Modulus Spectra Research Articles

FREQUENCY-DEPENDENT IMPEDANCE, MODULUS AND DIELECTRIC STUDIES OF POLYANILINE/MANGANESE DIOXIDE NANOCOMPOSITES

Structural properties, electric impedance, electric modulus and dielectric spectra properties have been used to investigate a Polyaniline/Manganese dioxide (PANI /MnO2) nanocomposites prepared by in situ polymerization method. Prepared nanocomposites were analyzed by AC impedance spectroscopy. Pure PANI and MnO2 nanoparticles have good crystalline nature, but when it was prepared to nanocomposites, crystalline nature could be change. When the concentration of MnO2 nanoparticles has increased in nanocomposites, crystalline behaviour has been increases. Impedance studies were used to explain the electrode process. The modulus data of nanocomposites were analyzed as a function of different frequency range at a particular temperature. At low-frequency range, all the values of a real part of the electric modulus remain almost near to zero. Dielectric constant and dielectric loss have explained in brief. The impedance analysis was confirming the non-debye nature of the materials

Mechano-Vibrational Spectroscopy of Tissues and Materials Using Vibrational Optical Coherence Tomography: A New Non-Invasive and Non-Destructive Technique

Elastic moduli of tissues and synthetic polymeric materials are important design properties needed to develop new implants. In this paper we report the use of vibrational optical coherence tomography (VOCT) to measure the resonant frequency and calculate the modulus of tissues and synthetic polymers non-invasively and non-destructively in vitro and in vivo. Values of tissue and polymer moduli were obtained by applying an audible sinusoidal sound wave to the surface of each specimen. The sound wave travels to the interior of the material and is reflected back to the surface from underlying layers. A spectrum of resonant frequencies and moduli are then obtained. By analyzing the frequencies at which the maximum displacements are observed the resonant frequencies are determined of the material components and the moduli can then be calculated from calibration equations. The characteristic spectrum of resonant frequencies measured is a finger print by which the composition of the underlying tissue components can be determined using VOCT. The resonant frequencies of cells and tissues range from about 40 Hz for fat to about 990 Hz for lamellar bone. The modulus for these tissues ranges from about 1 MPa (cells) to that for extracellular matrix components that range from 2 to 173 MPa (tissue macromolecular components). Measurements reported on synthetic polymers indicate that the resonant frequency ranges from 80 Hz (silicone rubber) to 2800 Hz (acrylonitrile butadiene styrene) and values of the modulus are found to be between 2 MPa and 2120 MPa, respectively. The resonant frequency and modulus are shown to decrease as a result of fatigue in Viton rubber. It is concluded that the width of the resonant frequency peak is related to the molecular weight distribution and that VOCT may serve as method to rapidly determine molecular weight distributions and properties after cyclic loading of uncrosslinked and crosslinked polymers.

Magneto-electric coupling and transport properties of LaFeO3–Pb(Zr0.58Ti0.42)O3–organic poly(vinylidene fluoride) nanocomposite

The magneto-electric material of LaFeO3–Pb(Zr0.58Ti0.42)O–poly(vinylidene fluoride) has been prepared by a chemical “pyrophoric reaction technique” and followed by “solid state route”. The formation of LaFeO3, Pb(Zr0.58Ti0.42)O3 and poly(vinylidene fluoride) phases is confirmed by X-ray diffraction technique. The magneto-electric coupling and electrical response have been carried out at room temperature (300 K). The prepared composite reveals the strain mediated magnetoelectric effect at room temperature with longitudinal and transverse configurations at lower frequency region under an external magnetic field. The impedance spectroscopy is used to study the complex electrical modulus and electrical transport properties of the prepared composites at room temperature. The complex modulus and impedance spectra study also helps to understand the mechanism of the electrical transport process, which depicts a non-Debye type of conduction mechanism of the system.

Dielectric relaxation and charge conduction mechanism in mechanochemically synthesized methylammonium bismuth iodide

In this work, methylammonium bismuth iodide [(CH3NH3)3Bi2I9] has been synthesized through the mechanochemical process. Indeed, (CH3NH3)3Bi2I9 emerges as promising alternative to lead-based inorganic–organic perovskite due to low toxicity and better stability. X-ray diffraction spectra reveal monoclinic structure of (CH3NH3)Bi2I9 with space group C2/c. Kubelka–Munk method is conducted to compute the bandgap (2.16 eV). The impedance and dielectric properties of (CH3NH3)3Bi2I9 have been investigated within frequency range of 4 Hz to 1 MHz for several temperatures in between 333 to 453 K. The complex impedance spectroscopy has analyzed by fitting the Cole–Cole plot with suitable grain and grain boundary contributions (rg, rgb). Conductivity and electric modulus spectra have been analyzed to enlight the shaded portion of transportation properties. The scaled coordination of modulus spectrum merges in a single master curve which signifies that the distribution of relaxation time is temperature independent. To compute the DC conductivity, AC conductivity data have fitted using Jonscher’s power law. The activation energy calculated from Arrhenius plot is 0.477 eV.

Structural and electrical characteristics of nanocrystalline La2Sn2O7 pyrochlore

Nanocrystalline La2Sn2O7 ceramic with pyrochlore structural phase was prepared by the chemical co-precipitation method followed by conventional sintering. Structural analysis by X-ray diffraction, transmission electron microscopy, and Raman spectroscopy revealed the pyrochlore phase formation. The Nyquist impedance plots measured at different temperatures (550–700 °C) exhibited a single semicircular arc and the relaxation times corresponding to grain interior and grain boundary were found to lie close to each other. The dielectric relaxation behavior in La2Sn2O7 was found to be of non-Debye type. The activation energy for conduction of oxygen ions was determined to be 0.87 eV. Frequency and temperature-dependent ac conductivity spectra were analyzed based on the Universal dielectric response model given by Jonschers’ power law. The conduction mechanism in La2Sn2O7 was discussed by employing the jump relaxation model and correlated barrier hopping (CBH) model. The maximum barrier height for the mobile ions to overcome for hopping was found to be 0.62 eV. The insights into the frequency and temperature dependence of the dielectric permittivity and dielectric loss in La2Sn2O7 were discussed using the Maxwell–Wagner model. The electric modulus spectra of La2Sn2O7 were manifested by the Kohlrausch-Williams-Watts (KWW) function. Further, the non-Debye type of relaxation was explicitly confirmed by the β values. Additionally, the universal scaling behavior was also demonstrated in La2Sn2O7 by the electrical modulus and impedance characteristics.

Electrical transport of chalcogenide glassy system: interpretation by Hunt’s model and microstructure

Ag2S doped Sulphur–Tellurium chalcogenide glassy system has been developed and their dielectric properties and electrical conductivity have been studied. Electrical conductivity via hopping of polarons in the present system is found to decrease due to large number of defects. TEM micrographs reveal the formation of Ag2S, Ag2Te and AgTe3 nanophases, whose sizes are found to decrease with compositions. Almond-West formalism has been used to analyze the thermally activated nature of conductivity spectra. Hunt’s model is used to reveal dielectric relaxation process with composition, which is justified by microstructure, revealed from TEM micrographs. Peak frequency (ωm) corresponding to imaginary modulus spectra shows Arrhenius relation. The results may reveal the opening for the development, significance and investigation of electrical and dielectric properties of chalcogenide glassy system.

Effect of temperature and humidity on dielectric and impedance properties of K(Nb0.8Ta0.2)0.99Mn0.01O3 electroceramics

We report the effect of humidity and temperature on the dielectric and impedance properties of lead-free potassium tantalum niobium oxide (KTN). It illustrates large dielectric constant ∼4500 at 1 kHz, low tangent loss in dry condition, which drastically changes under humidity condition. The nature and magnitude of dielectric constant and tangent loss were moderately different in both heating and cooling conditions. A series of phase transitions from rhombohedral to orthorhombic (below room temperature), and orthorhombic to tetragonal (∼185 °C) and tetragonal to Cubic (390 °C) have been obtained respectively over a wide range of temperature with a significant change in magnitude and nature in transition temperature during cooling mode. A detail transport properties have been carried out based on Impedance spectra, Modulus spectra, Nyquist Plot, and ac conductivity to establish a microstructure-property relation. The activation energy of the charge carriers determined that mainly electronic charge carriers contribute to transport properties in the low-temperature range while oxygen vacancies and cations near the high-temperature ferroelectric phase transition. The effect of moisture on room temperature capacitance, tangent loss, and impedance have been discussed.

$$\hbox {Bi}_2\hbox {O}_{3}\hbox {-doped}$$ $$\hbox {SnO}_{{2}}$$ varistors with low breakdown electric fields

This work presents $$\hbox {Bi}_{{2}}\hbox {O}_{\mathrm {3}}\hbox {-doped SnO}_{{2}}$$ ceramic varistors prepared through conventional ceramic processing in the sintering temperature range of 1290–1320°C. The sample sintered at 1300°C exhibits a breakdown electric field as low as 11.6 V $$\hbox {mm}^{\mathrm {-1}}$$. Scanning electron microscopy images reveal that all the samples have a compact structure, and energy dispersive spectroscopy results for the sample sintered at 1300°C indicate that Bi distributes homogeneously along the grain boundaries and aggregates inhomogeneously on the grain surfaces. With increasing sintering temperature, the grain boundary barrier height remains nearly constant at 0.80 eV. In both the dielectric loss and electric modulus spectra of the sample sintered at 1300°C, obvious relaxations were observed and the activation energies obtained from the respective spectra were 0.33 and 0.15 eV, which are expected to be related to oxygen vacancies and interstitial ions, respectively. Complex impedance spectra are employed to develop a non-typical equivalent circuit model for the $$\hbox {Bi}_{{2}}\hbox {O}_{\mathrm {3}}\hbox {-doped SnO}_{{2}}$$ ceramic varistors at low voltage that yields an excellent fit to the data.

The deficiency of chitosan:AgNO3 polymer electrolyte incorporated with titanium dioxide filler for device fabrication and membrane separation technology

In the present work the drawbacks of chitosan:AgNO3(CS:AgNt) mediated by TiO2 filler for polymer electrolyte fabrication and membrane separation technology were discussed. The phenomena of reduction of silver ions to metallic silver particles were explained based on various techniques such as UV–vis, XRD, SEM, EDX, OM and TEM. An increase in intensity and broadness of surface plasmon resonance (SPR) peak in the UV–vis absorption spectra revealed the formation of a high amount of silver nanoparticles (Ag NPs). The high dielectric constant of TiO2 filler was responsible for the reduction of more silver ions. The crystalline peaks in XRD pattern confirmed the formation of metallic silver particles. The OM images showed Ag NPs with bulk sizes. The SEM images and EDX spectra confirmed the existence of Ag NPs. The TEM images illustrated silver particles with small sizes in CS:AgNt system. To investigate the stability of silver ions, the electrical properties were performed. The increase of resistance and decrease in dielectric constant at high TiO2 concentration confirmed the deficiency of the prepared films for electrochemical device application. Distinct peaks appeared in the imaginary (Mi) component of electric modulus spectra and no peaks were seen in dielectric loss spectra.

AC Conduction Mechanism in (Cu)x/(CuTl)-1223 Nanoparticles–Superconductor Composites

Copper (Cu) nanoparticles (NPs) were prepared by sol–gel process, and superconducting (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ {(CuTl)-1223} phase was synthesized by conventional solid-state reaction. The desired (Cu)x/(CuTl)-1223, x = 0–4.0 wt% composites, were obtained by adding Cu NPs in superconducting (CuTl)-1223 phase. These composites were characterized by X-ray diffraction, DC-resistivity versus temperature (R–T) and AC conduction measurements. The tetragonal crystal structure with P4/mmm space group of the host superconducting (CuTl)-1223 phase remained dominant after the addition of Cu NPs. The zero-resistivity critical temperature Tc(0) (K) was increased, and normal state resistivity was decreased after addition of Cu NPs in CuTl-1223 phase. The frequency- and temperature-dependent AC conduction properties of (Cu)x/(CuTl)-1223 composites were explored via dielectric, impedance and electric modulus measurements. The dielectric constant (ɛr/, ɛr//) and loss tangent (tanδ) were suppressed, while AC conductivity (σac) was improved with the addition of Cu NPs in (CuTl)-1223 phase. Comparatively, the capacitance associated with grain boundaries regions was found to be greater than the capacitance associated with grain regions. The capacitive behavior of the grain boundaries was decreased, while that of the grains was increased with increasing operating temperature for all these composite samples. The shifting of peaks in imaginary part of the electric modulus (M//) versus frequency (f) spectra toward lower frequency regime with increasing Cu NPs contents in superconducting (CuTl)-1223 phase is witnessed for the existence of non-Debye relaxation in the material.

Revealing the Low-Temperature Fast Relaxation Peak in a Model Metallic Glass

By systematically investigating the relaxation behavior of a model metallic glass based on the extensive molecular dynamics (MD) simulations combined with the dynamic mechanical spectroscopy method, a pronounced ultra-low temperature peak on the loss modulus spectrum was discovered for the first time in MD simulations. It was found that the relation peak occurs at a much lower temperature than the typical temperature for the conventional β relation peak as reported in the literature. According to the atomic displacement analysis, we unravel that the atomic motions, rather than the thermal vibrations or local structural rearrangements, mainly contribute to this relaxation peak. We further identify the atomic level mechanism of this fast relaxation process by characterizing the local geometrical anisotropy. Furthermore, by tracing the dynamic behaviors of these reversible atoms, we demonstrate the intrinsic hierarchy of the local relaxation modes, which are triggered by atomic vibrations and gradually developed to the and irreversible atomic movements. Our findings shed light on a general picture of the relaxation processes in metallic glasses.

Structural, electrical and magnetic properties of Ni0.5Cu0.2Cd0.3LaxFe2-xO4 nano-ferrites due to lanthanum doping in the place of trivalent iron

By means of the sol-gel auto combustion technique, the mixed spinel Ni0.5Cu0.2Cd0.3LaxFe2-xO4 nano-ferrites have been synthesized. Crystallite sizes of the ferrite samples have been calculated from the XRD data, and particle sizes from TEM, and FESEM images. SAED pattern confirms the rings due to Miller indices of ferrites. EDS spectrum confirms the presence of all the stoichiometric elements. FT-IR spectra have detected two major absorption bands. Using the measured intrinsic magnetization by VSM, the M-H curve has been recorded. Dielectric parameters, electric modulus, impedance spectroscopy, and ac conductivity have been recorded by means of impedance analyzer from the range 20 Hz-15MHz. The complex modulus spectrum has been analyzed to understand the dynamics of the conduction process. From the Cole-Cole plot drawn from impedance spectra, the value of (Rgb) and (Rg) has been calculated. With the rise of frequency, an increase of ac conductivity for grain and grain boundary distinction has been observed.

Predominantly chain segmental relaxation dependent ionic conductivity of multiphase semicrystalline PVDF/PEO/LiClO4 solid polymer electrolytes

The solid polymer electrolyte (SPE) films comprise poly(vinylidene fluoride) (PVDF)/poly(ethylene oxide) (PEO) blend (75/25 wt/wt%) as host polymer matrix with lithium perchlorate (LiClO4) as ionic dopant for different salt concentrations (i.e., 5, 10, 15, 20, 25, and 30 wt%), and also varying compositional weight ratio PVDF/PEO blends (i.e., 75/25, 50/50, 25/75, and 10/90 wt/wt%) with 25 wt% concentration of LiClO4 were prepared by solution casting at 70 °C. The results obtained from X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy revealed that there is enormous alteration in the α- and β-phase crystals of the PVDF and the size and content of the PEO crystallites, and also the degree of crystallinity of these SPE materials with the variation of salt concentration and the polymer blend composition. Dielectric relaxation spectroscopy (DRS) was employed over the frequency range from 20 Hz to 1 MHz, at 27 °C for the study of the complex impedance, dielectric permittivity, dielectric loss tangent, ac electrical conductivity, and electric modulus spectra of the SPE films. All these spectra were analyzed separately and simultaneously by a novel ‘master curve representation’ procedure to unveil the contribution of various dielectric polarization processes (i.e., electrode, interfacial, molecular (dipolar), and the ionic) and their relaxations which are exhibited with increasing order of frequency and have substantial overlapping with the adjacent processes in these heterogeneous ion conducting materials. The loss tangent spectra of these materials manifest prominent dielectric relaxation peaks which attribute to the cation coordinated polymer chain segmental dynamics. The high frequencies ac electrical conductivity data of all these materials obey the power law, whereas the Nyquist plots of impedance data exhibit reasonably distinguishable bulk and electrode polarization frequency regions for the electrolytes having salt concentration ≥20 wt%. The inverse correlation observed between the relaxation time and the dc ionic conductivity establishes that the transportation of ions is predominantly coupled to the polymer chain segmental motion which assists the hopping between favourable conduction sites in the ion-dipole complexes. The SPE films are comparatively stiffer and have a slightly higher degree of crystallinity when the salt concentration is ≤ 15 wt% and they exhibit distinct dielectric, dc ionic conductivity, and relaxation behaviour as compared to that of the softer and lower crystallinity films having salt concentration ≥20 wt%. These SPE films possess good electrochemical performance and close-to-unity total ion transference numbers. Among these two sets of the SPE films, the maximum dc ionic conductivity was noted 2.01 × 10−5 S/cm at 27 °C for the 75PVDF/25PEO–30 wt% LiClO4 film from the set of different salt concentrations, and 5.61 × 10−6 S/cm for 25PVDF/75PEO–25 wt% LiClO4 film from the set of varying compositions of the polymer blend matrix. The considerable ionic conductivity values of these SPE films at ambient temperature and also their promising electrochemical performance corroborate them as novel ion conductors suitable for the development of solid-state rechargeable lithium-ion batteries.

Synthesis and characterization of Ruddlesden-Popper system (Ba1−xSrx)2SnO4

The samples of (Ba1−xSrx)2SnO4 with x = 0, 0.10, 0.20, 0.40, 0.80, 1.00 were synthesized by a high-temperature solid state ceramic route. Lattice parameters obtained from the Rietveld profile analysis; decreased with increasing Sr. The decreasing nature of lattice parameters indicated the complete solubility of Sr at Ba-site. Further, incorporation of Sr at Ba-site has been studied by Fourier transform infrared (FTIR) spectroscopy. The dielectric constant and dissipation factor increases with increasing Sr. Contribution of grain and grain boundary were resolved by complex modulus spectroscopy analysis. AC conductivity spectra of the entire sample follow Universal Jonscher's power law. The similar value of activation energy obtained from relaxation frequency and dc conductivity implies that the origin of conduction and relaxation mechanisms remains the same throughout the samples. The modulus and conductivity spectra of solid solutions nicely follow the time-temperature superposition (TTSP) principle. Further, conductivity spectra of solid solutions were studied by Ghosh and Summerfield scaling.

Improved dielectric properties of Na1/2Y1/2Cu3Ti4O12 ceramics synthesized by ball-milling and reactive sintering

Na1/2Y1/2Cu3Ti4O12 (NYCTO) ceramics with giant dielectric constant (ε′) were synthesized by simple reactive sintering. NYCTO nanopowder was first synthesized using high energy ball-mill. Then the pelletized powder was sintered in air at temperatures in the range 975 °C to 1050 °C for 10–20 h. The obtained ceramics showed pure CaCu3Ti4O12 (CCTO)-like cubic phase as revealed by x-ray diffraction measurements. Field effect-SEM observations showed that the grain size increases from 2 μm to 5 μm with increasing sintering temperature. NYCTO samples sintered at temperatures higher than 975 °C showed giant dielectric constant (103–104) over most of the frequency range. The minimum dielectric loss (tanδ) of ∼0.055 at 300 K has been approved for the ceramic sample sintered at 1050 °C. Impedance and modulus spectra of the current samples showed two relaxations related to semiconductor (grain) and high resistance (grain-boundaries) elements. The activation energy for conduction located in the range 0.1–0.5 eV highlighted the role of single ionized oxygen vacancies in the dielectric properties of the investigated NYCTO ceramics.

Spectroscopic, Optical and Dielectric Investigation of (Mg, Cu, Ni, or Cd) Acetates’ Influence on Carboxymethyl Cellulose Sodium Salt/Polyvinylpyrrolidone Polymer Electrolyte Films

Solid polymer electrolytes, which have a low bandgap and a high dielectric constant, are an interesting technology for optoelectronic applications and supercapacitors. This work studies the influence of Mg, Cu, Ni or Cd acetates on the structural and optical properties and the dielectric relaxation phenomena in carboxymethyl cellulose sodium salt (CMC)/polyvinylpyrrolidone (PVP) blends. The dielectric behavior, ac conductivity and electrical modulus formalism were investigated in a frequency range of up to 1 MHz at room temperature. X-ray diffraction energy dispersive x-ray, Fourier transform infrared spectroscopy and scanning electron microscopy, revealed modifications of the films’ structural and chemical compositions and their morphology. UV–Vis and dielectric properties measurements revealed that the Cu and Mg salts had more distinctive influences on the optical properties, ac conductivity ($$ \sigma_{\rm{ac}} ) $$ and relaxation behavior. Cu and Mg reduced the optical bandgap Eg of the CMC/PVP blends from 5.1 eV to 4.7 eV and 3.6 eV, respectively, but increased $$ \sigma_{\rm{ac}} $$ from 8.61 × 10−5 S/cm to 1.34 × 10−4 S/cm and 1.81 ×10−4 S/cm, respectively. The dielectric measurements revealed an increase in the dielectric constant and dielectric losses for the composite films, which reflect the enhancement of the dielectric polarization of the films. The electric modulus spectra, calculated relaxation time and Argand plots confirmed an improvement in the ionic conductivity of the composite films. These results indicate that the incorporation of the acetate salts is a simple approach to widening the technological importance of CMC/PVP blend films for some optoelectronic devices and Cu and Mg battery applications.

Magnetic Structured Nickel Core-Shell @ Silica/PMMA Nanocomposites from Synthesis to Applications

Incorporating Ni@SiO2 nanoparticles on poly-methyl methacrylate (PMMA) can alter electrical, optical, and magnetic properties of Ni nanoparticles to be used for energy storage applications, photo electronic devices and spintronic applications. The Ni@SiO2/PMMA nanocomposite samples are prepared by casting method. The morphology of the prepared nanoparticles was examined through high resolution transition electron microscope revealed the formation of SiO2 coating on ni nanoparticles. Furthermore, the topography of nanocomposites was characterized by the field emission scanning electron microscope. We investigated the formation of crystalline phase of Ni nanoparticles through X-ray diffraction. The Complex dielectric permittivity, electrical conductivity, electric modulus and impedance spectra of the PNC films were investigated in the frequency range from 0.1 Hz to 10 MHz. The real and imaginary parts of the permittivity decrease with increasing frequency due to an increase in Ni@SiO2 content. All the nanocomposites showed relatively low conductivity values and high impedance that could be used for nano-dielectrics. UV–Vis spectrophotometer was used to measure optical properties such as transmittance, and absorbance at normal incidence in the wavelength range of 200–1100 nm. The transmittance was found to decrease while the absorbance increases with increasing Ni@SiO2 nanoparticles. The indirect optical band gap of the composite films was calculated, and it was sharply decreased. Magnetic hysteresis plots at room temperature of composites Ni@SiO2/PMMA were studied. All samples demonstrate ferromagnetic behavior with well pronounced magnetic hysteresis.

Probing the ionic transport dynamics in ionic liquid incorporated CuBTC-Metal-Organic Framework based PVdF-HFP nanocomposite membranes

CuBTC-Metal-Organic Framework (MOF) has been prepared by solvothermal synthesis method and ionic liquid (IL) 1-butyl-3 methylimidazolium tetrafluoroborate (BMIMBF4) has been incorporated at different wt% into the CuBTC-MOF. The composite nanofiller has been dispersed in poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) polymer electrolyte system. Shifting of FTIR vibrational modes of carboxylate group is due to metal-ligand bond elongation upon interaction of ions of IL with CuBTC-MOF. The binding energy of Cu spin-orbit peak increases with incorporation of IL as obtained from XPS spectra suggesting motion of BF4− anions of IL towards the Cu metal nodes of MOF. Periodic oscillation and coordination structure of Cu K-edge are observed in k-space and R-space scanning EXAFS data. Non-Debye dielectric relaxation dynamics is observed from dielectric permittivity and modulus spectra with ionic conductivity of 8.7 × 10−3 Scm−1at 50 wt% of IL incorporation in the composite polymer electrolyte at 380 K. The electrochemical stability profile increases with increasing IL concentration and attains 6.1 V at 50 wt% of IL.

Dielectric relaxation and current conduction mechanism of Tb and Mn codoped bismuth ferrite grafted poly (vinyl alcohol) nanocomposite film

Abstract Investigation on current conduction mechanism through Tb and Mn codoped Bismuth Ferrite grafted polyvinyl alcohol (BTFMO-PVA) nanocomposite film above room temperature (300 K – 415 K) is reported here in detail. A detailed study on dielectric properties of the sample is done over a wide temperature range in a frequency range of 20 Hz - 2MHz. The conduction is attributed to correlated barrier hopping model. Bipolaron hopping dominates over single-polaron hopping in this system. Complex electric modulus spectra and complex modulus spectra are well explained by suitable models to understand the effective dielectric response. The sample responds to the externally applied magnetic field exhibiting negative magnetocapacitance at room temperature.

Dielectric dispersion and electrical conductivity of amorphous PVP–SiO2 and PVP–Al2O3 polymeric nanodielectric films

The biodegradable hybrid polymer nanocomposite (PNC) films comprising silica (SiO 2 ) and alumina (Al 2 O 3 ) nanoparticles as inorganic nanofillers and the poly(vinyl pyrrolidone) (PVP) as organic host matrix (i.e., PVP– x wt% SiO 2 and PVP– x wt% Al 2 O 3 for x = 0, 1, 3 and 5) have been prepared by aqueous solution-casting method. X-ray diffraction (XRD) study reveals that these nanocomposite materials are highly amorphous. The dielectric spectroscopy of these different nanofiller concentrations PNC films has been carried out in the frequency range from 20 Hz to 1 MHz at a fixed temperature and also for 3 wt% nanofillers containing PNC films with the temperature variation. The results confirm that the complex dielectric permittivity of these hybrid films is influenced by the interfacial polarization in the low frequency range of 20 Hz to 1 kHz, whereas in the high frequency range up to 1 MHz permittivity is mainly governed by the molecular polarization and remains almost independent of the frequency. These SiO 2 and Al 2 O 3 nanofillers containing PNC films at fixed temperature display anomalous behaviour of dielectric permittivity and ac electrical conductivity with the increase of nanofiller concentration, but these parameters significantly enhance at low frequencies with the increase of temperature of the films. The electric modulus spectra of Al 2 O 3 containing PNC film exhibit relaxation peaks below 100 Hz at higher temperatures which attribute to the interfacial polarization relaxation process. The frequency independent dielectric permittivity and significantly low loss of these PNC materials at radio frequencies confirm their suitability as polymeric nanodielectric (PND) substrate and insulator in the design and fabrication of biodegradable electronic devices and electrical components.