectra were also studied. At high frequency, the decreasing trend of permittivity was attributed to dipoles orientation. The VSM studies of filled samples depicted the hysteresis loops of the ferromagnetic characteristics. These results denote that PEO/CMC/Cu NPs films can be used in electromagnetic components, energy storage devices as well as in magneto-optical fields.

Effect of Ag2S on electrical conductivity and dielectric relaxation in Ag2O-MoO3-P2O5 ionic glassy systems

The influence of Ag2S incorporation on the electrical and dielectric properties of the host Ag2O-MoO3-P2O5 glassy matrix has been systematically studied in the present communication. By applying the well-known Archimedes principle, the density of the samples has been determined. The ionic property for all the as-prepared glassy systems has been explored methodically. The nearly identical obtained values of the crossover frequency and the activation energy for DC and AC conductivity suggest that the same mechanism is responsible for electrical conduction. For the purpose of inspecting the frequency and temperature dependent AC conductivity, the Almond-West formalism model has been used. The observed values of dielectric constant and dielectric loss are found to increase with the temperature rise and drop with rising frequency. The coinciding scaled complex electric modulus spectra suggest a non-Debye type dynamical relaxation mechanism, which also indicates that the relaxation mechanism is temperature independent but composition dependent.

Complex impedance, dielectric constant, electric modulus, and conductivity analysis of Cd doped ZnO nanostructures at high temperatures

Cd-doped zinc oxide (ZnO) nanostructures with a standard formulation Z n ( 1 − x ) C d x O (x = 0%, 3%, 6%, and 10%) were fabricated by a co-precipitation technique. The structural and morphological analyses were studied using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The Study of x-ray diffraction investigation indorses the existence of a wurtzite structure with a P 6 3 mc space group in all the samples. Impedance spectroscopy, dielectric measurements, and electrical conductivity at different temperatures of 300–460 K with a frequency range from 20 Hz to 2 MHz were performed using an impedance LCR meter. The complex impedance spectrum ( Z ´ ´ v s Z ´ ) for all samples were fitted with a parallel bulk resistance ( R b ) and capacitance ( C b ) combination circuit. The results of the dielectric measurements indicate that the parameters ε ´ , ε ´ ´ , and tanδ are reduced with the increasing frequency and increase with temperature. The complex electric modulus plots ( M ´ , M ´ ´ ) with frequency have explained the non-Debye type of relaxations mechanism due to interfacial and depolarization. The variation of ac ( σ a c ) conductivity with Cd concentration indicates a gradual increase because the impedance values with Cd-doped decrease. It is confirmed that the activation energies decrease with the doping of Cd concentration. Moreover, ac conductivity was then investigated by Jonscher's power law. Finally, the temperature-dependent exponent s fitted well with the correlated barrier hopping (CHB) conduction. • Cd-doped ZnO nanoparticles with different concentrations were fabricated by the co-precipitation method. • XRD studies revealed the incorporation of Cd into ZnO lattice. • Nyquist plots suggested the negative temperature coefficient of resistance behaviour. • The influence of Cd-doping on the electrical behaviour of ZnO was reported.

Structural, morphological, dielectric behavior and AC conductivity of GaxFe(3-x)O4

GaxFe(3-x)O4 (x = 0.0, 0.04, 0.1 and 0.4) are synthesized by auto combustion method and the structural, morphological and the dielectric properties with Ga3+ ion substitution in Fe3O4 are studied. Dielectric loss (tanδ), real (ε') and imaginary (ε'') portions of dielectric constant, AC conductivity (σAC), real (Z') and imaginary (Z'') portions of impedance, real (M') and imaginary (M'') portions of electric modulus, complex electric modulus (M*) and quality factor are evaluated with frequency (20 Hz to 10 MHz) and temperature (27OC – 500 °C) using impedance analyzer. AC conductivity (σAC) decreases with Ga3+ ion substitution that can be advocated on hoping mechanism. The dielectric loss (tanδ), dielectric permittivity (ε), AC conductivity (σAC) w.r.t. temperature and frequency could be described with Maxwell-Wagner’s interfacial polarization and hopping mechanism of ferro (Fe2+& Fe3+) ions. Variation in Cole-Cole plots exhibit decrease in electrical resistivity with temperature rise. The Nyquist plots exhibit an inherent phenomenon of conduction mechanism of Ga3+ ion substituted Fe3O4.

Dielectric response of a hybrid nanofluid containing fullerene C60 and iron oxide nanoparticles

Dielectric nanofluids based on transformer oil and magnetic nanoparticles are attractive due to the controllability of their physical properties by magnetic fields. Fullerene-based nanofluids often exhibit superior dielectric performance. In this study, we combine both iron oxide and fullerene nanoparticles into a transformer oil-based hybrid nanofluid. Using the method of dielectric relaxation spectroscopy, we examine the dielectric response of six samples with different fullerene-magnetic nanoparticle concentrations in the frequency range 0.1 mHz – 10 kHz. The study reveals that the dielectric response of magnetic nanoparticles dominates the dielectric spectrum of the hybrid nanofluids. The spectrum is characterized by a low-frequency Debye-like relaxation process associated with the interfacial polarization mechanism. The process is analyzed in the complex permittivity, electric modulus, and impedance plane. A logarithmic increase in relaxation times is observed with a linearly increasing concentration of fullerenes. The hybrid nanofluid with the highest fullerene concentration of 0.03 %w/V shows the lowest dielectric losses at the mains frequencies. When magnetic nanoparticles are absent, the dielectric spectrum of the fullerene nanofluid resembles that of the pure transformer oil. Around the mains frequencies, the dielectric losses of nanofluid containing only 0.01 %w/V of fullerene have been found lower than those of pure transformer oil. The complex impedance analysis revealed that the electrical conductivity of the hybrid nanofluids has a purely unidirectional character.

A high-k Cu-doped ZnO film formed via Ga-ion implantation: The acceptor-donor co-doping approach

Dielectric thin films having high permittivity (high-k) and low dielectric loss is essential for developing high performance capacitive devices like metal oxide field effect transistor or thin film transistor. Ga ion implantation performed on Cu-doped ZnO film fabricated by pulsed laser deposition with optimized doping concentrations and post-implantation annealing yielded film having high permittivity and low dielectric loss (ε = 87 and tan δ = 0.17 at the frequency of 1 kHz). Moreover, the permittivity exhibits good stability over a wide range of frequency from 20 Hz to 10 MHz. The high-k film was characterized by detailed dielectric studies, including frequency dependence of permittivity and dielectric loss, complex electrical modulus analysis, impedance spectroscopy and ac conductivity. The enhancement of the permittivity was attributed to the correlated potential barrier hopping of electrons between the neighboring acceptor-donor defect complex states in the band gap created by the co-doping, thus acting as electric dipoles polarizing the film. This work opens up future possibility for ‘dielectric engineering’. The three-dimensional dielectric spatial profile can be controlled via the selective area ion implantation with the depth controlled by the ion implantation energy. • A high-k Ga-Cu co-doped ZnO film formed via pulsed laser deposition and ion implantation method. • Optimized doping concentrations yielded high permittivity and low dielectric loss (ε=87 and tan δ=0.17 at 1 kHz). • Enhancement of permittivity was attributed to the correlated barrier hopping of electrons between neighboring defect complex.

Improving the electrical properties of poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene] by doping with camphor sulfonic acid for energy storage applications

This study examines a wide range of spectroscopic, structural and electrical properties of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/camphor sulfonic acid (CSA) composites. Incorporation of CSA into the polymer matrix is confirmed by FTIR, UV, PL, scanning electron microscope, and atomic force microscopy results, also DC conductivity analysis shows that it affects the electric nature of the polymer differently from linear change. On the other hand, when the frequency-dependent electrical properties are evaluated, it is seen that MEH-PPV composite with the highest CSA contribution stands out for energy storage applications compared to pure MEH-PPV with increased ε ′ and reduced ε ′ ′ values. Moreover, the electrical modulus analysis showes that the increased CSA contribution contributed to the long-range mobility of the charge carriers. Furthermore, Cole-Cole curves are drawn in the complex electric modulus plane both confirm a non-Debye type relaxation and support the existence of Maxwell–Wagner type polarization in the samples.

Structural and dielectric properties of Sr4Zn2Fe36O60 U-type hexaferrites with optimized Gd contents and sintered by a two-step process

The structural and dielectric properties of Gadolinium substituted U-type hexaferrites (Sr4Zn2Fe36O60) were investigated. The samples were synthesized via the Sol-gel auto combustion route. In a muffle furnace, these samples were sintered for 5 h at 1250 °C. The pellets of synthesized powder samples were characterized by XRD, PL, Dielectric, FTIR, and Raman spectroscopies. Structural elucidation of Sr4Zn2Fe36-xGdxO60 was done via XRD. The obtained XRD patterns were matched with the prior literature. The impact of Gd3+ substitutions was measured on all the lattice parameters. Lattice constants “a" and “c" were found between 5.871 and 5.900 Å and 111.76–112.23 Å, respectively. The PL spectra of Sr4Zn2Fe36-xGdxO60 demonstrated multiple emissions in the range of 630 nm–700 nm, and by analyzing PL spectroscopic results, a bandgap of 1.8742 eV was found for the un-doped sample. Many dielectric parameters, i.e., Dielectric constant (ε'), Dielectric losses (ε''), Loss tangents (tanδ), Complex electric modulus (M' & M″), and A.C conductivity (σac) were investigated at room temperature by changing the frequencies from 1 GHz to 6 GHz. The varying trends of dielectric parameters were analyzed with the assistance of the Maxwell-Wagner model. Various absorption bands were observed in the range of 500–4000 cm−1 by plotting the FTIR spectroscopic results of Sr4Zn2Fe36-xGdxO60. Raman spectra demonstrated a combination of strong and fragile peaks in 1–1800 cm−1. The obtained results of various spectroscopies suggested that the prepared materials can be used extensively for different Micro-Wave attenuation purposes.

Correlation between small polaron tunneling relaxation and donor ionization in Ga2O3

Pulsed laser deposition is employed to fabricate as-grown amorphous and post-growth annealed crystalline β-Ga2O3 films. The films annealed at temperatures above 600 °C are found to exhibit a pure monolithic phase with a bandgap of 4.7 eV. The thermally activated donor ionization and dielectric relaxation of these films are systematically investigated by temperature-dependent DC and AC conductivity measurements, and complex electric modulus analysis. A donor level at ∼180 meV below the conduction band edge and a small polaron tunneling (SPT) relaxation with an activation energy of ∼180 meV are observed in the as-grown amorphous Ga2O3 film but not in the monolithic β-Ga2O3 film. The SPT occurs between donor sites with its thermal relaxation of polarization being associated with the thermal ionization of the donor state. Thermal annealing of the amorphous films removes the 180 meV donors as well the corresponding SPT relaxation.

Dielectric Spectroscopy and Electric Modulus Analyses of Ti0.8O2 Nanosheets‒Ag Nanoparticles‒Cellulose Filter Paper Composites

We employ dielectric spectroscopy and the complex electric modulus formalism to characterize electrical properties of the Ti0.8O2 nanosheets‒Ag nanoparticles‒cellulose filter paper composites, intended for use as a triboelectric nanogenerator. The addition of these fillers (5–17 atom% Ti and 1–6 atom% Ag) increases both the dielectric permittivity and AC conductivity while typically keeping the low loss tangent. The observed exponent to the frequency-dependent universal power law indicates the three-dimensional (3D) hopping mechanism in the composited films, contrasting with the 1D- or 2D-conduction in the ceramics. The electrical responses are also distinct from those of sole nanosheets, indicating some filler-matrix interactions. Electric modulus analyses indicate that the Ti0.8O2 nanosheets act as a charge generation/reservoir, while the Ag nanoparticles generate long-range conduction paths. The relaxation time increases with the dielectric nanosheets content but decreases with metallic nanoparticle content. In addition, these co-fillers decrease the dielectric heating but increases the refractive index of the films. The simple analyses reported herein could be applied to other composites, providing a better understanding on the role of diverse functional co-fillers.

Impact of Charge Transfer Complex on the Dielectric Relaxation Processes in Poly(methyl methacrylate) Polymer.

The impact of the charge transfer complex on the dielectric relaxation processes in free poly(methyl methacrylate) (PMMA) polymer sheets was investigated. The frequency dependence of dielectric properties was obtained over the frequency range 0.1 Hz–1 MHz at temperatures ranging between 303 K and 373 K for perylene dye and acceptors (picric acid (PA) and chloranilic acid (CLA)) in an in situ PMMA polymer. The TG/dTG technique was used to investigate the thermal degradation of the synthesized polymeric sheets. Additionally, the kinetic parameters have been assessed using the Coats–Redfern relation. The dielectric relaxation spectroscopy of the synthesized polymeric sheets was analyzed in terms of complex dielectric constant, dielectric loss, electrical modulus, electrical conductivity, and Cole–Cole impedance spectroscopy. α- and β-relaxation processes were detected and discussed. The σ(ω) dispersion curves of the synthesized polymeric sheets show two distinct regions with increasing frequency. The impedance data of the synthesized polymeric sheets can be represented by the equivalent circuit (parallel RC).