DC Electrical Conductivity Research Articles

Electrochemical Performance of SrFeO3−δ for Application as a Symmetric Electrode in Solid Oxide Fuel Cells

SrFeO3−δ has been earlier reported to exhibit a large area-specific resistance even though it possesses high mixed ionic–electronic conductivity both in oxidizing and reducing conditions. The present study clarifies this aspect and investigates the defect chemistry and electrochemical performance correlations in SrFeO3−δ for the possible use as a symmetric electrode in solid oxide fuel cells. A conventional solid-state reaction method is adopted for powder synthesis. Structural characterization indicates an orthorhombic perovskite phase formation with a δ of 0.21. High dc electrical conductivities of ∼114.9 and 0.26 S·cm–1 are observed at 800 °C in air and reducing conditions, respectively. The area-specific resistance (ASR) for the SrFeO3−δ electrode is measured in a symmetrical half-cell configuration under various gas environments. At 800 °C, SrFeO3−δ offered low ASRs of 0.082, 0.055, and 0.122 Ω·cm2 in air, oxygen, and 3% H2O/H2, respectively. Although the ASR possesses excellent temporal stability in an oxidizing atmosphere, it increases to 0.42 Ω·cm2 after 100 h in reducing conditions owing to the brownmillerite phase formation. The redox cycling performance is also affected with the ASR rising from 0.13 to 0.24 Ω·cm2 at 800 °C in 3% H2O/H2 after 20 cycles. A maximum power density of 202 mW·cm−2 is achieved from the electrolyte-supported symmetric single cell based on the SrFeO3−δ electrodes at 800 °C. The results demonstrate the viability of using a SrFeO3−δ-based electrode for symmetrical solid oxide fuel cells.

Synthesis, Characterization and Study of DC Electrical Conductivity of Poly[MWCNT/Ester] Composites

The Poly [MWCNT/ester] composites were synthesized by solution blending method from reacted MWCNT-COOH with Hydroquinone (HQ), Catechol (CA) and Ethylene glycol (EG).The obtained poly-composites were characterized by FT-IR, UV-Vis, XRD, TEM, SEM, TGA, D

Insertion of Ga-MoO3 thin film at Cu/p-Si interface for the fabrication of MIS structure Schottky barrier diodes

The fabrication of a metal-insulator-semiconductor diode with a pure MoO3 and different weight % of Ga-MoO3 (5, 10, and 15 wt%) thin film insulator layer grown by JNSP techniques. The obtained films were characterized for structural analysis by XRD exposing multiphase of orthorhombic and monoclinic with 10 wt% of Ga-based film with higher crystallite size. FE-SEM images display plate-like structures. UV absorption measurements recorded a band gap of 3.15 eV for 10 wt% Ga doped film. X-ray photoelectron spectroscopy (XPS) investigates is described by the utmost oxidation state. The DC electrical conductivity of the films increased for higher wt% of Ga up to 10 wt%. The I-V characteristic curve of the Cu/Ga-MoO3/p-Si diode parameters n, ФB, PS, R, QE, and D* shows that, current flows predominantly across the interfaces as a result of carrier missioning. In addition, we observed significantly high photocurrent performance from the Cu/Ga-MoO3/p-Si diode under visible light illumination.

Dielectric characteristics of multiwall carbon nanotube-filled polyaniline

The dielectric properties of in-situ polymerized polyaniline-multiwalled carbon nanotubes (PANI/MWCNTs) nanocomposite sample were analyzed as a function of temperature (153–353 K) and applied frequency (1 Hz–1000 KHz) over a wide range. To introduce heterogeneity in PANI, MWCNTs (4 wt%) were embedded into the PANI matrix during the polymerization, whereas, to control the electrical conductivity, the synthesized material was reduced via chemical treatment with ammonia. FTIR spectroscopy studies confirm the synthesis of PANI/MWCNTs nanocomposite in lower conducting (emeraldine base) dielectric state. X-ray diffraction (XRD) pattern of the prepared sample reveals the semi-crystalline nature. Thermogravimetric analysis (TGA) investigation indicates that synthesized sample is more stable even at 800 °C. The dielectric studies reveal that the static dielectric constant of the prepared sample enhances with the enhancement in temperature and found to decrease with applied frequency. The enhancement in dielectric constant with temperature may be associated with the enhancement in mobility of the electric dipoles in the conducting polymer. The dielectric constant for the reduced PANI/MWCNTs composite (i.e. ∼1170) is high as compared to reduced pristine PANI (i.e. ∼538). The value of dc electrical conductivity has been decreased from 77 S/cm to 7.81x10−10 S/cm due to reduction of PANI/MWCNTs nanocomposite which indicates the enhancement in dielectric properties. The ac electrical conductivity of synthesized nanocomposite was also found to enhance with an increase in operating temperature, which may be endorsed to the enhancement in activated trapped charge carriers’ concentration.

Dielectric, electric, and piezoelectric properties of three‐phase piezoelectric composite based on castor‐oil polyurethane, lead zirconate titanate particles and multiwall carbon nanotubes

AbstractThe effects of multiwall carbon nanotubes (MWCNTs) on the electrical, dielectric, and piezoelectric properties of the ferroelectric ceramic/castor‐oil polyurethane (PUR) composite films were evaluated. The three‐phase piezoelectric composites were produced by keeping PUR concentration constant while varying lead zirconate titanate (PZT) volume fractions between 10 and 50 vol.%, at two MWCNT concentrations: above and below percolation threshold. Thedcelectrical conductivity analysis revealed that small amounts of MWCNTs dispersed within PUR/PZT composite films can significantly improve electrical and piezoelectric properties due to their ability to act as conductive bridges between PZT particles in the samples. Using Jonscher's power law, it was possible to determine that the electrical conduction inacregime occurs through spatial charge hopping between states located within the piezoelectric composite. Analyzing the piezoelectric properties through thed33coefficient, it was found that PUR‐MWCNT/PZT piezoelectric composite displayed higherd33values (20 pC/N) in comparison to the PUR/PZT two‐phase composite (9.5 pC/N) for all PZT loadings. According to these results, the dispersion of MWCNT nanoparticles influences the poling effectiveness of the PZT particles and increases thed33coefficient of three‐phase piezoelectric composites.

Polyaniline Chromium Nitrate Composites: Influence of Chromium Nitrate on Conductivity and Thermal Stability of Polyaniline

Thermal stability and electrical conductivity are the key to the technological feasibility and sustainability of conductingpolymers (CPs) and their composites in real-time applications. Notably, the impact of filler loading on above mentionedparameters of CPs needs to be examined and addressed with facile and easily accessible techniques. In the present study,Polyaniline (PANI) /chromium nitrate composites have been prepared via in situ polymerization of aniline through thechemical oxidative polymerization route. After that, the conductivity and thermal stability of PANI have been investigated atdifferent weight percentage loadings of chromium nitrate viz 5, 10, 20, and 40 % in the composite materials.The morphological and structural analysis of the pristine and composite samples were executed with Scanning electronmicroscopy (SEM), Fourier transforms infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) techniques. Thermalanalysis of proposed composites is carried out using the thermogravimetric analysis (TGA) method to evaluate variouskinetic parameters. The TGA thermogram and different calculated parameters revealed that the composites were morethermally stable than pristine PANI and that the composite having 20 wt % of chromium nitrate is thermally the most stable.The DC electrical conductivity data shows that PANI loaded with 20% chromium nitrate has the highest conductivity. Thisincrement in conductivity and thermal stability of the composites opens the path for many applications, such as sensors andelectronics.

Fabrication of PVA-MWCNT nanocomposite films for UV-shielding applications

Polyvinyl Alcohol (PVA) polymer nanocomposites are incorporated with Multiwall Carbon Nanotubes (MWCNT) of 20 nm diameter by solution casting. The SEM results show uniform dispersion of MWCNTs in the PVA matrix. The glass transition temperature (Tg) and the thermal decomposition temperature of PVA slightly increases with the incorporation of the MWCNTs. The DC electrical conductivity of PVA increases systematically from 4.1 × 10-13 S/cm to 8.1 × 10-8 S/cm for the highest 0.9 wt% MWCNTs. The direct band gap changes from 6.13 to 5.57 eV while the indirect band gap from 5.88 to 5.17 eV, also Urbach energy changes from 0.223 to 0.282 eV as the 0.9 wt% of MWCNTs reinforced in PVA.

Impact of Mn doping on structural, morphological and electrical properties of bismuth oxide

The impact of manganese (Mn) doping on structural and electrical properties of bismuth oxide nanomaterials is studied in this work. The Mn doped Bi2O3was synthesized by sol–gel method followed by auto combustion. The nanoparticles were presintered at 250 °C for three hours and finally sintered for four hours at 600 °C. Structural and morphological studies were carried out by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). XRD reveals the phase formation of the material. The particle size is calculated by using Debye-Scherrer formula which is in good agreement with the size (about 146 nm) calculated by using SEM images. The DC electrical conductivity measurement was carried out using four probe method. The values obtained are similar to reported values in literature.

Charge transport studies in flexible and rollable Polypyrrole-PVDF composite films

Polypyrrole has a unique place among conducting polymers discovered so far, due to its advantageous properties such as low-cost synthesis, stable electrical conductivity, non-toxicity, environmentally benign nature, etc. In this study, the polymerization of polypyrrole is carried out inside the porous structure of the polyvinylidene fluoride (PVDF) matrix using the chemical oxidation method to prepare flexible and rollable conducting films. The resistivity measurement of these flexible and rollable Polypyrrole-PVDF films were carried out using a standard four-point probe method in the temperature range of 320–10 K. The room temperature dc electrical conductivity of the film was found to be ∼ 50 S/m. To understand the charge transport mechanism in these films the experimental data were analyzed in the light of Mott’s variable range hopping model and Fluctuation assisted tunneling model. It was found that experimental data follows the three-dimensional variable range hopping behavior from 320 K to 90 K and below 90 K a crossover from hopping to fluctuation-assisted tunneling was observed. Mott’s parameters were measured in the temperature range of 320–90 K and the corresponding values for density of states at the Fermi level N(EF), average hopping distance (R), and average hopping energy (W) were found to be 5.54 × 1029m-3eV−1, 2.94 Å and 17.7 meV respectively.

Magnesium Spinel Ferrites Development for FDM 3D-Printing Material for Microwave Absorption

The magnesium nanosized ferrite powder with formula MgFe2O4 was synthesized via a pyrochemical sol–gel glycine–nitrate method and annealed consistently at temperatures of up to 1300 °C. The MgFe2O4 ferrite samples’ microstructure was studied by SEM and XRD methods. According to the results of the studies, the increase in MgFe2O4 nanoparticles size from about 15 nm to micron-sized particles was observed when increasing annealing temperatures. The DC electrical conductivity of MgFe2O4 also clearly shows the change in conduction behavior of samples with increased calcination temperatures. The electromagnetic microwave properties of micron-sized particles of MgFe2O4 ferrite powder for a 1200 °C annealing temperature were studied for composites in paraffin matrix with produced magnetic filler mass concentration at 40% and 50%. The filament composites of polymer polylactic acid with MgFe2O4 ferrite powder samples were prepared by the FDM 3D-printing process and their microwave-absorbing properties were investigated. The application of developed PLA–MgFe2O4 ferrite filament for fabricating magnetic microwave-absorbing components also was demonstrated.

Structural, morphological, optical and dielectric properties of sodium bismuth titanate ceramics

• The NBT ceramic was prepared by solid state reaction. • Modified Debye theory has been adopted to describe the phenomenon of relaxation. • The temperature dependence of Dc-conductivity of NBT followed the Mott’s Variable Range Hopping (VRH) law. This work focuses on the structural, optical and electrical properties of sodium bismuth titanate Bi 1/2 Na 1/2 TiO 3 (NBT) lead-free ceramic for its possible application in capacitors, batteries and as an electrolyte in SOFC. NBT material was prepared by the solid-state method. X-ray diffraction analysis performed at room temperature revealed a rhombohedral structure with R3c space group. Rietveld refinement confirmed a good agreement between the calculated and the observed pattern. Scanning electron microscopy analysis revealed a polycrystalline nature of the material with a grain size of 29.17 µm. FT-IR analysis showed the presence of different bonds. The band gap energy was extracted through diffuse reflectance spectroscopy and was found to be 2.61eV. Detailed studies of dielectric and impedance properties carried out in the frequency range of 40–10 7 Hz at different temperatures (from 400K-700K) provided many interesting properties. The dielectric loss and dielectric constant with frequency increase. This behavior could be interpreted by the Maxwell–Wagner type of polarization in agreement with Koop's theory. To explain the complex impedance plane plots, an equivalent circuit template was employed, reflecting semiconducting behavior of NBT. The Ac-conductivity spectrum satisfied Jonscher’s power law below 460K and followed Jonscher’s double power law (DPL) above 480K. The correlated barrier hopping (CBH) and small polaron hopping (SPH) models could explain the conduction mechanism at the studied temperature range. The study of the Dc-electrical conductivity confirmed that NBT followed the variable range hopping (VRH) model. The present work could give further insights into this kind of material from a physical point of view and thus enhance its presence in the industrial field.

Formation of zinc phthalocyanine on polymethyl methacrylate chain: Its nanographene‐based composite, thermal, electrical and optical behaviors

AbstractPoly[4‐((4‐vinylbenzyl)oxy) phthalonitrile‐co‐methyl methacrylate] [P(VBOPN10.7%‐co‐MMA)] was prepared by atom transfer radical polymerization (ATRP) method at 110°C. Green colored single chain polymer molecule via intramolecular formation of zinc phthalocyanine (SCP‐ZnPc) on polymer chain was synthesized using VBOPN as a precursor copolymer under conditions of dilute cyclohexanol and at 140–150°C. The successful formation of zinc phthalocyanine on a single chain molecule was confirmed using Fourier‐transform infrared spectroscopy (FT‐IR) and UV/Vis spectroscopy techniques. Nanogaphene‐based SCP‐ZnPc composite was prepared to employ 6 weight (wt)% of total weight and were investigated its thermal, electrical, dielectric and optical properties. The dielectric and DC electrical conductivity of SCP‐ZnPc/NG 6 wt% nanocomposite were found to increase depending upon temperature. And the conduction obeyed the Arrhenius relationship with the activation energy, Ea values for I. and II. regions were 0.345 eV and 0.275 eV, respectively. The optical constants (refractive index, real value of optical dielectric constant) and the optical band gap of SCP‐ZnPc/NG 6 wt% were estimated. The direct band gap and refractive index of SCP‐ZnPc/NG 6 wt% were estimated, and its direct band gap was estimated as 2.7 eV.

Influence on the efficiency of dye-sensitized solar cell using Cd doped ZnO via solvothermal method

In this report, the transition metal Cd doped ZnO nanoparticles synthesized by solvothermal irradiation method was used to fabricate ZnO-based dye-sensitized solar cells as photo sensitizers of Terminalia catappa fruit using ethanol as solvent. These prepared metal oxide semiconductor nanoparticles were studied by XRD, FE-SEM, TEM, FTIR, UV–Visible, XPS and DC electrical conductivity. Electrochemical parameters of open circuit voltage, short circuit current density, and fill factor were calculated using J-V characterization. The effect of Cd doping on the efficiency of ZnO-based DSSC is investigated, which results in enhanced DSSC light harvesting efficiency calculated. This obtained result confirms that the doping of ZnO nanoparticles is a valuable material for increasing the corresponding efficiency of a solar cell application.

Effect of Fe supplantation on structural and dielectric properties of La2CoMnO6

Double Perovskite system La2Co1-xFexMnO6 (x = 0, 0.2, 0.5, 0.8 and 1.0) has been synthesized by sol-gel route. XRD profiles confirmed the absence of any external phase in pure La2CoMnO6 phase. Rietveld refinement analysis confirmed the existence of monoclinic (ordered) as well as rhombohedral and orthorhombic (disordered) structures. Lattice parameters and unit cell volume are found to increase with increase in Fe content. Morphological and compositional analysis was done using FESEM with EDS. Frequency and temperature dependent dielectric characterization revealed the dispersion of both dielectric constant as well as loss tangent at low frequency and high temperature. The Nyquist plot of impedance (cole-cole) revealed negative temperature coefficient of resistance (NTCR) behavior of prepared samples and suggest a non-Debye type relaxation in these samples. An increasing trend with increase in frequency and temperature was exhibited by ac conductivity. Variation of dc electrical conductivity with temperature suggested a semiconducting behavior which can be explained by both small polaron hopping (SPH) and variable range hopping (VRH) conduction mechanisms.

Loss-of-function variant in the chymotrypsin like elastase 3B (CELA3B) predispose to non-alcoholic chronic pancreatitis

The ac and dc electrical conductivity of barium titanate doped bismuth-vanadate as-quenched and heat-treated materials was measured in the frequency range from 1 mHz to 1 MHz and in the temperature range from 153 K to 423 K with the impedance spectroscopy method. The microstructure was investigated by means of XRD, scanning electron microscopy (SEM), atomic force microscopy (AFM) and confocal microscopy.The obtained results showed that the structure of both as-quenched and heat-treated samples is not homogenous. Heat-treatment had significant influence on the amount, size and chemical composition of formed micro- and nanocrystallites. It also had great impact on the conduction process in investigated materials. As-quenched samples showed one relaxation process that was due to the overlapping polaron hopping. Conduction process in heat-treated samples may be caused by two different conduction mechanisms within nanostructures and in the matrix or by the interface polarization. Direct current conductivity increased and activation energies of this process decreased after heat-treatment. The experimental results were discussed based on a “core–shell” model and conductivity models collected by Elliot.

The effect of lithium doping on structural, thermal, optical and electrical properties of potash alum single crystals

• Pure and Li-doped potash alum single crystals were grown using slow evaporation. • Structural, thermal, optical and electrical properties of crystals were studied. • Doping potash alum crystal with Li made its room temperature phase more stable. • Optical band gap decreases and electrical conductivity increases by doping with Li. • Li-doped potash alum has better conditions for use in applications than pure one. At room temperature, supersaturated aqueous solutions were employed to grow single crystals of pure and Li-doped potash alum using the slow evaporation technique. The impact of lithium as dopant on the grown crystals' structural, thermal, optical and electrical properties was investigated. It was established that every crystal found during this work was potash alum, which has a cubic structure, space group Pa3 and Z = 4. Four peaks that indicated potash alum phase transitions were found during thermal investigation; these peaks moved with rising Li concentration. Li doping of potash alum increased the stability of the room temperature phase. This improvement in potash alum's stability after doping with lithium provided better conditions for its employment as an antibiotic and catalyst. The optical band gap energy of potash alum fell from 5.75 eV to 4.57 eV as Li concentration increased from 0 to 0.10 M. Potash alum's dc electrical conductivity increased as the Li content increased.

Broadband Photosensitive Medium Based on Amorphous Equichalcogenides

A photosensitive medium based on amorphous equichalcogenide thin films containing germanium and antimony is proposed with characteristics promising for applications in all-chalcogenide photonics, sensors, and photovoltaics. Optical properties, temperature, and exposure wavelength dependence of DC electrical conductivity are shown to be comparable with those for halide perovskites, which potentially makes amorphous equichalcogenides a very attractive alternative. The change in dark resistivity with temperature is found to follow exponential decay, covering 2 orders of magnitude over a 70 K temperature interval. Light exposure leads to several orders of relative changes in a current when compared to its dark value. A strong photocurrent response is observed under low power (milliwatts range) exposure across the entire 400–1000 nm range of the investigated wavelengths. An increase in temperature leads to a decrease in the photoresponse of the developed material, which is found to vanish at temperatures higher than 120 °C when only a few milliwatts of exposure power is used.

Nontrivial quantum geometry of degenerate flat bands

The importance of the quantum metric in flat-band systems has been noticed recently in many contexts such as the superfluid stiffness, the dc electrical conductivity, and ideal Chern insulators. Both the quantum metric of degenerate and nondegenerate bands can be naturally described via the geometry of different Grassmannian manifolds, specific to the band degeneracies. Contrary to the (Abelian) Berry curvature, the quantum metric of a degenerate band resulting from the collapse of a collection of bands is not simply the sum of the individual quantum metrics. We provide a physical interpretation of this phenomenon in terms of transition dipole matrix elements between two bands. By considering a toy model, we show that the quantum metric gets enhanced, reduced, or remains unaffected depending on which bands collapse. The dc longitudinal conductivity and the superfluid stiffness are known to be proportional to the quantum metric for flat-band systems, which makes them suitable candidates for the observation of this phenomenon.

Synthesis, electrical, magnetic and LPG sensing behavior of conducting polymer/ZnO nanocomposites

CPs nanocomposites have been synthesized by using in-situ chemical reaction method. The Polypyrrole nano composite characterizations were done by FTIR, X-ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), the conductivity measurement were carried out at different temperature and frequency using two probe method. The SEM image shows a substantial change in morphology after incorporating nano particle in composites.The AC and DC electrical conductivity increases with increasing nanoparticle concentration in polymer nanocomposites and achieved maximum conductivity for 50 wt. %. The magnetic properties of CPS nanocomposites are larger at 50 wt% and decreses with decreasing the concentration of nanoparticles in CPs composite . nanocomposite material is a prominent candidate for LPG sensing and potential applications.

Studies of Structural, Dielectric, and Impedance Spectroscopy of KBT-Modified Sodium Bismuth Titanate Lead-Free Ceramics.

Lead-free ceramic materials produced from bismuth sodium titanate (Na0.5Bi0.5TiO3, NBT)–bismuth potassium titanate (K0.5Bi0.5TiO3, KBT) have been developed through a solid-state reaction technique. The structural, dielectric, and piezoelectric characteristics of the ceramic materials were analyzed. Based on the XRD investigation, the morphotropic phase boundary (MPB) was determined for the composition (x (%) = 16 and 20). The effects of the KBT phase on the NBT lattice were examined using the charge density distribution. Furthermore, the dielectric properties indicated the presence of a negative dielectric constant (εr′) as a function of frequency between 1 kHz and 2 MHz. Negative permittivity was observed globally in the (1 – x)NBT–xKBT ceramic which reflects the effect of the dielectric resonance. The grain conduction effect is revealed through the complex impedance spectrum in the form of a semicircular arc within the Nyquist plot. In addition, the samples studied revealed a non-Debye relaxation phenomenon. The relaxation time was determined based on the Vogel-Fulcher law for all samples. DC conductivity was carried out on the ceramics material and revealed that the resistance decreases with increasing temperature indicating a negative temperature coefficient of resistance. The AC conductivity as a function of frequency for different temperatures suggests the presence of a thermally activated conduction mechanism. The activation energy has been determined based on the Arrhenius plot of the DC electrical conductivity as well as the relaxation frequency.