Universal Dielectric Response Research Articles

Investigation of dielectric properties and conductivity of polyvinyl chloride composites by terahertz time-domain spectroscopy

Polyvinyl chloride (PVC) composites have been studied using terahertz time-domain spectroscopy (THz-TDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) to highlight the prospects for their applications. The terahertz dielectric properties and conductivity of PVC composites in the frequency window of 0.2–1.6 THz have been investigated. The universal dielectric response model has been applied to fit the real part of THz conductivity. It shows that a super-linear behavior is presented in the conductivity, and the conductivity can be tuned by varying the content of PVC and the type of composite. In addition, relationships are established among the types and concentrations as well as the dielectric properties and conductivity. These results are expected to be applied to the preparation of terahertz devices and to the monitoring of materials in industrial production.

Universal Dielectric Response in Electronically Correlated Functional Oxides CaCu3Ti4O12, LaFeO3, YFe0.5Cr0.5O3 and their Nanocomposites: A Comparative Study

AbstractCaCu3Ti4O12 (CCTO), LaFeO3 (LFO) and YFe0.5Cr0.5O3 (YFCO) were synthesized via conventional sol–gel auto–combustion method using citric acid as gelling agent. The X‐ray diffraction analysis revealed the phase purity of the samples. The energy dispersive X‐ray (EDX) analysis confirms the stoichiometry of the pristine phases. The average particle size obtained from the field emission Scanning electron microscopy (FE−SEM) images revealed that CaCu3Ti4O12 exhibits a broad range of particle size starting from a couple of hundreds of nanometer to micrometer, whereas that for LaFeO3 and YFe0.5Cr0.5O3 are about 110 nm and 50 nm, respectively. We have fabricated the new composites: CCTO–LFO, CCTO–YFCO and LFO–YFCO. The grain sizes of the composite phases are consistent with the pristine phases as they are prepared by at lower sintering temperatures and duration. The dielectric properties of these ceramic composites were compared to those of the pristine phases. The temperature and frequency dependent dielectric measurements reveal a wide range of dielectric constant with moderate tan δ values. The temperature dependent dielectric constant of the investigated samples varies from 100 to 1500 at room temperature and the data have been analyzed using universal dielectric response (UDR) model.

Probing of structural, electrical, and dielectric properties of samarium doped composite of barium titanate (Ba0.5Sm0.5TiO3) and cobalt ferrite (Co0.5Sm0.5Fe2O4)

Multiferroic composites exhibit remarkable magnetoelectric (ME) characteristics, offering diverse applications. The study investigated samarium (Sm) doped composites, specifically (1 − x)Ba0.5Sm0.5TiO3–xCo0.5Sm0.5Fe2O4 (x = 0.0,0.02,0.04,0.06), formed by combining Sm doped BaTiO3 and CoFe2O4 using the solid-state reaction method. X-ray diffraction analysis revealed a tetragonal structure in Ba0.5Sm0.5TiO3 (SmBT) and a cubic spinel secondary phase in Co0.5Sm0.5Fe2O4 (SmCF), suggesting uniform distribution of grains. The optical bandgap in SmBT and the composite showed a slight decrease (from 3.14 eV to 3.01 eV) with increasing Sm concentration, as observed in optical studies. The dielectric measurements showed that the dielectric constant of SmBT was higher (ϵ′ = 526.3) between 80 Hz and 8 MHz, while the composites had a lower dielectric constant (ϵ′ = 438.4) at lower frequencies and the real part of dielectric was fitted by Havriliak–Negami (H–N) model shows that the dielectric curves exhibit a characteristic dispersion pattern known as the cole–cole mode (grains) also confirmed by cole–cole plot. The response exhibited linearity, adhering to the universal dielectric response model. Ferroelectric behaviour in the underlying material confirms SmBT non-centrosymmetric character and the storage efficiency (η) of all composites surpassed 90%, reaching a peak of 94.8% with a ferrite content of 0.02. The versatility of the Sm-doped composites offers opportunities for diverse applications in fields such as electronics, telecommunications, and biomedical devices. Notably, these materials can be utilized in Memory Devices, Actuators, and other relevant applications.

Tailoring the structural, optical, electrical and multiferroic properties of Sm1-xRxFeO3 (x = 0.0 and 0.5; R = Pr, Nd, and Gd) and their synergistic photocatalytic activity

In this work, nanocrystalline Sm1-xRxFeO3 (x = 0.0 and 0.5; RPr, Nd, and Gd) samples have been synthesized via auto-combustion method and characterized to understand their microstructural, optical, electrical and multiferroic properties. X-ray diffraction data in combination with the FTIR spectra revealed the monophase and distorted orthorhombic configuration of all the samples with Pbnm space group. Rietveld refinement displayed a reduction in the bond length as well as the bond angle in the Sm0.5Gd0.5FeO3 sample. Raman spectra exhibit compressive strain in Sm0.5Gd0.5FeO3 nanoparticles; this finding is further supported by the XRD analysis. UV–visible spectroscopy manifests a reduction in the optical energy bandgap on moving Gd to Pr in Sm0.5R0.5FeO3 system. Transmission electron microscopy (TEM) images in combination with energy dispersive x-ray (EDX) spectra reveal the non-uniform surface morphology with the agglomerated nature of nanoparticles and affirm the elemental compositions of all the samples. The room temperature P-E and M − H loops infer the multiferroic nature of all samples. Electron paramagnetic resonance (EPR) analysis divulges the weakening of the super-exchange interactions in Sm0.5R0.5FeO3 system. DC electrical resistivity measurements reflect semiconductor-like behaviour in all prepared samples. The dielectric behaviour of the samples is in accordance with the “universal dielectric response” model. The temperature-dependent dielectric measurements of all prepared samples have been performed at 1 kHz to determine the Néel temperature (TN). The photocatalytic investigation depicts the superior photocatalytic response of Sm0.5Pr0.5FeO3 nanoparticles under solar-light irradiation through the synergism of semiconductor-photocatalyzed oxidation and heterogeneous Fenton-like reaction.

Enhancement of dielectric and ferroelectric properties of (Sr, Ni) Co-doped BaTiO3 ceramics

In the present study, systematic investigations on dielectric and ferroelectric properties of pure and (Sr, Ni) co-doped BaTiO3 nanocrystalline powder samples fabricated via microwave-assisted co-precipitation method have been reported. XRD patterns divulge the formation of mono-phase tetragonal crystal structure with P4mm space group. The fingerprint bands in the FTIR spectra further assure the formation of desired crystal structure. The dielectric responses have been examined by virtue of the universal dielectric response mechanism with remarkable improvement in the dielectric properties for the (Sr, Ni) co-doped sample. The P-E loop measurement corroborates ferroelectricity in the system and augmentation in the maximum polarization for the co-doped sample. The improved dielectric and ferroelectric properties in (Sr, Ni) co-doped BaTiO3 suggest its potential in various technological applications.

Ab-initio study of structural, morphological and optical properties of multiferroic La2FeCrO6

The current research is concerned with the structure, morphology, and physical properties of a double perovskite La2FeCrO6. The crystallite size of the sample was determined to be 22.46 nm using the modified Scherrer equation. The elemental composition of La2FeCrO6 was confirmed through X-ray photoelectron-spectroscopy (XPS), which detected La, Fe, Cr, and oxygen, as well as oxygen deficiencies that significantly impact the observed ferroelectric behavior in the investigated sample. High-resolution transmission electron microscopy (HRTEM) verified the nanoscale preparation of the sample with an average particle size of 33.32 nm. Thermogravimetric analysis (TGA) was employed to investigate the thermal properties of the sample including the calculation of thermodynamic functions such as changes in enthalpy (ΔH) and entropy (ΔS) for La2FeCrO6. The material exhibits an optical direct transition with a band gap value of 3.4 eV and an Urbach energy of 2.5 eV. Due to its large specific surface area and band gap value, La2FeCrO6 shows promise in applications such as photocatalysis and water purification. The ac conductivity of La2FeCrO6 follows the universal dielectric response (UDR), and the P-E loop of the sample demonstrates its ferroelectric behavior.

Structural, optical, electrical and magnetic properties of lithium zinc ferrite – Silica nanocomposites

Lithium zinc ferrite - silica nanocomposites; with a formula [Li0.5−x/2ZnxFe2.5−x/2O4]30%[SiO2]70%, have been synthesized using ultrasonic assisted sol-gel auto combustion method. Thrust of the study is to investigate effect of zinc substitution in lithium ferrite (dispersed in silica matrix) on structural, optical, electrical and magnetic properties. X-ray diffraction (XRD), UV Visible (UV-Vis), Transmission Electron Microscopy (TEM), Complex Impedance Spectroscopy (CIS) and Vibrating Sample Magnetometry (VSM) have been employed to investigate the samples. XRD patterns confirm the phase purity and revealed that incorporation of Zn2+ at Li+ sites expand the unit cell dimensions from 8.3281 Å to 8.4398 Å, strain and crystallite size escalates from 0.29 to 1.42 and 18.28–27.50 nm respectively. Results from TEM and XRD match well indicating least agglomeration. Optical bandgap and refractive index show a significant effect on increasing zinc content. The impedance (Z) is found to reduce with increase in Zn2+ and may be attributed to enhancement in crystal boundaries. Dielectric properties were explored using cole-cole theoretical fitting of permittivity (ε), universal dielectric response (UDR) model, Koop’s theory and Maxwell–Wagner (M-W) mechanism. Complex electrical modulus (M*) formulation has been employed to explore the transport mechanism. Cole-cole plots in M* reveal that all the samples, except x = 0.50, show relaxation originating from grain boundaries whereas x = 0.50 sample shows contributions from both, grain and grain boundaries. Equivalent circuits have been derived using M* spectrum and are presented with circuit parameters. Frequency dependent AC conductivity (σac) curves have been fitted successfully using Jonscher’s power law; σac for a typical sample x = 0.50 was fitted using double power law. All samples have η ≤ 1, confirming correlated barrier hopping (CBH) mechanism of conductivity. Present system exhibits lower dc conductivity due to highly resistive silica in the samples. Magnetic properties have been studied using Vibrating Sample Magnetometry (VSM). Zn2+ substitution has a significant impact on magnetization due to migration of cations.

Irradiation effect on structural and electrical properties of YMnO3/ITO/glass thin film

In this communication, the structural, microstructural and electrical properties of YMnO3/ITO/glass thin films have been thoroughly studied. Moreover, the electrical properties of this film have been studied in the absence of magnetic field and in the vicinity of applied magnetic field of 1 T. In addition to it, the YMnO3/ITO/glass thin films were grown using sophisticated pulsed laser deposition (PLD) technique which was further irradiated by 120 MeV Ag+9 ions with different ion fluence of 5 × 1011–5 × 1013 ions/cm2. In order to calculate crystallite size of the film, Scherrer’s formula and W-H plot are plotted. For the investigation of surface morphology, Atomic force microscopy (AFM) has been performed. Variation in electrical properties have been discussed in the context of average grain size, grain boundary density, rms surface roughness, defect density and oxygen vacancies. To understand the dielectric response of pristine and all the irradiated thin films under zero and 1 T applied magnetic fields, universal dielectric response (UDR) model and relaxation model have been fitted. Frequency dependent a.c. conductivity have been fitted by Jonscher’s power law and from its calculation maximum barrier height have been estimated. Average normalized constant (ANC), which provides the grain boundary density, have been analyzed from impedance data.

Spinodal decomposition-derived giant polarization in TiO2–SnO2 generated from a metastable phase

Spinodal decomposition (SD) was incorporated into Nb-doped metastable TiO2–SnO2 to achieve giant interfacial polarization. The dielectric characteristics were analyzed using an equivalent circuit involving electron migration, where the SD bulk is given by the universal dielectric response relation. Both the Nb–TiO2 and the Nb–SnO2 layers showed semiconductive behaviors. With increasing SD treatment temperature, the SD volume fraction increased, as did cation interdiffusion at the SD interface, resulting in a large dielectric loss. The optimal SD temperature was determined as 1100 °C, where the Maxwell–Wagner capacitance showed a very high value of 44.6 μF corresponding to the permittivity at the lowest frequency exceeding 106. Such colossal polarization was considered due to an accumulation of trapped electrons at the Schottky barrier at SD layers with different conductivities.

Ionic conducting characteristics of the solid electrolyte LiMgPO4

Li+ ion-conducting properties in Lithium magnesium orthophosphate compound were investigated in the present study. Our compound was prepared with the standard ceramic method.Vibrational study and impedance spectroscopy were explored to understand the ion dynamics and dielectric properties. The surface morphology of the sample was examined by SEM analysis. Rietveld's refinement of the X-ray diagram shows that the synthesized material was well crystallized in the orthorhombic olivine structure with the Pnma space group.The complex impedance spectra analysis reveals that the electrical properties of the material are heavily dependent on frequency and temperature, indicating a relaxation phenomenon and semiconductor-type behavior.A typical universal dielectric response in the frequency-dependent conductivity at different temperatures was found. The alternative current conductivity is discussed in the framework of Jonscher's model. The Correlated Barrier Hopping "CBH" conduction process is proposed to investigate the transport properties in the dynamic region of the studied compound.Cationic disorder plays a major role in the charge carriers transport. Fitting parameters obtained from the theoretical aspect have been discussed.

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.

Investigation on transport properties of GdMnO3 based bilayer thin films

Two heterostructures (Al-ZnO/GdMnO3/SrTiO3 and ZnO/GdMnO3/SrTiO3) were fabricated using Pulsed Laser Deposition System. The lattice parameters of the hexagonal (Al-ZnO and ZnO) and orthorhombic (GdMnO3) films are determined from the analysis of the x- ray diffraction patters. To study the surface morphology of prepared heterostructures Atomic Force Microscopy (AFM) were performed which revels that both heterostructures have homogenous island type of growth. To understand the transport behaviour of semiconductor-ferromagnetic (S-F) bilayers/films the resistivity measurement and field dependent dielectric measurements show and one Variation/Comparison in resistivity and dielectric behaviour of both heterostructures discussed based on Variable Rang Hopping (VRH) model and Universal dielectric response (UDR) Model.

Study of Structural and Electrical Properties of CuFe-CGN for Renewable Energy Applications

Renewable energy source is a clean energy production source and can overcome climatic challenges caused by the excessive use of fossil fuels. The nanocrystalline material of composition Cu0.2Fe0.2(Ce0.6Gd0.4-xNdx)0.6O2-x has been synthesized by WOWS sol-gel process by varying Neodymium as such x= 0.0, 0.05. These samples were calcined at 500°C for 2 hours and the pellets were sintered at 750°C for 5 hours. X-Ray Diffraction technique confirms the cubic fluorite structure of the material. The doped material has showed high dielectric constant value and low dissipation factor and increased AC conductivity. AC conductivity obeys the Universal Dielectric Response. The material shows the potential for applications such as an electrode/electrolyte for fuel cells or also as a dielectric resonator.

Spin reorientation behavior and enhanced multiferroic properties of co-doped YFeO3 towards a monophasic multiferroic ceramic Co0.05Y0.95Fe0.95Ti0.05O3

Monophasic nanocrystalline lead-free relaxor ferroelectric samples of YFeO3 and Co0.05Y0.95Fe0.95Ti0.05O3 were prepared via the standard sol-gel synthesis method. The influence of Co and Ti co-doping on the structural, dielectric, ferroelectric, and magnetic properties were investigated using X-ray, Neutron Diffraction, Electric Polarisation, and magnetization measurement techniques. The structural analysis by the Rietveld method revealed an orthorhombic (Pnma) distorted perovskite structure. The analysis of the neutron diffraction data showed a spin reorientation from IR Γ4 to Γ2 in the doped sample. The universal dielectric response (UDR) phenomenon was used to explain the dielectric behavior. The temperature-dependent dielectric constant measurement shows a shift in the ferroelectric to paraelectric phase in Co0.05Y0.95Fe0.95Ti0.05O3. The observed P-E loops indicate lossy ferroelectric nature for YFO and CYFTO. Enhancement in the value of saturation magnetization at room temperature was observed on co-doping. Furthermore, the presence of magnetodielectric coupling was established for the co-doped sample. Co-doping with Co and Ti in YFeO3 enhanced the multiferroic properties of the pristine sample which may be helpful for future device applicability.

Fully 3D‐Printed, Ultrathin Capacitors via Multi‐Material Microsputtering

AbstractThis study reports the first fully additively manufactured capacitors as a proof‐of‐concept demonstration of direct‐write, ultrathin‐film electronic components made via multi‐material microplasma sputtering. This is also the first demonstration of a cleanroom‐quality, multi‐material electrical device produced entirely through additive manufacturing. Ultrathin metal and dielectric films are deposited at <80 °C and atmospheric pressure conditions on a substrate using a novel, continuously fed, dual target microsputtering printhead. The conductive films are created by sputtering gold in an air atmosphere and shown to attain near‐bulk electrical resistivity. The dielectric films are created by sputtering aluminum in a gas blend of argon and air; the aluminum oxidizes in the high‐energy, high‐collisionality plasma, forming alumina nanoparticles that are deposited on the substrate. Ultra‐thin (35 nm) alumina films showed extremely high resistivity (100 GΩ‐m) and dielectric strength (6.2 GV m−1). Also, the frequency response of the capacitor is satisfactorily described by the universal dielectric response typically found in heterogenous dielectrics. It is hypothesized that the dielectric response is the result of the presence of condensed water in the pores of the alumina film.

Dielectric behaviour of BZT-BCT nano pseudobinary system near TCP-assisted morphotopic phase boundary

The present study investigates the comparative dielectric studies in nano pseudobinary system synthesized by conventional and hybrid microwave sintering. The material was formed near Tri Critical Point (TCP)-assisted Morphotropic Phase Boundary (MPB) region from equal weight percentage of Lead Zirconate Titanate (BZT) and Barium Calcium Titanate (BCT) employing high energy ball milling. In the temperature dependent LCR study, a diffused phase transition (DPT) behaviour was identified for both conventional and hybrid microwave sintered samples. In each case, modified Currie-Weiss relation indicates an anomaly in the paraelectric state. Further, another approach using macroscopic composition-fluctuation model also exhibits the anomalous behaviour. Universal dielectric response (UDR) demonstrates that such behaviour is created by a temperature assisted relaxation phenomena by the formation of oxygen vacancies. Beyond 260 °C, microwave sintering creates more oxygen vacancies across grain boundary region as compared to the conventional sintering and in turn plays the key role for enhanced dielectric permittivity.

Mechanism of hopping conduction in Be\u2013Fe\u2013Al\u2013Te\u2013O semiconducting glasses and glass\u2013ceramics

Electrical properties of beryllium-alumino-tellurite glasses and glass–ceramics doped with iron ions were studied using impedance spectroscopy. The conductivity was measured over a wide frequency range from 10 mHz to 1 MHz and the temperature range from 213 to 473 K. The D.C. conductivity values showed a correlation with the Fe-ion concentration and ratio of iron ions on different valence states in the samples. On the basis of Jonscher universal dielectric response the temperature dependence of conductivity parameters were determined and compared to theoretical models collected by Elliott. In glasses, the conduction process was found to be due to the overlap polaron tunneling while in glass–ceramics the quantum mechanical tunneling between semiconducting crystallites of iron oxides is proposed. The D.C. conductivity was found not to follow Arrhenius relation. The Schnakenberg model was used to analyze the conductivity behavior and the polaron hopping energy and disorder energy were estimated. Additionally, the correlation between alumina dissolution and basicity of the melts was observed.

Co-ferrite nanostructures prepared by solvothermal route; new ultra-low k dielectrics

Co spinel ferrite nanoparticles were successfully prepared using a solvothermal route. Their structure, morphology and cationic distribution were studied by X-ray diffraction, Transmission Electron Microscopy and 57Fe Mössbauer Spectrometry. Though, their electric conductivity and dielectric relaxation were studied on nanostructured pellets resulting from the compaction of nanoparticles, by complex impedance spectroscopy in the frequency range 1–106 Hz from 25 up to 250 °C. The dielectric properties are investigated in detail. The presence of two thermally activated relaxation peaks in the modulus loss spectra confirms the contribution of grains and grain boundaries to the electrical behavior of the material. The main dielectric relaxation comportment and the conduction process are governed by the grain boundaries. Ac-conductivity, which deviates from the usual Universal Dielectric Response, can be described by a double power-law evidenced by a Nearly Constant Loss trend followed by a Super-Linear Power Law that decreases with increasing temperature. The change in the cationic distribution in CoFe2O4, deduced from the 57Fe Mössbauer spectra, may explain the observed trend in conductivity. The classical dielectric relaxation behavior is observed and very low values of permittivity are estimated. This compound can therefore be classified as an ultra-low-k dielectric.

Structural and electrical properties of pure and doped lanthanum oxide

In this communication, structural and electrical properties of rare earth oxides La2O3 (LO) and LaNdO3 (LNO) have been studied. To understand the structural properties of the LO and LNO samples, X-ray diffraction (XRD) measurement was carried out at room temperature. The XRD patterns have been analyzed by Rietveld refinement to confirm the single-phase nature of both the samples. The crystal structures of studied samples were created from the derived parameters of Rietveld parameters. The crystal size and lattice strain have been estimated using Williamson–Hall (W–H) plot analysis. Frequency-dependent dielectric constant and loss tangent have been studied for a frequency range of 20 Hz to 2 MHz. To estimate the relaxation time and contribution of the charge carriers in the studied samples, relaxation mechanism and universal dielectric response (UDR) model have been employed. The ac conductivity measurements were carried out for the same frequency range (i.e., 20 Hz to 2 MHz) which has been understood on the basis of Jonscher’s power law. The barrier height has been calculated by fitting the power law. Frequency-dependent impedance behavior has been discussed in the context of grains and grain boundaries for both the samples under study.

High thermal stability of the YNbO4 − CaYTiNbO7 composites for radio frequency and microwave applications

The present work shows present the dielectric properties of YNO – CYNTO ceramic composites at Radio Frequency (RF) and Microwave (MW) regions. X-ray diffraction showed that the addition of CaTiO3 (CTO) on YNbO4 (YNO) caused the formation of the CaYTiNbO7 (CYNTO) phase. In the RF analysis, a typical universal dielectric response in the frequency of the temperature-dependent conductivity was found; the frequency-dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated. Regarding the values of the temperature coefficient of capacitance (TCC) was observed a change of signal with the increment of CTO. Besides, the activation energies of composites were calculated and demonstrated an increase with addition of the CTO. In the MW range, it was observed that permittivity and dielectric loss enhance with the addition of CTO. Moreover, the addition caused the improvement of the thermal-stability of YNO where τf value for YCT5% was equal to +0.64 ppm.°C−1. The composites were analyzed as antennas presenting a reflection coefficient below - 10 dB at the resonant frequency, realized gain of 5.10–5.45 dBi, bandwidth of 129–355 MHz and radiation efficiency above 95%. The results obtained indicate that YNO – CYNTO system would be interesting candidates in microwave operating devices.