Modulus Spectroscopy Research Articles

Polaron assisted hopping mechanism in microwave processed Nd doped second layered aurivillius SrBi2Nb2O9 ceramics

The polycrystalline Sr0.8Sn0.2Bi1.75Nd0.25Nb2O9 (NdSBN) was synthesized using the green synthesis microwave sintering method, which significantly reduced the processing parameters of the NdSBN ceramics. Orthorhombic crystal structure with A21am symmetry was revealed by Rietveld refinement study, whereas the doping-induced strain and crystallite size was studied using the Williamson Hall method. Crossectional SEM micrographs confirm the plate-like structure, with an average grain size of 273.7 nm. A diffuse type of phase transition was observed at 345 °C, which usually arises due to compositional fluctuations and mobile oxygen vacancies; further, the diffusiveness of the NdSBN was studied using Uchino and Nomura function, a modified version of Curie-Weiss law (CW). The frequency and temperature-dependent dielectric study of NdSBN ceramics display a Maxwell-Wagner relaxation with a high loss in a low frequency regime, possibly due to the presence of leakage current in the solid solution. Frequency dependent AC conductivity obeys Jonscher's power law, whereas DC conductivity supports polaron assisted hopping in NdSBN composition with dual activation energies of 0.55 eV and 0.75 eV, which correspond to electrons and ions, respectively. The non-Debye type relaxation mechanism in conjunction with negative temperature coefficient of resistance (NTCR) behavior was demonstrated by temperature dependent impedance spectroscopy, while modulus spectroscopy confirmed the multiple relaxation processes in NdSBN ceramics.

Dielectric relaxation and electrical conductivity in lead-free organic ferroelectric diisopropylammonium bromide (dipaBr)

In this communication, we explore the dielectric relaxation behavior of the novel organic salt Diisopropylammonium Bromide (dipaBr), focusing on the universal relaxation law. We conduct dielectric relaxation and conductivity analyses across a broad spectrum of temperatures (325K–443K) and frequencies (20 Hz–20 MHz). The irregularity in peak broadening observed in complex modulus spectroscopy indicates a distribution of relaxation periods with varying time constants, confirming that the relaxation is of the non-Debye type. To interpret the experimental findings, we utilize the Havriliak-Negami (HN) formula in our investigation of dielectric relaxation. The parameters derived from the model are discussed. The relaxation process in the material appears to depend on temperature. The ac conductivity profile follows Jonscher's universal power law, and the relationship between bulk DC conductivity and temperature follows an Arrhenius-like pattern.

Achieving high acousto-optic properties and low thermal expansion anisotropy in TeO2 single crystals via Mn-doping

TeO2 single crystals have been widely used in military and civilian fields as an excellent acousto-optic (AO) material. However, due to its significant thermal expansion anisotropy and poor mechanical properties, there is a considerable risk of cracking, which hinders further applications in the AO field. Here we successfully grew a TeO2 single crystal doped with 2 % Mn4+ ions (TeO2:0.02Mn4+). This single crystal demonstrates excellent characteristics, including lower acoustic attenuation (α) and larger refractive index values. In addition, it also possesses a higher AO figure of merit (M2) of 832 × 10−15 s3/kg than TeO2 single crystal (∼793 × 10−15 s3/kg). More importantly, the TeO2:0.02Mn4+ single crystal demonstrates low thermal expansion anisotropy within a temperature range of up to 450 °C, indicating a greater practical value. The high AO performance may be attributed to manganese ion doping. The doping of Mn increased the refractive indices by enhancing the electronic polarizability and achieved lower acoustic attenuation by improving mechanical properties. Combining the results of elastic modulus and Raman spectroscopy analysis, it is observed that manganese doping optimizes crystal structure disorder, thus improving the issue of thermal expansion anisotropy. These results indicate that this TeO2:0.02Mn4+ single crystal has significant potential in designing and manufacturing AO devices.

Dynamics of charge carriers in La2CuO4 cuprates: Conductivity variation, scaling formalisms, and electric modulus study

In this work, we conducted a detailed investigation of the structural properties and the dynamics of the charges in the La2CuO4 Ruddlesden–Popper system that is prepared via the conventional solid-state process. Via the X-ray diffraction data and using the Rietveld refinement, we found that the compound exhibits a single crystallographic phase with a Bmab space group. The DC-conductivity investigation shows that the studied ceramic exhibits two electrical behaviors. Below 460 °C, the occurrence of a semiconductor behavior is attributed to the effect of the Variable range hopping conduction process. At high temperatures, the electrical nature of the material is linked to the thermally activated small polaron hopping conduction process via an activation energy Ea = 1.40 eV. Over the explored temperature range, conductivity spectra of the Ruddlesden–Popper are analyzed using the universal Double Jonscher power law. The dispersion region can be attributed to the coexistence of both hopping and tunneling processes. The conductivity spectra of the La2CuO4 Ruddlesden–Popper nicely follow the time-temperature superposition (TTSP) principle. This confirms that similar sources are responsible for relaxation and conduction processes. Using the Summerfield scaling approach, the superposition of the conductivity spectra into a single master curve confirms that the relaxation process is the microstructure's response independent. From the electrical modulus investigation, we found that the studied compound exhibits a non-Debye relaxation nature, over the explored temperature interval. Contribution of grain and grain boundary were resolved by complex modulus spectroscopy analysis. In addition, we found the absence of the electrode contribution at low frequencies. The correlation between both Z″ and the M″ peaks indicates that the conduction and relaxation processes are not related to the same origins.

Co-relation between Rietveld analysis, dielectric studies and impedance spectroscopy of the Ba1−xSrxTiO3 ceramics

Barium strontium titanate (BST), with varying Sr doping levels (x = 0, 0.05, 0.075, 0.1, 0.15, 0.3), was successfully synthesized using the solid-state reaction technique. The aim was to investigate the microstructural, dielectric, and impedance properties as Sr doping increases. X-ray diffraction analysis revealed a tetragonal phase structure for these materials, belonging to the P4mm space group, confirmed via Rietveld refinement using the Fullprof suite. SEM analysis indicated the decrement in grain sizes ranging from 0.198 to 0.0582 μm as doping concentration increases. The temperature and frequency dependencies of the dielectric constant were examined, with the Curie temperature observed in the range of 295 to 351 K with decreasing trend with substitution of strontium in pure barium titanate, showing an increase in dielectric constant with rising temperatures and non-relaxor behavior. P–E loops of BST samples illustrated bulk ferroelectric behavior, with maximum values of retentivity and coercivity reaching 1.56 and 13.97, respectively, in the highly doped BST sample. Various analytical techniques, including Nyquist plots, real and imaginary components of impedance, conductivity measurements, modulus formalism, and determination of charge carrier activation energy, were employed to elucidate the relationships between microstructure and electrical properties. Temperature-dependent resistivity demonstrated the negative temperature coefficient of resistance (NTCR) behavior in Sr-doped barium titanate. Impedance studies revealed semicircular arcs in Nyquist plots, indicating contributions from both grains and grain boundaries. The formation of well-defined grains in the BST samples was further confirmed through modulus spectroscopy.

21‐2: Modulus Spectroscopy and Capacitance‐Voltage Measurement of OLEDs as Tools for Estimating Charge Dynamics

In the past few decades, the injection and transporting characteristics of charge carriers in organic light emitting diodes (OLEDs) have been analyzed using hole‐only and electron‐only devices (HODs and EODs). However, such methods cannot fully explain the dynamic characteristics of OLEDs such as charge accumulation and recombination. In this study, we well‐established the combination of modulus spectroscopy and capacitance‐voltage measurement and applied it to describe the carrier dynamics in OLED devices.

Investigation of structural, dielectric and optical properties of the (Bi0.5La0.5Fe)0.5(Bi0.5Na0.5Ti)0.5O3perovskite for some electronic devices

This paper outlines the investigation of structural, dielectric, complex impedance and optical properties of lanthanum-modified (Bi[Formula: see text]La[Formula: see text]Fe)[Formula: see text](Bi[Formula: see text]Na[Formula: see text]Ti)[Formula: see text]O3 (BLF–BNT) single perovskite oxide synthesized by conventional solid-state reaction method. From Rietveld refinement, the crystal structure of the BLF–BNT ceramic has confirmed a tetragonal and the estimated average crystallite size is found to be 43.6[Formula: see text]nm. The dielectric properties of the La-doped BLF–BNT ceramic reveal the presence of Maxwell–Wagner-type dielectric dispersion. This suggests the occurrence of charge accumulation at grain boundaries and interfaces within the material. The complex impedance and complex electric modulus studies were employed to gain insight into the microscopic dielectric relaxations and conduction processes of the material. The electric modulus spectroscopy reveals the existence of nonDebye-type relaxation processes, including localized and long-range relaxation processes. The Nyquist and Cole–Cole plots show the semiconducting nature of the BLF–BNT ceramic. With the help of the Arrhenius method based on the imaginary portion of the electrical impedance and modulus, activation energies and relaxation times have been estimated. These parameters contribute to a deeper understanding of the electrical properties and conduction mechanisms within the material. Further, Raman spectroscopy, a nondestructive chemical analysis technique, was conducted to confirm the composition and structural integrity of the proposed system through its atomic vibrations. Also, the bandgap energy of the material has been estimated using Tauc’s relation and is found to be 1.69[Formula: see text]eV. This signifies that the BLF–BNT ceramic possesses a suitable bandgap for certain device applications, making it a promising candidate in various technological fields. Moreover, the overall comprehensive study of the proposed ceramic provides valuable insight and opens new possibilities for its potential applications in various electronic devices.

Analysis of the Degree of Blending (DoB) of recycled asphalt mixtures with variation in mixing temperature, type, and RAP content

Presently, there is a significant increase in studies dedicated to the reuse of Reclaimed Asphalt Pavement (RAP) material obtained from the recycling of asphalt coatings. This procedure aims to reduce production costs and minimize environmental impacts. To carry out the reuse of this material, it is crucial to understand the interaction mechanisms between the aged binder of the RAP and the new binder. These mechanisms can be assessed through the Degree of Binder Activity (DoA) and the Degree of Blending (DoB). DoA represents the quantity of aged binder available for the new mixture, being an intrinsic property of each RAP. On the other hand, DoB indicates the degree of blending between the aged and new binders, being influenced by external factors such as mixing parameters, thus presenting a challenge in quantification. This study sought to establish a predictive model to quantify DoB based on Dynamic Modulus and Fourier-Transform Infrared Spectroscopy (FTIR) tests. These tests were conducted on mixtures containing four different RAPs, varying in different content levels and mixing temperatures. In each RAP, DoA was quantified, and a statistical analysis was performed to verify the significance of independent variables in dynamic modulus results. After this step, four modeling attempts were made, choosing the one that not only presented significant independent variables but also obtained the highest predicted R² value. The chosen model was validated and demonstrated small variations compared to DoB obtained by the generated equation. Thus, it is concluded that the DoB modeling conducted in this study highlights that mixing temperatures and RAP content influence factors such as DoA, dynamic modulus, FTIR, and consequently, DoB. Additionally, the practicality of the model was emphasized, as it successfully predicted DoB using a single mechanical and chemical test.

Multiple relaxation mechanisms in SrBi2Nb2O9 ceramic tweaked by tin and samarium incorporation in assistance with single-step microwave sintering

Non-stoichiometric lead free polycrystalline Sr0.8Sn0.2Bi1.75Sm0.25Nb2O9 (SSBSN) ferroelectric ceramics were synthesized through conventional solid step route method by incorporating ball milling and microwave sintering method. X-ray diffraction along with the Rietveld refinement technique confirms the single-phase orthorhombic structure with A21 crystal symmetry. Additionally, the short-range ordering was confirmed by Raman spectroscopy. Doping induced crystallite size and strain were further calculated from the Williamson-Hall plot, which comes around 150 nm and 1.48 × 10–3 respectively. A plate like morphology with an average grain size of 0.41 μm was confirmed by scanning electron microscopy (SEM). A diffuse type ferroelectric to paraelectric phase transition was recorded at 395 °C, mostly arising due to structural heterogeneity at the inter-ferroelectric phase boundary. The temperature and frequency-dependent dielectric measurement of SSBSN ceramic reveal a Maxwell–Wagner relaxation, with prominent dielectric loss in a low frequency regime perhaps due to the generation of leakage current in the SSBSN system. Frequency dependent ac conductivity indicates the polaron assisted hopping mechanism in SSBSN, which further obeys Jonscher’s formulation. The intra and intergranular contributions to impedance in SSBSN ceramics were probed by the complex impedance spectroscopy (CIS) technique. A non-Debye type relaxation mechanism in SSBSN ceramics was indicated by the Cole–Cole plot, whereas the conduction mechanism and transport properties were briefly studied using modulus spectroscopy.

Structural, microstructural, dielectric, electrical, and magnetic properties of a scandium-modified bismuth ferrite

ABSTRACT This paper reports on the synthesis method and characterisation of a binary polycrystalline material (Pb0.6Bi0.2Sc0.2)(Fe0.4Ti0.6)O3 ceramic. The room temperature XRD pattern confirms an orthorhombic crystal structure with average crystallite size of 25.3 nm. Study on SEM micrograph reveals the homogeneous dispersal of grains and well-defined grain boundaries and also the compactness of the grains implies the development of a highly dense material. The purity and composition of this material are verified using EDX, and confirms presence of all the constituent elements (Pb, Bi, Sc, Fe, Ti, and O) both in weight and atomic percentage. According to research on dielectric spectra as a function of temperature range of 25°C to 500°C and frequency range of 1 kHz to 1 MHz, there may be Maxwell–Wagner-type dispersion at low frequencies, which considerably decreases towards higher frequencies because of decreasing space charge polarisation. The negative temperature coefficient of resistance behaviour is observed from impedance spectroscopy. The research of modulus spectroscopy demonstrates the existence of a non-Debye type of relaxation. The thermally activated charge carriers regulate the study of the conduction mechanism. The semicircular arcs found both in Nyquist and Cole–Cole plots provide an evidence for the semiconducting nature. The magnetic study reveals the superparamagnetic nature of the sample.

Ionic conductivity of nanocrystalline γ-AgI prepared by high-energy ball milling

Abstract The compound AgI crystallizes, depending on temperature and pressure, with various crystal structures. While α-AgI is the stable form at elevated temperatures, the β and the γ forms exist at lower temperatures. Variants with stacking sequences different than in pure β-AgI and γ-AgI enrich the complex crystallographic situation for AgI. In the study presented here, we converted a mixture of β-AgI and γ-AgI into nanostructured γ-AgI by mechanical treatment, that is, by high-energy ball milling of such a mixture under ambient conditions. Our work extends an earlier study by Ahmad (Z. Naturforsch. 2015, 70b, 17). We used variable-temperature, potentiostatic conductivity spectroscopy as well as electric modulus measurements to characterize the electric transport parameters. For the case that the sample is heated to temperatures near and above 420 K, preliminary information on the “resistance” of the electric conductivity against healing of defects are also collected. As compared to the unmilled but mixed sample, whose Ag+ ionic transport is dominated by those ions residing in the γ-phase of AgI (0.25 eV vs. 0.46 eV in β-AgI), ball milling only leads to a small increase in overall electric conductivity (by a factor of 3–4) for nanocrystalline γ-AgI (0.25 eV). This observation is perfectly in line with a recent observation for the fast ion conductor Li10GeP2S12 (Hogrefe et al., J. Am. Chem. Soc. 2022, 144, 9597): In materials with already rapid diffusion pathways, nanostructuring and the introduction of defects and distortions do not lead to significantly enhanced ion transport. Here, a careful analysis of data from conductivity and modulus spectroscopy helps identify which dynamic parameters are mainly responsible for the change in the overall conductivity upon mechanical treatment of coarse-grained γ-AgI.

Dielectric relaxation studies in Sm2O3 doped boro-zinc-vanadate glasses

In this work, the conventional melting procedure was adopted to synthesize glasses with a composition of (ZnO)0.3 – (V2O5)0.3 – (B2O3)0.4-x – (Sm2O3)x, x = 0.002, 0.005, 0.007, 0.01 and 0.02 mol%. The dielectric properties of these glasses were measured. The dielectric constant (εʹ) and dielectric loss (εʹʹ) of glasses are found to vary in the range from 1.9177x102 to 3.9456x103 and from 1.5751 to 6.9095x105 respectively for the temperature range 343 K – 573 K and frequency range 50 Hz to 10 MHz. With increase of frequency, both dielectric constant and loss decreased and increased with increase of temperature. The analysis of dielectric constant and dielectric loss confirmed that the phenomenon of dielectric relaxation is mainly due to the frequency-dependent polarization mechanism. Electric modulus and impedence spectroscopy revealed non-Debye type and a single phase relaxation process. Activation energy for dc conductivity and dielectric relaxation are found to be of same size indicating that the potential barrier encountered by the charge carriers is same in both the processes. The master curves suggested that temperature-independent relaxation is occurring in the present glasses. The high values of measured dielectric parameters suggest that the present glasses are suitable in semiconducting and energy storage applications.

Structural Elucidation of Electrical and Optical Properties in Lead‐free Organic‐Inorganic Copper Bromide [(CH3)4N]2CuBr4 Single Crystals

AbstractOrganic‐inorganic metal halide single crystals have attracted a lot of attention due to their flexible structural design and excellent optoelectronic applications. This study details the synthesis of copper‐based [(CH3)4N]2CuBr4 hybrid metal halide single crystals via a slow evaporation method. The crystal structure, crystal habit, chemical groups, intermolecular interactions, electrical properties of the sample were studied via single crystal x‐ray diffraction, scanning electron microscopy, Raman and Fourier transform infrared spectrometer, Hirshfeld surface analysis, impedance spectroscopy, and modulus spectroscopy, respectively. An orthorhombic crystal system with the non‐centrosymmetric space group Pna21 was identified at room temperature. The deformation in the tetrahedra was calculated by the bond angle and bond length deformation index. The Cole‐Cole plot displayed the existence of depressed semicircles, which indicated the predominant distribution of grains, further confirmed by the SEM image. The deformed semi‐circular arcs on the electric modulus curve undeniably prove that the bulk effect dominates the material‘s electrical properties. Significantly, the compound presents a phase transition at ~240 K and excellent thermal stability up to a temperature of 400 K. Therefore, our research sheds light on the temperature dependence of electrical responses in these hybrid crystals and gives inspiration for the development of single crystal‐based efficient energy devices.

The study of Correlated Barrier Hopping (CBH) conduction mechanism and modulus spectroscopy of YFe0.5Co0.5O3 compound

This research paper studied the electrical properties of Yttrium orthoferrite by substituting 50-mol percent of Co into the Fe-site. The crystalline morphology of the obtained compound, YFe0.5Co0.5O3, was studied using XRD and Rietveld refinement with FullProf software. A low-temperature solid-state reaction technique was used to make this compound. X-ray diffraction results indicate that the obtained compound has an orthorhombic structure with space group Pbnm. X-ray peak broadening analysis was used to evaluate crystallite size and strain using Williamson-Hall plots (W–H plot). FESEM with EDX data revealed the phase purity of the obtained compound. XPS studies showed the presence of multiple oxidation states of Fe and Co in the compound. The Nyquist plots show non-Debye-type behavior in all samples. The CBH (Correlated Barrier Hopping) Model was adopted to explain the conduction mechanism.

SnS/MnSe heterostructures for enhanced optoelectronics and dielectric applications.

In this work, we synthesized SnS and MnSe compositions using a hydrothermal method and then prepared the SnS/MnSe heterostructure. By using X-ray diffraction, the structural characteristics of these compounds were examined. It was discovered that both the pure phases MnSe and SnS appeared in the SnS/MnSe sample, confirming the heterostructure formation. The Raman analysis also confirmed the formation of a heterostructure of the SnS/MnSe sample containing two phases, MnSe and SnS. The individual MnSe and SnS compositions show good optical properties, having bandgap values around 1.3 and 1 eV, respectively, whereas the prepared heterostructure shows a very low bandgap value of around 0.4 eV. The SnS sample shows nano sheet-like morphology, and MnSe shows rectangular-like shapes, whereas the SnS/MnSe heterostructure shows the presence of both shapes. The EDX study shows all the constituent elements in the SnS/MnSe heterostructure sample. The electrical study also shows that the properties of the prepared heterostructure are different from those of pure compositions. Investigating the dielectric characteristics with respect to temperature and frequency allowed for a thorough analysis of several parameters, including the electric modulus, dielectric constant, AC conductivity, and impedance spectroscopy. Applications for electronic and energy storage devices may benefit from the aforementioned optical, electrical, and dielectric characteristics of the SnS/MnSe heterostructure.

Sol–gel synthesized (Bi0.5Ba0.5Ag)0.5 (NiMn)0.5O3 perovskite ceramic: An exploration of its structural characteristics, dielectric properties and electrical conductivity

This manuscript delves into the multifaceted exploration of the perovskite ceramic (Bi0.5Ba0.5Ag)0.5(NiMn)0.5O3, synthesized via the sol-gel technique. Unveiling the structural, morphological, dielectric, and electrical facets, the material's orthorhombic structure, affirmed through Rietveld-refined XRD data, showcases an average crystallite size of approximately 33 nm. Dielectric investigations illuminate the presence of Maxwell-Wagner-type dispersion, hinting at charge accumulation along grain boundaries and interfaces. Employing complex impedance and electric modulus analyses reveals microscopic dielectric relaxation intricacies and the material's conduction mechanisms. Electric modulus spectroscopy uncovers non-Debye-type relaxation, encompassing both localized and long-range processes. Nyquist plots attest to the ceramic's semiconducting nature. Applying the Arrhenius law to the imaginary part of electrical impedance and conductivity yields activation energies and relaxation times, significantly enriching our understanding of the material's electrical properties. This comprehensive scrutiny unravels the ceramic's potential applications, offering fresh insights for diverse device implementations.

Voigt Profile is Suitable for Impedance Spectroscopic Analysis of BLSF Ceramics

Abstract: In our earlier studies, samarium-modified bismuth layer-structured ferroelectrics (BLSF), namely SmxBi3-x TiNbO9 (SBTN); (x=0, 0.2, 0.4, 0.6. 0.8, and 1.0), prepared by solid-state reaction method, have shown broad dielectric relaxations. Among all the compositions, Bi2.6Sm0.4TiNbO9 (BST-0.4) has shown a lower tolerance factor, high remnant polarization (Pr) value, and low stretching factor. In addition, the compound has shown interesting broad dielectric relaxation and non-Debye nature. The specific reasons for the broad relaxation remain unclear. To gain more insights, we synthesized multi rare earth ion substituted compounds, namely, Bi2.6La0.2Sm0.2TiNbO9 (sample A) and Bi2.6La0.2Gd0.2TiNbO9 (sample B), using the conventional solid-state reaction method. A single impedance spectroscopic approach alone may not be sufficient to explain the asymmetric or non-Debye behavior, therefore Lorentzian, Gaussian, and Voigt fitting were adopted in the present investigation. From the analysis, the Voigt profile (Vf and Vʹf) is found to be a valuable alternative tool to understand the broad impedance non-Debye relaxations. Finally, results were corroborated by dc-conductivity data. Keywords: BLSF, Modulus spectroscopy, Relaxation, Defect-mechanism, Gaussian, Lorentz and Voigt fitting, Dc conductivity.

Revealing the relaxation kinetics of curcumin based dye-sensitized solar cell

DSSCs have garnered significant attention as a promising technology for renewable energy generation. The carrier kinetics, or the dynamics of charge carriers, play a vital role in the efficiency of DSSC. However, numerous of its optoelectronics characteristics at low frequencies are highly contested. Here, we thoroughly investigated the carrier dynamics of curcumin-based sensitized cell using impedance spectroscopy and modulus spectroscopy under illumination and dark condition. It is revealed that the dielectric relaxation in curcumin-based DSSC follows the interfacial (Maxwell-Wagner type) polarization probably ascribed to the grain boundary effect. Moreover, the comparative evaluation of impedance and modulus spectra at lower frequencies demonstrates the localized type of charge-carrier relaxation in this curcumin-based sensitized cell, which has been related with the conductivity hopping phenomena. These results illustrate the potential of curcumin as a promising new sensitizer for DSSCs and highlight the importance of continued research into new and innovative materials for sustainable energy technology.

Investigation of Temperature‐Activated Charge‐Carrier Dynamics and Dielectric Relaxation in Fe, Cu–Doped CeO2

Cerium oxide (CeO2) is a material with unique dielectric properties that make it a promising candidate for various applications. High electrical resistance and a wide bandgap of pristine CeO2 limit its applicability in photovoltaics and photo‐electrocatalysis. CeO2 is co‐doped with transition metals (Fe+2/Fe+3 and Cu+2), which reduces its optical bandgap energy and electrical resistance. This study aims to investigate the dielectric relaxation behavior and charge‐carrier dynamics of Fe, Cu–CeO2. The enhanced charge‐carrier dynamics in the Fe, Cu–doped CeO2 compared to pristine CeO2 are reported. Using temperature‐dependent electrochemical impedance spectroscopy (TD‐EIS), the dielectric relaxation and carrier dynamics in pristine CeO2 and Fe, Cu–doped CeO2 in the temperature range 313–473 K along with the modulus spectroscopy are investigated. It is observed that Z′ values reduced with the temperature, thus showing the negative temperature coefficient of resistance in the frequency range 6.28–1.005 105 radians s−1. Furthermore, a correlated study of –Z″ and M″ shows the charge‐carrier relaxation behavior changes from ideal Debye type to non‐Debye type with temperature rise in Fe, Cu–doped CeO2.

Origin of non-universal percolation/scaling and universal non-Debye relaxation in PVDF/MWCNT polymer nanocomposites

Polymer Nanocomposites (PNC) comprising polyvinylidene fluoride (PVDF)/Multi-walled Carbon Nanotubes (MWCNT) were studied. The structural composition and thermal stability were confirmed from XRD and DSC/TGA data, respectively. The extent of distribution of MWCNT in the PNC increases and the clustering of MWCNT also increases with an increase in the volume fraction of MWCNT ([Formula: see text], as confirmed by FESEM. The PNC shows an insulator-to-metal transition (IMT), with both non-universal percolation threshold [Formula: see text] of [Formula: see text] and scaling exponents [Formula: see text], respectively, attributed to adhesiveness/cold pressing and the higher aspect ratio/conductivity of MWCNT. Modulus spectroscopy confirms a non-Debye type universal relaxation behavior [Formula: see text] only for the percolative sample due to Maxwell–Wagner–Sillars/interfacial polarization, while only dipolar relaxation was probed or the samples below [Formula: see text]. The [Formula: see text] with static effective dielectric constant [Formula: see text] and low tan [Formula: see text] may be suitable for charge storage applications.