Electric Modulus Spectroscopy Research Articles

Dielectric and impedance spectroscopic studies of 0.8BaTiO3–0.2Bi0.5K0.5TiO3lead-free ceramics

0.8 BaTiO3–0.2 Bi0.5K0.5TiO3(BT–BKT20) lead-free ceramics were prepared by conventional solid state reaction method followed by high energy ball milling. The formation of a single phase tetragonal structure in the material was confirmed by X-ray diffraction. Frequency and temperature-dependent dielectric studies show relaxor behavior in the BT–BKT20 which was found to obey modified Curie–Weiss law with degree of diffuseness 1.573. Complex impedance and electric modulus spectroscopy studies reveal temperature-dependent relaxation process in the material. The Cole–Cole plots were measured at high temperatures at which grain effect was observed. Impedance and electric modulus spectroscopy studies show non-Debye kind of conductivity relaxation process in the present material. Activation energies were calculated from impedance and electric modulus spectroscopy and the values of activation energy indicated that the conduction is ionic in nature. AC and DC conductivity have been measured and studied at different temperatures.

Dielectric and magnetic properties of Nickel ferrite ceramics using crystalline powders derived from DL alanine fuel in sol–gel auto-combustion

Dielectric and magnetic properties of NiFe2O4 ceramics prepared with powders using DL-alanine fuel in the sol–gel auto combustion technique are studied. DL-alanine fuel yields crystalline as-burnt powders, and when used for ceramic processing yields varying microstructure at different sintering temperatures. The dielectric properties are influenced by the resulting microstructure and the magnetic properties show slight change in saturation magnetization Ms (~44 – 46emu/g). The coercive fields, dielectric losses and dispersion are reduced considerably at higher sintering temperatures (1200–1300°C). The influence of changing microstructure is analyzed through dielectric response, complex impedance analysis and electrical modulus spectroscopy in the frequency range (10−2–107Hz) to understand the interactions from the grain and grain boundary phases. Sintering at 1200°C, is found to be optimum, yields lower losses & reduced dielectric dispersion, and high resistivity (3.4×108Ωcm).

Revisiting the low-temperature dielectric properties of ZnO

Electric modulus spectroscopy and impedance analysis were used to investigate the low-temperature (∼100–333 K) dielectric properties of ZnO crystals. Two relaxations were observed. The low-temperature relaxation (R1) features a thermally activated behavior resulting from the bulk response. Our results convincingly demonstrate that this relaxation is a polaronic relaxation. The relaxing species for R1 are localized holes created by zinc vacancies instead of the commonly agreed oxygen vacancies. The high-temperature relaxation (R2) is a Maxwell-Wagner relaxation due to skin-layer effect as it can be eliminated by grinding off the sample surface. The inhomogeneous distribution of zinc interstitials leads to the formation of the skin layer. Interestingly, an abnormal dielectric behavior contrary to the thermally activated behavior was found for the R2 relaxation. This abnormal behavior was confirmed to be related to the positive temperature coefficient of resistance due to the metal-insulator transition occurring within the skin layer.

Electrical modulus and dielectric spectroscopy behavior of spin coated perylene-monoimide semiconductor films

Perylene-monoimide (PMI) semiconductor films produced by spin coating were investigated for use in electronic and optoelectronic devices. We provide an electric modulus and dielectric spectroscopy study on perylene-monoimide between 30kHz and 1MHz and at the various biases (0.11–0.59V with steps 0.02V). The real dielectric constant (ε′), imaginary dielectric constant (ε″), loss tangent (tanδ), ac conductivity (σac), real (M′) and imaginary electric modulus (M″) values of perylene-monoimide thin film were determined. It is observed that the ε′ and ε″ have a high value at lower frequencies. At the same time, the M″ versus frequency curve of the sample has a peak at lower frequncies and at all voltage values. This peak is attributed to the dielectric relaxation. The variation of Cole–Cole plots of the device presents that there is one relaxation.

Investigation of conduction and relaxation phenomena in BaZrxTi1−xO3 (x=0.05) by impedance spectroscopy

In present study we have prepared ferroelectric BaZrxTi1−xO3 (x=0.05) ceramic by conventional solid state reaction route and studied its electrical properties as a function of temperature and frequency. X-ray diffraction (XRD) analysis shows single-phase formation of the compound with orthorhombic crystal structure at room temperature. Impedance and electric modulus spectroscopy analysis in the frequency range of 40Hz–1MHz at high temperature (200–600°C) suggests two relaxation processes with different time constant are involved which are attributed to bulk and grain boundary effects. Frequency dependent dielectric plot at different temperature shows normal variation with frequency while dielectric loss (tanδ) peak was found to obey an Arrhenius law with activation energy of 1.02eV. The frequency-dependent AC conductivity data were also analyzed in a wide temperature range.

Defect induced modifications in the optical, dielectric, and transport properties of hydrothermally prepared ZnS nanoparticles and nanorods

Zinc sulfide nanoparticles (particles size range 10–20 nm) and nanorods (particles size range 20–35 nm) were prepared through a hydrothermal method. The influence of surface defects and lattice strain on the optical, dielectric, and electrical transport properties was investigated. The spectral shifts and modification in bandgap are explained based on effective mass approximation model. Photoluminescence and ESR studies clearly showed the presence of large density of surface defects in the samples. The Raman spectra were thoroughly studied using the Gaussian confinement model. Dielectric studies using impedance and electric modulus spectroscopy showed enhanced grain boundary conductivity. Both nanoparticles and nanorods were found to exhibit Cole–Cole type dielectric relaxation. The enhanced ac electrical conductivities observed in both the nanostructures were successfully explained using the correlated barrier hopping model. Parameters like hopping time, barrier width, and defect densities were calculated.

Electrical and Dielectric Behavior of Nano-bio Ceramic Filler Incorporated Polymer Electrolytes for Rechargeable Lithium Batteries

A series of nanocomposite solid polymer electrolytes (NCSPE) consisting of PMMA as host polymer, lithium bisoxalatoborate (LiBOB) as doping salt and nano-hydroxy apatite as filler have prepared by membrane hot-press method. To enhance the electrochemical properties and stiffness of polymer electrolyte film, a bioactive ceramic filler nano-hydroxy apatite is incorporated in the polymer matrix. The prepared different weight contents of NCSPE films are subjected to various electrochemical characterizations such as ionic conductivity, electric modulus and dielectric spectroscopy studies. The complexation behavior and structural reorganization in polymer electrolytes are confirmed by means of FT-IR (Fourier-Transform Infra Red Spectroscopy) analysis. The electrical response and relaxation of dipole in polymer electrolytes are investigated by means of electric modulus and dielectric studies. The addition of nano-hydroxy apatite significantly enhances the ionic conductivity and blocking the reorganizing tendency of polymer matrix. The maximum ionic conductivity is found to be in the range of 10-4.8 S/cm for sample containing 10 wt. % nanoceramic filler.

Electrical conduction in (Bi0.5Na0.5)0.94Ba0.06TiO3-PVDF 0-3 composites by impedance spectroscopy

The present work describes the use of ac complex impedance and electric modulus spectroscopy techniques to obtain the electrical parameters like electrical conductivity and activation energy of (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT06)-PVDF 0-3 composites with (a) 10, (b) 20 and (c) 30 vol. percentage of BNBT06 in the frequency range 100 Hz-5MHz over a temperature range of 35 o C-150°C. SEM micrographs showed almost homogeneous distribution of grains with less porosity for all the compositions and the EDAX patterns confirmed the presence of different constituent elements of the composite samples. Complex impedance spectroscopic analysis indicated the presence of non-Debye type dielectric relaxation in the composites. The bulk resistance showed the NTCR character of the composite materials and the presence of grain-boundary effect along with the bulk contribution, especially in the lower frequency and higher temperature regime, was indicated by the modulus spectroscopic analyses, thus confirming the non-Debye type of multiple relaxations in the system. The ac electrical conductivity data as a function of temperature also endorsed the NTCR character of BNBT06-PVDF 0-3 composites. The ac conductivity based activation energy data allowed insight into the mechanism of the occurring conduction processes in the composite system which are explained on the basis of hopping model of charge carriers. Keywords- Ceramic-polymer 0-3 composites; Grains /grain-boundaries; Hopping conduction; Complex impedance/ modulus spectroscopy; Ac conductivity; Activation energy

Dielectric relaxation behavior of CdS nanoparticles and nanowires

The dielectric relaxation and scaling behavior of CdS nanoparticles and nanowires were investigated in the frequency range 102–106 Hz and in the temperature range 373–573 K by complex impedance spectroscopy and electric modulus spectroscopy. Studies on the complex permittivity revealed that the dielectric relaxation in CdS nanostructures deviates from Debye like behavior. A detailed study on the grain and grain boundary charge transport was carried out. The charge carrier transport in CdS nanostructures was identified to be hopping of polarons. From the combined analysis of the variation of imaginary part of electric modulus and complex impedance with frequency, it was found that at high temperatures localized conduction is dominant in CdS nanoparticles where as the long range hopping process is dominant with nanowires. It was also found that the scaling behavior of CdS nanoparticles varied considerably from that reported earlier.

A diffuse phase transition study on Ba 2+ substituted (Na 0.5Bi 0.5)TiO 3 ferroelectric ceramic

Polycrystalline perovskite lead free material (Na 0.5Bi 0.5) 0.91Ba 0.090TiO 3 was prepared by solid state reaction method. The crystal structure examined by X-ray powder diffraction indicates that the material was single phase with tetragonal structure. Dielectric studies exhibit a diffuse phase transition and characterized by a strong temperature and frequency dispersion of permittivity which relates cation disorder at A-site and exhibits relaxor behaviour. The dielectric relaxation has been modeled using the Vogel–Fulcher relationship, the calculated activation energy found to be E a = 0.021 eV. Complex impedance analysis indicates the system undergoing a polydispersive non-Debye type relaxation. Also, used to characterize grain and grain-boundary resistivities of Ba substituted (Na 0.5Bi 0.5)TiO 3 ceramic. The phenomenon was also interpreted by accounting for microstructural differences. The corresponding relaxation times were also used to confirm the interpretation of complex impedance spectra. Overlapping of grain boundary and electrode relaxation processes can be separated above about 4000 C. Electrical modulus spectroscopy studies have been performed. The conductivity parameters such as ion-hopping rate ( ω p) and the charge carrier concentration ( K 1) have been calculated using Almond and West formalism.

Impedance spectroscopy analysis for high‐Tc BaTiO3‐(Bi1/2Na1/2)TiO3 lead‐free PTCR ceramics

AbstractThe ac impedance measurement was used to investigate the yttrium (Y)‐doped 0.99BaTiO3‐0.01Bi1/2Na1/2TiO3 (0.99BT‐0.01BNT) lead‐free positive temperature coefficient of resistivity (PTCR) ceramics in the frequency range from 40 Hz to 2 MHz and in the temperature range from room temperature to 240 °C. The resistivity and capacitance of each electrical component can be obtained from the complex impedance and electric modulus spectroscopy. These obtained data were discussed and compared with directly experimental measured results. In addition, the surface acceptor‐state density and depletion layer thickness were calculated. The grain‐boundary potential barrier of the samples was also estimated according to the Heywang model, the value was between 0.17 and 0.55 eV in the temperature range of 150–240 °C.

Morphology, structure, optical, and electrical properties of AgSbO3

The morphology of defect pyrochlore-type, AgSbO3 microparticle/nanoparticles obtained via solid state reaction evolve from irregular to Fullerene-like polyhedra before finally decomposing into metal-organic framework-5 like particles with increase in sintering temperature. The defect pyrochlore-type AgSbO3 particles are slightly Ag deficient while the valence of the antimony ion is shown to be +5 giving rise to a probable stoichiometry of Ag1−xSbVO3−x/2, with x∼0.01–0.04. A highly structured diffuse intensity distribution observed via electron diffraction is interpreted in terms of correlated displacements of one-dimensional (1D) silver ion chains along ⟨110⟩ directions. A redshifting in the absorption edges in UV-visible absorption spectra is observed for samples prepared at sintering temperatures higher than 1000 °C and attributed to the surface plasma resonance effect associated with small amounts of excess metallic Ag on the Ag1−xSbVO3−x/2 particles. An electrical properties investigation of the silver antimonate samples via dielectric, conductivity, and electric modulus spectroscopy shows a prominent dielectric relaxation associated with grain boundaries. The silver ion conductivity is associated with correlated displacements of 1D silver ion chains along ⟨110⟩ directions.

Frequency–temperature response of CaBi 4Ti 4O 15 ceramic prepared by soft chemical route: Impedance and modulus spectroscopy characterization

Polycrystalline CaBi 4Ti 4O 15 ceramic has been prepared through a modified chemical reaction technique. Room temperature X-ray diffraction (XRD) analysis shows the formation of a single phase orthorhombic perovskite structure. Simultaneous analysis of the complex impedance ( Z∗), and electric modulus ( M∗) spectroscopy was carried in the temperature range of 100–850 °C. The dielectric relaxation is found to be of non-Debye type. The Nyquist plot shows the negative temperature coefficient of resistance type behavior. Two different conduction mechanisms are may be due to: (a) the dielectric relaxation processes due to localized conduction associated with oxygen vacancy; and (b) the non-localized conduction corresponding to long range conductivity associated with extrinsic mechanisms fundamentally associated due to the chemical inhomogeneity caused due to the difference in the ionic environment of Ca 2+ and Bi 3+ and their sharing in the A site of perovskite and [Bi 2O 2] 2+ slabs. Different conductivity components are recognized inside the grain: long range dc conductivity at low frequency region, a capacitive behavior at higher frequencies, and a universal power law behavior in an intermediate-frequency region where grain boundary contributions are neglected.

Cr을 첨가한 ZnO의 결함과 입계 특성

In this study, we investigated the effects of Cr dopant (1.0 at% <TEX>$Cr_2O_3$</TEX> sintered at <TEX>$1000^{\circ}C$</TEX> for 1 h in air) on the bulk trap (i.e. defect) and interface state levels of ZnO using dielectric functions (<TEX>$Z^*$</TEX>, <TEX>$M^*$</TEX>, <TEX>$Y^*$</TEX>, <TEX>$\varepsilon^*$</TEX>, and <TEX>$tan{\delta}$</TEX>), admittance spectroscopy (AS), and impedance-modulus spectroscopy (IS & MS). For the identification of the bulk trap levels, we examine the zero-biased admittance spectroscopy and dielectric functions as a function of frequency and temperature. Impedance and electric modulus spectroscopy is a powerful technique to characterize grain boundaries of electronic ceramic materials as well. As a result, three kinds of bulk defect trap levels were found below the conduction band edge of ZnO in 1.0 at% Cr-doped ZnO (Cr-ZnO) as 0.11 eV, 0.21 eV, and 0.31 eV. The overlapped defect levels (<TEX>$Zn^{..}_i$</TEX> and <TEX>$V^{\cdot}_0$</TEX>) in admittance spectra were successfully separated by the combination of dielectric function such as <TEX>$M^*$</TEX>, <TEX>$\varepsilon^*$</TEX>, and <TEX>$tan{\delta}$</TEX>. In Cr-ZnO, the interfacial state level was about 1.17 eV by IS and MS. Also we measured the resistance (<TEX>$R_{gb}$</TEX>) and capacitance (<TEX>$C_{gb}$</TEX>) of grain boundaries with temperature using impedance-modulus spectroscopy. It have discussed about the stability and homogeneity of grain boundaries using distribution parameter (<TEX>$\alpha$</TEX>) simulated with the Z"-logf plots with temperature.

Study of Structural and Electrical Properties of Conventional Furnace and Microwave‐Sintered BaZr0.10Ti0.90O3 Ceramics

Structural, dielectric, piezoelectric, and ferroelectric properties of Zirconium‐doped barium titanate (BaZr0.10Ti0.90O3) ceramics prepared by microwave (MWS) and conventional (CS) sintering process are compared. X‐ray diffraction and Raman spectroscopy indicate clearly the structural changes and confirm the effective diffusion of zirconium with the MWS technique to form BZT. Scanning electron microscopy reveals a fine grain, and a dense microstructure in the MWS ceramics processed under 4 h of cycle time (including heating, cooling, and holding time) in comparison with CS requiring 22 h. At room temperature the microwave sintered samples exhibit improved electrical properties exhibiting higher resistivity, higher dielectric constant, a lower dielectric loss, and a reduced dependence on frequency. Impedance and electric modulus spectroscopy analysis in the frequency range (40 Hz–1 MHz) and high‐temperature range (573–873 K) suggests two relaxation processes attributed to bulk and grain boundary effects in the impedance plots for the both MWS and CS ceramics. The microwave‐sintered BZT ceramics are found to be more attractive for room temperature device applications with improved properties, however, at higher temperatures they tend to degrade in comparison with the CS ceramics.

Mn을 첨가한 ZnO-TeO2세라믹스의 소결과 전기적 특성

We investigated the sintering and electric properties of ZnO-1.0 at% <TEX>$TeO_2$</TEX> (ZT1) and 1.0 at% Mn-doped ZT1(ZT1M1) system. <TEX>$TeO_2$</TEX> itself melts at <TEX>$732^{\circ}C$</TEX> in air but forms the <TEX>$ZnTeO_3$</TEX> or <TEX>$Zn_2Te_3O_8$</TEX> phase with ZnO as increasing temperature and therefore retards the densification of ZnO to <TEX>$1000^{\circ}C$</TEX>. In ZT1M1 system, also, the densification of ZnO was retarded up to <TEX>$1000^{\circ}C$</TEX> and then reached > 90% of theoretical density above <TEX>$1100^{\circ}C$</TEX>. It was found that a good varistor characteristics(nonlinear coefficient <TEX>$a{\sim}60$</TEX>) were developed in ZT1M1 system sintered at <TEX>$1100^{\circ}C$</TEX> due to Mn which known as improving the nonlinearity of ZnO varistors. The results of C-V characteristics such as barrier height (<TEX>${\Phi}_b$</TEX>), donor density (<TEX>$N_D$</TEX>), depletion layer (W), and interface state density (<TEX>$N_t$</TEX>) in ZT1M1 ceramics were <TEX>$1.8{\times}10^{17}cm^{-3}$</TEX>, 1.6 V, 93 nm, and <TEX>$1.7{\times}10^{12}cm^{-2}$</TEX>, respectively. Also we measured the resistance and capacitance of grain boundaries with temperature using impedance and electric modulus spectroscopy. It will be discussed about the stability and homogeneity of grain boundaries using distribution parameter (<TEX>$\alpha$</TEX>) simulated with the Z(T)"-logf plots.

Crystallization and dielectric properties of borate-based ferroelectric PbTiO3 glass-ceramics

Bulk crystallized PbTiO3 (PT) was the major crystalline phase in borate-based glass ceramics with starting composition 39PbO–1BaO–25TiO2–9.8Al2O3–1SiO2–24.2B2O3 (mol%). Crystallization of PT starts at ≥520 °C and the crystal size and c/a ratio of PT were approximately the same for all samples heat treated between 520 and 700 °C. Two transient unidentified phases were induced when crystallized between 520 and 650 °C. The first at 520 °C followed by a second at 550 °C. At >650 °C, PbTi3O7 was present in addition to PbTiO3. The electrical properties of glasses heat treated between 550–700 °C were investigated by fixed frequency capacitance measurements and impedance spectroscopy, IS. No permittivity maximum or Curie temperature, Tc, for the PT phase was observed from fixed frequency capacitance measurements for glasses heat treated below 700 °C, however IS data analysis using electric modulus (M″) spectroscopy revealed the PT phase to have Tc ∼480 and 440 °C for samples heat treated at ∼550 and 700 °C, respectively. The conductivity of the PT phase and the dc conductivity of the glass heat treated at 700 °C were significantly higher than those of glasses heat treated at lower temperatures suggesting there is significant compositional differences between the glass heat treated at 700 °C compared to those treated at ≤650 °C.

Conductivity mechanism analysis at high temperature in bismuth titanate: A single crystal with sillenite-type structure

Conductivity behavior of the Bi12TiO20 single crystal was investigated by the electric modulus spectroscopy, which was carried out in the frequency range from 5 Hz to 13 MHz and at temperatures higher than 400 °C. The resistance curve exhibits a set of properties correlated to a negative temperature coefficient thermistor. In the temperature range investigated, the characteristic parameter (β) of the thermistor is equal to 4834 °C. Temperature coefficients of the resistance (α) were derived being equal to −3.02×10−2°C−1 at 400 °C and equal to −9.86×10−3°C−1 at 700 °C. The nature of the electric relaxation phenomenon and magnitude dc conductivity are approached.

Mixed cation effects, site selectivities and electric modulus spectroscopy in β-alumina solid electrolytes

Mixed-cation effects in Na/K and Na/Ag β-aluminas have been examined by electric modulus spectroscopy using the Kohlrausch-Williams-Watts formalism, having previously determined cation site occupancies by X-ray structure refinement. One can distinguish losses in conductivity caused by blocking effects (amenable to percolation theory), which are associated with “modulus broadening”, from the situation where there is a decrease in microscopic ion mobilities, and “modulus narrowing” occurs. Further mechanistic insights are expected from an extension of this treatment to β”-aluminas and to glassy electrolytes.

An investigation of β-alumina electrolytes by electric modulus spectroscopy

Various types of β-alumina (including single-crystal cylindrical boules, Monofrax flakes polycrystalline sinters) have been investigated by electric modulus spectroscopy. The complex electric modulus is identical with the inverse complex permittivity, ie M *  ( e *) −1, and also related to the complex impedance by the equation M *  jω C 0 Z *; the modulus spectra are obtained by plotting the imaginary component, M″, vs log (frequency). The single-crystal specimens of β-alumina have spectra markedly broader than simple Debye curves, and in this respect they resemble vitreous and molten electrolytes rather than alkali halide crystals. The more complicated spectra of the polycrystalline samples show the marked effects of anisotropic conductivity. At the lowest temperatures studied (−160°C), the current appears to follow a series pathway through crystals in two distinct orientations, and it is apparently not able to seek out a preferred pathway as is the case at higher temperatures.