Ac Conductivity Measurements Research Articles

Dielectric, conductivity relaxation, conduction mechanisms and thermal behavior in 2-D Ruddlesden-Popper manganese bromide perovskite hybrid

Powder X-ray diffraction of [NH3(CH2)7(NH3)]MnBr4 perovskite hybrid crystallizes in the triclinic system with space group P‾1. Five phase transitions are identified by differential scanning calorimetric technique. Dielectric and AC conductivity measurements, in the temperature range (300–400) K and frequency range (0.06 kHz– 60 kHz) are in good agreement with DSC phase transitions. Proton conduction and bromide ion migration predominates in the intermediate and high temperatures respectively. The frequency dependence of the conductivity was fitted according to super-linear power law. Conduction mechanism is different in the different phases, (OLPT) and (NSPT) tunneling dominate in the temperature range (300–334) K, whereas correlated barrier hopping (CBH) is the mechanism at higher temperatures, with different carrier binding energies (Wm) for the different phases.

Typical superparamagnetism with improved electrical properties of nano modified bismuth ferrite multiferroic composites

Multiferroic composites with the chemical formula, (0.5) BiFeO3 + (0.5) Ni0.5Zn0.5Fe2O4, in bulk and nano forms were synthesized by preparing bismuth ferrite (BiFeO3 or BFO) in bulk (B) and nano (N) forms and nickel zinc ferrite (Ni0.5Zn0.5Fe2O4or NZFO) in nano form. Single phase BFO was synthesized using conventional solid-state reaction as well as sol-gel autocombustion methods and NZFO powders were prepared by using sol-gel autocombustion method, respectively. X-ray diffraction (XRD) studies reveal the existence of rhombohedrally distorted perovskite structure for BFO and cubic spinel phase for NZFO in single phase as well as composite samples. Microstructural studies and energy dispersive spectroscopy (EDS) data reveal the formation of grains, intergranular porosities and chemical purity of the synthesized samples. Dielectric and AC conductivity measurements confirm the existence of space charge polarization along with the small polaron model in these composites. Ferroelectric and magnetic studies show that there was a considerable enhancement in the ferroelectric and magnetic orders for the nano form of the BFO (N) + NZFO composite. The observed remnant polarization values 2.80388 & 7.75901 μC/cm2, saturation magnetization values 37.96072 & 40.47491emu/gm for bulk BFO (B) + NZFO and nano BFO (N) + NZFO composites, respectively. Interestingly, both the samples exhibit superparamagnetic behaviour at room temperature with coercivities close to zero. This typical behaviour is attributed to the corresponding anisotropic contributions originated from the individual constituents. The observed variations in BFO (N) + NZFO sample attributed to the corresponding structural modifications brought about by the variations due to its size effect in the present work.

Synthesis and ionic conductivity of phosphate-sulfate fluorapatites Ca10-xNax(PO4)6-x(SO4)xF2 (x = 0, 3, 6)

Phosphate-sulfate fluorapatites Ca10-xNax(PO4)6-x(SO4)xF2 (x = 0, 3, 6) have been synthesized by the solid-state reaction at high temperature. The samples have been characterized by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman scattering spectroscopy and Transmission Electron Microscopy (TEM) techniques. XRD study shows that these materials crystallize in the hexagonal system with P63/m as a space group. An impedance analysis has been used to analyze the electrical behavior of the samples at different temperatures. Evidence of temperature-dependent electrical relaxation phenomena is observed. The bulk resistance decreases with increasing temperature, showing a typical negative temperature coefficient of resistance (NTCR). Ac-conductivity measurements have been performed on a wide range of frequencies and temperatures. The ionic conductivity follows the Arrhenius and the Jonscher laws.

Insights into ion transport in biodegradable solid polymer blend electrolyte based on FTIR analysis and circuit design

This study reports the use of the solution casting method to prepare a biodegradable polymer blend electrolyte composed of chitosan (CS) and potato starch (PS). Different concentrations of potassium thiocyanate (KSCN) salt as an ionic provider were added to the CS:PS host. The results of X-ray diffraction (XRD) revealed a substantial reduction in the crystalline phase of the host polymers of up to 40 wt% of the added KSCN salt. Fourier transform infrared (FTIR) spectroscopy was used to detect microstructural modifications to the films to explore the complexation between the blended polymer chains and ions of the salt. Deconvoluted FTIR spectra were used to compute the free ions, contact ion pairs, and ion aggregates, which were then used as a sensitive method to determine the parameters of ion transport, including mobility (μ), carrier density (n), and the diffusion coefficient (D). Electrochemical impedance spectroscopy (EIS) was used based on electrical equivalent circuit modeling to study the electrical properties of the electrolyte films. A circuit design for each electrolyte was presented based on the curves of fitting of the EIS data. The parameters associated with elements of the circuit were of significant interest, especially for determining the conductivity of the films. The sample with the highest KSCN concentration of 50 wt% exhibited a reduction in conductivity due to the formation of ion pairs, the recrystallization of salt, and a decline in the amorphous fraction of the system, which was also visualized from its surface morphology by using an optical microscope. An analysis of properties of the dielectric manifested an enhancement upon the addition of salt, with characteristics of dispersive relaxation that verified the non-Debye behavior of the solid polymer electrolyte films. This behavior was further confirmed through the appearance of a distorted arc in the Argand plot. A decrease in the relaxation time was noted with the addition of salt, where this was in agreement with the results of EIS and AC conductivity measurements. An examination of the electric modulus revealed the process of viscoelastic relaxation whereby ion hopping was supported by coupling with segmental chain dynamics.

Effect of TiO2 as Filler in NaCl: Possible Applications in Ionic Storage Systems

High dielectric capacitors are increasingly used for energy storage in sustainable nanotechnologies. Here, we observed large enhancement of dielectric constant by 3 order at frequency 1kHz with moderate loss when TiO2 is added as a filler in NaCl bulk matrix. The TiO2 nanoparticles are synthesized via sol gel process and is subsequently added in varying weight percentage x in the ionic matrix of NaCl, which is represented as TiO2(x)NaCl. The parameters like dielectric constant, dissipation Loss and ac conductivity are measured with varying fraction of TiO2 in frequency range less than 25 KHz. The steady increase of dielectric constant with increasing filler content at low frequency indicates percolation type behavior which accounts for the first dielectric peak at x= 50. The dielectric loss is found to be around 1 for x< 45 whereas it tends to increases with higher filler fraction. Moreover, the frequency dependent polarization in this composite system also accounts for hopping type behavior of mobile charge carriers contributed by TiO2 as confirmed from ac conductivity measurement. Further, the samples are characterized by X-ray diffraction and Field emission scanning electron microscopy in order to study the structure and morphology of the samples. Overall, TiO2 incorporation strongly improves the dielectric behavior of the ionic matrix at low frequency, making it suitable for super dielectric material (SDM).

Effect of zinc oxide nanoparticles on physical properties of carboxymethyl cellulose/ poly (ethylene oxide) matrix

Zinc oxide nanoparticles (ZnO NPs) with sizes 20–80 nm were successfully prepared using the Sol-Gel technique. They were loaded with different weight ratios (wt.%) ∼ 0, 0.3, 0.8, 2, 4, and 6 wt% on a polymer blend of carboxymethyl cellulose (CMC)/polyethylene oxide (PEO) (70:30) utilizing the solution casting route. The formed ZnO NPs loaded with CMC/PEO blend demonstrate a notable decrement in the bandgap from 4.51 to 3.34 eV. A significant increase in the refractive index from 1.79 to 1.97 was observed with increasing ZnO NPs content from 0 to 6 wt %. AC conductivity (σac) measurements at 298 K revealed a measurable enhancement in conductivity and dielectric parameters with the increase of ZnO NPs contents reaching their optimum values at 2 wt%. Furthermore, the temperature dependence of the σac and dielectric parameters was investigated for the optimum concentration, highlighting its unique characteristics for solid-state supercapacitors.

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 properties of hot-pressed Poly(vinylidene fluoride)/Functionalized carbon nanotube composites

This work reports the structural and dielectric properties of poly(vinylidene fluoride) (PVDF) composites with functionalized carbon nanotube (FCNT) prepared by the hot pressing method. XPS, SEM, TEM, and TGA techniques were employed to understand the extent of functionalization of CNT with acid treatment. Permittivity, Electric Modulus, and AC conductivity measurements of hot pressed samples are compared with samples prepared by the solvent casting method. It was found that the PVDF-FCNT composites were formed with more γ phases. Hot pressing the samples increases the overall polar phases, especially the β phase. The permittivity, electric modulus, and AC conductivity studies reveal the dielectric behavior and conductivity changes with hot pressing samples.

AC conductivity of amorphous and polycrystalline Cd3As2 films on single crystal substrates of Al2O3

In this work, we present first AC conductivity measurements of both amorphous and polycrystalline Cd3As2 thin films ( ∼50nm) in the frequency range 25–106Hz and temperature range 10–300 K. Cd3As2 thin films were grown by non-reactive AC magnetron sputtering. Both samples show a strong frequency dependence of the total conductivity in the order of 104Ω−1 cm−1. It was found that the DC conductivity, deduced from the total conductivity of Cd3As2 thin films, increases with increasing temperature. The experimental results indicate exponent values s>1 and s>2, which contradicts the universal dynamic response. In Cd3As2 films is observed a crossover of metal–semiconductor type at low temperatures, which is characteristic of topological materials. The results show a clearly frequency dependence of the mechanism of AC conductivity of Cd3As2 films in a wide range of temperatures.

The real role of Cu metallic interlayer on the dielectric dispersion and conduction mechanism of TiO2/Cu/TiO2 nanolaminates

In the present work, the effect of interference of highly transparent and conducting TiO2/Cu/TiO2 nanolaminated films with various Cu metallic interlayer thickness grown on Si (100) substrates by atomic layer deposition (ALD) and magnetron sputtering techniques on the dielectric properties and the AC conductivity of the as-prepared thin films, in the frequency range of 0.1–1000 kHz and in the temperature range of 300–393 K was investigated. The main goal of the studies performed was to compare the dielectric properties and the AC conductivity in two different Cu interlayer thicknesses (20 and 40 nm) and also to assess and relate the resulting properties with several experimental parameters. The AC conductivity measurements showed semiconducting behavior. The variation of the frequency exponent r has been explained in terms of different conduction mechanisms, the correlated barrier hopping (CBH), beside the quantum mechanical tunneling (QMT) models, depending on the Cu metallic interlayer thickness. It is found that the value of the maximum barrier height (Wm) decreases with increasing the Cu interlayer thickness and agree with that proposed by the theory of hopping of charge carriers. The study of the dielectric dispersion reveals that the Debye-type relaxation process was observed at the lower Cu interlayer thickness and fades as the Cu interlayer thickness increases. An observed decrease of dielectric loss with frequency downto low values indicates the suitability of the present samples for several energy storage applications. A new parameter related to the AC conductivity and dielectric constant ratio was studied and analyzed. The present outcome suggests that the thickness of the Cu metallic interlayer plays a vital role in the electric and dielectric properties of the films under investigation.

Investigation on Electrical properties of PEO/CMC solid polymer blend electrolyte

The solid polymer blend sample films of Poly (ethylene Oxide) (PEO)/Sodium Carboxy methyl cellulose (CMC) with 10/90, 30/70, 50/50, 70/30 and 90/10 compositions were prepared by solution cast technique and electrical properties were investigated by Dielectric studiesassociated with dielectric constant (ɛ′ ) and dielectric loss (ɛ′')including AC conductivity (σac) measurements. Dielectric constant and dielectric loss are found to decrease with the increase of frequency, and laterremains constant for all blend compositions in higher frequency range. Conductivity studyreveals that,the blend of 10/90 composition exhibits higher electrical conductivity of 2.707X10−5 Sm−1 and is found to be decreased with increase inwt.% of CMC in the blend matrix. The deviation in the trend of conductivity has been observed at 70/30 and 90/10 composition due to the miscibility.

Multitasking Performance of Fe3O4/BaTiO3/Epoxy Resin Hybrid Nanocomposites

In this study, hybrid nanocomposites consisting of Fe3O4/BaTiO3/epoxy resin were prepared with varying amounts of filer content. Structural and morphological characterization, conducted via X-Ray Diffraction patterns and Scanning Electron Microscopy images, revealed the successful fabrication of composites and fine dispersion of inclusions. Thermomechanical properties are studied via Differential Scanning Calorimetry, Thermogravimetric Analysis, Dynamic Mechanical Analysis and static mechanical tests. Hybrid composites exhibit enhanced thermal stability and improved mechanical response. Indicatively, Young’s modulus, tensile strength and fracture toughness increase from 1.26 GPa, 22.25 MPa, and 3.03 kJ/m3 for the neat epoxy to 1.39 GPa, 45.73 MPa, and 41.08 kJ/m3 for the composites with 20 or 15 parts per hundred resin per mass (phr) of Fe3O4, respectively. Electrical behavior is investigated via Broadband Dielectric Spectroscopy and ac conductivity measurements. The real part of dielectric permittivity reaches the value of 11.11 at 30 °C for the composite with 40 phr of Fe3O4. The ability to store and retrieve electric energy on the nanocomposites is examined with the following parameters: the filler content and the applied voltage under dc conditions. Retrieved energy reaches 79.23% of the stored one, for the system with 15 phr of Fe3O4. Magnetic response is studied via a Vibrating Sample Magnetometer. Magnetic saturation, for the system with the highest magnetic filler content, obtains the value of 25.38 Am2/kg, while pure magnetic powder attains the value of 86.75 Am2/kg. Finally, the multifunctional performance of the nanocomposites is assessed regarding all the exerted stimuli and the optimum behavior is discussed.

Effect of Annealing and Ion Beam Irradiation on AC Electrical Properties for Gold Sputtered PM-355

Deposition of different gold thickness on PM-355 cleaned by ethanol forming thin films using magnetron sputtering. Gold layer with thickness 300, 400, 500, 700, 1000, 1300, and 1500 nm were deposited to prepare Au / PM-355 thin films. Then, ac electrical properties response of thin films for a wide frequency range 20Hz - 5MHz were measured at roomtemperature. Meanwhile, the measurements of ac conductivity, dielectric constant, and dielectric loss factor were plotted at different frequencies to determine the optimum thickness. Hence, the comparison was done between optimum Au thickness thin films cleaned by two organic solvents and ethanol before annealing at different frequencies. Also, study the effect of annealing and ion beam that extracted radially from conical anode and disc cathode ion source on optimum Au thickness thin film electrical properties. It is found that the annealing increases both dielectric constant, dielectric loss, and ac conductivity of optimum Au thin film at different frequencies. Despite, the nitrogen ion beam effected on these thin films by decreasing the dielectric constant and ac conductivity for all thin films except the chloroform one. Finally, study the comparison between the annealing and followed by ion irradiation thin films. It is noticed the decrease in ac electrical conductivity and dielectric constant at different frequencies.

Gate Length-Dependent Thermal Impedance Characterization of PD-SOI MOSFETs

Thermal impedance is required to describe static and fast dynamic thermal behavior in silicon-on-insulator (SOI) devices. This study presents an empirical physical model, which accounts for gate length, for calculating the thermal impedance of multi-finger partially depleted (PD) SOI MOSFETs at room temperature. For the first time, the parameters of the model are obtained from measurements of ac conductance and the characteristic thermal frequency determination. The model shows decreasing thermal resistance and linearly augmented thermal capacitance with increasing gate length from 0.18 to 2.50 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>. Thus, thermal time constants of &#x007E;760 ns, extracted from a variety of gate lengths, are correctly predicted.

Electrical response on the nickel-ion containing organic–inorganic hybrid system for the sensing of dopamine

A complexation mediated route has been applied for the synthesis of Ni(II)-HMDA (hexamethylenediamine) hybrid system and the synthesized complex material was tailored as a sensing platform of dopamine. The electric field induced polarization study exhibited the hysteresis loop for Ni(II)-HMDA and with the gradual addition of dopamine to the complex, a steady increase of maximum polarization value of the loop was noticed. The increment of the polarization hysteresis loops were associated with the ligand exchange mechanism between HMDA and dopamine. The dopamine sensing performance of Ni(II)-HMDA hybrid system was further studied using the dielectric capacitance, AC-conductivity measurement and impedimetric techniques.

Structural, dielectric and ac electrical properties of nano-structured Mn0.6Co0.2Ni0.2Fe2O4 ternary ferrite synthesized by citrate-gel auto-combustion technique

The present paper reports the structural, dielectric and ac electrical properties of nanoparticles of mixed polycrystalline spinel ferrite ternary compound Mn0.6Co0.2Ni0.2Fe2O4 synthesized by using the citrate-gel auto-combustion technique. The standard characterization techniques such as EDAX, XRD and FTIR were primarily employed to confirm the elemental stoichiometry, crystallized single-phase, IR-functional groups. These measurements ascertained the formation of monophasic and pure ferrite compound. The powder X-ray diffraction analysis was done to determine the lattice constant(0.8420 nm), crystallite size(21 nm), X-ray density (5.16 g/cm3), distribution of cations among the tetrahedral and octahedral sites of spinel lattice(with iron-Fe3+ distribution ratio among A and B sites is 0.25), bond angles and bond lengths. The theoretical lattice constant is found to be 0.8422 nm. The nature and position of the IR-bands were observed through FTIR spectroscopy. The high-frequency band v1 (A-site vibrations) lies at 563.07 cm-1 while the low-frequency band v2 (B-site vibrations) lies at 462.59 cm-1 . The force constants for the tetrahedral site (kt) and octahedral site (ko) were deduced 1.33×102 N/m and 1.27× 102 N/m, respectively. Frequency dependence of dielectric constant and tangent loss has been explained by the Maxwell Wagner model and Koop's theory. The Jonscher’s power low was used to describe the ac conductivity measurements. The Nyquist and cole-cole plots indicated presence of grain contribution in the conduction mechanism.

The influence of ZnO nanoparticles on the structural, optical and dielectric properties of Polyvinyl alcohol films

Polyvinyl alcohol/Zinc oxide (PVA/ZnO) nanocomposite films with various weight percentages of ZnO nanoparticles (0 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%) were prepared by solution casting method. The structural, optical and morphological properties of the synthesized samples were characterized by X-ray diffraction (XRD), UV–Visible spectroscopy, Fourier transform Infrared spectroscopy (FTIR) and Scanning electron microscope (SEM). X-ray diffraction studies confirms the formation of PVA/ZnO nanocomposites. From the UV–vis absorbance spectra, the band gap energy of the samples was calculated and its value decreases with increasing the wt% of ZnO into the PVA matrix. The transmittance of the nanocomposites in the visible region is decreased with increasing the concentration of ZnO into the PVA matrix and completely blocked in the UV region. These behaviours suggests that the nanocomposite materials could be used as UV shielding materials. The FTIR analysis indicates physical interaction between hydroxyl group of PVA and ZnO. SEM shows the dispersion of ZnO on the surface of PVA matrix. The dielectric properties and AC conductivity measurement in the frequency range 100 Hz to 1 MHz reveals the maximum dielectric constant at PVA/5 wt% ZnO nanocomposite.

Correlation among the structural, electric and magnetic properties of Al3+ substituted Ni-Zn-Co ferrites.

This study explored the structural, electrical, and magnetic properties of diamagnetic aluminium (Al3+) substituted nickel-zinc-cobalt (Ni–Zn–Co) mixed spinel ferrites, though the research on this area is in the infancy stage. Single-phase cubic spinel structures with the Fd3̄m space group of the synthesized Ni0.4Zn0.35Co0.25Fe(2−x)AlxO4 (0 ≤ x ≤ 0.12) ferrite samples were confirmed by X-ray diffraction (XRD) analysis. The average particle size ranged from 0.67 to 0.39 μm. Selected area electron diffraction (SAED) patterns were indexed according to the space group Fd3m, representing the particle's crystallinity. The optical band gaps ranged from 4.784 eV to 4.766 eV. Frequency-dependent dielectric constants and ac conductivity measurement suggested that the prepared ferrites were highly resistive. Relaxation times were reduced to a low value from 45.45 μs to 1.54 μs with the composition x. The Curie temperatures (Tc) were 615–623 K for all samples. Real part permeabilities (μ/) were relatively stable up to an extended frequency range of 106 Hz with relative quality factors (RQF) of around 103. Tuning of the properties indicates that the fabricated ferrites may be promising for high-frequency electronic devices.

Structure and ac conductivity of (Cu/Co)Fe2O4 spinel materials

In this piece of research, we throw light on the synthesis, structure and other physical properties of Co1-xCuxFe2O4 [x = 0.00, 0.25, 0.5, 0.75, 1.00] spinel ferrites. These materials were synthesized by employing the double calcination solid-state method. To confirm structured acquired by the synthesized samples, we characterized our samples by X-ray diffraction technique, FTIR spectroscopy and inelastic Raman scattering technique. XRD studies reveal that all the samples are present in cubic crystal structure (Fd-3m). The desired phase formation was confirmed from Raman and FTIR spectra analysis also. To emphasize on electrical properties, we carried out room temperature frequency dependent ac conductivity measurements also.

PPy/NiO nanocomposite: synthesis and characterization

Polypyrrole (PPy) is one of the most stable conducting polymers and easy to synthesis. In this work, PPy and nano nickel oxide (NiO) doped PPy were prepared by the chemical oxidative polymerization method. The structure, morphology and particle size of NiO/PPy nanocomposites were investigated by FT-IR, SEM-EDX and XRD analysis respectively. From FT-IR, based on the obtained results for nano NiO doped PPy, the vibrational band at 428 cm−1 confirms the presence of NiO. The XRD pattern reveals that pure PPy is amorphous. In contrast, NiO doped PPy nanocomposite shows a crystalline structure as confirmed by the sharp peak of 2θ value, which is 43.16°. SEM microphotograph shows that the agglomeration exists in nano NiO doped PPy due to the presence of nanomaterial. The AC conductivity measurements done for n-NiOPPy exhibits a remarkable change in electrical conductivity response. The properties of pure PPy and its composites after doping are compared.