Ac Conductivity Studies Research Articles

Relaxation dynamics and conductivity in poly(vinylidene fluoride)/graphene oxide composites

The αc relaxation, which originates from the crystalline phase of Poly(vinylidene fluoride), is studied in the composite system of Poly(vinylidene fluoride) and Graphene oxide. PVDF/GO composites were prepared using solvent casting. The crystalline phases in PVDF/GO composites were identified using XRD and quantified using FTIR. The thermal properties were analyzed using DSC, and the crystallization degrees were calculated. The electric modulus formalism is employed to understand the relaxation mechanism with temperature. AC conductivity studies reveal the activation energy for conduction in these composites.

Systematic investigation of the influence of magnetic and non-magnetic ion substitutions in BiFeO3 under similar internal chemical pressure

Polycrystalline Bi1-xRxFeO3 (RHo and Y, x = 0.00, 0.05 and 0.10) compounds were prepared to perform a systematic investigation of the role of chemical nature and effect of internal chemical pressure on the structural, microstructural, magnetic, electric, ferroelectric and optical properties of the compounds. Structural analysis revealed that lattice distortions observed in Ho and Y-substituted compounds were not the same. The lattice parameters were larger in the case of the Y-substitution compared to the Ho-substituted counterpart. Scanning electron micrographs confirmed the formation of dense, well-connected grains exhibiting a reduction in size with increasing substitution. The magnetic properties of BiFeO3 were enhanced through the suppression of the spin structure with the substitution. The substitution of magnetic (Ho3+) ions led to an improvement in remanent magnetization and coercive field, whereas the substitution of non-magnetic (Y3+) ions resulted in enhanced maximum magnetization with negligible coercive field at room temperature. The ferroelectric measurements evidenced that both remanent polarization and coercive fields improved in substituted compounds, attributed to a decrease in charge carriers. Furthermore, the Y3+ ion substitution positively influenced ferroelectric properties by reducing leakage currents compared to the Ho3+ ion substitution. The optical absorption measurements indicated a decrease in the energy band gap of BiFeO3 with substitution, implying alterations in the material's optical characteristics. The ac conductivity studies demonstrated a discernible reduction in the conductivity of the substituted compounds. Specifically, Ho-substitution exhibited a more pronounced magnitude in the decline in conductivity relative to Y-substitution. This outcome signifies the potential efficacy of Ho-substitution in exerting control over the insulating characteristics of the compounds.

Defect tuning and its effect on conductivity, dielectric properties of combustion derived nano CeO2: A fuel dependent approach

Oxalyldihydrazide (ODH) and coffee extracted fuel (CEF) were used to synthesize Ceria (CeO2) nanoparticles by solution combustion synthesis route. The cubic fluorite structure, crystalline nature, crystallite size and particle size of ceria nanoparticles were confirmed using the powder X-ray diffraction (PXRD) and High-Resolution Transmission Electron Microscope patterns respectively. Field Emission Scanning Electron Microscope (FESEM) images were used to understand the Surface morphology of the synthesized samples. Based on XRD results the volume of coffee husk extract for the optimum phase formation is found to be 40 mL. The fluorite structure of the samples and the presence of oxygen vacancies in the samples were confirmed from the Raman spectral analysis. ESR (Electron Spin Resonance) studies confirmed formation of relatively more intrinsic defects in CEF-ceria nanoparticles compared to ODH-ceria nanoparticles. The semiconducting nature of the synthesized samples was confirmed by analysing UV–visible absorbance spectra. The functional group confirmation was obtained by analysing Fourier Transform Infrared (FTIR) spectra of both the samples. AC conductivity and dielectric relaxation studies of the samples in pellet form were carried out over a wide frequency (20Hz–10 MHz) and temperature (200–640 °C) range using a precision impedance analyser. A higher value of dielectric constant was observed for CEF-ceria nanoparticles.

Dielectric Properties and AC Conductivity Studies in PEDOT-PSS/EG/GO Composites with Ultrahigh Permittivity

Dielectric Properties and AC Conductivity Studies in PEDOT-PSS/EG/GO Composites with Ultrahigh Permittivity

Synthesis and Characterizations of BiFeO3 Nanoparticles for Photocatalytic Application

AbstractBismuth ferrite (BiFeO3) nanoparticles were synthesized using sol‐gel method and annealed at 450 °C, 550 °C, 650 °C, and 750 °C for 2 hours. The role of annealing temperature on structural, optical, magnetic, and dielectric properties of BiFeO3 nanoparticles was studied. XRD patterns of BiFeO3 nanoparticles confirm the rhombohedral structure with a mean crystallite size of 40 nm. The optical bandgap of the BiFeO3 nanoparticles increased from 1.9 eV to 2.02 eV with annealing temperature. From photoluminescence spectra, it was observed that the BiFeO3 nanoparticles showed a clear emission peak at 565 nm and its intensity decreased with annealing temperature. Magnetic properties of the BiFeO3 nanoparticles were studied at room temperature and different magnetic behaviours were found in BiFeO3 nanoparticles. The BiFeO3 nanoparticles exhibited ferromagnetism at low annealing temperatures and diamagnetic nature at high annealing temperatures. The AC conductivity studies showed that BiFeO3 nanoparticles possess a dielectric constant of 170 with the least dielectric loss. The BiFeO3 nanoparticles annealed at 750 °C were studied for photocatalytic properties and showed good photocatalytic activity in the visible region. A prominent absorption peak at 663 nm in absorption spectra due to MB and it confirm the utility of BFO as photocatalyst applications.

Probing of CoO-induced nano-sized defects in Li2SO4–MgO–P2O5 glasses: Insights from positron annihilation lifetime spectroscopy

This study investigates the influence of CoO doping on concentration and characteristics of nano-sized cavities in Li₂SO₄-MgO-P₂O₅ glasses using positron annihilation lifetime spectroscopy (PALS). These defects are known to significantly impact the physical properties of glasses. Glasses with compositions of 20 Li₂SO₄-20MgO-(60-x) P₂O₅: x CoO (0 ≤ x ≤ 1.0 mol%), were prepared using melt-quench technique. PALS analysis revealed a strong dependence of positronium (e⁺- e⁻ pair) lifetime on CoO concentration. The analysis of the results further indicated that the fraction of free volume Δf/f0) and cavity radius (R) reached minimum values between 0.6 and 0.8 mol% CoO, but increased with further CoO doping. This suggests that cobalt ions prefer Oh sites, act as network modifiers, and create a larger concentration of free volume defects when CoO is increased beyond 0.8 mol%. Notably, the PALS-derived free volume defect concentration with CoO concentration is found to follow nearly same trend exhibited by the results of optical absorption and AC conductivity studies.

A Comprehensive Study of Cerium-Modified Bi2FeMnO6 Double Perovskite: Synthesis, Structure, Properties and Applications

This paper presents a detailed synthesis method by solid-state reaction route and typical characterization (structural, microstructural, dielectric, impedance, modulus, and optical properties) of a double perovskite material Bi2FeMn[Formula: see text]Ce[Formula: see text]O6. An orthorhombic crystal structure having an average crystallite size of 32.2[Formula: see text]nm is suggested by X-ray diffraction data (XRD). Scanning electron microscope (SEM) micrograph detects the presence of cylindrical nanorod-shaped distinct grains and well-defined grain boundaries in this material and the average grain size is 5.82[Formula: see text][Formula: see text]m. Furthermore, the purity and the presence of all constituent elements in the material were confirmed from energy dispersive X-ray (EDX) analysis and color mapping. Dielectric, impedance, modulus, and AC conductivity properties are studied within the temperature range of 25–500∘C and frequency range of 1[Formula: see text]kHz to 1[Formula: see text]MHz. The high dielectric constant at a low-frequency zone and low dielectric loss found in this material make it a promising candidate for better energy-storing devices. The negative temperature coefficient of resistance (NTCR) behavior is observed from the impedance study. The non-Debye relaxation is detected in the modulus study. The semiconducting nature of this material is verified by semicircular arcs observed in both Nyquist and Cole–Cole plots. The thermally activated conduction mechanism is confirmed by an AC conductivity study. The existence of Bi–O, Fe–O, Mn–O and Ce–O stretching vibrations are observed from the FTIR study and explain the presence of all constituent elements in the sample. The bandgap energy of 1.7[Formula: see text]eV is calculated from UV-DRS analysis and hence this material can be used for advanced optoelectronic and photovoltaic applications.

Effect of doping and preparation parameter on AC conductivity and dielectric modulus formalism of Al doped DLC thin films

Here, we report the composite effect of aluminum doping on the dielectric response of Diamond-Like Carbon (DLC) thin films. In addition, the contribution from preparation parameters like acetylene flow rate is also considered to understand sample behavior. AC conductivity study shows the existence of a nonlinear increase of conductivity with frequency leading toward the Jump Relaxation Model (JRM). The transition frequency (ft) is observed, which increases with conductivity. The study reveals that dielectric response is influenced by space charge conductivity, prompting us to adopt the modified Debye law. Deviation from ideal Debye behavior is also confirmed in dielectric modulus analysis. The deviation is frequency-dependent, and a higher deviation is observed in the high-frequency region. Plotting of the Master curve shows the presence of different relaxation dynamics in different samples. A current-voltage (I-V) study of different samples is also undertaken, showing higher values (greater than unity) of the ideality factor.

Investigation of AC and DC Electrical Conductivity in Ethyl Cellulose (EC) and Poly Methyl Methacrylate (PMMA) Polyblends

The study of AC and DC electrical conductivity is crucial for understanding the behavior of charge carriers within materials and their mobility. Ethyl cellulose (EC) stands out among cellulose ethers due to its favorable electrical, mechanical, and weathering properties. Poly Methyl Methacrylate (PMMA) is a thermoplastic known for its rigidity, transparency, and outdoor durability, making it a valuable material. Despite being insulating materials, both EC and PMMA exhibit limited free charge carriers and low mobility. In this research, AC and DC electrical properties of Ethyl Cellulose (EC), Poly Methyl Methacrylate (PMMA), and their blends doped with tetrahydrofuran (THF) film were investigated using isothermal evaporation techniques. The investigation focused on the effects of temperature, electric field, and frequency on electrical conduction mechanisms. Measurements were conducted across frequencies ranging from 1 KHz to 1 MHz at temperatures between 323 K and 373 K. Results indicate that AC electrical conductivity of Ethyl Cellulose (EC), Poly Methyl Methacrylate (PMMA), and their blend (EC/PMMA) increases with higher frequencies of the applied electric field. Meanwhile, DC electrical conductivity of Ethyl Cellulose (EC), Poly Methyl Methacrylate (PMMA), and their blend (EC/PMMA) rises with increasing temperature. X-ray diffraction (XRD) analysis further supports these conductivity changes in the blend.

Structural and temperature dependent dielectric behaviour of BxFe(3−x)O4 nanoferrite particles

AbstractThe auto‐combustion technique was employed to synthesize nano particles of BxFe(3−x)O4 (x = 0.0, 0.7, 1.18, 1.36 and 1.54). The resulting structural and dielectric properties of the boron doped Fe3O4 were evaluated. XRD analysis confirmed the presence of a single spinel structure with crystallite dimensions ranging from 21.18 to 26.43 nm and lattice parameters of 8.211 to 8.487 Ǻ. The morphological images revealed homogenous and spherical grain sizes, while EDX confirmed the presence of constituent elements used. The X‐ray density increased whereas the bulk density and the porosity decreased with boron substitution. The study of dielectric properties and AC conductivity (σAC) was demonstrated and the AC conductivity decreased with increasing boron concentration, indicating a hopping mechanism. Moreover, noticeable variations in dielectric loss, AC conductivity, and dielectric permittivity with temperature and frequency were observed. These observations were attributed to the Maxwell–Wagner interfacial polarization and the hopping of charges between Fe3+ and Fe2+ ions.

Microstructural and dielectric characteristics of the Ce-doped Bi\(_{2}\)FeMnO\(_{6}\)

A double-perovskite material Bi2FeMn0.94Ce0.06O6 (BFMCO) was synthesized by solid state reaction technique and characterized it by various techniques (structural, microstructural, dielectric, impedance and modulus properties). The material has an orthorhombic crystal structure with an average crystallite size of 52.4 nm, as revealed by X-ray diffraction data (XRD). The scanning electron microscope (SEM) image shows the presence of nano rod-shaped grains and well-defined grain boundaries in this material, with an average grain size of 21.8 µm. The Energy dispersive X-ray (EDX) analysis and color mapping confirm the purity and the composition of the material. The dielectric, impedance and modulus properties are investigated in the temperature range of 25℃ to 500℃ and frequency range of 1 kHz to 1 MHz. The material exhibits a high dielectric constant at low frequency region and a low dielectric loss, which make it a suitable candidate for better energy storage devices. The impedance study reveals the negative temperature coefficient of resistance (NTCR) behavior of the material. The modulus study indicates the non-Debye relaxation of the material. The semi-conducting nature of the material is verified by the semi-circular arcs observed in both Nyquist and Cole-Cole plots. Thermally activated conduction mechanism is confirmed from ac conductivity study.

Investigating the charge transport mechanism and dielectric properties in nickel oxide polyaniline nanocomposites

A simple precipitation method was employed to synthesise Nickel Oxide (NiO) nanoparticles and in-situ polymerization method was employed to synthesise Polyaniline (PANI) and PANI/NiO nanocomposites. To investigate the charge transport mechanism, DC and AC conductivity studies have been carried out. The drastic decrease in DC conductivity by two orders with an addition of NiO is noticed. Impedance and AC conductivity characteristics of these composites were examined in the frequency ranging from 10 Hz to 8 MHz. All samples obey Jonscher's Power law of disordered material at higher frequencies. The values of dielectric constant as well as dielectric loss decreased with an increase in applied frequency for all the samples. The samples show non-Debey relaxation mechanism verified by Havriliak – Negami model. Composite sample 5 wt % NiO show low tangent loss behaviour which are of importance in high frequency device applications. The obtained results are promising applications for energy storage applications and organic electronic devices.

Existence of monoclinic and tetragonal zirconia in MgO substituted alumina zirconia composites and studies of dielectric behavior

Magnesia stabilized zirconia-alumina composite were processed by auto-combustion method followed by solid-state sintering. Tetragonal zirconia with orthorhombic alumina phase has been ensured from XRD patterns and from Raman spectra. The optical band gap energy for 2%, 4% and 6% magnesium oxide substituted zirconia-alumina composites are 4.91, 5.03 and 3.48 eV, respectively. The dielectric behavior between the frequency range of 1 kHz–1 MHz shows frequency independent nature of dielectric constant with low loss tangent at various temperatures. The non-Debye type and grain-grain boundary effects were confirmed from Nyquist plot. Both PTCR and NTCR behavior were observed from AC conductivity study.

Effect of calcination temperature on structural, magnetic, and dielectric properties of Mg0.75Zn0.25Al0.2Fe1.8O4 ferrites

Based on the desire to improve material properties, the effects of temperature have begun to be investigated. It was found that for nano-sized powder materials, such as ferrites, the structural properties like crystal structure and grain size, as well as many magnetic and electrical properties depending on them, change with the calcination temperature. Considering these changes, the effect of calcination temperature on the structural, magnetic, and electrical properties of MZA ferrites (Mg0.75Zn0.25Al0.2Fe1.8O4) prepared by co-precipitation was investigated in this study. The produced MZA ferrites were calcined at three different temperatures (600, 700, and 800 °C). The X-ray diffraction results showed that the samples exhibited a cubic spinel structure. It was found that the crystal sizes (D_sch) calculated using the Debye-Scherrer equation increased with increasing calcination temperature (22.47, 33.53, and 42.53 nm). From the Williamson–Hall (W–H) plots, crystal sizes were calculated almost same as Debye–Scherrer crystal sizes. The nano-sized particles were examined by scanning electron microscope (SEM). Elemental analysis was performed using EDX. ν1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ u }_{1}$$\\end{document} and ν2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ u }_{2}$$\\end{document} absorption bands and O–H and C–H vibrations were detected in the FTIR spectra. Magnetic measurements were carried out at room temperature and in the range of ± 60 kOe under the applied field. Magnetic results are explained by superparamagnetism. Dielectric measurements were performed at room temperature and a frequency range of 20 Hz to 10 MHz. The dielectric properties can be explained by Maxwell–Wagner theory. Impedance spectroscopy study revealed that the relaxation mechanism is consistent with the Cole–Cole model. In AC conductivity studies at room temperature, it was found that the sample calcined at 600 °C would be suitable for energy storage devices.

Collegial effects of CeO2/SiC nano-fillers on dielectric, thermal, impedance and conductivity behavior of PVDF-HFP matrix for flexible energy storage applications

ABSTRACT In the current study, novel Poly(vinylidene fluoride-co-hexafluoropropylene)/Cerium oxide/Silica carbide (PVDF-HFP/CeO2/SiC) flexible polymer nanocomposites were synthesized by solution casting technique. Structural changes involved in the composite formation between nano-fillers and host polymers were analyzed by X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. SEM results confirm the homogeneous dispersion of nano-fillers (CeO2 & SiC) within the host polymer. Thermogravimetric analysis (TGA) was used to identify the thermal stability of the polymer nanocomposite with about 56% of residual residue for increased nano-fillers loading. Tauc plots confirm that the energy band gap of pristine host polymer decreased with the incorporation of nano-fillers. The dielectrics, impedance, and AC conductivity studies were investigated in temperature ranging from 50°C to 150°C and the frequency range between 50 Hz and 10 MHz measured by an impedance analyzer. As a function of nano-filler loading, the nanocomposites show a significant increase in the dielectric constant (ε′ = 272.92, 50 Hz, 50°C) with low dielectric loss (tan(δ) = 1.98, 50 Hz, 150°C) values. Impedance and the AC conductivity results suggested that addition of nano-filler decreases the impedance and improves the AC conductivity value from 1.67 × 10−4 S/m for pristine PVDF-HFP to 1.44×10−3S/m for 15% SiC. These results justify the material being efficiently applicable for flexible energy storage applications.

Dielectric Property, AC Conductivity, and Electric Modulus Studies of Pristine and Green‐Synthesized ZnO Nanoparticles

Frequency‐dependent dielectric constant and dielectric loss of pristine and green‐synthesized (using Tabernaemontana divaricata flower extract) ZnO nanoparticles (NPs) are studied at different temperatures. Below 1 kHz frequency and at temperatures above 100 °C, ZnO NPs have giant dielectric constant values (≈3 × 104). At lower frequencies and at/below 100 °C, the nature of temperature dependence of dielectric constant for pristine and green‐synthesized ZnO NPs are reversed, and this anomalous temperature dependence is correlated with the in‐plane and out‐of‐plane thermal expansions of ZnO. A temperature‐dependent poly‐dispersive relaxation mechanism in ZnO has been observed. The electrical conduction mechanism is found to be significantly modulated by the use of flower extract. The electric modulus study suggests similar mechanism of electrical conduction and dielectric polarization followed in these materials. A plausible growth mechanism of the ZnO NPs in presence of the flower extract is explored. Variations in the dielectric constant, dielectric loss, conductivity, and polarization mechanisms of the ZnO NPs are understood as signatures of the capping effect of the phytochemicals present in the flower extract on the crystal growth and formation of grain boundaries.

Studies of structural, dielectric and impedance spectroscopy of Bi4Ti2.8Sn0.2O12

The polycrystalline sample Bi4Ti2.8Sn0.2O12 was synthesized using the solid-state reaction method at 850 °C. The sample was formed in a single-phase orthorhombic structure and having space group B2ab, according to the XRD study at room temperature. The dielectric behaviors of the sample have been studied for the frequency range 1 kHz-1 MHz and a wide range of temperature 25-500 °C, which provide some important properties of the synthesized sample. The Nyquist plots provide the effect of grains and grain boundaries to the total resistance and capacitance of the synthesized compound. From ac-conductivity studies, various kinds of conduction mechanisms have been examined. The J–E characteristics support the Ohmic character of the prepared sample. The ferroelectric property at room temperature at frequency 50 Hz has been studied from polarization study.

Study of Structural, Dielectric, and Electrical Properties of Gadolinium-Modified Bismuth Lanthanum Oxide

In this article, synthesis (solid-state reaction) and characterization (structure, microstructure, and electrical) of the gadolinium (Gd) modified bismuth lanthanum oxide (LaBi0.9Gd0.1O3, and LBGO) are reported. Rietveld refinement of the x-ray diffraction (XRD) data was done using MAUD software, which adopts an orthorhombic crystal symmetry. The average crystallite size in the prepared sample was calculated using Scherer’s relation. Scanning electron microscope (SEM) micrograph analysis reveals that grains are uniformly distributed over the sample’s surface through well-defined grain boundaries so that a dense sample is formed, which may be a possible reason for elevated dielectric properties. The study of energy dispersive analysis of the x-ray (EDX) spectrum confirms the presence of all constituent elements (Bi, La, Gd, and O) in the studied sample. The presence of Maxwell–Wagner type of dispersion is confirmed from the study of dielectric properties as a function of frequency. The analysis of the modulus study confirms the presence of a non-Debye type of relaxation. The negative temperature coefficient of resistance (NTCR) nature of the sample is confirmed by the impedance study. The study of ac conductivity suggests the presence of a thermally activated relaxation process in the studied sample. Again, analysis of the Nyquist plots confirms the semiconducting character and may be suitable for some energy storage devices applications.

Structural and electrical characteristics of manganese modified BaTiO3 ceramic

The material Ba(Ti0.5Mn0.5)O3 synthesized through the conventional solid-state reaction method has hexagonal structure free from any impurity phase. The complex dielectric dispersion, temperature and frequency-dependent dielectric, impedance, AC conductivity, and leakage behavior of the sample are studied. The impedance study of the material encloses non-Debye type relaxation, negative temperature coefficient of resistance nature and the grain and grain boundary effects. The ferroelectric to paraelectric phase transition occurs at T C ∼ 270 °C. The dielectric constant and loss-tangent values are found to be less as compared to that of the parent barium titanate sample. R g < R gb, that is, grain boundary has greater opposition than the grain region. The material follows correlated barrier hopping model. The carrier transport process through AC conductivity study obeys the Jonscher’s power law and the Arrhenius relation while varying with the frequency and temperature.

Understanding role of cadmium substitution on thestructural, microstructural, transport properties of ferrites synthesized by different methods

The structural studies (XRD and SEM), the dielectric constant (??), dielectric loss (tan ? or ??), AC conductivity studies (?ac), and Cole-Cole plot studies are carried out for Co0.5Zn0.5Cd1.5xFe2-xO4 (Cd doped Co-Zn ferrites) with x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 series synthesized by co-precipitation (CPP) method and solid state reaction (SSR) method, and for Co0.5Ni0.5Cd1.5xFe2-xO4 (Cd doped Co-Ni ferrites) with x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 series synthesized by co-precipitation (CPP) method. The XRD confirms the cubic spinel structure of all the samples. The SEM images show the agglomeration of particles observed to be increasing with increase in Cd doping. The dielectric constant increased with Cd concentration. The dielectric constant is observed to be higher for samples prepared CPP method compared to SSR. Dielectric loss graphs have shown the resonance for certain frequencies. The AC conductivity increased with Cd doping. The samples prepared by CPP method shown lower AC conductivity compared to samples synthesized by SSR method. The Cole-Cole plots show the dual contribution of grain and grain boundaries in conductivity.