Electric Modulus Spectra Research Articles

Effect of annealing temperature on dielectric properties of iron oxide prepared by sol–gel auto combustion method

In this study, different phases of iron oxide have been synthesized by sol–gel auto combustion route followed by annealing. Temperature and frequency-dependent dielectric properties have been studied in detail which provide the information on the contribution of grain and grain boundary in charge transport. Conductivity and electric modulus spectra have also been analyzed. The scaled coordination of impedance spectrum merges in a single master curve which signifies that the distribution of relaxation time is temperature independent. Complex impedance spectra have been used to evaluate activation energy (Ea ) by using Arrhenius relation. The activation energy calculated for α-Fe2O3 is 1.36 eV.

Ionic conduction and relaxation mechanisms in three-dimensional CsPbCl3 perovskite

Ionic conduction and relaxation for the cubic phase of three-dimensional CsPbCl3 perovskite with a mean crystal size of 500 nm, synthesized via a facile solution based method, have been investigated in wide temperature and frequency ranges by dielectric spectroscopic measurements. Dielectric data have been analyzed in terms of the complex impedance spectroscopy, AC conductivity and the complex electric modulus by using Maxwell–Wagner equivalent circuit model, universal power law, Havrilliak–Negami, and Kohlrausch–Williams–Watts models to explore the fundamental aspects of the ionic transport and relaxation mechanism in CsPbCl3 perovskite. Nyquist plots indicate the individual grain and grain boundary contributions to the total impedance. The temperature dependence of the DC conductivity and the relaxation time obtained from the analysis was observed to follow the Arrhenius behavior. The activation energy for the DC conductivity was found to be ∼0.25 eV, which was very close to that for the relaxation time. The scaling of the AC conductivity and the electric modulus spectra at different temperatures indicates the validity of the time-temperature superposition principle, i.e., common ionic conduction and relaxation mechanisms at different temperatures in CsPbCl3 perovskite.

Thermal and dielectric properties of carbon nanotubes/graphite/polyester ternary composites

Binary and ternary composites were synthesized using a polyester matrix reinforced by two types of carbon inclusions, namely, carbon nanotubes (CNT) and graphite (Gt) (CNT/Gt/Polyester). Thermal analyses were performed, using thermogravimetry and differential scanning calorimetry, which allowed us to observe significant changes in glass transition temperatures and degradation temperatures of the composites. Dielectric measurements were performed in a frequency range from 100 Hz to 1 MHz and temperature from –33 to 107°C. The dielectric permittivity values of the CNT/Gt/Polyester ternary composites, compared to the Gt/Polyester binary composites, indicate that the addition of CNT particles to the Gt/Polyester binary system significantly improved the dielectric permittivity, due to the enhanced interfacial polarization of the host matrix, while the frequency dependence of the electrical modulus spectra revealed a Maxwell–Wagner–Sillars dielectric relaxation process that was found to follow the Cole–Davidson approach.

Impedance spectroscopy and magneto-dielectric analysis of La3+ substituted Co2Z hexaferrite

Single phase Ba3Co2Fe24O41 (Co2Z) and Ba2.8La0.2Co2Fe24O41 (La-Z) were prepared by solid state ceramic method. The dielectric, impedance and electric modulus were systematically investigated as a function of temperature from 50 °C–250 °C and in the frequency range of 1 Hz–1 MHz. Frequency dependent imaginary impedance and electric modulus implies that La3+ substitution significantly affect hopping and relaxation mechanism of charge carriers. Cole-Cole plots (Z" vs Z') has been fitted with suitable equivalent circuit for both Co2Z & La-Z. The obtained grain and grain boundary resistances confirmed that charge carriers experienced lower resistance in La-Z. Arrhenius plots of relaxation time (τ) vs 1/T showed parallel conduction mechanism in system. Complex electric modulus spectrum distinguished the capacitive contribution of grain, grain boundary and electric effect. A very high magnetodielectric effect at low frequencies has been observed for La-Z.

Relaxation behavior of sandwich-structured fluorinated graphene/poly(vinylidene fluoride-hexafluoropropylene) composites by dielectric relaxation spectroscopy

The sandwich-structured fluorinated graphene (FGN)/poly(vinylidene fluoride-hexafluoro- propylene) [P(VDF-HFP)] composites with various FGN constituents were fabricated via a layer-by-layer solution casting technique, and their dielectric relaxation phenomenons of the trilayered composites were studied in a systematic way by dielectric relaxation spectroscopy (DRS) at various temperatures (25°C–200 °C) in the range of 20 Hz to 5 M Hz. The variations in dielectric parameters (ε′and ε") with frequency at each studied temperature show that ε′and ε" increase with the rise of temperature and ε" significantly decreases with the addition of FGN. Moreover, the asymmetric shapes of electric modulus spectra (M″) and Cole-Cole plots exhibit the relaxation process of non-Debye, especially in trilayered FGN/P(VDF-HFP) composites. AC conductivity is irrelevant to frequency and temperature under low frequency-high temperature, but frequency sensitive under high frequency region. Furthermore, the two activation energies (Eτ and Eσ) gradually increased with the addition of FGN, showing that the mobility of charge carriers is suppressed, thus they are unable to overcome the relaxing and conducing barrier.

Influence of Sr ions on the structure and dielectric properties of Cu/Nb Co-doped BaTiO3 ceramics

Sr-modified Cu/Nb co-doped BaTiO3 ceramics were prepared using solid-state reactions and the structures and dielectric properties were studied. All the samples had single-phase perovskite structures with no detectable secondary phases. In the low-temperature range, the dielectric constant decreased as the Sr content increased in the high- and low-frequency ranges. Two dielectric constant plateaus accompanied by dielectric relaxation peaks were present in the loss curves, and the relaxation process deviated from the Arrhenius law at low temperatures. The dielectric constants of different plateaus were related to inhomogeneous structures such as grain interiors and grain boundaries. The polarization strength of the grain boundaries in the low-frequency range increased with the temperature and that of the grain interiors demonstrated paraelectric behaviour in high-temperature ranges. An analysis of the electric modulus spectra indicated a close relationship between the relaxation process and resistivity of the grains for high-frequency relaxation. The impedance spectra at high temperatures consist of three electrical responses, corresponding to the effects of grains, grain boundaries, and electrodes. The dielectric relaxation appeared in high temperature range was related to the electrical properties of the grain boundaries.

Impact of neodymium doping on the dielectric and electrical properties of CCTO synthesized by a facile sol–gel technique

In this work, Ca1–xNdxCu3Ti4O12 (x = 0, 0.3 mM) ceramics were prepared by a facile sol–gel technique. The structure and crystalline nature of the samples were analyzed by X-ray diffraction characterization technique. FESEM analysis envisaged the inhomogeneous formation of ceramic material and confirmed the grain size was greatly affected by the dopant. The EDS analysis confirmed the existence of Ca, Cu, Nd, Ti, and O which illustrates the purity and stoichiometric ratios of the products. A colossal dielectric constant (ɛr = 5.5 × 105) was achieved for Neodymium-doped CaCu3Ti4O12 ceramics in comparison with undoped CaCu3Ti4O12 ceramics dielectric constant ɛr = 1.1 × 105 at 50 Hz and temperature 500 °C. Complex impedance analysis indicates that the existence of a non-Debye type of relaxation phenomenon of the material, which is further substantiated from the electrical modulus spectrum. Dielectric relaxation time for various temperatures of undoped and neodymium-doped CaCu3Ti4O12 ceramics were calculated from both imaginary parts of impedance spectrum and electric modulus spectrum. The activation energy was considerably varied 0.2102–0.1910 eV for undoped and 0.2741–0.2425 eV for Neodymium-doped CaCu3Ti4O12 ceramics, which suggests that the electrical conduction behaviour was primarily originated with the mobility of ionized oxygen defects.

Dielectric and mechanical properties of nickel silica core-shell reinforced PMMA nanocomposites

This paper study the dielectric and mechanical properties of poly (methyl methacrylate)-nickel silica core-shell nanocomposite. Ni@SiO2/PMMA nanocomposite films were prepared by incorporating Ni@SiO2nanoparticles in PMMA matrix using the solution casting method. The morphology of the prepared nanoparticles was examined through a High-resolution transition electron microscope (HRTEM), which revealed the formation of SiO2shell at Ni magnetic nanoparticles. The dielectric properties of the nanocomposite films were studied as a function of temperature and frequency in the ranges of 30–180°C and 100 Hz – 5 MHz respectively. The incorporation of the nano Ni@SiO2to PMMA has a positive effect on the dielectric constant ε′ of the nanocomposites, as well as, ε′ improved with increasing temperature. The real electric modulus (M′) of composites confirms the occurrence of dispersion in all composites at all temperatures. While dielectric loss tangent ε ″ and the loss part of electric modulus spectra (M) exhibit relaxation peaks which characterize possible relaxation of interfacial polarization in the interface between Ni@SiO2core-shell and PMMA matrix, these peaks have shifted towards higher frequency with temperature. The relaxation and activation energies, Ecand Eavalues decreased from 0.49 to 0.40 eV and from 0.87 to 0.70 eV respectively as Ni@SiO2content increased. The ac conductivity of the nanocomposite films has deeply increased with increasing temperature and Ni@SiO2content. The longitudinal modulus (L), shear modulus (G), Young's modulus (E), and bulk modulus (B) of films were studied and they increased as the filler increased from 0 to 15 wt.%.

Dielectric and optical properties of alumina and silica nanoparticles dispersed poly(methyl methacrylate) matrix-based nanocomposites for advanced polymer technologies

Dielectric behaviour of the polymer nanocomposite (PNC) films comprise alumina (Al2O3) and silica (SiO2) nanoparticles (1, 3, and 5 wt%) dispersed in poly(methyl methacrylate) (PMMA) matrix was investigated in the frequency span of 20 Hz to 1 MHz at 30 °C and also with temperature variation (30–60 °C) for the 3 wt% nanofillers containing PNC films. Some changes in the dielectric permittivity and electrical conductivity were observed with the increase of nanofiller content, frequency variation, and rise in temperature of these films. Electric modulus spectra confirmed a broad relaxation peak at the lower frequencies for the Al2O3 loaded PNC films which attribute to the PMMA bulky side ester groups rotation, whereas this relaxation was not observed for the SiO2 filled PNC films in the same experimental frequency range. The UV–Vis absorbance, transmittance, and reflectance spectra of these PNCs showed a gradual variation with the increase of Al2O3 and SiO2 contents in the films. The energy bandgap decreases, whereas the Urbach energy, refractive indices, and optical conductivity enhance with the increase of filler concentration in these composites. The X-ray diffraction (XRD) study revealed the predominantly amorphous nature of these materials and the homogeneity of the hybrid was evidenced by their SEM images. The energy dispersive X-Ray (EDX) mapping revealed the purity of these hybrid composites. The results demonstrated that these PNC films are low permittivity polymeric nanodielectrics (PNDs), and their controllable optical parameters with the filler contents could be technologically important in the design and development of some advanced microelectronic and optoelectronic devices.

Polymer nanocomposites comprising PMMA matrix and ZnO, SnO2, and TiO2 nanofillers: A comparative study of structural, optical, and dielectric properties for multifunctional technological applications

Abstract Polymer nanocomposite (PNC) films consisted of poly (methyl methacrylate) (PMMA) matrix and wide energy bandgap semiconductor nanocrystallite fillers viz. zinc oxide (ZnO), tin oxide (SnO2), and titanium dioxide (TiO2) were prepared by a sonicated suspension of nanoparticles in polymeric solutions followed by the casting method. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterization revealed successful nanocomposite formation of these hybrids. The ultraviolet–visible (UV–Vis) spectroscopic study explained that the absorbance and energy bandgap of these PNC films largely differed with the type of metal oxide nanofillers and their concentrations (i.e., 1–5 wt%). The UV-absorbance was found relatively high for the PMMA/TiO2 films and low for the PMMA/SnO2 films at the same concentration of the fillers. The film thickness dependent study confirmed that the increase of film thicknesses significantly enhanced the UV–Vis absorbance and reduced the energy bandgaps of the same composition PMMA/TiO2 composites. The dielectric permittivity of the ZnO and SnO2 containing PNC films was found to be appreciably increased with the increase of concentration of these nanocrystallite fillers, whereas the films bearing TiO2 nanoparticles exhibited a decrease in permittivity as compared to that of the host PMMA matrix film at the temperature of 30 °C. Further, a gradual decrease in the permittivity of these nanocomposite materials was noted with the increase of experimental electric field frequency from 20 Hz to 1 MHz range. The electric modulus spectra exhibited a single relaxation process in the lower frequency region which attribute to the ester group rotations of the PMMA chain repeat units and it was found to be largely influenced by the fillers and their concentrations in these nanocomposites. The AC electrical conductivities of all these PNC films were observed slightly increased and showed a linear behaviour with the frequency variation. The wide range tailorable behaviour of the optical and dielectric parameters with the change of nanofillers and their concentrations evidence that these PNCs could be promising multifunctional materials for UV-shielders, optical sensors, and bandgap tuners in developing various advanced optoelectronic and organoelectronic devices, and also their use as low permittivity nanodielectric insulators and substrates to architect the next-generation flexible-type electronic devices.

High-temperature dielectric behavior of hexagonal HoMnO3

The ac electrical response of hexagonal HoMnO3 was investigated in the temperature range 340≤T≤700K. The combination of impedance and electrical modulus spectra reveal a single dielectric relaxation. However, the ac conductivity in the range 340≤T≤600K revealed two electro-active regions with dissimilar activation energies associated with grain and grain boundary regimes. We suggest that grains have the largest capacitance, whereas grain boundary dominates the overall resistance of the sample. The most interesting was the first-hand observation of a positive temperature coefficient of resistance (PTCR) effect in HoMnO3, and the sample behaves as an extrinsic semiconductor material. Both bulk effects and grain boundary were observed to contribute together to the PTCR phenomena. A correlation between the ac conductivity and dielectric data was built up. Results show that oxygen non-stoichiometry and associated electron holes are liable for the complex dielectric behavior. The scaling behavior of ac conductivity was studied using different formalisms.

Enhanced electrical and magnetic properties of CuO/MgO nanocomposites

The present work deals with the synthesis, characterization, and testing of copper oxide (CuO)/magnesium oxide (MgO) nanocomposites formed with two different ratios. The composites formed by the sol-gel synthesis route were thoroughly characterized for physicochemical properties like powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM), dielectric, and magnetic behavior. From the powdered XRD analysis, the synthesized composites were found to be associated with high crystallinity, where the monoclinic phase was noted for the cupric oxide while the cubic phase for magnesium oxide, in addition to the measurement of crystallite sizes by Scherer formula. The FESEM and FTIR analysis provided the surface morphology and functional groups present at the surface of CuO/MgO nanocomposite. Further, the nanocomposite’s dielectric behavior and impedance properties were studied in the frequency range of 100 Hz–5 MHz at different temperatures (308–563 K). The complex impedance spectra show the negative temperature coefficient of resistance (NTCR) behavior of synthesized nanocomposites and further it is confirmed with electric modulus spectra. The AC conductivity increases with increasing frequency which obeys the Jonscher’s universal power law σAC(ω)=Aωs, the values of frequency exponent (s) > 1, indicates that the motion involves the localization or reorientation hopping and is assisted by a large polaronic mechanism among the neighboring sites. Finally, the studies of magnetic behavior by making use of a vibrating sample magnetometer (VSM) indicated the presence of a small hysteresis loop for the CuO/MgO nanocomposite at room temperature.

Sol-gel derived cobalt containing Ni–Zn ferrite nanoparticles: Dielectric relaxation and enhanced magnetic property study

A systematic study of transitional metal ion doped nickel-zinc ferrite (NZF) nanoparticles with its magnetic properties and conductivity relaxation mechanism are the objectives of this research. We have prepared cobalt doped NZF nanoparticles (NZCo) via a facile chemical route. X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) analyses suggest the formation of single phase nearly spherical nanoparticles around 60 nm in size. UV–Vis study reveals the redshift of the optical band gap for doped samples. Estimation of particle size using the effective mass model agrees well with TEM/XRD results. The electrical modulus spectra have been analyzed using Harvilliak-Negami model function. Migration energy has been found to be the minimum for 10 mol % doped sample. Frequency-dependent modulus spectra have been converted to time domain data and the relaxation process shows Kohlrausch–Williams–Watts (KWW) type behavior. Carrier motion inside the lattice has been found to be strongly correlated. Room temperature magnetization curve shows that very weak AFM/PM contribution and strong FM interaction inside the system as well as non-collinear spin arrangements between interstitial sites. Law of Approach (L.A.) analysis of the AFM/PM part subtracted hysteresis curve delineates the enhanced magnetic properties such as saturation magnetization, anisotropy constant and coercivity. Multi-functional materials of such kind with optimum behavior at specific doping percentages can be fruitful for electronic industries.

Detecting Traces of 17α-Ethinylestradiol in Complex Water Matrices

Hormones have a harmful impact on the environment and their detection in water bodies is an urgent matter. In this work, we present and analyze a sensor device able to detect traces of the synthetic hormone 17α-ethinylestradiol (EE2) below 10−9 M in media of different complexities, namely, ultrapure, mineral and tap waters. This device consists of solid supports with interdigitated electrodes without and with a polyethylenimine (PEI) and poly (sodium 4-styrenesulfonate) (PSS) layer-by-layer film deposited on it. Device response was evaluated through capacitance, loss tangent and electric modulus spectra and the data were analyzed by principal component analysis method. While the three types of spectra were demonstrated to be able to clearly discriminate the different media, loss tangent spectra allow for the detection of EE2 concentration, with a sensitivity of −0.072 ± 0.009 and −0.44 ± 0.03 per decade of concentration, for mineral and tap water, respectively. Detection limits values were found to be lower than the ones present in the literature and presenting values of 8.6 fM (2.6 pg/L) and of 7.5 fM (22.2 pg/L) for tap and mineral waters, respectively. Moreover, the obtained response values follow the same behavior with EE2 concentration in any medium, meaning that loss tangent spectra allow the quantification of EE2 concentration in aqueous complex matrices.

Influence of nano SrTiO3 and ultrasonic irradiation on the properties of polymer blend electrolytes

ABSTRACT Lithium (Li+) ion conducting nanocomposite polymer blend electrolytes (NCPBEs) based on poly(ethylene oxide) (PEO), poly(vinylidene fluoride hexafluoropropylene) (P(VdF-HFP)) as polymer hosts, lithium perchlorate (LiClO4) as an electrolyte and strontium titanate (SrTiO3) as a nanofiller have been prepared by both the conventional stirring and ultrasonic irradiation methods. Complex formation and hence the structural changes of the prepared samples have been confirmed by X-ray diffraction analysis. Conductivity studies have been carried out by means of AC impedance spectroscopy. In order to highlight the role of ultrasonic irradiation, conductivity values have been compared with the values obtained through conventional mechanical stirring method. It has been found that the system with 15 minutes of ultrasonic irradiation resulted in better homogenous dispersion of SrTiO3 in PEO/P(VDF-HFP)/LiClO4 matrix. Maximum ionic conductivity of 2.519 × 10−4 Scm−1 has been obtained for 6 wt% of SrTiO3 system which is a magnitude higher than the ionic conductivity value, 2.031 × 10−5 Scm−1 obtained for the original NCPBE prepared using conventional mechanical stirring at room temperature. Further, ionic conductivity value increases with the increase of temperature and it exhibit the Arrhenius relation. Higher degree of free ionic motion in the samples has been proven by the increase in intensity of photoluminescence spectra peaks. The dielectric properties of the prepared samples have also been studied using the complex dielectric permittivity spectra and complex electric modulus spectra. The morphology and hence the surface roughness of the samples have been depicted through AFM study.

Temperature and frequency dependent dielectric response of C3H7NH3PbI3: A new hybrid perovskite

Propylammonium lead iodide (C3H7NH3PbI3), a promising hybrid perovskite, is successfully synthesized by a solgel technique. Structural, optical, and dielectric properties have been studied in detail. The dielectric constant, loss factor, electric modulus, and AC and DC conductivity of this hybrid perovskite exhibit strong temperature dependence over the frequency range of 10 Hz ≤ f ≤ 8 MHz. The Nyquist plot reveals the distinct contributions of grain and grain boundary to the total impedance. The dielectric constant is found to increase with temperature in the high frequency region. The modified Cole–Cole plot shows that the space charge and free charge conductivity increase with the elevation of temperature, whereas the relaxation time decreases with the rise in temperature. From the modified Kohlrausch–Williams–Watts equation, we perceived asymmetrical nature in electric modulus spectra at various temperatures, which corresponds to the non-Debye type nature of perovskite. It has also been found that, with the elevation of temperature, the imaginary part of electric modulus spectra shifts from the non-Debye type toward the Debye type nature, though failing to acquire exact Debye type response, and emerges as a semiconductor material. AC conductivity of PAPbI3 is illustrated on the basis of the correlated barrier hopping (CBH) mechanism. Activation energy estimated from both modulus spectra and DC conductivity matches well, affirming the similarity between relaxation behavior and conduction mechanism. Along with all these, PAPbI3 possesses a high dielectric constant associated with a small dielectric loss, making it a potential candidate for energy harvesting devices.

Significantly enhanced dielectric properties and chain segmental dynamics of PEO/SnO2 nanocomposites

Poly(ethylene oxide) (PEO) matrix- and tin oxide (SnO2) nanofiller-based polymer nanocomposite films were prepared by solution cast followed by melt press. The effect of SnO2 concentration (i.e. 1, 3, and 5 wt%) on the structure, dielectric permittivity, and chain segmental motion of PEO was investigated with X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and dielectric relaxation spectroscopy (DRS) techniques. Results reveal that the dispersion of SnO2 nanoparticles has enormously altered the contents of different crystallite phases of the PEO and some amount of the degree of crystallinity. The DRS study in the range of 20 Hz–1 MHz at 30 °C confirmed that the complex dielectric permittivity and electrical conductivity at lower frequencies increased largely on the dispersion of SnO2 nanoparticles in the PEO matrix which was attributed to the contribution of interfacial polarization effect, moreover, a significant increase was also noted in the molecular polarization at higher frequencies. The relaxation processes corresponding to Maxwell–Wagner–Sillars mechanism and PEO chain segmental motion were analysed from the electric modulus spectra. The chain segmental dynamics and dc electrical conductivity have nonlinearly enhanced with the increase in SnO2 content in the polymer structure. The temperature-dependent dielectric and relaxation behaviour of PEO-3 wt% SnO2 film was also reported. It was observed that the relaxation time and electrical conductivity of the film exhibited Arrhenius behaviour of low activation energies.

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

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.