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Impedance measurements were made on technological important ferroelectric ceramics, namely PZT and La_0.75 Bi_3.25Ti₃O₁₂ (BLT), in the frequency range of 100 Hz to 1 MHz, from room temperature to 500°C. Combined impedance and modulus spectroscopic analysis along with the detailed conductivity (ac and dc) data was used to understand the heterogeneity of the ceramics and the results were corroborated with temperature coefficient of dc-conductivity (figure of merit) data for the further understanding. AC-conductivity plots against frequency at different temperatures for PZT and BLT suggest the response of obeying Jonscher's and modified Jonscher's law, respectively.

Impedance spectroscopic studies on polycrystalline sintered discs of lanthanum doped Na_1/2(La_xBi_1-x)_1/2TiO₃ ceramics with x = 0, 0.1, 0.15 and 0.2, have been carried out in the temperature region ranging from room temperature to 550°C and in the frequency range of 100 Hz to 1 MHz. Impedance data is presented in frequency explicit plots and Cole–Cole plots. The relaxation behavior of the charge entities in the above samples is studied as a function of temperature. The structural phase transitions present in the samples showed interesting changes with composition frequency and temperature. An attempt is made to correlate the results obtained to the phase transitions present in the samples.

The Caputo–Fabrizio (C–F) definition, which solves the singularity problem in the Caputo definition, has been preliminarily applied in the field of circuit system modeling. However, the complex characteristics of the C–F definition-based circuit systems are still understudied. Therefore, this paper proposes a C–F definition-based fractional-order RLC (CF-FORLC) circuit model and analyzes its basic characteristics. First, the effects of different component orders on the performance parameters including the impedance, quality factor, and bandwidth are analyzed, which gives insights into the design of CF-FORLC. Then, the analytical solutions and the frequency-domain characteristics of CF-FORLC with different capacitance and inductance orders under arbitrary input are derived. Finally, the data of actual circuits are fitted to obtain the parameters of the CF-FORLC model, and the orders of the C–F definition-based capacitors and inductors are estimated. The results of the comparative experiments show that the proposed modeling scheme can improve the consistency of the dynamic performance of the model with that of the actual circuit. In addition, the proposed CF-FORLC model shows higher accuracy and flexibility with more adjustable parameters.

Three different types of current-collecting plates for air-hydrogen PEM fuel cell were manufactured and tested: unmodified titanium plates; gold-plated titanium plates and titanium plates treated by carbon ions implantation. It was shown that the applied surface modifications reduce contact resistance between titanium plate and carbon gas diffusion layer. Total ohmic resistance of fuel cell is reduced by 1.8 and 1.4 times in case of gold-plated titanium and carbon-implanted titanium, respectively, in comparison with uncoated titanium. Although gold plating turned out to be more profitable than carbon ion implantation in terms of electrical characteristics, in the last case, the performance enhancement was reached without using precious metals, which at mass production must play more important role. This technology promises to reduce the cost of bipolar plates manufacturing, while maintaining high electrical performance of PEM fuel cells.

In this investigation, $\alpha$-Fe₂O₃ was prepared via co-precipitation and nano-NiO and NdFeO₃ were synthesized using the sol–gel method. For NdFe${}_{0.5}$Ni${}_{0.5}$O₃ synthesis, Nd₂O₃, $\alpha$-Fe₂O₃, and nano-NiO compounds were mixed via the solid state method. The effect of each component and that of nano-NiO on the NdFe${}_{0.5}$Ni${}_{0.5}$O₃ crystal properties was characterized by using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), ultraviolet-visible (UV–Vis), vibrating sample magnetometer (VSM), impedance and bandgap analyses. The orthorhombic perovskite structure was confirmed by the XRD data. With the doping of nano-NiO, the unit cell volume was found to decrease. The UV–Vis spectroscopy showed that the nano-NiO-doped optical bandgap ($E_g$) had increased. The VSM analysis demonstrated that by doping nano-NiO to weak ferromagnetic NdFeO₃, the resulting NdFe${}_{0.5}$Ni${}_{0.5}$O₃ was rendered superparamagnetic. The real and imaginary parts of dielectric permittivity ($𝜀$′ and $𝜀$″) and the loss tangent (tan$\delta$) characteristic of the compounds were measured at AC-signaled frequencies of 100 Hz–10 MHz and a voltage range of 0–20 V DC. The increase in active charge transmission with the doping of nano-NiO reduced the $𝜀$′ values. In addition, the large differences between the $𝜀$′ values were thought to be caused by the breakdown voltage ($E_b$) effect of the compounds. The $𝜀$″ and tan$\delta$ changes revealed the dipole formation of the compounds at different voltages, their relaxation regions and their polarization mechanism type. The dielectric loss behavior of the compounds demonstrated their good dielectric material properties. This study investigated the effect of method difference and doped material particle size on magnetic and dielectric properties.

Polycrystalline SrBi₄Ti_3.975Zr_0.025O₁₅ (SBTZ) was prepared using solid-state reaction technique. SBTZ was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis indicated the formation of a single-phase orthorhombic structure. Particle size was found using SEM. The dielectric, ferroelectric, piezoelectric, modulus and impedance spectroscopy studies on SBTZ were investigated in the frequency range 1 Hz–1 MHz from room temperature (RT) to 600°C. Piezoelectric charge and electromechanical coupling coefficients were calculated from resonance and anti-resonance frequencies. Impedance and modulus plots were used as tools to analyze the sample behavior as a function of frequency. Cole–Cole plots showed a non-Debye relaxation. Conductivity measurements were performed on SBTZ.

Lead-free $x$(0.50(Ba${}_{0.7}$Ca${}_{0.3})$TiO₃–0.50Ba(Zr${}_{0.2}$Ti${}_{0.8})$O${}_3)$-($1-x)$PVDF ceramic–polymer nanocomposites with $x=0.025$, 0.05, 0.10, 0.15, 0.20, 0.25 were prepared using melt-mixing technique. The distribution of nanoceramic filler particles (0.50(Ba${}_{0.7}$Ca${}_{0.3})$TiO₃–0.50Ba(Zr${}_{0.2}$Ti${}_{0.8})$O${}_3)$ in the PVDF matrix were examined using scanning electron microscope. Impedance analysis indicated the negative temperature coefficient of resistance character of all the test specimens. Filler concentration-dependent piezoelectric coefficient ($d_{33})$ data followed exponential growth types of variation. The data for ac conductivity were found to obey Jonscher’s power law. The correlated barrier hopping (CBH) model was found to explain the mechanism of charge transport occurring in the system. The low value of loss tangent ($\sim 10^{-2}$) along with the high value of $d_{33}$ foreshadowing the prospect of present nanocomposite is a better nonlead option for piezo-sensing/detection applications, especially in bio-medical area.

LaFe${{}_{1-}}_x$${\text{Zn}}_x$O₃ ($x$ = 0.03, 0.05, and 0.07) ceramics were prepared in two steps: preparation of the powder form by a sol–gel method followed by sintering-annealing treatments to form the bulk-phase. X-ray diffraction analysis revealed that all ceramics were crystallized in the orthorhombic perovskite structure with Pbnm symmetry. Grain size distribution and morphological characteristics were investigated by scanning electron microscopy. Specific surface area was analyzed through BET–BJH methods. Electrical impedance analysis was investigated as a function of frequency at various temperatures. It was found that the electrical behavior is dominated by grain boundary contribution, i.e., electrical conductivity. The frequency dependence of the complex conductivity was analyzed through Joncher’s power law and the dominance of translational motion with a sudden hopping mechanism in the electrical conduction mechanism increased with increasing Zn content. Activation energy decreased with increasing Zn content.

Lithium ion batteries have been attracting considerable interest worldwide in the past few years in the field of rechargeable batteries because they posses high energy density, long cycle life, good safety, and wide range of working temperatures. Lithium batteries based on vanadates such as LiNiVO₄, and LiCoVO₄ have gained a new interest since such material based electrodes display a large Li acceptance/removal at low voltages. A new electrode material LiBiVO₄ has been prepared using solid state reaction method. The formation of the compound has been characterized by XRD analysis. The Laser Raman Spectroscopy reveals the structural and phase analysis of LiBiVO₄. The electrical characterization has been carried out using the Impedance spectroscopy method in the frequency range of 50 Hz to 5 MHz. The bulk resistance of the material has been extracted from the impedance analysis and it is found to be 4.96 × 10^-7 Ω cm^-1 at 473 K. The modulus peak maximum shifts to higher frequency with increase in temperature and broad nature of the peaks indicate the non-debye nature of the material.

The blend polymer electrolyte membranes comprising PVAc-PVdF with various LiClO₄ concentrations have been characterized. FT-IR, XRD studies indicate the polymer-salt complex formation. The ac impedance cole-cole plot shows the high frequency semi-circle which is due to the bulk effect of the material and the depression in the semi circle shows the non-Debye nature of the material. The bulk conductivity is found to vary between 3.2 × 10^-7 to 1.3 × 10^-4Scm^-1 at 303K with the increase of salt concentration of blend polymer electrolytes. The ionic transference number has been found by Wagner's polarization method and the results reveal that the conducting species are ions. The low frequency dispersion of the dielectric constant implies the space charge effects arising from the electrodes.

Proton conducting polymer electrolytes based on Poly (vinyl acetate) (PVAc) and perchloric acid (HClO₄) has been prepared by solution casting technique with various compositions. FTIR spectra analysis reveals the interaction between proton and ester oxygen of Poly (vinyl acetate) (PVAc). Ac impedance spectroscopy reveals that 75m%PVAc:25m%HClO₄ exhibits maximum conductivity, 6.2×10⁻²Scm⁻¹ at room temperature (303K). The increase in conductivity with increase in dopant concentration and temperature may be attributed to the enhanced mobility of the polymer chains, number of charge carriers and rotations of side chains. The temperature dependence of conductivity shows non-arrhenius behaviour at higher temperatures. Dielectric loss spectra show two relaxations α (high temperature) and β (low temperature) relaxations in low and high frequency range respectively