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The structural, dielectric and transport properties of modified Bismuth Sodium Titanate (BNT) are reported. Mn and Sr-modified BNT (Bi0.35Na0.35Sr0.3Ti0.9Mn0.1O3) was synthesized by a solid-state reaction route. Structural analysis based on Rietveld refinement of X-ray diffraction data confirms the single-phase characteristic without change of hexagonal crystal structure with R3C space group of BNT. The dielectric characteristics of the modified BNT are recorded in the frequency range of 20 Hz to 1 MHz at temperatures of 50 °C and 200 °C. Using the frequency-dependent, real and imaginary parts of the dielectric constant, ϵ′(ω)-ϵ″(ω) dipolar and hopping conduction-based carrier polarization properties are discussed. The dipole parameters such as relaxation time, static and high-frequency dielectric constant etc. are estimated by using Cole-Cole relaxation model. [ABSTRACT FROM AUTHOR]

Electrical characteristics of living cells have been proven to reveal important details about their internal structure, charge distribution and composition changes in the cell membrane, as well as the extracellular context. An impedance flow cytometry is a common approach to determine the electrical properties of a cell, having the advantage of label-free and high throughput. However, the current techniques are complex and costly for the fabrication process. For that reason, we introduce an integrated dual microneedle-microchannel for single-cell detection and electrical properties extraction. The dual microneedles utilized a commercially available tungsten needle coated with parylene. When a single cell flows through the parallel-facing electrode configuration of the dual microneedle, the electrical impedance at multiple frequencies is measured. The impedance measurement demonstrated the differential of normal red blood cells (RBCs) with three different sizes of microbeads at low and high frequencies, 100 kHz and 2MHz, respectively. An electrical equivalent circuit model (ECM) was used to determine the unique membrane capacitance of individual cells. The proposed technique demonstrated that the specific membrane capacitance of an RBC is 9.42 mF/m-2, with the regression coefficients, p at 0.9895. As a result, this device may potentially be used in developing countries for low-cost single-cell screening and detection. [ABSTRACT FROM AUTHOR]

In the present work, the Sr(Fe0.5Nb0.5)1-xMnxO3 powders were synthesized via a molten salt technique. Pure phase perovskite was obtained at 800 °C which was very low compared to previous works prepared by solid state reaction technique (> 1200 °C). XRD analysis for the Sr(Fe0.5Nb0.5)1-xMnxO3 ceramics revealed that the unit cell had an orthorhombic symmetry. Examination of dielectric measurement showed that all ceramic samples exhibited very high dielectric constants (εr,max > 200,000 at 1 kHz). The dielectric data showed that all ceramics exhibited a relaxor like behavior. Loss tangent value tended to decrease with increasing Mn, especially at low temperature range. The obtained loss tangent values were found to be lower than those reported in previous works. Impedance spectroscopy analysis revealed that the relaxor like behavior could be related with bulk grain, grain boundaries and electrode responses, where the samples had a heterogeneous conduction. Type of electrode and applied voltage had strong effects on the dielectric behavior. [ABSTRACT FROM AUTHOR]

Tragacanth Gum is a natural gum that has been widely used in food, pharmaceutical, and cosmetic industries. The electrochemical properties of the gum have not been explored yet. Therefore, in the present work solid polymer electrolytes based on Gum Tragacanth (GT) and Lithium nitrate (LN) have been synthesized by solution casting method. The dissociation and complexation of the salt with the host polymer are confirmed using XRD and FTIR studies. Impedance analysis was carried out using electrochemical impedance spectroscopy (EIS) in the temperature range of 308–343 K. The highest ionic conductivity at room temperature is found to be 8.28 × 10−3 Scm−1. The temperature dependence of the system GT:LN was found to obey Arrhenius behavior. Dielectric studies were carried out using impedance spectroscopy in the frequency range 10 Hz-4 MHz. Transference number study showed that the main charge carriers were ions and electrochemical stability window for the highest conducting electrolyte was studied using Linear sweep voltammetry. Thermogravimetry studies showed that thes electrolytes are thermally stable. [ABSTRACT FROM AUTHOR]

Perovskite BiFeO3 (BFO), and Bi1-xLaxFe0.98Cu0.02O3 (x ≤ 0.05) multiferroic ceramics were prepared by conventional sol-gel method. The influence of (La, Cu) co-doping on the structure, morphology, magnetic, ferroelectric and dielectric behavior were studied comprehensively. X-ray diffraction confirmed that the BFO samples possess rhombhedral structure. The crystallite size, lattice constant, etc were affected by La doping. Ferromagnetic properties were distrubed due to external doping. Enhanced ferroelectic properties like increased remanant polarization and reduced leakage current were achieved by La-substitution. Significant enhancement of dielectric constant may be attributed to Maxwell-Wagner effect. Impedance spectroscopy analysis suggests the effect of grain and grain boundary on the electrical properties of the BFO ceramics. Cole-Cole plots specifies non-Debye type of behavior. Enhanced dielectric constant, reduced loss and decreased leakage current of (La, Cu) doped BFO suggest these ferrites to be promising room temperature perovskite multiferroic materials for lead-free photovoltaic devices. [ABSTRACT FROM AUTHOR]

A non-lead electronic sample with chemical composition Bi(Ni2/3V1/3)O3 (BNV) has been fabricated via a conventional ceramic technology. The resistive, capacitive and conducting properties of the specimen are examined experimentally. The formation of the sample with orthorhombic crystal system is ensured through X-Ray diffraction spectrum. Detailed analysis of the temperature-frequency dependent dielectric properties affirms the fabricated specimen as a dielectric. The conductivity study gives information about the nature and conduction mechanism of the fabricated dielectric. The impedance spectroscopic technique reveals the role of grain and grain boundaries on the capacitive and resistive properties of the sample. The current density based electric field characteristics show that the sample has low leakage current density (1.2 × 10−9 A/cm2). This dielectric component entails high dielectric permittivity (98 × 102), lower loss (8) and excellent excitation response to an electric field, thus it props up to be a potential component in different high-temperature industrial applications. [ABSTRACT FROM AUTHOR]

In this article, we report the results of the Rietveld and impedance analysis of Eu doped La1–xEuxMnO3 (LEMO; x = 0.10, 0.30, and 0.50) perovskite manganites synthesized by solid-state reaction method. Structural studies through Rietveld analysis confirm that a mixed-phase nature of all LEM samples having a hexagonal unit cell structure with a less detectable impurity (Eu2O3) ceramics. The patterns are zanalyzed in detail with structural distortion and strain in LEM manganites ceramics. Dielectric constant and modulus are found to increase with increasing Eu concentration. The samples LEM-0.10 shows the negative capacitance at low frequency and temperature, respectively. [ABSTRACT FROM AUTHOR]

A non-lead electronic sample with chemical composition Bi(Ni2/3V1/3)O3 (BNV) has been fabricated via a conventional ceramic technology. The resistive, capacitive and conducting properties of the specimen are examined experimentally. The formation of the sample with orthorhombic crystal system is ensured through X-Ray diffraction spectrum. Detailed analysis of the temperature-frequency dependent dielectric properties affirms the fabricated specimen as a dielectric. The conductivity study gives information about the nature and conduction mechanism of the fabricated dielectric. The impedance spectroscopic technique reveals the role of grain and grain boundaries on the capacitive and resistive properties of the sample. The current density based electric field characteristics show that the sample has low leakage current density (1.2 × 10−9 A/cm2). This dielectric component entails high dielectric permittivity (98 × 102), lower loss (8) and excellent excitation response to an electric field, thus it props up to be a potential component in different high-temperature industrial applications. [ABSTRACT FROM AUTHOR]

In this paper, we report the influence of A-site substitution on dielectric and electrical behavior of Mn3O4 based modified spinels at room temperature. All the three spinels substituted with Mn, Zn and Co at A-site showed slight decrease in relative permittivity (ε′) and dissipation factor (tanδ) in the studied frequency range of 40 Hz to 8 MHz. However, the influence of A-site substitution was noticeable because of it dominant influence on relative permittivity and dissipation factor over pure Mn3O4 spinel. The relative permittivity increased from ∼ 16 to 95 after substitution of Zn in A-site whereas the substitution of Co increased the magnitude upto 40. Similar trend was observed with tan δ measurement after A-site substitution. The frequency dependent impedance measurement revealed the better conducting behavior of pure and modified spinels because of its low impedance range and better frequency dependent ac-conductivity. [ABSTRACT FROM AUTHOR]

The present work mainly focuses on the preparation of magnesium-doped nickel ferrite nanoparticles via hydrothermal technique. Diffraction pattern attributes the formation of pure cubic spinel phases after microwave heating the samples at 500 °C for 10 min. In addition to the diffraction study, the removal of lepidocrocite (γ-FeO (OH)) signal in an infrared spectrum also confirms the phase purity due to microwave heating. Larger optical band gap (Eg) values are acquired for nanostructures varying between 1.73 and 1.86 eV. The surface morphology is analyzed using transmission electron microscope. The obtained particle sizes are in the range of ∼50–85 nm. The M-H loop analysis shows that 50% of Mg-dopant in Ni-ferrite system exhibits the highest saturation magnetization ∼191 emu/g. The behavior of complex dielectric modulus is illustrated in the specific frequency range of 100 Hz to 5 MHz for investigating the space charge polarization mechanism. [ABSTRACT FROM PUBLISHER]

A new blend polymer electrolyte based on poly(vinyl alcohol) and polyacrylonitrile doped with lithium nitrate (LiNO3) has been prepared and characterized. The complexation of blend polymer (92.5 PVA:7.5 PAN) with LiNO3has been studied using X-ray diffraction and Fourier transform infrared spectroscopy. Differential scanning calorimetry thermograms show a decrease in glass transition temperature with the addition of salt. The maximum ionic conductivity of the blend polymer electrolyte is 1.5 × 10−3Scm−1for 15 wt% LiNO3doped–92.5 PVA:7.5 PAN electrolyte. The conductivity values obey Arrhenius equation. Ionic transference number measurement reveals that the conducting species are predominantly ions. [ABSTRACT FROM AUTHOR]

The poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) and reduced graphene oxide (rGO)/PEDOT:PSS have been prepared by spin coating as counter electrodes (CEs) for dye-sensitized solar cells. The optimized 1wt% rGO was dispersed in a solution of PEDOT:PSS for the highest electrical conductivity. The cyclic voltammogram result shows that rGO/PEDOT:PSS CE has a good catalytic activity towards the I−/I3−redox couple compared to Pt CE and PEDOT:PSS CE. The rGO/PEDOT:PSS CE showed a high energy conversion efficiency of 5.1% accompanied by a fill factor of 0.68, which was comparable to those of the Pt CE (4.6%) and PEDOT:PSS (2.4%). Hence, the rGO/PEDOT:PSS is expected to replace the expensive Pt as a promising CE catalyst. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cell (SOFC) is considered as a potential candidate for clean and efficient alternate energy source. Efforts are being made to reduce their operating temperature for SOFCs commercialization. However, the reduction in operating temperature increases the polarization effect in the existing cathodes. In the present study, Bi0.5Sr0.5MnO3was synthesized and studied for its structural, thermal, and electrical properties. Bi0.5Sr0.5MnO3was synthesized by conventional solid state reaction method. The as-prepared sample was characterized by x-ray diffraction, scanning electron microscope, thermogravimetric analysis, dilatometer and impedance spectroscopy. The Rietveld refinement results confirm that Bi0.50Sr0.50MnO3shows the tetragonal symmetry withp4 mmspace group. Scanning electron microscopy study shows that the distribution of grains is uniform and the grains are well connected to each other due to better sinterability of the samples. The dilatometric curve shows linear behavior up to 600°C and after that becomes steeper. This can be due to the loss of lattice oxygen at higher temperatures and creation of oxygen vacancies. The thermal expansion coefficient of the system is ∼8.9 × 10−6°C−1and total conductivity of the sample is ∼4.78 × 10−3 S/cm. [ABSTRACT FROM AUTHOR]

The polycrystalline sample of a new tungsten bronze ferroelectric vanadate, Li2Pb2La2W2Ti4V4O30, was prepared at a relatively low temperature using a mixed-oxide technique. The formation of the material under the reported conditions has been confirmed by an X-ray diffraction technique. A preliminary structural analysis exhibits orthorhombic crystal structure of the material at room temperature. Studies of dielectric properties (ϵ, tanδ) of the above compound as a function of temperature (273–600K) at frequencies 10, 100, 1000 KHz exhibits a ferroelectric phase transition of diffuse type. The electrical properties of the material have been studied using ac impedance spectroscopy technique. Detailed studies of impedance and related parameters exhibit that the electrical properties of the material are strongly dependent on temperature, and bear a good correlation with its microstructures. The temperature dependence of electrical relaxation phenomenon in the materials has been observed. The bulk resistance, evaluated from complex impedance spectra, is found to decrease with rise in temperature, exhibiting a typical negative temperature co-efficient of resistance (NTCR) –type behavior similar to that of semiconductors. A small contribution of grain boundary effect was also observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. The ac conductivity spectra exhibit a typical signature of an ionic conducting system, and are found to obey Jonscher's universal power law. [ABSTRACT FROM PUBLISHER]

Dictyostelium discoideum cells respond to periodic signals of extracellular cAMP by collective changes of cell-cell and cell-substrate contacts. This was confirmed by dielectric analysis employing electric cell-substrate impedance sensing (ECIS) and impedance measurements involving cell-filled micro channels in conjunction with optical microscopy providing a comprehensive picture of chemotaxis under conditions of starvation. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) blends with single and double soft-templates (polyvinylpyrrolidone – PVP and/or sodium dodecylbenzenesulfonate – SDBS) were synthesized using interfacial polymerization. Fourier transform infrared (FTIR) spectral study confirmed blend formation. Polyaniline-polyvinylpyrrolidone (PANI-PVP) blend had submicron aggregates of 50–150 nm nanoparticles while PANI-SDBS blend had extensively agglomerated large size flakes/grains. Polyaniline-polyvinylpyrrolidone-sodium dodecylbenzenesulfonate (PANI-PVP-SDBS) blend had larger aggregates, besides significant number of smaller grains. Alternating current (AC) impedance analysis was performed to determine their electrical properties. At room temperature the AC conductivity of the blend materials was in the increasing order, PANI < PANI-PVP < PANI-SDBS < PANI-PVP-SDBS. But other parameters, like critical frequency and power law index s, exhibited a decreasing trend in the blend materials. With regard to frequency-dependence, all the materials showed constant AC conductivity at low frequencies, but at higher frequencies and at higher temperatures conductivity increased gradually. The obeyance of a universal power law and the range of s values (0.12 < s < 0.78) suggested a correlated barrier hopping (CBH) mechanism for AC conductivity of all the materials. The trends in electrical properties that were characteristic of the role of single/double soft-templates were explained in terms of improved π-electron delocalization and hopping mechanism. [ABSTRACT FROM AUTHOR]

Polycrystalline Ba5HoTi3V7O30 compound has been prepared by solid-state reaction technique. Compound is found to be single phase by XRD studies. SEM study indicates average grain size to be ∼3 μm. Dielectric studies carried out in temperature regime RT-773 K and frequency range 1 Hz-100 kHz, show ferroelectric phase transition at 550 K at 100 kHz. The impedance spectra show three distinct regions in temperature range 543-663 K corresponding to electrode polarization, grain boundary and grain interior contributions and indicate ionic behavior. The activation energy has been evaluated following Arrhenius equation to be 0.51 eV. [ABSTRACT FROM AUTHOR]

The quartz crystal microbalance (QCM) is a very accurate sensor for measuring small changes of mass of thin films spread on the quartz surface. Under certain conditions, the resonance frequency of a quartz crystal can be used for monitoring the mass change caused by solvent adsorption or dissolution inside a film. However, when a quartz crystal is immersed in a high-pressure non-inert gas, various effects such as pressure, viscosity, roughness on the surface of the quartz crystal, adsorption of gas or even gas film formation slipping at the solid-gas interface can influence the resonance frequency of the quartz crystal and consequently complicate the relation between mass and frequency changes. In order to determine experimentally such effects in contact with carbon dioxide in the neighborhood of the critical conditions, the resonance curve of a quartz crystal under gas pressure was examined with a network analyzer which is able to determine both resonance frequency and half-band-half-width on several overtones. [ABSTRACT FROM AUTHOR]