Behavior Of Dc Conductivity Research Articles

Design, structural, and electrical conduction behavior of Zr-modified BaTiO3-BiFeO3 perovskite ceramics

This study employs the solid-state reaction method to synthesize [(Ba0.7 Bi0.3) (Ti0.7-y Zry) Fe0.3] O3 (y = 0.0, 0.2, 0.3, 0.4, 0.6) for investigating their structural and DC conduction behavior. XRD analysis suggests a perovskite phase for all the compositions having a cubic crystal structure. Initially, average crystallite size increases for y ≥ 0.3 and then decreases for y = 0.4. The temperature-dependent DC electrical conductivity demonstrated the semiconducting nature for all the compositions. The introduction of Zr modifies the material’s structure and electrical properties evident in the observed variations in crystallite size and conductivity behavior. These findings contribute to the understanding of Zr-modified [(Ba0.7 Bi0.3) (Ti0.7-y Zry) Fe0.3] O3 ceramics, shedding light on their potential applications in semiconductor devices and solid-state electronics. The investigation underscores the importance of tailoring composition parameters for fine-tuning material characteristics, opening avenues for optimized utilization in electronic and energy-related technologies

Analyzing the strong influence of the cationic environment on the charge carrier’s jumping in a superionic conductor

In this work the relationship between the structure of a solid ionic material and its ionic dynamics has been studied by impedance spectroscopy, differential scanning calorimetry and molecular dynamics simulation. Nanometric samples of AgI were synthesized to study the cation dynamics when it reaches its superionic behavior. The observed thermal events corresponded to the changes obtained on the dc conductivity behavior. This correspondence was microscopically explained by the ion dynamics revealed in the molecular dynamics simulation. The comprehensive analysis made it possible to confirm the weak short-range interactions between silver cations and iodide anions and exposed that the most mobile cation jumps are constrained by their neighbor cations. This finding explains the Kohlrausch–Williams–Watts β parameter value of 0.9 in the α phase where the AgI becomes a superionic conductor, an aspect that becomes essential to design a superionic conductor by doping ionic conductor materials.

Impurity-driven metal-insulator transitions in holography

In this work, we study Metal-Insulator transition in a holographic model containing an interaction between the order parameter and charge-carrier density. It turns out that the impurity density of this model can drive the phase transition whose ordered phase corresponds to the insulating phase. The temperature behavior of DC conductivity distinguishes the insulating phase from the metal phase. We confirm this behavior by a numerical method and an analytic calculation. As a byproduct, we show the existence of a ‘quantum phase transition’ supported by the Breitenlohner-Freedman bound argument.

Studies on the electrical properties of polyaniline with cadmium oxide nanocomposites

In situ polymerization method was used to prepare cadmium oxide nanoparticles (NPs) with polyaniline nanocomposites, by varying different weight percentages of cadmium oxide NPs, and the oxidizing agent as ammonium per sulfate as starting materials. The AC and DC conductivity behavior of PANI with CdO nanocomposites has been studied as a function of frequency and temperature. The XRD and SEM techniques were used to explore how the establishment of PANI and its nanocomposites impacts the structural and morphological properties of the materials.The structure of CdO NPs was found to be cubic phase confirmed from XRD. The electrical conductivities, DC conductivity of polyaniline and its nanocomposites were measured at 27 to 180°Celsius. According to the AC conductivity frequency variation, CdO NPs concentration increases along with AC conductivity in the low-frequency zone.

Ultralow dielectric loss in Tb + Ta‐modified TiO2 giant dielectric ceramics via designing defect chemistry

AbstractThe environment‐friendly materials exhibiting colossal permittivity play an increasingly important role in the electronics industry. In this work, (Tb0.5Ta0.5)xTi1−xO2 (x = 0, 0.005, 0.01, 0.02, and 0.04) ceramics with new defect clusters were fabricated to enhance the dielectric response. Significantly, all ceramic samples exhibit large dielectric constants (εr > 104), whereas the ceramic with x = 0.005 exhibits an ultralow loss (tan δ) of about 0.008 at room temperature and 1 kHz. The origins of its excellent dielectric properties were revealed by XRD, X‐ray photoelectron spectroscopy, and dielectric response analysis, which were mainly caused by defective dipoles associated with oxygen vacancies (). These defective dipoles limiting the long‐range hopping of electrons lead to the electron pinning effect. Additionally, the frequency spectrum under DC bias and conductivity behavior suggests that grain boundary and electrode effects also contribute to the dielectric constant. This study not only explores the dielectric response properties of a new giant dielectric (Tb0.5Ta0.5)xTi1−xO2 ceramics but also offers a candidate material suitable for ceramics capacitors.

Influence of SrO on structural, optical and electrical properties of LiF-MgO-Bi2O3- SiO2 glasses for energy storage applications

Lithium strontium magnesium bismuth silicate glasses having composition 40SiO2 - 20Bi2O3- 20LiF - (20 - x) MgO–xSrO (x = 0, 5, 10, 15, and 20 mole%) were prepared using melt quenching technique. The prepared samples were characterized using XRD and FTIR techniques. Physical, optical and electrical properties have been investigated in order to understand the mixed modifier effect of MgO and SrO on these glasses. It was found that the addition of strontium at the expense of magnesium increases the density while decreasing the molar volume of the prepared samples. The XRD patterns showed that replacing magnesium with strontium led to enhance the vitreous formation of the prepared samples. Absorbance spectra, energy band-gap and Urbach energy were measured and calculated and the present glass system shows indirectly allowed transitions. Broadband Dielectric Spectroscopy measurements were carried in the frequency range 0.1 Hz to 10 MHz using a high resolution alpha dielectric analyzer in a temperature range from 25 to 200 °C. It was found that the dielectric parameters are enhanced with the increase in MgO content at the expense of SrO and with increasing temperature. The conductivity of the glass shows no dc conductivity behavior except at high temperature and yet it is non-conducting glass. However, the data suggest that the prepared glasses are promising for energy storage glass applications.

Electrical and Optical characterization of Malonic acid doped Poly Vinyl Alcohol polymer electrolytes

Novel proton conducting solid polymer electrolyte membranes based on Poly vinyl alcohol (PVA) with Malonic Acid as dopant are prepared by solution cast technique with varying doping concentrations up to 40 wt.%. The electrical conductivity and optical absorption of pure PVA and Malonic aciddoped PVA electrolytes are investigated. DC conductivity behavior is studied in the range 303K to 373K. It is found that PVA: Malonic acid (70:30) electrolyte exhibits the maximum conductivity. The electrical conductivity initially increases with increasing dopant concentration and then showed a decrease beyond 30 wt.% concentration. The increase in conductivity is attributed to formation of charge transfer complexes while the decrease for concentrations above 30 wt.% is due to segregation. Optical absorption studies are made in the wavelength range 200-600 nm and the values of optical band gap (direct and indirect) are estimated. The results obtained are presented and discussed.

Porous SnO2 ceramic-based hydroelectric cells for green power generation

Recently, it has been observed that few drops of water on the surface of oxide materials can generate electricity which is eco-friendly and cost effective. This hydroelectric cell (HEC) may serve as an unconventional source of electrical energy. HEC production cast is very low. Porous SnO2 samples for hydroelectric cell have been prepared by solid-state sintering method. Phase formation and structural analysis of the sample was confirmed by X-ray diffraction pattern using Rietveld analysis. The surface morphology of the sample was determined using field emission scanning electron microscopy. Average grain size of porous sample was depicted 65 nm using image j software. The pore size distribution and specific surface area of SnO2 nanoparticles were examined by the Barrett–Joyner–Halenda technique. A circular pellet having diameter of 2 inch and a square pellet having a side of 2 cm was prepared to study the hydroelectric properties. Peak current value 72.1 mA was observed in circular pellet with almost constant voltage of 0.981 V whereas peak current and voltage values for the square pellet were 12.5 mA and 0.972 V respectively. Dissociation of water and conduction phenomenon have been confirmed using dielectric and DC conductivity behavior of samples.

Swelling and DC Conductivity Behaviour of Gelatin-Based Ferrogels

Gelatin-based systems have great potential in bio-medical applications. Here, we report the solvent uptake and DC conductivity of glutaraldehyde-crosslinked gelatin hydrogels and ferrogels. Both the parameters are found to depend on cross-linker (glutaraldehyde) and dopant (carbonyl iron) concentrations. Higher cross-linker proportions cause decrease in solvent uptake, equilibrium swelling ratio and DC conductivity. Solvent uptake is seen to increase while equilibrium swelling ratio and DC conductivity decrease with dopant concentration in the ferrogels. The solvent uptake and DC conductivity behaviour of the studied systems are explained on the basis of variations in pore size and polymer segmental mobility which, themselves, are functions of cross-linker and dopant concentrations. The diffusion process in the hydrogels and ferrogels obeys the second-order kinetic model.

Synthesis and characterization of advanced functional dysprosium doped Sr2MgSi2O7 nanopowders for white LED application

Dy3+ doped Sr2MgSi2O7 (0–11 mol%) nanopowders were prepared by low-temperature solution combustion technique which is based on the propellant chemistry concepts. Powder X-ray diffraction study confirms the crystalline nature with a crystallite size of about 30 nm and single-phase formation with space group P4̅21m. The optical band gap and refractive indices were estimated by diffused reflectance spectroscopy. Purity of the samples and the molecular bonding strengths were identified through Fourier-transform infrared spectroscopy. Transmission electron microscopic images shows the rod-like shape with polycrystalline nature. Scanning electron microscope indicates the non-uniform and irregular shaped particles. Photoluminescence studies exhibited emission peaks at 479 nm (blue), 575 nm (yellow) and 668 nm (red) for the excitation wavelength at 348 nm attributes to white light-emission. The intensity parameters and various radiative properties were estimated using the Judd- Ofelt theory to support the optical transitions. AC Conductivity, dielectric constant studies were studied in the range of 100 Hz to 1 MHz and DC conductivity behaviors were also reported. Prepared samples showed the high dielectric constant with low dielectric loss. Hence, these silicate samples are useful for white LED components and as an electrical insulation material in nanopacking applications.

Influence of the chemical functionalization of carbon nanotubes on low temperature ac conductivity with polyaniline composites

We report the ac conductivity measurement of polyaniline (PANI) composites with carbon nanotubes (CNT) and functionalized carbon nanotubes (fCNT) with different degrees of functionalization from 300 K–4.2 K in the frequency range 40 Hz–5 MHz. The ac conductivity of PANI follows the universal power law and the charge transport is dominated by small polaron tunneling. In the CNT/PANI composite, metallic behaviour emerges, and ac conductivity does not obey the power law which is explained by the Drude model. Due to the chemical functionalization of CNT, disordered semiconducting behaviour appears in the transport below 50 K and follows the Johnscher’s power law. The enhancement of polaron formation due to the polar interaction between fCNT and PANI is reflected in the ac conductivity of the composites. The charge transport is manifested by single electron tunneling for a lower degree of fCNT/PANI (6 h) composite which changes to small polaron tunneling transport for a higher degree of fCNT/PANI (48 h) composite. The dc conductivity behaviour is explained by Mott’s VRH model and the characteristic Mott temperature increases with an increasing degree of chemical functionalization.

Temperature Dependence of THz Conductivity in Polyaniline Emeraldine Salt-Polyethylene Pellets

Using terahertz time-domain spectroscopy, the frequency-dependent conductivities of polyaniline emeraldine salt-polyethylene (PAni-PE) pellets were measured at different mass concentrations. THz conductivities were compared to the behavior of DC conductivities measured using impedance spectroscopy. The DC conductivity behavior with mass concentration showed a low percolation threshold. The frequency-dependent behavior in the THz region follows the Mott-Davis behavior which shows stronger correlation at higher PAni concentration. At the same time, the conductivity increases exponentially with increasing PAni concentration over the frequency range studied without an apparent percolation threshold. The mechanisms in the two regions studied suggest that there is more dominant localization in the THz regime in contrast with a more dominant percolative transport in the Hz-MHz region. Temperature-dependent measurements showed a decreasing value of parameter S with increasing temperature consistent with a correlated barrier hopping model. Lastly, the parameter S increases in magnitude with a decreasing amount of PAni in the composites reflective of varying conducting and nonconducting compositions.

DC Conductivity in P-Toluenesulphonic Acid Doped Poly (2-Methylaniline)

Para-toluenesulphonic acid doped Poly(2-methylaniline) (PmANI) was synthesized by chemical method using ammoniumpersulphate (APS) as an oxidant. It was synthesized along with optimization studies w.r.t. varied dopant-monomer ratios for better DC conductivity. Various spectroscopies like XRD, UV-Vis and FT-IR were used to characterize the polymer. The behavior of DC conductivity with variation in temperature was studied with in the temperature range of 300 - 425 K and it was observed that conductivity rised to ~four orders with the surge in temperature. The experimental conductivity data was fitted with various conduction models to find the proper charge transport mechanism in this polymer.

Electrical transport properties of cobalt-doped MgAl2O4 nanoparticles

The electrical transport properties of MgAl2−xCoxO4 (where x = 0.0, 0.5, 1.0, 1.5, 2.0) were investigated at room temperature. The dielectric behavior of the samples, and the contribution of the grains and the grain boundary regions to the electric response of the samples were observed using impedance spectroscopy in the frequency range of 20 Hz to 2 MHz. The DC conduction behavior was studied by measuring current density J against electric field E. It was observed that the grains and grain boundaries both contribute equally to the variation in electric response caused by changing the dopant concentration of cobalt in MgAl2O4. The combined Z″ and M″ spectroscopic plots indicated the presence of small polaron hopping conduction in the grain region of the samples. Moreover, the 25% doped sample showed minimum conductivity among all samples, which was two orders of magnitude less than that of the pure sample.

The effect of filler loading ratios and moisture on DC conductivity and space charge behaviour of SiO2 and hBN filled epoxy nanocomposites

Nanocomposites that exhibit good insulation properties have already attracted a variety of research and their electrical properties are believed to be related to charge dynamics in bulk of materials. However, it is still unclear on how nanofiller loading ratios, surface treatment and resultant changes in morphology will influence the charge dynamics of nanocomposites. In this paper, we have clearly mentioned the influence of adding nanoparticles into epoxy resins and the characteristics of the movement of charges in the materials based on combining analysis on morphology, DC conductivity and space charge measurements. The presence of spherical nanoparticles (SiO2) introduced additional traps in bulk, which impaired the charge injection and reduced the mobility of charge carriers in samples of low filler loading ratios (e.g. 0.5 wt%). However, in silica-based samples of higher filler loadings, more nanoparticles further caused a higher density of traps, which resulted in lower average distance between arbitrary traps/inter-particle surface distances and thus charge carriers required less energy when moving from one to another by hopping or the quantum tunnelling mechanism. The surface treatment of SiO2 particles introduced deep traps which helped the separation of particles or related traps, and to some extent restricted the transport of charge carriers. In addition, hBN particles seem to act as barriers to charge injection and movement due to the layered structures and large numbers of resultant shallow traps in bulk. In terms of the moisture effect, the presence of water led to an obvious increase in charge injection and mobility, and resulted in the higher mobility of charge carriers in both base materials and within traps/particles of nanocomposites. The existence of water shells around spherical particles could contribute to a higher probability of the quantum tunnelling process and the formation of conductive percolation channels.

Structural distortion, piezoelectric properties, and electric resistivity of A-site substituted Bi3TiNbO9-based high-temperature piezoceramics

High-temperature piezoceramics Bi3-xCexTiNbO9+δ (BCTN-100x, x=0, 0.02, 0.04, 0.06, 0.07, 0.08, 0.10) were prepared by a solid-state reaction method. The crystal structure, microstructure, dielectric behaviour, piezoelectricity, temperature stability and electrical conduction mechanisms of BCTN-100x ceramics were studied. All Ce-doped Bi3TiNbO9 ceramics had a single Aurivillius phase structure. Ce substitution influenced the crystal structure, leading to a high piezoelectric constant (d33=17 pC/N) but decreasing the Curie temperature slightly (TC=883 °C). The resistivity of Ce-doped BTN ceramics increased by two orders of magnitude compared with that of the pure BTN. Furthermore, the dc and ac conduction mechanisms were studied, indicating that the conduction mechanism is closely related to temperature for dc and ac conduction behaviour. In addition, we analysed the dielectric relaxation processes and attributed them to the motion of oxygen vacancies, which deviates from the ideal Debye-model.

Vibrational spectra, dielectric properties, conductivity mechanisms and third order nonlinear optical properties of guanidinium 4-aminobenzoate

The frequency response of dielectric permittivity measurements at temperatures 35 °C and 100 °C suggests enhanced inherent optical quality and few defects in the crystal. The Cole-Cole plot shows the presence of grain and grain boundary, it is found that single relaxation is observed in the crystal. The ac and dc conductivity and dielectric behavior of the grown crystal were systemically investigated as a function of frequency and temperature. The third order nonlinear optical property extensively studied by z-scan technique revealed high third order nonlinearity in the form of self-defocusing and two-photon absorption with saturable absorption. The strong intermolecular charge transfer interaction evident from NBO and AIM studies confirms the NLO property of the material. The detailed vibrational assignments were carried out on the basis of potential energy distribution (PED) analysis and scaled quantum mechanical force field calculation using MOLVIB program. The red shifted NH stretching wavenumbers and the broadening of corresponding bands in the solid state as well as the gas phase spectra, optimized molecular geometry and NBO analysis have confirmed the presence of N-H⋯O hydrogen bonding in G4AB.

Ferroelectric and magneto-dielectric properties of yttrium doped BaTiO3–CoFe2O4 multiferroic composite

Multiferroic composites of ferroelectric and ferrite phases having general formula xCoY0.1Fe1.9O4—(1 − x) Ba0.95Y0.05TiO3 (where x = 0.05, 0.1 and 0.15) were prepared using the conventional solid-state reaction method. X-ray diffraction studies were done to confirm the presence of constituent phases. The microstructural analysis revealed an increase in density with the increase of ferrite content in the ferroelectric matrix. Dielectric studies of the composites, in the temperature range 100–550 K revealed two ferroelectric phase transitions. Variation of dielectric constant and dielectric loss with frequency in the range of 20–3 MHz was carried out at room temperature. The low-temperature dc conductivity behaviour follows Motts law, confirming the variable range hopping mechanism in all the composites. All the composites showed P–E and M–H hysteresis loops; which confirm the ferroelectric and ferrimagnetic nature of the composites. At temperatures below 173 K, an increase in coercivity and saturation magnetization is observed due to frozen spins. The coupling between ferroelectric and ferromagnetic ordering was confirmed by room temperature magneto-dielectric studies. The decrease in real part of dielectric constant and dielectric loss was observed with an increase in the applied magnetic field. An appreciable increase in percentage magneto-capacitance was observed at lower frequencies and with the increase of ferrite content in the composites. The magneto-electric coupling coefficient was calculated by using the expansion of the thermodynamic potential φ (for x = 0.15) and was found to be 3.397 × 10−2 (emu/g)−2.

Variable range hopping and relaxation mechanism in graphene oxide sheets containing sp3 hybridization induced localization

The temperature dependent electrical properties of graphene oxide prepared by the modified Hummers method are investigated using broadband dielectric spectroscopy. The morphology and structure are confirmed by X-ray diffraction pattern and scanning electron microscope images. In the present work, we have studied the electrical properties of graphene oxide employing a recently proposed novel approach of the combined conduction and dielectric Cole–Cole formalism. The extracted dc conductivity values varies from 1.9 × 10−8 to 3.5 × 10− 5 S cm−1 as a function of temperature (153–353 K), show power-law behaviour, which is explained through Mott’s variable range hopping conduction mechanism. The density of states was found to be 6.02 × 1018 cm−3 eV−1. The conduction relaxation timescales and dielectric relaxation timescales of GO are following the power law. The physical origin of the non-Arrhenius dc conductivity behaviour of charge carriers is explained through structural heterogeneity in graphene oxide introduced due to sp2 and sp3 hybridization of carbon atoms. The range of hop was calculated to be 4.7–3.8 nm with hopping energy changing from 0.37 to 0.69 eV as a function of temperature.

Nonlinear DC Conduction Behavior in Graphene Nanoplatelets/Epoxy Resin Composites

Graphene nanoplatelets (GNPs)/Epoxy resin (ER) with a low percolation threshold were fabricated. Then the nonlinear DC conduction behavior of GNPs/ER composites was investigated, which indicates that dispersion, exfoliation level and conductivity of GNPs in specimens are closely related to the conduction of composites. Moreover, it could be seen that the modified graphene nanoplatelets made in this paper could be successfully used for increasing the electric conductivity of the epoxy resin, and the GNPs/ER composites with nonlinear conduction behavior have a good application prospects in the field of intelligent electromagnetic protection.