Ac Conductivity Studies Research Articles

Energy storage, electrocaloric and optical property studies in Ho-modified NBT – BT lead-free ferroelectric ceramics

A comprehensive investigation of structural, microstructural, optical, electrocaloric, and energy storage properties of Ho-modified NBT-BT lead-free ceramics was conducted from room temperature to a high-temperature region. Rietveld refinement confirms the coexistence of dual-phase monoclinic (Cc) and tetragonal (P4mm) phases in Ho-modified NBT-BT ceramics. A prominent monoclinic distortion was found with increasing Ho composition up to x=0.02, and then an abrupt decrease for x=0.03 ceramic was noticed. Of particular importance is the composition of x = 0.02, which exhibits a high electrocaloric temperature change (ΔT) of 0.73 K @ E = 20 kV/cm at a temperature of 373 K, and an optimal high recoverable energy storage density (Wrec) of 1.8846 J/cm3 along with an efficiency 83% was achieved. The frequency dependence ac-conductivity study promotes the reduction of oxygen vacancies at room temperature and the dominance of single ionized oxygen vacancies at very high temperatures well above 300 °C. A small considerable increase in the energy bandgap values with the Ho3+ ion substitution in NBT-BT was observed. Under the excitation of 532 nm light, the two most prominent red fluorescence emission peaks were emitted, where the first emission band with weak intensity was observed at 657 nm which corresponds to the 5F5→5I8 transition, and a strong 2nd peak at 756 nm corresponds to the 5F4/5S2→5I7 level transition of the Ho3+ ion. These findings provide a feasible multifunctional property in the applications of power electronic devices with lead-free NBT-BT ceramics via rare-earth substitution.

Effects of Mn doping on structural properties and conduction mechanism of NaCu0.2Fe0.8−xMnxO2 (x = 0.4; 0.5; 0.6; 0.7) materials

The NaCu0.2Fe0.8−xMnxO2 (x = 0.4; 0.5; 0.6; 0.7) samples were synthesized using conventional solid states method. Analyzing the DXR measurement through the use of FullProf allowed us to prove the purity of these samples and to corroborate that they crystallize in hexagonal system in the R-3 m space group. The refinement of the crystalline structure revealed the O3 structure type for compounds whose x = 0.4 and x = 0.5 and the P3 structure type for compounds whose x = 0.6 and x = 0.7. It is to be noted that the impedance spectroscopy results expressed in terms of a Nyquist diagram demonstrated three contributions which are grain, grain boundary and electrode effects. The conduction mechanism deduced from the study of ac conductivity goes in good agreement with the overlapping large polaron (OLPT) to compounds whose x = 0.4 and 0.5. However, for the sample whose x = 0.6 and 0.7, the conduction process was determined through the correlated barrier hopping (CBH) model. Furthermore, we examined the influence of Mn substitution on structural and electrical properties. Therefore, by increasing the Mn amount, we inferred that the structure changed from O3 to P3, which affected the electrical properties and enhanced the grain conductivity owing to the decreasing volume of the sodium site.

Investigation on growth, growth kinetics and characterization of L-valine L-valinium perchlorate monohydrate single crystal

The ultimate focus of this paper is on nucleation and growth kinetics, structural and dielectric behavior of l-valine l-valinium perchlorate monohydrate (LVPM) single crystal. LVPM single crystals were grown by conventional slow evaporation technique at room temperature. Salient nucleation parameters, essential for the growth of good quality crystal were estimated with the help of solubility curve and Classical Nucleation Theory (CNT). Single Crystal X-ray Diffraction (SC-XRD) analysis reveals that the synthesized crystal (LVPM) possesses monoclinic structure with lattice parameters as a = 11.227 Å, b = 5.82 Å, c = 13.08 Å, α = γ = 90º and β = 91º. The above results were also confirmed by powder XRD study. The structure of the grown crystal was analyzed by using SHELXT-2014/7 program. It is found that grown crystal belongs to non-centrosymmetric space group P21. All the functional groups and also carboxyl and amino functional groups of LVPM crystal were identified and confirmed by Fourier Transform Infra-red (FTIR) spectroscopy. The molecular structure of the grown crystal and in particular, the presence of amino group was discussed by using 1H and 13C Nuclear Magnetic Resonance (NMR) spectra. The low values of dielectric constant and dielectric loss at higher frequencies indicate that the grown crystal enhances the Second Harmonic Generation (SHG) efficiency. The activation energy of the grown crystal was estimated as 0.1433 eV from AC conductivity study. Kurtz and Perry powder experiment was performed to explore the Nonlinear Optical (NLO) properties of LVPM and its SHG efficiency was found 1.5 times of KDP (1.5’ KDP). The grown material was also found possessing SHG efficiency nearly five times higher than most of the l-arginine compounds. Since the grown material belongs to non-centrosymmetric group and exhibits improved structural, NLO and dielectric behavior, the material will be useful in optoelectronic devices, fiber optic communication, computing, optical switching, image reconstruction, optical storage technology, 3D-images, etc.

Non-overlapping small polaron and overlapping large polaron assisted conduction relaxation in polycrystalline YFe0·9Cr0·1O3 – An impedance spectroscopic and AC conductivity studies

Detailed ac electrical investigations within the frequency range 100 Hz-1 MHz have been conducted on the polycrystalline YFe0·9Cr0·1O3 samples prepared via solid state reaction route, in a broad thermal interval of 298–673 K. A systematic development of grain, grain boundary and electrode polarization contribution have been observed with increasing temperature. The thermal variation of the grain resistance (R g) and grain boundary resistances (R gb) followed the non-adiabatic small polaron hopping (SPH) model and is responsible for the long-range conduction with different values of the activation energies at different thermal regimes. The ac conductivity of the material exhibited series of dispersive regions with broad region, where the slope changes occurred up to 473 K. Above 473 K, appreciable dc conductivity in the material can be seen. Different dispersive regions in the conductivity spectrum obeyed single power law and power law variation (Aωn).

Structural, morphological, electrical, and magnetic characteristics of 20MnFe2O4-80SiO2 nanocomposite synthesized by the one-pot auto-combustion route

We report an investigation of the structural, morphological, the ac-dc electrical, magnetic, and Mössbauer spectroscopy properties of 20MnFe2O4-80SiO2 nanocomposite prepared using a one-step and facile auto-combustion approach. XRD pattern shows the formation of MnFe2O4 nanocrystallite without any crystallization of the SiO2 phase. However, the presence of a secondary phase of the nanosized α-Fe2O3 particles was also detected. The morphological analysis showed aggregation of polygonal magnetic nano-crystallites dispersed non-uniformly in a silica matrix. The dc electrical measurements performed on a wide range of temperatures from 120 to 400 K showed the semiconducting nature of the nanocomposite. The temperature dependence of dc conductivity could be perfectly fitted to the nearest neighborhood hopping model with activation energy, ΔENNH, of 0.45 eV. The Nyquist plots demonstrated a nonmonotonous thermally activated trend and non-Debye relaxation behavior. An equivalent circuit was successfully fitted to the complex impedance spectra. The variation of both grain and grain boundary conductivities as a function of temperature exhibited three distinct regions, semiconducting-metallic-semiconducting with different activation energies over the measured temperature window. The provided description of such behavior is further advocated by the ac conductivity and dielectric modulus studies. VSM measurements revealed that the nanocomposite magnetic behavior deviates from the ideal non-interacting superparamagnetic picture, due to the presence of α-Fe2O3 nanocrystalline impurities and relatively intensive exchange interactions between ions. Mössbauer spectra showed the presence of Fe3+ ions with sixfold environment and also confirmed the existence of a sextet related to α-Fe2O3 with a quantity of about 20% out of magnetic components. Fe3+ superparamagnetic doublets were also found within the fitting procedure.

Role of copper alumina nanoparticles on the performance of polyvinylchloride nanocomposites

AbstractPoly(vinyl chloride) (PVC) nanocomposites with different contents of copper alumina (Cu‐Al2O3) nanoparticles were prepared by the solution casting method. The effects of the nanoparticles on structural, thermal, electrical, contact angle and mechanical properties were thoroughly examined. The presence of Cu‐Al2O3 in the macromolecular chain was confirmed through Fourier transform infrared (FTIR) spectroscopy. The X‐ray diffraction (XRD) analysis of PVC nanocomposites showed the systematic arrangement of Cu‐Al2O3 nanoparticles within the polymer, which indicated the higher crystallinity of the nanocomposites. The surface morphology of PVC was changed into hemispherical shaped particles by the inclusion of nanofiller was analyzed from SEM images. The glass transition temperature of the nanocomposites obtained from differential scanning calorimetry (DSC) was found to be increased with an increase in loading of nanoparticles in the polymer. The AC conductivity and dielectric studies revealed that the inclusion of nanofiller increases the electrical properties of the material and the composite with 7 wt.% sample showed the maximum conductivity and dielectric constant. The mechanical properties such as modulus, tensile strength, hardness, and impact properties of the PVC nanocomposites were significantly enhanced by the reinforcement of nanoparticles into the PVC matrix. The reinforcing mechanism behind the increase in tensile strength with the addition of nanoparticles was correlated with different theoretical models. The highest mechanical and electrical properties were observed for 7 wt.% Cu‐Al2O3 loaded nanocomposite. Contact angle measurements of PVC with various loadings of Cu‐Al2O3 nanofillers demonstrated that the nanoparticle attachment increased the hydrophobicity of the polymer matrix.

Effects of Cr and Fe substitution at Mn-sites of GdMn1-xTxO3 (x = 0, 0.10) on its structural and complex dielectric properties

The observation of insulators to metallic conduction leads to vigorous study in transition metal-doped GdMnO3. Present study reveals the detailed study of structural correlation to electrical properties of transition metal element doped polycrystalline GdMn1-xTxO3 (where T = Cr, Fe; x = 0, 0.10) solid solution. The structural properties and phase purity of the synthesized samples have been analyzed by XRD. The Rietveld refinement of XRD patterns shows that the samples are crystallized in orthorhombic symmetry having the Pnma space group. However, the doping of Cr and Fe affects the octahedral distortion and structural parameters. The Mn–O octahedral distortion in Cr and Fe doped GdMn1-xTxO3 is reduced compared to pure GdMnO3, which is confirmed by the Raman spectroscopy. The X-ray photoelectron spectroscopy study is further observed to study the multiple valence state of Cr, Fe, and Mn in the material, which affects the structural and electrical properties of doped GdMn1-xTxO3. The low-temperature complex dielectric, complex Impedance, and ac conductivity study reveal the anomalous change in the dielectric behavior of Cr and Fe doped GdMn1-xTxO3 compared to pure GdMnO3. Dielectric constant and impedance show a relatively high value in GdMnO3, but the values decrease after Cr and Fe doping. A rapid change with decreased dielectric constant values in GdMn0.9Cr0.1O3 is observed compared to GdMn0.9Fe0.1O3 and GdMnO3 in the temperature range of 300 K–80 K. The ac conductivity and activation energy study of polycrystalline GdMn1-xTxO3 reveal the transformation from insulator to semiconducting nature of the material.

Extended study into the prominence of aluminum content in controlling optical parameters, thermal properties, electrical conductivity and dielectric behavior of amorphous Al-Se-Te thin films for optoelectronic applications

In the initial step of the current work’s scenarios, the AlxSe70Te30-x (x = 0, 15, and 30 wt.%Al) chalcogenide glasses were synthesized. The alloy-derived thin films with a thickness (∼200 nm) were prepared. The optical spectra (transmittance T(λ) and reflectance R(λ)) were measured in the range of (300–2500 nm). Calculation of the optical parameters included determining the energy bandgap, Eg and tail energy, Ee. The results revealed a decrease in the bandgap energy of the direct transition and an increase in the tail energy with increasing Al-content. The X-ray dispersive analysis (EDX) detected the presence of the elemental components in the three studied systems. As well, by analyzing X-ray diffraction patterns (XRD) and s canning electron microscopy (SEM), the amorphous state of the films was confirmed. In addition, differential scanning calorimetry (DSC) at a heating rate of 5 K/min was used to determine the pre-crystallization and crystallization parameters. For the study of DC conductivity, the temperat ure dependence of sheet resistance was measured and its related parameters were extracted. While, the study of AC conductivity began by measuring the temperature dependence of capacitance and conductance at 5 kHz. Electrical conductivity has been studied in a temperature range of (300–500 K). It was found that there are two types of conduction pathways. The activation energies, Mott parameters, barrier potential energy, and density of localized states around the Fermi level were all evaluated using Mott's variable range hopping model as a benchmark. The dielectric constant, loss factor, complicated electrical modules, and impedance spectroscopy parameters were all shown to be substantially dependent on temperature and Al-content.

Influence of (0.19HfO2-0.81ZrO2) ceramics filler content on structural and dielectric properties of PVDF polymer

The rapid evolution of modern technology for the sustainable development of human beings demands eco-friendly, flexible, cost-effective, and lightweight smart materials. Ceramics-polymer composites are those novel materials with improved features, which fulfill the prerequisite conditions for application in flexible devices. Pristine PVDF is one of such electroactive flexible polymers which exhibits good dielectric, ferroelectric and piezoelectric properties. But, its functional properties in the perspective of device application still need improvement and this can be achieved by adding filler to the pure PVDF. In this communication, we have reported the influence of Hafnia-Zirconia (HZ) ceramics (0.19HfO2-0.81ZrO2) filler on structural, microstructural, dielectric, and electrical properties of pure PVDF matrix. The polymer-ceramics flexible composites are synthesized by an eco-friendly and cost-effective method i.e., solution casting method. The phase formation of flexible composites is confirmed from the room temperature XRD spectra. The degree of crystallinity increases with an increase in filler content. The degree of β-phase crystallinity is found to be maximum for 5 wt% of the ceramics filler. An enhanced dielectric constant of ~53 and 20 was observed (as expected) for 5 and 10 wt% of HZ ceramics filler respectively at 100 Hz due to the enrichment of polar β-phase for these two ceramics-polymer composites. The influence of filler content on the dielectric properties was explained based on the percolation model. Relaxation and conduction mechanisms of flexible composites are analyzed from the impedance spectroscopy and ac conductivity study, respectively.

Optical, dielectric and electrical properties of Gd3+ ions doped barium hexaferrite ceramic compounds for microwave device applications

The present work reports synthesis, optical, dielectric and electrical properties of M-type BaFe12−xGdxO19 (x = 0, 1, 1.25, 1.5, 1.75 and 2 mol%) ceramics. Auto combustion synthesis technique was applied for the preparation of the ceramics. Structural analysis was done using PXRD patterns which confirms the hexagonal structure of prepared ceramics. The average particle size of the prepared samples was found to be 25.29 nm and the lattices parameters 'a' and 'c' values ranges from 5.8864 Å to 5.9282 Å and 23.2135–23.3981 Å respectively. UV-Visible spectroscopy and Photoluminescence (PL) analysis were used to investigate the optical characteristics of the prepared samples. The PL emission spectra show that the emission peaks were observed at 689 nm due to the optical transition 6GJ to 6PJ emission. The direct band gap (Eg) of BaFe12O19 is 4.07 eV and Eg value decreases from 4.07 eV to 3.92 eV with substitution of Gd3+ ions. The indirect band gap value also decreases with Gd3+ substitution. The electrical properties were investigated through CIS (complex impedance spectroscopy), EMS (electrical modulus spectroscopy), ac-conductivity and dielectric studies. The dielectric behavior of the samples is explained by Maxwell- Wagner’s two-layer model. NTCR behavior of the prepared powder samples are confirmed from CIS studies. The ac-conductivity studies follow the universal power law. By the substitution of Gd3+ ions, the dielectric constant value increases up to four times and value of dielectric loss decreases by four times, so the BaFe12−xGdxO19 samples can be used in various microwave devices.

Effect of Sintering Temperature and Polarization on the Dielectric and Electrical Properties of La0.9Sr0.1MnO3 Manganite in Alternating Current

The electrical characterization ofa La0.9Sr0.1MnO3 compound sintered at 800, 1000 and 1200 °C was investigated by means of the impedance-spectroscopy technique. As the results, the experimental conductivity spectra were explained in terms of the power law. The AC-conductivity study reveals the contributions of different conduction mechanisms. Indeed, the variation in the frequency exponents (‘s1’ and ‘s2’) as a function of the temperature confirms the thermal activation of the conduction process in the system. It proves, equally, that the transport properties are governed by the non-small-polaron-tunneling and the correlated-barrier-hopping mechanisms. Moreover, the values of the frequency exponents increase under the sintering-temperature (TS) effect. Such an evolution may be explained energetically. The jump relaxation model was used to explain the electrical conductivity in the dispersive region, as well as the frequency-exponent values by ionic conductivity. Under electrical polarization with applied DC biases of Vp = 0.1 and 2 V at room temperature, the results show the significant enhancement of the electrical conductivity. In addition, the dielectric study reveals the evident presence of dielectric relaxation. Under the sintering-temperature effect, the dielectric constant increases enormously. Indeed, the temperature dependence of the dielectric constant is well fitted by the modified Curie–Weiss law. Thus, the deduced values of the parameter (γ) confirm the relaxor character and prove the diffuse phase transition of our material. Of note is the high dielectric-permittivity magnitude, which indicates that the material is promising for microelectronic devices.

Effect of Al3+ substitution on structural, magnetic and dielectric properties of cobalt ferrite synthesized by sol-gel method and its correlation with cationic distribution

The structural, magnetic and dielectric properties of Co(Fe1-xAlx)2O4 (x = 0, 0.02, 0.05, 0.15 and 0.20) synthesized by sol-gel method sintered at 1100 °C have been reported. Structural analysis from the XRD patterns and FT-IR measurements confirms the formation of single phase spinel structure. The saturation magnetization decreases with Al3+ substitution with the exception of x = 0.02 sample. The x = 0.02 sample exhibits an enhanced value of saturation magnetization, due to the cationic re-distribution within the tetrahedral and octahedral sites. The coercive field is found to be prominently influenced by magnetocrystalline anisotropy. The dielectric constant decreases with Al3+ substitution. For x = 0.20 sample, the dielectric constant shows a sharp rise around 1 MHz due to LC resonance effect between the sample and measuring leads. The study of ac conductivity suggests that above 383 K, the conduction mechanism does not follow Jonschers’ Power law, exhibited by most spinel ferrites.

Dielectric properties of hot-pressed Poly(vinylidene fluoride)/Functionalized carbon nanotube composites

This work reports the structural and dielectric properties of poly(vinylidene fluoride) (PVDF) composites with functionalized carbon nanotube (FCNT) prepared by the hot pressing method. XPS, SEM, TEM, and TGA techniques were employed to understand the extent of functionalization of CNT with acid treatment. Permittivity, Electric Modulus, and AC conductivity measurements of hot pressed samples are compared with samples prepared by the solvent casting method. It was found that the PVDF-FCNT composites were formed with more γ phases. Hot pressing the samples increases the overall polar phases, especially the β phase. The permittivity, electric modulus, and AC conductivity studies reveal the dielectric behavior and conductivity changes with hot pressing samples.

Ternary poly(2-ethyl-2-oxazoline)-polyvinylpyrrolidone-graphene nanocomposites: Thermal, electrical, dielectric, mechanical, and antibacterial profiling

Graphene-based poly(2-ethyl-2-oxazoline) (PEOX) and polyvinylpyrrolidone (PVP) blend-matrix nanocomposites were prepared employing different weight percentages of graphene nanoplatelets as filler by ultrasonication assisted solution casting method. These nanocomposites were explored for their thermal, electrical, dielectric, and mechanical properties, and antimicrobial efficiency. Thermogravimetric analysis demonstrated that graphene operates as a barrier to limit thermal diffusion across the PEOX-PVP blend matrix, and hence, improve thermal stability of nanocomposites. The dielectric and electric properties such as dielectric constant, dielectric loss, loss tangent and electrical conductivity of PEOX-PVP-10 wt% graphene nanocomposite were found to increase with temperature. The presence of semi-circles in the Cole-Cole plot indicated the existence of a relaxation process in the conduction mechanism of the nanocomposite. AC electrical conductivity, σAC, of PEOX-PVP-10 wt% graphene nanocomposite was found to obey Jonscher's power law. The temperature-dependent behavior of frequency exponent, s, of σAC discusses the applicability of correlated barrier hopping (CBH) model. The extracted DC conductivity from AC conductivity studies was found to be temperature-dependent and obey Arrhenius relation with activation energy of conduction, Ea, of 0.41 eV and 0.39 eV in the lower and higher temperature regions, respectively. The mechanical properties of nanocomposites were enhanced dramatically when graphene loading was increased, demonstrating that a better interaction exists between graphene and the PEOX-PVP blend matrix. PEOX-PVP-15 wt% graphene nanocomposite showed superior mechanical properties (tensile strength: 9.18 MPa and Young's modulus: 3.19 MPa) among the synthesized nanocomposites. Further, the antibacterial activities of these nanocomposites against Gram-negative (E. coli) and Gram-positive (E. facecalis) bacteria revealed differential action.

AC conductivity and dielectric parameters studies in multilayer TiO2/ZnO thin films produced via ALD technique

In this paper, the effect of frequency and temperature on AC conductivity and dielectric parameters of multilayered TiO2/ZnO thin films have been reported. Among other techniques, the multy layer deposition (ALD) seems to be a promice approach. The fabricated multilayer thin films were grown on Si (100) substrate at 373 K and were nominally 100nm thick with alternating TiO2 and ZnO layers of varying number and thickness. AC conductivity and dielectric studies of different thin films were studied in the frequency range of 100 Hz – 1 MHz and the temperature range of 303 K to 393 K.The observed behavior of AC conductivity and frequency exponent s,on frequency and temperature, can be understood on the basis of correlated barrier hopping (CBH) model. The value of the maximum barrier height Wm has been determined. The analysis of the dielectric constant ε1 and the dielectric loss ε2 reveals their dependence on the frequency and the temperature. The main goal of this study is to evaluate how the thickness and the number of TiO2/ZnO bilayer affects the dielectric properties, which allows us to positively influence the electrical properties of the multilayer. The imply results based on AC conductivity and dielectric properties can be utilize in the future to improve the desirable properties of lightweight electronic and optoelectronic devices.

Insights into the conduction mechanism of magneto-dielectric BaFe10.5In1.5O19: an impedance spectroscopy and AC conductivity study

Insights into the conduction mechanism of magneto-dielectric BaFe10.5In1.5O19: an impedance spectroscopy and AC conductivity study

Low-temperature Electrical Properties and Correlated Barrier Hopping Conduction Mechanism in CdTiO3

CdTiO3 nanoparticles were synthesized by solid-state reaction technique. X-ray diffraction (XRD) confirms the formation of rhombohedral CdTiO3 nanoparticles and scanning electron microscopy (SEM) shows the irregularly shaped nanoparticles. The ac conductivity data was fitted using Jonscher’s power law to find the frequency exponent "s". Correlated barrier hopping (CBH) is found to be prevailing conduction mechanism from 300 K to 160 K. The density of states (DOS) calculated by applying CBH model lie in the range of 2.89 x 1020 eV-1cm-3 to 2.96 x 1021 eV-1cm-3. The calculated minimum hopping distance (Rmin) was 2.13 x 10-9 m. The low values of tangent loss (< 1) at all temperatures suggest CdTiO3 as a potential material in electrical devices with low energy losses. The shifting of maxima towards higher frequencies with the decrease in temperature in imaginary modulus plots suggests the thermally triggered hopping process in CdTiO3 nanoparticles. The modulus studies confirm that hopping is the dominant conduction mechanism in CdTiO3 nanoparticles as suggested by ac conductivity studies

Electrochemical and AC Conductivity Studies of PVA based Gel Polymer Electrolytes for Silver Ion Batteries

An effort has been made to synthesize PVA based gel polymer electrolyte films by means of solution casting technique doped with silver ion in different concentration of polymer and salt (80:20, 70:30 and 60:40 wt.%). The resulting PVA and CH3COOAg gel polymer electrolyte (GPE) material came to be analyzed through various characterization methods for instance XRD, FTIR and UV-Vis spectrophotometry. The analysis of FTIR and XRD confirmed the polymer and salt complexation. The ionic conductivity for prepared GPE was evaluated by means of AC impedance studies at room temperature. The highest value of ionic conductivity found for PVA: CH3COOAg (30 wt.%) system was found to be 1.422 × 10-5 S cm-1. The optical and cyclic voltammetric analysis have been examined and excellent cyclic, reversible performance was observed for the electrolyte PVA:CH3COOAg (70:30 wt.%) up to 10 cycles.

Synthesis and electrical properties of Ba(Fe0.5Nb0.5)O3-(Na0.5Bi0.5)TiO3 ceramics

This work presents the electrical properties of (1-x)Ba(Fe0.5Nb0.5)O3-x(Na0.5Bi0.5)TiO3; 0 ≤ x ≤ 1.0 ceramics (BFN-NBT) using complex impedance spectroscopy method in a wide range of frequency (1 Hz − 1 MHz) and temperature (50 °C − 500 °C). The solid-state reaction process has been adopted to prepare these ceramics. The crystal structure and microstructure of the ceramic samples were studied. The impedance and ac conductivity studies suggested the negative temperature coefficient of resistance character as well as hopping type electrical conduction in all cases. The variation of the modulus spectrum is an intriguing temperature-dependent hopping type of mechanism for charge transport in the materials. AC conductivity data followed Jonscher’s power law, and the correlated barrier hopping explained the charge carrier transport mechanism in the system.

The C6H4(NH3)2(NO3)2 assembly investigations: Crystal structure, optical properties and impedance spectroscopy, electrical relaxation with Ac conductivity studies

The assembly involving ([C6H4(NH3)2]2+/(NO3)–) hybrid as building units has been conceived to carefully produce hybrid-supramlecules with H- bonded nitrogen, which is expected to replace conventional optical materials. Successfully obtained, a new hybrid compound, C6H4(NH3)2(NO3)2 by hydrothermal methods and characterized using single-crystal X-ray diffraction method, Hirshfeld surface analysis, IR / CP MAS- NMR spectroscopy and UV–vis spectrophotometry. Electrical properties and ac conductivity of the title compound has been reported in the temperature and frequency range from 303 to 413 K and 1–106 Hz, respectively. The impedance and electrical modulus spectral data and the frequency and temperature correlation analysis of the Nyquist plots has shown that the grains and grain boundaries contribute to the electrical properties of the prepared materials.The single crystals were obtained by a hydrothermal method. It was found to crystallize in the monoclinic system P21/c with the following lattice parameters: a = 12.6966(17) Å; b = 7.9444(11) Å c = 10.3904(14) Å; β = 105.68(0) and Z = 4. The structural analysis shows that the presence of a layer arrangement perpendicular to the c-axis: planes of [C6H4(NH3)2]2+ cations alternated with planes of two anionic group (NO3)– anions. The cohesion of the molecular arrangement is ensured by hydrogen bonding C–H…O and N– H…O. Hirshfeld Surface analysis of intermolecular interactions confirmed that the hydrogen bonds: C/H, H/C, H/O/H/O and H/H contacts, play a dominant role in the crystal structure of the investigated compounds. Infrared and MAS NMR spectroscopic measurements were carried out to confirm the results obtained by X-ray diffraction. In optical studies, data analysis revealed the existence of optical direct with the band gap energy equal to 5.03 eV.The ac electrical conductivity is investigated at the frequency and temperature. The two semicircles observed in the complex impedance clearly show the contribution of the grain interior and grain boundaries to the electrical response of the material. The equivalent circuit based on the Z-View-software is proposed and the conduction mechanisms are determined. Dielectric data are analyzed using complex electrical modulus M* at various temperatures. The variation of the dielectric parameters (ε’’) is found .Moreover, the temperature dependence study of frequency exponent n (T) is investigated to explain the conduction mechanism in the different range of temperature and frequency.