Conductivity Relaxation Behavior Research Articles

Investigation of electrical conductivity and oxygen relaxation behavior for BaBi0.98Sr0.02Nb5-xTixO15-δ ceramics

Investigation of electrical conductivity and oxygen relaxation behavior for BaBi0.98Sr0.02Nb5-xTixO15-δ ceramics

Comprehensive understanding of charge and mass transport in BaZr0.1Ce0.7Y0.1Yb0.1O3−δ

This work reports transport properties of BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb1711), studied during oxidation/reduction and hydration/dehydration using electrical conductivity relaxation (ECR) measurements. The oxidation/reduction displayed typical monotonic conductivity relaxation behavior, attributed to the ambipolar diffusion of oxygen vacancies (Vo∙∙) and electron-holes (h∙), and oxygen surface exchange coefficient (k) were >1 order of magnitude higher than bulk diffusivities (D˜), indicating a diffusion-controlled process. Whereas, hydration/dehydration displayed a temperature-dependent gradual transition from monotonic to non-monotonic relaxation profile. At lower temperatures, transient defect concentration profile indicated that overall hydration/dehydration involved an acid-base-type reaction, comprising the diffusion of oxygen vacancy (Vo∙∙) and proton (Hi∙) couples. However, at higher temperatures and high [h∙], it involved a combination of a hydrogenation reaction (comprising component H via diffusion of h∙ and Hi∙ couple) and an oxidation reaction (involving component O via diffusion of h∙ and Vo∙∙ couple), thus giving rise to a two-fold non-monotonic relaxation profile. The k and D˜ values for oxygen vacancies (kVO∙∙; DVO∙∙) were lower than those for protons (kHi∙;DHi∙) with the respective Ea being 57.51 ± 3.14 and 60.72 ± 1.48 kJ∙mol−1 for oxygen-vacancies and 68.78 ± 12.65 and 71.05 ± 13.87 kJ∙mol−1 for protons.

AC conductivity and dielectric relaxation behavior of lamellar benzyltrimethylammonium/V2O5 nanocomposite

Lamellar benzyltrimethylammonium/V2O5 nanocomposite has been prepared hydrothermally. Electrical and dielectric properties as a function of temperature and frequency of the nanocomposite were reported. The decrease in Z′ with increasing temperatures indicates the existence of a negative temperature resistance coefficient (NTCR) characteristic of the semiconductor material. For T > 432 K, the values of the exponents decrease with increasing temperature indicating that the CBH model is the likely mechanism. When T < 432 K, the NSPT model is an adequate mechanism to characterize electrical conduction. Variation of log(σdc) versus 103/T reveals a rupture around 432 K and the average activation energy values are of the order of 0.240 and 0.085 eV. It has been found that the dielectric constant and the dielectric loss decrease when frequency increases which is explained by the hopping of electrons between V4+/V5+. Moreover, the presence of non-Debye type of relaxation was detected by the complex modulus analysis.

A porous cobalt(II)-organic framework exhibiting high room temperature proton conductivity and field-induced slow magnetic relaxation.

A two-dimensional (2D) cobalt(II) metal-organic framework (MOF) constructed by a ditopic organic ligand, formulated as {[Co(Hbic)(H2O)]·4H2O}n (1) (H2bic = 1H-benzimidazole-5-carboxylic acid), was hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction shows that the distorted octahedral Co2+ ions, as coordination nodes, are bridged to form 2D honeycomb networks, which are further organized into a 3D supramolecular porous framework through multiple hydrogen bonds and interlayer π-π interactions. Dynamic crystallography experiments reveal the anisotropic thermal expansion behavior of the lattice, suggesting a flexible hydrogen-bonded 3D framework. Interestingly, hydrogen-bonded (H2O)4 tetramers were found to be located in porous channels, yielding 1D proton transport pathways. As a result, the compound exhibited a high room-temperature proton conductivity of 1.6 × 10-4 S cm-1 under a relative humidity of 95% through a Grotthuss mechanism. Magnetic investigations combined with theoretical calculations reveal giant easy-plane magnetic anisotropy of the distorted octahedral Co2+ ions with the experimental and computed D values being 87.1 and 109.3 cm-1, respectively. In addition, the compound exhibits field-induced slow magnetic relaxation behavior at low temperatures with an effective energy barrier of Ueff = 45.2 cm-1. Thus, the observed electrical and magnetic properties indicate a rare proton conducting SIM-MOF. The foregoing results provide a unique bifunctional cobalt(II) framework material and suggest a promising way to achieve magnetic and electrical properties using a supramolecular framework platform.

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.

Influence of Sn, in on ac electrical conductivity and dielectric relaxation behavior of Se–Te chalcogenide glass films

Influence of Sn, in on ac electrical conductivity and dielectric relaxation behavior of Se–Te chalcogenide glass films

Electrical Conductivity and Oxygen Relaxation Behavior in Babi1-Xsrxnb5o15-Δ Tungsten Bronze Ceramics

Electrical Conductivity and Oxygen Relaxation Behavior in Babi1-Xsrxnb5o15-Δ Tungsten Bronze Ceramics

Electrical conductivity and oxygen relaxation behavior in BaBi1-xSrxNb5O15-δ tungsten bronze ceramics.

BaBiNb5O15 (BBN) based oxide-ion conductors have great potential for application in intermediate-temperature solid oxide fuel cells. In this work, electrical property enhancement is achieved by Sr2+ ion doping and sintering process improvement. The BaBi1-xSrxNb5O15-δ samples are prepared by the traditional solid-state reaction to investigate their electrical properties and oxygen relaxation behavior. Upon increasing the Sr2+ doping amount, the bulk conductivity of BaBi1-xSrxNb5O15-δ compounds increases first and then gradually decreases, and the bulk conductivity of the sample is the best when the doping concentration is 2 mol%. With the increase of Sr2+ doping, the activation energy shows a first decreasing and then increasing trend. Compared with the traditional sintering method, the total conductivity of the BaBi0.98Sr0.02Nb5O15-δ sample prepared by the two-step sintering method is greatly improved. These results have great implications for improving the electrical performances of BBN-based oxide conductors and studying their sintering process.

Effects of boron nitride and carbon nanotube on damping properties, thermal conductivity and compression stress relaxation behavior of BIIR

AbstractAs highly integrated electronic components and devices are used under high electrical power and mechanical vibration, the thermal conductivity, damping properties, and compression stress relaxation of protection materials have become critical factors which affect the long‐term durability and reliability of the materials. Damping rubbers are widely used, but their thermal conductivity and compression stress relaxation are rarely studied. Herein, the effects of boron nitride (BN) and carbon nanotube on the damping properties, thermal conductivity, and compression stress relaxation behavior of brominated butyl rubber (BIIR) are investigated. BN increases the damping factor of BIIR and widens its effective damping temperature range. The maximum damping factor of BIIR composite with 12.3 wt% BN is 0.95, and the effective damping temperature range is −41 to 60°C. Moreover, the thermal conductivity of BIIR with 12.3 wt% BN is 0.46, much higher than that of BIIR. With increasing BN content, the thermal conductivity of BIIR/BN composites increases gradually, while their stress relaxation rate decreases. Carbon nanotube can further increase the thermal conductivity of BIIR/BN composites. BIIR/BN composites with high damping properties and thermal conductivity have a great application potential in the heat dissipation and vibration reduction of electronic devices.

Analysis of the electrical transport, conductivity, and dielectric relaxation behavior of La0.75 Ba0.10 Sr0.15 Fe O2.875-δ (δ = 0.375 and 0.50) brownmillerite oxides

The topotactic reduction of La0.75Ba0.10Sr0.15FeO2.875 with titanium metal leads to a new isostructural material of the composition La0.75Ba0.10Sr0.15FeO2.875-δ (δ = 0.375 and 0.50). XRD analysis of phases confirms that the obtained compound adopts a brownmillerite-type structure. A slight distorted monoclinic P2/m was found to describe the crystal structure. The transport properties have been investigated by current–voltage (I–V). The electric and dielectric measurements were carried out covering a wide range of temperature (300–600 K). Our materials display semiconducting properties as well as mixed ionic and electronic conductivity. At high temperatures, the activation energy values proved to be around 907–630 meV, which refers basically to oxygen vacancies conduction. The analysis of dielectric properties and dielectric losses (ε’, tanδ) of both compounds vs temperature at different frequencies demonstrates two relaxer attitudes. A low dielectric loss and low electrical conductance were displayed. Relying upon these values, these materials stand for perfect candidates for micro-electronics devices.

A family of lanthanide metal-organic frameworks based on a redox-active tetrathiafulvalene-dicarboxylate ligand showing slow relaxation of magnetisation and electronic conductivity.

The reaction of the redox-active tetrathiafulvalene ligand and lanthanide ions is an important approach to prepare photo-electro-magnetic multifunctional metal-organic framework materials. A series of isostructural lanthanide metal-organic frameworks (Ln-MOFs) based on the in situ generated tetrathiafulvalene dicarboxylate (TTF-DC) ligand, {[Ln4(TTF-DC)6(DMF)4(H2O)2]·4DMF}n (Ln = Gd (1-Gd), Tb (1-Tb), Dy (1-Dy) and Er (1-Er)), was synthesized and characterized. These Ln-MOFs display tunable redox-active properties and semiconductor performance, and their electronic conductivities have been significantly improved after oxidation. All MOFs except 2-Tb exhibit slow magnetic relaxation under an applied dc field. 1-Dy and 2-Dy show field-induced single-molecule magnet (SMM) behaviour with energy barriers (Ueff) of 30.77 K (τ0 = 5.23 × 10-8) and 26.41 K (1.04 × 10-8 s), respectively.

Electrical Conductivity and Relaxation Behavior Studies of Corning Glass By Impedance Spectroscopy

Impedance Spectroscopy was applied to study conductivity and dielectric relaxation behavior of Corning’s glasses. The electrical behavior of several glass composition was studied over a wide range of frequency (1Hz -1MHz) and temperature (RT-500C). The relaxation time were calculated by analysis of electrical modulus. The calculated activation energy associated with dielectric relaxation and activation energy of dc conductivity are similar. The obtained values of conductivity confirm dependence of conductivity on number and mobility of ions at glass with different composition. With increasing conductivity, the relaxation time decrease. It was observed, that through entire temperature range, the dielectric relaxation is governed by the same mechanism.

Effects of calcium oxide on the surface properties of industrial sludge by analyzing rheological and electrical properties

Rheological properties in the dynamic regime and complex conductivity measurements were performed on the wastewater sample containing different calcium oxide content. The complex viscosity (η*), the elastic (G’) and loss moduli (G’’) exhibited a linear behavior as a function of angular frequency. These rheological properties were well described by a power-law. Therefore; The values of G’0, G’’0 and η0 corresponding to angular frequency (ω = 1 rad/s) were extracted. Their evolution as a function of calcium oxide content showed that there is a critical amount of calcium oxide content (3 %), from which these parameters showed a net transition indicating the existence of two regions. Similar behavior has been observed from the analysis of the complex conductivity. The hopping conductivity, the ionic strength and the associated relaxation time showed also a net transition at (3 %). A conductivity relaxation behavior was observed in the high frequency and a more detailed analysis of such behavior is reported. This behavior was attributed to the localized relaxation process due to the short-range hopping motion of ions trapped inside the aggregations. The evolutions of the rheological and the electrical properties were analyzed by an equation including two power laws. This equation was able to fit very well their evolution as well to predict the optimal amount of calcium oxide (3 %) needed to achieve the coagulation process.

A quantitative analysis of two-fold electrical conductivity relaxation behaviour in mixed proton–oxide-ion–electron conductors upon hydration

Electrical conductivity relaxation experiments on oxides with three mobile charge carriers, H+, O2- and e-, yield in (de-)hydration experiments kinetic parameters (diffusion coefficients and surface reaction constants). In addition, three amplitude factors are obtained, but they have not been given further consideration because quantitative expressions for their forms are lacking. In this study, the forms of the amplitude factors are derived for a diffusion-limited and a surface-reaction-limited case and a mixed case. In order to demonstrate the benefits of the approach, the electrical conductivity relaxation behaviour of lanthanum tungstate (La5.4WO11.1, LaWO54) was investigated experimentally over the temperature range 923 ≤ T/K ≤ 1223. A switch from two-fold non-monotonic relaxation behaviour at high temperatures to two-fold monotonic behaviour at low temperatures upon hydration was observed. The switch in sign of the fast kinetics' amplitude factor can be assigned to the electrochemical mobility of protons surpassing the electron-hole mobility with decreasing temperature.

AC/DC conductivity and dielectric relaxation behavior of ionic solutions of 1-butyl-3-methylimidazolium chloride in methanol

The complex relative dielectric function, ε*(f) of solutions of 1-butyl-3-methylimidazolium chloride ([BMiM][Cl]) in methanol (MeOH) of varying concentration and temperature have been measured in lower (20 Hz–2 MHz) and microwave (200 MHz–20 GHz) frequency regimes using precision LCR meter and Vector Network Analyzer (VNA) respectively. Complex ac conductivity, σ*(f) of the liquid samples were determined from the measured low frequency ε*(f). DC conductivity, σdc of the samples were also determined. The influence of concentration and temperature variation on the complex permittivity and electrical conductivity of the solutions is discussed. σdc of pure [BMiM][Cl] and pure MeOH is significantly enhanced in diluted to moderately concentrated solution of [BMiM][Cl] in MeOH. Experimental values of σdc at different concentrations were fitted to the empirical Casteel-Amis (CA) equation. Static dielectric constant of ionic solutions was determined from complex permittivity measurements in the microwave frequency range, using which, information about the molecular interaction between [BMiM][Cl] and MeOH was revealed. Viscosity (η), molar conductivities (Λm), infinite dilution conductance (Λ0) and Walden product (W) of the solutions were also determined. Orientational relaxation behavior of the mixture solutions in microwave frequency region is not influenced by variation in concentration of [BMiM][Cl] in MeOH. Different contribution arising in the dielectric spectra are discriminated.

AC conductivity and broadband dielectric spectroscopy of a poly(vinyl chloride)/poly(ethyl methacrylate) polymer blend

Alternating-current (ac) conductivity and dielectric relaxation behaviour of a poly(vinyl chloride)/poly(ethyl methacrylate) polymer blend have been investigated intensively in a frequency range from \(1 \times 10^{-1}\) to \(2 \times 10^{7}\) Hz through a temperature range from 300 to 393 K. The variation of \(\sigma _{\mathrm{ac}}\) of pure and polyblend samples showed a plateau region at high temperature and low frequency and this plateau region is decreased with decreasing temperature. Values of the exponent n are less than unity indicative of the correlated barrier hopping for conduction. The values of the exponent n are used to calculate the binding energy (\(W_{\mathrm{m}})\) of the charge carriers. The investigation of the frequency dependence of \(\varepsilon ^{\prime }\) for pure and polyblend samples showed a dielectric dispersion. The high values of dielectric constant at a low frequency and high temperature are attributed to the effects of space charge due to the electrode polarization. The complex electric modulus (M*) of pure and polyblend samples has been investigated. It is found that the real part of the complex electric modulus, \(M^{\prime }\) is increased non-linearly as the frequency increased and reached the steady state at higher frequencies for all samples. On the other hand, the imaginary part of the complex electric modulus, \(M^{\prime \prime }\) is characterized by a relaxation peak. The different modes of relaxation, such as interfacial polarization and dipolar relaxation, are detected in low and high frequency regions in the variation plot of \(M^{\prime \prime }\) against frequency. The activation energy values of both interfacial polarization and \(\upalpha \)-relaxation are calculated.

Impedance analysis of TeO2-SeO2-Li2O nano glass system

Abstract Nano crystallization in tellurium selenite glasses (TeO2-SeO2-Li2O) is achieved by the conventional heat treatment method. The structural phase transformation of glass samples is verified by X-Ray diffraction. The morphology, crystallinity, and the size of crystals were determined by Field Emission Scanning Electron Microscopy. The main crystalline phases detected are Li2Te2O5|α- Li2Te2O5, TeO2, Li2TeO3, SeO2, Li2Te2O5|β - Li2Te2O5, Se. It is found that nanoparticles are agglomerated into a rod-like structure having size in the range of 20–93 nm. Conduction mechanism and relaxation behavior in the present glass system is studied with a function of temperature and frequency. The conductivity is slightly increased from 1.04 × 10−4 to 2.87 × 10−4 Ω−1m−1 as the temperature is increased from 100 to 250 °C. It is observed that the electrical resistance decreases as the Li2O concentration is increased from 10 to 20 mol %. From the modulus spectra, the presence of both grain and grain boundary effect is observed. From the data, the hump is observed around temperature 200 °C in the tested glass system and indicates transition which represents resonance in the glass system due to nano crystalline behavior in the glass matrix. The power law exponent is calculated by fitting the data and suggesting those ideal long-range pathways, diffusion-limited hopping in the glass sample. Based on exponent values, ionic conductivity exists in the glass sample.

Influence of A-site off-stoichiomety on grain conductivity and oxygen relaxation behavior of Na0.5Bi0.5TiO3 ceramics

The electrical performances and relaxation behaviors of the Na0.525Bi0.475TiO2.975 and Bi-deficient Na0.51Bi0.48TiO2.975 sample were investigated. The grain conductivity of the Na0.525Bi0.475TiO2.975 sample is able to reach 1.51 × 10−3 S/cm at 673 K. In the temperature range of measurement, the grain conductivity of the Bi-deficient Na0.51Bi0.48TiO2.975 sample is lower than that of the Na0.525Bi0.475TiO2.975 sample. By the internal friction and dielectric relaxation spectrum, the activation energy and relaxation time at infinite temperature were determined as (0.82 eV, 2.47 × 10−14 s), (0.67 eV, 5.82 × 10−12 s) and (0.85 eV, 5.8 × 10−13 s), (0.52 eV, 2.55 × 10−10 s) for the Na0.525Bi0.475TiO2.975 and Na0.51Bi0.48TiO2.975 samples at the different temperature regions. In the Na0.525Bi0.475TiO2.975 compound, there is larger specific free volume, higher mobile oxygen vacancy content and better oxygen vacancy mobility, which cause the higher grain conductivity in the Na0.525Bi0.475TiO2.975 compound. To some extent, by the Bi-deficient method, oxygen vacancies can be introduced into the Na0.51Bi0.48TiO2.975 compound and the grain conductivity may be improved, but the other side of Bi-deficiency harms the oxygen vacancy diffusion capacities in the Na0.5Bi0.5TiO3 compound.

Tailoring of microstructure, magnetic properties and charge carrier dynamics of YIG nanoparticles by Gd doping

Effect of gadolinium doping on growth mechanism, microstructure, magnetic properties and conductivity relaxation behavior of sol-gel prepared yttrium iron garnet (YIG) nanoparticles is studied in detail. Rietveld microstructural analysis of XRD data confirms the growth of single phase nanocrystalline YIG. Gd doping created oxygen vacancies inside the system which played an important role in controlling transport properties. Switching field distribution (S.F.D.) and Law of Approach to saturation (L.A.S.) techniques were adapted to analyze magnetic properties which delineate an improvement of coercivity and anisotropy constant. Impedance spectroscopy revealed the grain contributions only to the conduction process and frequency dependent conductivity follows universal power law. Harviliak-Negami (H.N.) formalism was adapted to analyze the modulus data in the frequency domain. Scaling of conductivity and electrical modulus data established that the conduction and relaxation process are temperature and composition independent. Non-Debye type correlative motion of charge carriers was established via analysis of decay function of electric field ϕ(t) inside the material which was described by Kohlrausch-Williams-Watts (K.W.W.) function. Improvements of magnetic and electrical properties in the prepared system can be beneficial for different applications.

Yttrium doped cobalt ferrite nanoparticles: Study of dielectric relaxation and charge carrier dynamics

We report the effect of yttrium (Y) doping on structural, optical properties and conductivity relaxation behavior of cobalt ferrite (CFO) nanoparticles prepared via citrate auto-ignition route. Microstructural analysis using XRD study confirms the growth of single phase nanocrystalline CFO, HRTEM images delineate faults in the crystal stacking sequence. UV–vis absorption spectra show a blue shift for optical band gaps of the doped samples. Impedance spectroscopy suggests that both grain and grain boundaries contribute to the conduction process. A universal power law dependence of the conductivity spectra has been observed. Scaling of the conductivity spectra resulted the conduction mechanism to be independent of composition and temperature. Stretched behavior of the dielectric response has been elucidated by Harviliak-Negami (H.N.) model based functions. Defects in the crystal structure played important role on the overall transport properties of the system.