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This study explores the structural, dielectric, impedance, and optical characteristics of the perovskite compound Sr(Mn${}_{0.45}$Fe${}_{0.05})$Nb${}_{0.5}$O₃. The compound was prepared by the solid-state mixed-oxide method. X-ray diffraction analysis confirmed a single-phase tetragonal crystal structure ($a=5.6425$ Å, $b=5.6425$ Å, $c=7.9468$ Å, space group I4/mcm). Morphological analysis revealed an almost uniform grain distribution with minimal spacing. The Maxwell–Wagner phenomenon was observed in the frequency-dependent dielectric properties by considering various polarization mechanisms. A dielectric anomaly indicating a ferroelectric to paraelectric phase transition was observed around 260^∘C during the temperature-dependent dielectric study. Impedance analysis demonstrated the NTCR behavior of the material. According to Jonscher’s power law, conduction is governed by nonoverlapping small polaron tunneling, explaining the relationship between conductivity with frequency. The activation energies for relaxation and conduction suggest electron hopping. Estimated band gap of 1.91eV is applicable for optoelectronic devices. The temperature-dependent resistance analysis indicates potential applications in N-type thermistors. The M–H hysteresis loop’s nonlinearity curve suggests weak ferromagnetism at low temperatures.

The capacitance and loss tangent of thermally evaporated zinc phthalocyanine, ZnPc, semiconducting thin films were measured in the temperature range of 180–430 K and frequency between 0.1 and 20 kHz. Aluminum and gold electrical contact electrodes were employed to sandwich ZnPc films. For both electrode types, the capacitance and loss tangent showed strong dependence on both temperature and frequency. Such dependence is related to the relevant temperature and frequency range under consideration. The capacitance has strong temperature dependence for T>240 K and frequency below 3 kHz, while it becomes a constant at higher frequencies and all temperatures. The loss tangent dependence on temperature is more evident at low frequencies and a minimum or an indication of a minimum was observed in tan δ versus f curves. Loss tangent variation with temperature was not monotonic for all frequencies. An anomaly (maximum) in tan δ was observed approximately between 300 and 360 K. This maximum was attributed to the presence of oxygen molecules in the sample and their subsequent exhaustion as the temperature is increased. The behavior of capacitance and loss tangent (for both Al and Au-electrodes) may be explained qualitatively and successfully in terms of an equivalent circuit model.

Polycrystalline La_3/2Bi_3/2Fe₅O₁₂ (LBIO) compound was prepared by a high-temperature solid-state reaction technique. The complex impedance of LBIO was measured over a wide temperature (i.e., room temperature to 500°C) and frequencies (i.e., 10²–10⁶ Hz) ranges. This study takes advantage of plotting ac data simultaneously in the form of impedance and modulus spectroscopic plots and obey non-Debye type of relaxation process. The Nyquist's plot showed the presence of grain effects in the material at high temperature. The ac conductivity spectrum was found to obey Jonscher's universal power law. The dc conductivity was found to increase with rise in temperature. The activation energy of the compound was found to be 0.24 and 0.51 eV in the low and high-temperature region, respectively, for conduction process.

In this communication, structural and electrical properties of rare earth oxides La₂O₃ (LO) and LaNdO₃ (LNO) have been studied. To understand the structural properties of the LO and LNO samples, X-ray diffraction (XRD) measurement was carried out at room temperature. The XRD patterns have been analyzed by Rietveld refinement to confirm the single-phase nature of both the samples. The crystal structures of studied samples were created from the derived parameters of Rietveld parameters. The crystal size and lattice strain have been estimated using Williamson–Hall (W–H) plot analysis. Frequency-dependent dielectric constant and loss tangent have been studied for a frequency range of 20 Hz to 2 MHz. To estimate the relaxation time and contribution of the charge carriers in the studied samples, relaxation mechanism and universal dielectric response (UDR) model have been employed. The ac conductivity measurements were carried out for the same frequency range (i.e., 20 Hz to 2 MHz) which has been understood on the basis of Jonscher’s power law. The barrier height has been calculated by fitting the power law. Frequency-dependent impedance behavior has been discussed in the context of grains and grain boundaries for both the samples under study.

The strontium-modified barium titanate $({\mathrm{\text{Ba}}}_{0.7}{\mathrm{\text{Sr}}}_{0.3}{\mathrm{\text{TiO}}}_3)$ ceramic was fabricated by high temperature compound reaction route. The pattern of X-ray diffraction confirms a single-phase compound with better crystallization. The dielectric properties (permittivity/loss) are investigated as a function of temperature and frequency. The relaxation mechanism and correlation with the physical properties are studied using complex impedance spectroscopy. The Nyquist plot shows the association of various effects (grain and grain boundary) by fitting electrical circuits at various temperature regions. This study tells the nature and conduction mechanism of the prepared sample. The Jonscher’s universal power law is being followed by the frequency-dependent ac conductivity.

A spectrophotometric study of 1:1 donor–acceptor complex, cobalt (III) acetylacetonate (donor) and iodine (σ-acceptor) has been preformed. The equilibrium constants, (K) and the absorpitivity (ε) for the formation of the iodine complex have been calculated. The predicted structure of the solid triiodide charge-transfer complex reported in this study is further supported by thermal, far and mid infrared spectroscopic measurements. Electron transfer from Co (acac = 2, 4-pentanedionate)₃ to iodine leads to the formation of an organic semiconductor with the formula of . The kinetic parameters (nonisothermal method) for their decomposition have been evaluated by graphical methods using the equations of Freeman–Carroll (FC), Horowitz–Metzger (HM) and Coats–Redfern (CR). The ac conductivity and dielectric properties of have been measured over the frequency 50–10⁶ Hz at temperature 298 K.

The copper oxide, CuO, and copper hydroxide, Cu(OH)₂ nanomaterials have been prepared by a simple copper salt aqueous solution reaction. The powder X-ray diffraction (XRD) analysis showed the successful formation of Cu(OH)₂ and CuO nanoparticles. The average crystallite size of these Cu(OH)₂ and CuO nanoparticles was estimated and found to be around 17nm (Cu(OH)₂) and 10nm (CuO). The surface morphology and size of the CuO particles were confirmed by Scanning Electron Microscope (SEM) and High-resolution transmission electron microscope (HRTEM). The Raman analysis, dielectric and conductivity of CuO nanoparticles have been performed. The frequency variation of the capacitance (real dielectric constant) and dielectric loss was studied. The capacitance of the CuO nanoparticles is high at low frequencies and decreases rapidly when the frequency is increased. The frequency dependent ac conductivity follows Johnscher’s power law.

The glass composition 40Li₂O–5WO₃–(55−x)B₂O₃: xV₂O₅ for x = 0.2, 0.4, 0.6 and 0.8 is chosen for the present study. The glass samples were synthesized by conventional melt-quenching technique. The dielectric properties such as constant (ε′), loss (tan δ) and ac conductivity (σ^ac) are carried out as a function of temperature (30–270°C) and frequency (10²–10⁵ Hz). The glass sample (at x = 0.6) exhibited highest ac conductivity (σ^ac) and spreading factor (β) among all the samples. All glasses exhibited mixed conduction (both electronic and ionic) at high temperatures. The frequency exponent s denotes the ac conduction mechanism is associated with both QMT model (at low temperatures) and CBH model (at high temperatures).

The compositional dependence of ac conductivity (${\sigma }_{\mathrm{\text{ac}}}$), real ($\sigma$′) and imaginary ($\sigma$′′) parts of complex electric conductivity ($\sigma$*) was investigated as a function of temperature ($T$) and frequency ($f)$ for Mn${}_{0.7{+x}_{}}$Zn${}_{0.3}$Si_xFe${}_{2–{2x}_{}}$O₄, $x=0.0$, 0.1, 0.2 and 0.3 spinel ferrite system. The compositional dependence of lattice constant values suggested that the most of the substituted Si${}^{4+}$-ions reside at grain boundaries and only a few Si-ions are inside grains. The variation of ${\sigma }_{\mathrm{\text{ac}}}(x$, $f$, $T)$ is explained on the basis of segregation and diffusion of Si${}^{4+}$ ions at grain boundaries and grains, respectively, and the electrode effect. Thermal variation of ac conductivity at fixed frequency suggested two different mechanisms which could be responsible for conduction in the system. It is found that $\sigma$* is not the preferred presentation for dielectric data and the scaling process of real part of conductivity by normalized frequency and the scaled frequency were found unsuccessful. The fitting results of ac conductivity data with path percolation approximation were found suitable in low-frequency regime while in high-frequency regime, effective medium approximation (EMA) was found successful.

The frequency-dependent percolation and scaling behavior of a variety of polymer/metal composites (PMC), based on polyvinylidene fluoride (PVDF) matrix and various types of fillers such as; metal/alloy particles of different sizes, prepared through cold/hot pressing process conditions have undergone investigation. The universal percolation behavior in the vicinity of percolation threshold ($f_c$), i.e., ${\sigma }_{\mathrm{\text{eff}}}(\omega ,f_{\mathrm{\text{con}}}\approx f_c)\propto {\omega }^x$ and ${\epsilon }_{\mathrm{\text{eff}}}(\omega ,f_{\mathrm{\text{con}}}\approx f_c)\propto {\omega }^{-y}$ is well satisfied, which suggests $f_c$ to be independent of frequency, where ${\sigma }_{\mathrm{\text{eff}}}$ and ${\epsilon }_{\mathrm{\text{eff}}}$ are the effective ac conductivity and effective dielectric constants of the composite and $\omega$ is the frequency of applied ac signal. The obtained experimental values of the exponents are consistent with the inter-cluster polarization model ($x=0.72$ and $y=0.28$), satisfying $x+y=1$. The widely used percolative equations are well fitted with the experimental results of all PMC at all values of the frequency. The value of $f_c$ is found to be independent of frequency of the applied signal, suggesting the studied PMC are real percolating systems. The critical exponents ($s$ and $s^{\prime }$) which characterize the divergence of ${\epsilon }_{\mathrm{\text{eff}}}$ and ${\sigma }_{\mathrm{\text{eff}}}$ in the vicinity of $f_c$ are found to decrease with the increase of frequency. The rate of decrease of ‘$s$’ and ‘$s^{\prime }$’ with increase of frequency is attributed to the method of preparation, size of the fillers, adhesiveness of polymer/filler and the rate of decrease of ${\epsilon }_{\mathrm{\text{eff}}}$ with frequency (due to the absence of different extents of contributions of various types of conventional polarizations).

The perovskite (${\text{La}}_{0.7}$${\text{Ba}}_{0.3})$(${\text{Mn}}_{0.5}$${\text{Fe}}_{0.5}{){}_{1-}}_x$${\text{Zr}}_x$O₃, where $x$ = 0.1, 0.2 and 0.3, ceramics were synthesized by solid-state reaction method. The introductory structural studies were followed through by X-ray diffraction technique and the results have disclosed that all the samples were crystallized into an isolated phase. The Zr substitution in the resulting solid solutions increases the electrical conductivity and the maximum value of ac conductivity has been found to be $\sim$118.8 S ${}^{.}$ cm${}^{-1}$ for $x$ = 0.3 at 200${}^{\circ }$C (at 1 MHz). The frequency dependence of ac conductivity data follows Jonscher’s power law. The variation of the exponent $n$ versus temperature follows the nonoverlapping small polaron tunneling (NSPT) model. The dielectric relaxation has been observed to be of non-Debye nature for all measuring temperatures (50–200${}^{\circ }$C). The impedance spectroscopy reveals that all the samples exhibit negative temperature coefficient of resistance (NTCR) behavior. The prepared samples (for $x$ > 1) are supposed to be suitable for cathode materials in SOFCs.

The scaling properties of the ac conductivity of ion-conducting glasses have, in the last several years, led to considerable revision of our understanding of microscopic ion dynamics. Although the notion that frequency dependent dispersion of the ac conductivity is evidence for correlated (as opposed to purely random) ion motions remains intact, notions about the role of ion-ion interactions as a source for the correlated behavior are clearly inconsistent with the scaling properties of the ac conductivity. Instead, certain systematic variations in the dispersion highlight the possible importance of the cation’s local structural environment to influence the correlated motion. Here, I review some of the recent scaling ideas and their consequences with the goal of providing the casual impedance spectroscopist a set of practical guidelines for how scaling analyses may help in understanding ion conductivity measurements.

Due to lack of good proton conductive polymer electrolyte working at ambient temperatures, search for the new systems have been hotly pursued in the past few years. Hence an attempt has been made to synthesis PVA based polymer electrolyte with various compositions of ammonium nitrate using solution casting technique. The formation of the complex has been confirmed by FT-IR spectral studies and XRD analysis. In the impedance response curve, the absence of the high frequency semicircular portion leads to the conclusion that the current carriers are ions & therefore the total conductivity is mainly the result of ion conduction. The high ionic conductivity at ambient temperature is found to be 7.5×10⁻³Scm⁻¹ for 20mol% ammonium nitrate doped PVA. Dielectric behaviour is analyzed using dielectric constant(ɛ') and dielectric loss (ɛ") of the samples .The low frequency dispersion of the dielectric constant implies the space charge effects arising from the electrodes. The dielectric loss spectra show the very large (~10⁶) dielectric loss at lower frequencies due to free charge motion within the material.