Jonscher's Power Research Articles

Comparative analysis of the structural, optical, mechanical, and electrical properties of PMMA/PU blend‐based nanocomposites with FeVO4 nanofiller for energy storage devices

AbstractThe best materials for enhanced energy storage capacitors in electrical systems are polymer nanocomposites films. Therefore, using the solution casting approach, we created a unique series of FeVO4 nanofiller‐embedded polyurethane (PU) and polymethyl methacrylate (PMMA)‐based composites. Various techniques were used to describe the prepared films. XRD spectra were used to assess the crystallinity and crystallite size of nanocomposites. The XRD spectra were used to assess the crystallinity and crystallite size of nanocomposites. With rising nanoparticles (NPs) content up to samples with 1.5 weight percent of FeVO4, XRD demonstrated an increase in the amorphous phase of the polymer mixture, which was further supported by UV–Vis measurements. FTIR was used for determining the complexation of the FeVO4 with the polymer mixture. Calculations were used to determine optical properties such as the Urbach energy and energy bandgap. With a rise in FeVO4 NP concentration, the energy bandgap decreases while the Urbach energy increases. All samples' AC conductivity spectra exhibit Jonscher's power law (JPL) behavior. Studies on dielectric permittivity and electric modulus have also been conducted in order to comprehend the charge storage characteristics and conductivity relaxation. Whereas the frequency‐dependent increase in AC electrical conductivity, the ε′ and ε″ of PU/PMMA–FeVO4 nanocomposites drop with the rising of the electric field frequency. The high level of FeVO4 was shown to improve the AC conductivity, ε′ and ε″ values of the nanocomposites. Tensile strength was improved by 38% with the addition of FeVO4 NPs into the PU/PMMA blend. Experimental outcomes show that these polymer nanocomposites materials are multifunctional and can be used as low‐permittivity nanodielectric insulators and substrates to design the next generation of flexible electronic devices and also there can be used to create a variety of advanced optoelectronic and organic electronic devices.

Lead-free complex double perovskite SrLiFeWO6: Structural, microstructure, electrical and optical study

In this work, synthesis (solid-state reaction) and characterizations (structural, microstructure, dielectric, conductivity, Raman & UV–vis) of a newly prepared lead-free complex perovskite SrLiFeWO6 are reported. Preliminary X-ray diffraction (XRD) analysis suggests a tetragonal phase. The scanning electron microscope (SEM) micrograph and energy dispersive x-ray analysis (EDX) spectrum show the well-grown grains and sample purity. The study of Raman active lines determines the vibrational modes of the constituent molecules in the reported compound. Dispersed dielectric plots were explained by the Maxwell-Wagner polarization effect. The modulus study reveals the presence of a non-Debye type of relaxation. Jonscher's Power Law is fitted in ac conductivity data which follows a correlated barrier hopping mechanism. The direct bandgap energy of the studied sample is found to be 1.68 eV, which may be a good range for photovoltaic applications. For NTC thermistor applications, the analyzed thermistor constant and sensitivity factor are found to be within the permissible range. The idea of ferroelectric nature is opened up by the study of polarization versus electric field. The examination of current density versus electric field reveals that the sample has an ohmic character in the low region and a space charge-limited conduction (SCLC) mechanism in the higher field region.

Characterization of BiFeO3–Al2O3 nano-composites: A study of structural, microstructural, electrical, and magnetic properties

Results: of the studies on the structural, magnetic, and electrical properties of BiFeO3–Al2O3 nanocomposites prepared using the sol-gel method have been reported. The X-ray diffraction results confirm bi-phase structure of the composites with the presence of some impurity phases of Bi25FeO40 and Bi24A12O39. Field emission scanning electron microscopy images revealed the crystalline nature composed of grain and grain boundaries of both the pure and composite samples. Energy-dispersive X-ray spectroscopy confirms the absence of unwanted components. Magnetic characterization reveals weak ferromagnetic behaviour of BiFeO3 and composites while diamagnetic behaviour of Al2O3. The maximum saturation magnetization in the pure BFO sample is ∼ 6 emu/gm, but this magnetization is lowered by up to 63% and is determined to be ∼ 3.8 emu/gm with the 30% addition of Al2O3 in the BFO matrix. Electrical measurements demonstrate that the addition of Al2O3 nanoparticles leads to a reduction in the dielectric constant, loss tangent, and ac conductivity. A.C. conductivity was found to follow Jonscher's universal power law and to be dominated by the correlated barrier hopping mechanism in the conduction process, according to frequency-dependent ac conductivity analysis. Additionally, impedance analysis reveals a field-induced excitation of charge carriers, resulting in a noteworthy reduction in sample impedance. Overall electrical properties have been discussed in the context of oxygen vacancies, secondary phases, defects, and disorder in details

Tuning electrical properties of BaTiO3 with iron modification

BaTiO3 plays an important role in advanced functional devices owing to its fascinating properties. Though it is an excellent ferroelectric material, its magnetism can be switchable via suitable modification. In this report, we have studied iron-modified BaTiO3, which has been prepared using cost-effective high-temperature solid-state reaction techniques. The Fe-modified BaTiO3 maintains its crystallinity in the tetragonal phase with P4mm space group with a slight variation of tetragonality ratio to 1.002 from 1.008 of BaTiO3 of the identical synthesis method. This is confirmed by Rietveld refinement. Field emission scanning electron microscopy (FESEM) and EDX (energy dispersive X-rays) spectrum along with an elemental mapping analysis has provided the feature of the Fe-modifed BaTiO3. Atomic force microscope (AFM) has been employed to get the detailed surface topology (2D and 3D) and surface roughness of the developed systems. This deformation caused by the incorporation of Fe significantly modifies the electrical properties of barium titanate. The ferroelectric-paraelectric phase transition temperature (Tc) of Fe-modified BaTiO3 has been diffused and shifted to 300 °C from 120 °C of pure BaTiO3, suggesting the materials for the high-temperature capacitive application. The room temperature M-H hysteresis of Fe-modified BaTiO3 indicates the ferromagnetism developed in the BaTiO3 with the introduction of Fe. The ac conductivity is in the order of 10−4 Ω−1cm−1, and its frequency response obeys Jonscher's power law. Different charge carriers are responsible for diverse conduction processes in different temperature ranges confirmed by the Arrhenius plot. Impedance spectroscopy studies reveal the existence of NTCR characteristics of the developed system. Well defined ferroelectric hysteresis loop indicates the existence of ferroelectricity in the developed system. The analysis of various electrical parameters has provided information on the material's dielectric relaxation and conduction mechanisms for possible application in functional devices.

Studies of structural, dielectric, and electrical properties of polycrystalline barium bismuth tungstate for thermistor application

In this communication, preliminary investigation of structural and detailed analysis of electrical proprties of a new barium bismuth tungstate of a chemical composition Ba3Bi2WO9, produced via a standard high-temperature solid-state reaction method, is presented. The basic crystal structure of the compound is monoclinic (a = 8.4621 Å, b = 6.7358 Å, c = 6.9064 Å and β = 109.94°). The homogeneous distribution of grains (average grain size = 1.717 μm) is studied via surface morphology demonstrating the feasibility of fabricating a high-density sample under experimental conditions. This compound shows ferroelectric and related properties, which have been experimentally verified by examination of the frequency-temperature dependence of capacitance, impedance, and other related behaviors. The variation of ac conductivity of the material under alternating current varies according to Jonscher's universal power law. The ferroelectric property of the material (Pr = 0.331C/cm2, Ec = 0.207 kV/cm) is demonstrated by the electric field-dependent polarisation (P-E loop) study. The temperature dependence of resistance yields a thermistor constant (β) and temperature coefficient of resistance (TCR), which may be useful for fabricating thermistor-based device applications.

Distinct dominant dielectric relaxation mechanisms in CaCu3Ti4O12 – LaMO3 (M = Mn and Fe) perovskite oxide solid solution

Two synthesized perovskite oxide solid solutions, CaCu3Ti4O12 – LaMnO3 and CaCu3Ti4O12 – LaFeO3, possess a crystalline structure embracing an amalgamation of two distinct phases, namely, hexagonal and orthorhombic phases in CaCu3Ti4O12 – LaMnO3 and cubic and orthorhombic phases in CaCu3Ti4O12 – LaFeO3. Examination of dielectric properties reveals colossal dielectric constant (εr), the peak magnitude of εr at 1 kHz being approximately 6×103 and 2.5×104 for Mn and Fe based compound, respectively. Further, complex impedance investigation (CII) establishes the activation energy (Ea) of grains (0.21 eV and 0.07 eV for Mn and Fe based solid solution, respectively) and grain boundaries (0.19 eV and 0.19 eV for Mn and Fe based solid solution, respectively). The deviation in Ea of grains and grain boundaries, as established through CII, in both, Mn and Fe based samples validates the existence of Maxwell-Wagner (M − W) relaxation. The AC conductivity spectrum for both the samples obeying the Jonscher's universal power law (JUPL): σ(ω,T)=σdc+Aωn. The Ea of bulk samples (0.37 eV and 0.19 eV for Mn and Fe based solid solution, respectively) authenticates predominant M − W relaxation (interfacial polarization) with polaron hopping playing the secondary role in Mn based sample, while both, polaron hopping and M − W relaxation being identical contributors towards dielectric nature of Fe based sample.

Effect of tungsten metal-oxide addition on physical, structural, and electrical properties of borophosphate glasses

Demand for electrical energy storage (EES) is growing, necessitating the development of improved batteries. Inorganic glassy materials are a class of essential electrodes due of their excellent conductivity and stable structures, they are appropriate for both cathode and anode applications. The most important characteristics that determine the dynamic behavior and rate performance of batteries are the ionic and electronic conductivities of active materials. In this sense, many crystalline, vitreous, and glass ceramics are investigated for their electrical properties. To create uniformly mixed glasses within the xLi2WO4–(50–x)Li2O–40P2O5–10B2O3 system, the melt-quenching technique is employed. Glasses containing up to 50 mol% Li2WO4 are synthesized with a substantial region of glass formation. They are homogeneous, transparent, and bubble-free. The structural approach and selected physical parameters of these glasses, such as density, molar volume, electrical conductivity, and glass transition temperature, are evaluated. The study emphasizes that an increase in the Li2WO4 amount leads to an elevation in both the density (ρ) and molar volume (Vm). Infrared spectroscopy identifies the presence of numerous structural units within the glass framework. Electrical conductivity measurements of the glasses are investigated using impedance spectroscopy. The measurements are taken over a wide frequency range of 10 Hz to 1 MHz and across temperatures ranging from 303K to 403K. It is highlighted that the electric conductivity rises as the Li2WO4 content is added. The glass with x = 30 mol% exhibits a dc conductivity of 8.63 × 10−7 (Ω−1 cm−1) at room temperature and 8.90 × 10−5 (Ω−1 cm−1) at 150°C. To gain insight into the conductivity relaxation mechanism, the frequency dependence of the glasses' conductivity is investigated. The results indicate that the ion transport in the glasses is governed by the correlated barrier hopping mechanism, which follows Jonscher's power behavior. The scaling conductivity spectra reveal that the conduction mechanism in the glasses is influenced by both temperature and composition.

Investigations of Structural, Magnetic, and Electrochemical Properties of NiFe2O4 Nanoparticles as Electrode Materials for Supercapacitor Applications.

Magnetic nanoparticles of NiFe2O4 were successfully prepared by utilizing the sol-gel techniques. The prepared samples were investigated through various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), dielectric spectroscopy, DC magnetization and electrochemical measurements. XRD data analysed using Rietveld refinement procedure inferred that NiFe2O4 nanoparticles displayed a single-phase nature with face-centred cubic crystallinity with space group Fd-3m. Average crystallite size estimated using the XRD patterns was observed to be ~10 nm. The ring pattern observed in the selected area electron diffraction pattern (SAED) also confirmed the single-phase formation in NiFe2O4 nanoparticles. TEM micrographs confirmed the uniformly distributed nanoparticles with spherical shape and an average particle size of 9.7 nm. Raman spectroscopy showed characteristic bands corresponding to NiFe2O4 with a shift of the A1g mode, which may be due to possible development of oxygen vacancies. Dielectric constant, measured at different temperatures, increased with temperature and decreased with increase in frequency at all temperatures. The Havrilliak-Negami model used to study the dielectric spectroscopy indicated that a NiFe2O4 nanoparticles display non-Debye type relaxation. Jonscher's power law was utilized for the calculation of the exponent and DC conductivity. The exponent values clearly demonstrated the non-ohmic behaviour of NiFe2O4 nanoparticles. The dielectric constant of the nanoparticles was found to be >300, showing a normal dispersive behaviour. AC conductivity showed an increase with the rise in temperature with the highest value of 3.4 × 10-9 S/cm at 323 K. The M-H curves revealed the ferromagnetic behaviour of a NiFe2O4 nanoparticle. The ZFC and FC studies suggested a blocking temperature of ~64 K. The saturation of magnetization determined using the law of approach to saturation was ~61.4 emu/g at 10 K, corresponding to the magnetic anisotropy ~2.9 × 104 erg/cm3. Electrochemical studies showed that a specific capacitance of ~600 F g-1 was observed from the cyclic voltammetry and galvanostatic charge-discharge, which suggested its utilization as a potential electrode for supercapacitor applications.

Development of a novel triple perovskite barium bismuth molybdate material for thermistor-based applications

In this communication, development (synthesis and characterization) of a novel triple perovskite sample Ba3Bi2MoO9 (BBMO) is reported. The material has monoclinic crystal symmetry. A detailed study of microstructure and compositional analysis of the sample by using scanning electron microscopy (SEM) and EDX (energy dispersive X-rays) spectrum has provided the quality of the BBMO ceramic. The topological and surface roughness of the novel material has been analyzed to clarify the surface texture and compactness of the sample surface. The variation of conductivity under the alternating current of the material varies according to the Jonscher's universal power law. The high dielectric constant and low tangent loss are applicable for fabrication of various electrical instruments. The resistance decreases with an increase in temperature supports the NTCR (negative temperature coefficient of resistance) behavior, which is clarified by using TCR and β (thermistor constant) for NTC thermistor application.

Impedance spectroscopy and conduction mechanism analysis of bulk nanostructure Prussian blue pellets

The structure and morphology of the fabricated Prussian Blue (PB) pellets are examined using FTIR, XPS, XRD and FESEM techniques. The morphology of the crystalline Prussian blue (PB) revealed a nanostructure with an average crystallite size of 91 nm. The frequency (42 Hz–1 MHz) and temperature (303–393K) of the Prussian Blue (PB) in Bulk form are dependent. In the medium region (1 kHz–100 kHz), the electric dipoles relax and start to lag the applied ac electric field signal and the estimated activation energy of 0.247 eV. The investigated Nyquist plots (Z″ versus Z′) of the Prussian Blue (PB) samples at different temperatures (303–393 K) are interpreted by an equivalent parallel RgCg circuit. The bulk resistance of Prussian Blue samples was estimated at various temperatures, and its behaviour exhibited temperature dependence; generally, it follows the Nearest Neighbor Hopping (NNH) model. According to Meyer–Neldel rule, the calculated activation energy is 0.565 ± 0.001 eV. The evidence of localized states is investigated, and its density, N(EF) ∼ 5.47 × 1018 eV−1 cm−3. The ac conductivity, σac, merges into a plateau of two parts: the first is a frequency-independent dc conductivity, σdc, which is strongly temperature-dependent. The rest of the plateau at higher frequencies showed the temperature-insensitive ac conductivity obeying Jonscher's power law. The values of the exponent s were investigated to figure out the intimate conduction mechanism in Prussian Blue (PB) samples; it follows the correlated barrier hopping (CBH) theoretical model. The hopping distance and energy have values ∼ unity and ≥ kBT, respectively. The experimental results revealed a linear relationship between hopping distance and energy against temperature, with the first decreasing and the second increasing linearly.

Investigation on structural, optical and electrical properties of BiFeO3:ZnO nano–micro particles–matrix composite

A new class of materials called matrix-nano composites has the ability to meet the needs of modern advanced applications and technology. To prepare the BiFeO3:ZnO composite, BiFeO3 nanoparticles were prepared using a low–cost sol–gel method, to which ZnO in its micron-sized form was added in varying concentrations of 5%, 10%, and 15%. The structural, morphological, and optical properties of the pure and composite materials were characterized using XRD, FESEM, EDAX, PL spectra, and UV-Visible spectroscopy. The dielectric properties of the pristine and composites were investigated at room temperature. The a.c. conductivity fit with Jonscher's power law and CBH model described the charge conduction behaviour in all pure and composite materials. The temperature-dependent dielectric and loss measurements showed a temperature dependent relaxation process. UV–vis and PL characterization show that the composite materials exhibited improved charge separation efficiency and wider band gaps with increasing BFO content.

Effect of Cr3+ substitution on the magnetic and dielectric properties of cobalt ferrites

Co(Fe1-xCrx)2O4 (x = 0.02, 0.10, 0.15, 0.30, 0.50) samples are synthesized by the sol-gel method. The XRD patterns and subsequent Rietveld refinement provided structural analysis and confirmation of the samples' single-phase formation. XPS measurement reveals the existence of the elements Co, Cr and Fe in 2+ and 3+ oxidation states. The saturation magnetization (Ms), coercivity (Hc) and magnetocrystalline anisotropy (K1) are observed to decline to as low as 10 emu/g, 35 Oe and 0.50 (106 erg/cm3) following Cr substitution, which indicated that the samples transform to a soft magnetic material. Cr substitution also lowers the ferrimagnetic (FiM) to paramagnetic (PM) transition temperature, Tc, from 752 K for x = 0.02 to 307 K for x = 0.50. With Cr replacement, the dielectric constant and dielectric loss values decrease, indicating it to be a potential contender for high frequency applications. The dielectric constant for x = 0.30 and x = 0.50 samples rises sharply around 1 MHz owing to the LC resonance effect between the samples and the measurement leads. The ac conductivity plots are found to be in conformity with Jonscher's single power law, and the conduction process is revealed to be attributable to the small polaron hopping mechanism.

Formation of silver particles in [PVA:CS:PEG]-AgNO3 based biopolymer electrolyte membranes: Structural and electric transport properties study

[Chitosan (CS)-poly(vinyl) alcohol (PVA)-polyethylene glycol (PEG-200)]+xwt% silver nitrate (AgNO3) (x = 0, 10, 20, 30, 40) based biopolymer blend electrolytes (BPBEs) were prepared using solution casting method. FTIR results show the interaction of Ag+/NO3− with the constituents of polymers CS/PVA. XRD results reveal that the amorphousness increases with increasing AgNO3 concentration. Optical morphological (OM) images show that the silver, Ag(o) particles are agglomerated on the surface of the membrane. Temperature dependent dc conductivity (σdc) and dielectric relaxation frequency (fr) for BPBEs follow the Arrhenius type behavior and the sample containing 30 wt% salt has optimum dc conductivity, σdc∼1.7×10−4 S/cm at 30oC with lowest activation energy∼ 0.16 eV. The ac conductivity spectra follow the Jonscher's power law (JPL) with power law exponent, s > 1. The scaling of AC conductivity and loss tangent (tanδ) spectra were performed with respect to temperatures/concentrations of salt. The dielectric permittivity study reveals that the electrode polarization effect predominates at low frequencies. The Ionic Transference Number (ITN) measurement was used to determine the nature species of charge carrier, either ionic or electronic. The linear sweep voltammetry (LSV), result shows that 30% AgNO3containing sample has the electrochemical stability window (ESW) ∼+1.5 to -1.5 V.

Modification and development in the microstructure of PVA/CMC-GO/Fe3O4 nanocomposites films as an application in energy storage devices and magnetic electronics industry

We used casting method to create nanocomposites films from carboxymethylcellulose (CMC)/polyvinyl alcohol (PVA) and GO/Fe3O4 as nanofiller. Various analyses such as structural, vibrational, optical, conductivity, dielectric and magnetic studies reveal promising properties of the prepared polymer nanocomposites (PNCs) films. The amorphous phase of the polymer blend increased with increasing GO/Fe3O4 concentration up to samples containing 0.05%GO/1%Fe3O4 nanofiller, according to X-ray diffraction. The complexation of the nanofiller with the polymer blend's –OH, –COO, CO, and –CH groups through a coordinate bond/hydrogen bond was confirmed by Fourier-transform infrared analysis. While the Urbach energy showed a trend in the opposite direction, the optical bandgap gradually turned red as the nanofiller concentration increased. The interaction of GO/Fe3O4 ions with the CMC/PVA matrix is attributed to the changes in optical properties of CMC/PVA. The Jonscher's power law (JPL) is observed in all samples' ac conductivity spectra. To comprehend the charge storage competences, research of dielectric permittivity was also conducted. A study of dielectric permittivity was also conducted to comprehend the charge storage competences. While AC conductivity increases with frequency, dielectric characteristics decrease with frequency. With the addition of nanofiller, AC conductivity and dielectric characteristics increase. For 0.05%GO/1%Fe3O4 nanofiller loaded sample, the highest AC conductivity and dielectric constant were attained. The results of vibrating sample magnetometer (VSM) revealed that synthesized nanocomposite films exhibit superparamagnetic features. The unique features of CMC/PVA-GO/Fe3O4 films enable their employment in a variety of industries, including magnetic electronics, energy storage devices, and optoelectronics.

Investigation of frequency dependent dielectric properties of La-doped BaSnO3-ZnSnO3 solid-solutions

In this study, we report the structural, optical, and dielectric properties for La-doped BaSnO3 and ZnSnO3 solid solutions, La0.03(Ba1−xZnx)0.97SnO3 (x = 0,0.1,0.5,1) prepared at 1100 °C by isovalent substitution of Zn+2 at the Ba+2 site using the conventional solid-state reaction route. Structural data shows the transformation from cubic perovskite to orthorhombic perovskite structure as the amount of Zn increases in La-doped BSO samples. A minor pyrochlore phases, La2Sn2O7 and Ba2SnO4 were found in the XRD. This paper mainly focuses on understanding the contribution of physical phenomena of ac conductivity in terms of dielectric properties. The dielectric properties of the composites follow non-Debye type behavior. There was a moderate increase in the dielectric constant from 10.07 to 334 at 20 Hz, and 2.99–133 at 1 kHz, respectively, as we increased the amount of Zn, which is high as compared with other reported dielectric materials. By using Jonscher's power law, ac conductivity was found to increase in LZSO samples. This conduction mechanism due to the hopping of ions between coordination sites present in the composite and can be understood by the classically correlated barrier hopping phenomenon. Furthermore, the trivial loss of electromagnetic waves over a given frequency range demonstrates the great potential of La-doped ZnSnO3 materials to be utilized in ground penetrating radar systems, communication systems, and energy storage devices.

Structural study and temperature dependent relaxation and conduction mechanism of orthorhombic tungsten bronze Ba4La28/3(Zr0.05Ti0.95)18O54 ceramic

In this study, the Ba4La28/3(Zr0.05Ti0.95)18O54 ceramic was prepared using the solid-state technique. The X-ray diffraction technique was used in this study to investigate the Ba/La order in the solid solution Ba4La28/3(Zr0.05Ti0.95)18O54. We have developed a structural model, to represent the order within the structure. The formula of model [Ba4−a□a]A2[La8+2b3□2−2b3]A1,A1′(Zr0.05Ti0.95)18O54 is described as perovskite layers with a thickness of 3 octahedral parallel to the xOz plane. Scanning electron microscopy (SEM) showed that Ba4La28/3(Zr0.05Ti0.95)18O54 ceramic exhibits a typical columnar grain with a heterogeneous distribution over the entire surface. Complex impedance spectroscopy was used to analyze the dielectric and electrical properties of Ba4La28/3(Zr0.05Ti0.95)18O54 materials over a frequency range of 10 Hz to 1 MHz and a temperature range of 350°C to 400°C. An appropriate equivalent electrical circuit was also used to investigate the contributions of grains and grain boundaries. The AC-conductivity data was analyzed using Jonscher's universal power law. The thermal behavior of the exponent parameter "s" indicates that the dominant conduction mechanism in our compound is the non-overlapping small polaron tunneling (NSPT) model. The activation energies calculated from the conduction and relaxation mechanisms are nearly identical for the Ba4La28/3(Zr0.05Ti0.95)18O54 ceramic.

Features of immittance spectra as performance indicators for cement-based concretes

Design for durability and performance-based standards and specifications for reinforced concrete infrastructure is limited by the lack of rapid, science-based test methods for characterising the deterioration resistance of concrete. In this paper, this issue is addressed though the application of two-point electrical impedance measurements taken within the frequency range 100 Hz–10 MHz. Data are presented for a range of industry-standard cement-based concrete mixes with and without supplementary cementitious materials. Nyquist plots (−iZ″(ω) against Z′(ω)) and Bode plots (Z*(ω) and θ against frequency) clearly highlight the frequency dependence of the electrical response. However, when presented in the form of permittivity and conductivity, a region of dispersion was evident over the entire frequency range for all concretes. The features of this response, which could be gainfully exploited as durability indices for assessing the long-term performance of concrete, are identified and discussed. A range of formalisms is presented and it is shown that, within this frequency range, conductivity was found to obey Jonscher's universal power law. Two novel durability parameters are presented based on features of Jonscher's model; from a practical viewpoint, the power-law model can be evaluated using conductivity measurements obtained at three, easily measured, spot frequencies (10 kHz, 1 MHz and 10 MHz).

Origin of improved Na+ ionic conductivity in the NASICON-type solid state electrolyte with Sm modification

The NASICON-type (Na1+xZr2SixP3-xO12, 0≤x ≤ 3) sodium-ion solid state electrolyte (SSE) has emerged as an alternative for liquid electrolyte due to its good chemical/electrochemical stability, high thermal stability and high safety. However, the insufficient ionic conductivity and poor understanding of Na+ transport mechanism hinder the further development of sodium-ion SSE. Herein, we report Sm modified Na3+xZr2-xSmxSi2PO12 (0≤x ≤ 0.4) electrolytes with a highest ionic conductivity of 2.25 × 10−3 S cm−1 at 25 °C when x = 0.2. The introduction of Sm element adjusts the Si/P ratio in NASICON phase and densifies the electrolyte pellets by formation of Na3Sm(PO4)2. To get a deep insight into the enhanced mechanism of Na + transport in grains, low-temperature electrochemical impedance spectra (LT-EIS) and Jonscher's power law relationship are employed to analyze the electrical behavior of grains. The results demonstrate that the regulation of Si/P ratio can evoke lower migration energy, more charge carrier concentration and higher hopping frequency, which synergistically improve the ionic conductivity in grains.

A multifunctional transition metal based double perovskite Ba2(FeW)O6: Structural, microstructural, optical, electrical and ferroelectric properties

In this article, synthesis (solid-state reaction) and characterizations (XRD, SEM-EDX, RAMAN, UV–Vis, LCR & P-E measurements) of a polycrystalline double perovskite Ba2(FeW)O6 are reported. The prepared sample crystallizes in tetragonal symmetry with an average crystallite size of 60.7 nm and lattice strain of 0.00045 respectively. Vibrational modes of the molecules in the prepared sample are investigated using Raman spectroscopy. Analysis of scanning electron microscope (SEM) and energy dispersive analysis of x-ray (EDX) supports homogenous distribution of grains and compositional consistency. Optical investigation calibrates direct energy bandgap of 2.72 eV; which may be suitable for photocatalytic and photovoltaic devices. Dielectric, impedance, and modulus spectra have been studied over a wide range of frequencies (1 kHz–1 MHz) and temperatures (25 °C–500 °C). Wide dielectric dispersion at low-frequency encounters space charge polarization with the Maxwell-Wager effect. Study of impedance plots reveals negative temperature coefficient resistance (NTCR) character while existence of non-Debye relaxation mechanism is confirmed from modulus plots. Frequency dependence ac conductivity obeys Jonscher's Power Law (JPL) and confirms the presence of a non-overlapping small polaron and correlated barrier hopping process (CBH). The study of activation energy (Ea), sensitivity factor (α) and thermistor constant (β) values from resistance versus temperature supports NTC thermistor behaviour and explore the possible applications related to temperature-based sensors.

Anisotropic electrical properties of 200 MeV Ag+15 ion irradiated manganite films

In the present communication, the investigations on the structural, morphological, electrical and magnetodielectric (MD) properties of pulsed laser deposited La0.90Ca0.10MnO3 (LCMO) nanostructured thin films grown on SNTO substrate followed by irradiation using 200 MeV Ag+15 ions have been carried out. Structural properties were studied using X–ray diffraction (XRD) technique. The lattice mismatch was calculated from the XRD spectra in order to get insights on the interfacial strain in all the thin films. Morphological properties were determined using atomic force microscopy (AFM) to study the irradiation induced alterations in the LCMO nanostructured thin films. Dielectric spectroscopy as a function of frequency was carried out to study the electrical properties of pristine and irradiated samples. The anisotropic MD properties were measured by employing the external magnetic field of 1 T in two different geometries, i.e. magnetic field perpendicular and parallel to the samples' plane. Various theoretical models such as relaxation time and universal dielectric response model were employed to explain the mechanisms governing the electrical properties. The ac conductivity and impedance were also measured under the presence of external magnetic field and compared with the measurements carried out in the absence of the magnetic field. The measured ac conductivity was modeled using Jonscher's power law which signified the conduction mechanism in the presently studied samples.