Frequency Dependence Of Dielectric Loss Research Articles

Study of electrical conduction behaviour of Y6-xBa4(SiO4)6O2 oxyapatite doped with ytterbium ions

This paper reports the electrical conduction behaviour of Yttrium Barium Silicate Oxyapatite Y6-xBa4Ybx(SiO4)6O2, synthesized by solution combustion method where x varies from 0.01 mol% to 0.05 mol%.. The scanning electron microscopy was done for morphological analysis which shows the spheroidal shaped grains with average grain size of 35μm. The dielectric behaviour of the material was studied in the frequency range of 100Hz – 100KHz and temperature varying from 50°C - 400°C. The frequency dependent dielectric constant and dielectric loss has been plotted for different temperatures. Decrease in dielectric constant and dielectric loss with increase in frequency has been observed for YBaSiO:Yb compounds.

Nickel Doping Effects on the Structural and Dielectric Properties of Ba(Zn1/3Nb2/3)O3 Perovskite Ceramics

The effects of nickel doping into Ba(Zn1/3Nb2/3)O3 (acronym: BZN) ceramics is structurally, morphologically and electrically investigated. The nickel substitution in sites of Zn which was carried out by the solid state reaction technique strongly enhanced the structural, morphological and electrical performances of the BZN. Specifically, while the lattice constant and crystallite sizes increased, the microstrain and the defect density decreased. The relative density of the BZN ceramics increased from 95.40% to 98.24% upon doping of Ni with content of x = 0.05. In addition, the Ni doping increased the values of electrical conductivity without significant changes in the dielectric constant values. It is also observed that the doping the BZN ceramics highly altered the temperature dependent variation of the relative dielectric constant. In the temperature range of 293–473 K, the x = 0.05 Ni doped BZN samples were less sensitive to temperature. The dynamics of the temperature dependent dielectric response is dominated by the coupled defects excitation mechanisms. Both of the temperatures and frequency dependent dielectric constant, dielectric loss and electrical conductivity suggests that the Ni doped Ba(Zn1/3Nb2/3)O3 ceramics is more appropriate for electronic device fabrication than the pure ones.

Structural and electrical properties of sol–gel grown nanostructured ZnO and LaMnO3 particle-based nanocomposites

In this communication, structural and electrical properties have been discussed for chemically grown ZnO–LaMnO3 (ZnO–LMO) nanocomposites. Nanocomposites were prepared by mixing the different weights, i.e., ratios of ZnO to LMO, 100:0, 95:5, 90:10, 85:15, and 0:100 wt% of ZnO:LMO in their composite form. X-ray diffraction (XRD) measurement shows that all the pure and composite samples possess single-phase nature without any detectable impurity. Particle size and shape were identified using transmission electron microscopy (TEM) measurement. Frequency-dependent dielectric constant (e′), loss tangent (tanδ), real and imaginary parts of the electric modulus (M′ and M′′), and a.c. conductivity have been carried out at room temperature for all the samples. Dielectric behavior has been understood in the context of universal dielectric relaxation (UDR) model and relaxation mechanism fits well throughout the frequency range studied. Variation in a.c. conductivity has been discussed on the basis of Jonscher’s universal power law.

Preparation, microstructure, dielectric and electrical analysis of Fe-modified PZT piezoceramics

PZT-based piezoceramics have been widely explored for electronic device applications. In this study, iron (Fe)-modified PZT abbreviated as Pb1-3x/2 Fex(Zr0.53Ti0.47)O3 ceramics (PFZT) for x ≤ 0.05 were prepared by a semi-wet method. The effects of Fe doping on the crystal structure, surface morphology, dielectric and electrical behavior of PFZT ceramics were investigated systematically. Room temperature XRD patterns show a perovskite structure with a minor pyrochlore phase. FE-SEM demonstrates uniform and dense microstructures. Temperature and frequency-dependent dielectric constant and dielectric loss establish its importance for the purpose of device applications. During the experimentation, it has been shown that PFZT ceramics with x ≤ 0.05 are frequency-dependent in nature, whereas PFZT ceramics for x = 0.04 exhibits improved dielectric properties (er~6045 at Tc~325 °C). The impedance spectroscopy studies show that electrical properties are highly influenced by the grain and grain boundaries.

In-situ photochemical synthesis and dielectric properties of nanocomposite thin films containing Au, Ag and MnO nanoparticles

Thioxanthone-Anthracene (TX-A) was used as a one-component Type II photoinitiator for the photopolymerization of PEGMEA/PEGDA monomer mixture consisting of AgNO3, HAuCI4 and MnCI2 metallic salts. In this study, we have seen that nanoparticles (NPs) are distributed differently in solution and in polymer matrices and that the particle size also changes. The size of the AuNPs (8–16 nm) synthesized in the solution in the presence of air atmosphere is smaller than the AuNPs (18–25 nm) synthesized in the polymer matrix. It is also important to state the effect of the atmosphere on the shape and size of the NPs. Thanks to the endoperoxide formation in air atmosphere, the formation of AgNPs in the range of 45–53 nm is possible in solution, while the size of AgNPs increased up to 1900 nm in nitrogen atmosphere. Additionally, radical spin densities were calculated with Density Functional Theory to understand which radical is mainly responsible for the reduction of metal ions to form metal and metal oxide nanoparticles. Peroxy radicals were found to be mainly responsible due to their much higher electron spin density compared to the other radicals. Moreover, the dielectric properties of in-situ formed AuNPs, AgNPs and MnONPs in the nanocomposite films were investigated at room temperature. For all nanocomposite films containing metal NPs, the frequency dependent dielectric constant and dielectric loss are higher than the polymeric films up to about 50 times.

Efficient magnetoelectric dispersion in Ni and Co co-doped BiFeO3 multiferroics

Pure and Ni/Co co-doped BiFeO3 samples were prepared through sol‒gel auto-combustion technique. The synthesized samples were calcined at 500 °C for 1 h before further characterizations. The rhombohedrally distorted cubic perovskite structure was confirmed for all samples through X-ray diffraction analysis. The surface morphology of each sample was visualized using scanning electron microscopy which elaborated the formation of spherical grains along with some agglomerations. Energy dispersive X-ray spectra revealed the presence of Bi, Fe, O, Ni and Co atoms in the same atomic and weight percentages as expected from their empirical formulae. The frequency dependent dielectric constant, tangent loss and impedance characteristics were investigated using impedance analyzer. It was also noticed that the ac conductivity increased when Ni and Co were substituted at equal amounts. The magneto-electric analysis witnessed the coupling between different ferroic orders in these samples.

Vanadium Doped ZnS Nanoparticles: Effect of Vanadium Concentration on Structural, Optical and Electrical Properties

Vanadium (V) doped zinc sulfide (ZnS) nanoparticles have been synthesized in the doping concentration of 0.2, 0.4, 0.6, 0.8, and 1 wt% by chemical co-precipitation method, where de-ionized water was used as solvent and the precursors were Zn(CH3COO)2⋅2H2O, Na2S and V2O5. The synthesized nanoparticles have been characterized by XRD, UV–Vis spectroscopy, FTIR spectroscopy and precision impedance analyzer (PIA). XRD studies revealed that all the samples exhibit cubic structure and confirmed the incorporation of V into ZnS lattice. The calculated average crystallite size was varied in the range of 2.16–2.82 nm. The red shifting of the absorption edge was observed from the UV–Vis study and the direct optical band gap (Eg) was decreased from 3.63 to 3.35 eV with increasing the doping concentrations. The various vibrational modes were observed by the FTIR spectroscopy. The characteristic vibrational peaks were found near at 666, 615 and 478 cm−1. The PIA study showed that frequency dependent dielectric constant, loss tangent and ac resistivity were high at the lower frequency, while the ac conductivity was low at higher frequency. The bandgap tuning behavior of ZnS nanoparticles with V-doping concentrations may find interesting applications in optoelectronic devices.

Investigation of electrical conduction in Ca6-xNa2Y2(SiO4)6F2:xEu3+ ceramic by complex impedance and electric modulus spectroscopy

The electrical conduction mechanism of Ca6-xNa2Y2(SiO4)6F2:xEu3+ fluorapatite ceramic with (x = 0–0.05 mol%) synthesized by solution combustion method has been investigated by dielectric, complex impedance and electric modulus spectroscopy. Microstructural analysis was carried out by scanning electron microscopy (SEM) which shows that the spheroidal and ellipsoidal grains were distributed uniformly in the prepared ceramic with average grain size of the order of 3 μm. The electrical and dielectric studies of the ceramic were done in the frequency range of 100 Hz–100 KHz and temperature range of 50 °C–500 °C. The temperature and frequency dependent dielectric loss and dielectric constant decreases with an increase in frequency due to the ceasing effect of polarization. Dielectric relaxation behaviour of the prepared ceramics were studied using Complex impedance spectroscopy (CIS). Nyquist plots show that with increase in Eu3+ ion concentration the resistance of grains and grain boundaries decreases for the prepared ceramics. The investigation of charge transport phenomena was done by electric modulus spectroscopy. The drastic increase in a. c conductivity with increase in temperature shows that the ceramic follow the Jonscher’s power law and appear Debye in nature.

Enhanced piezoelectricity properties of reduced graphene oxide (RGO) loaded polyvinylidene fluoride (PVDF) nanocomposite films for nanogenerator application

Flexible and lightweight films of Polyvinylidene fluoride (PVDF) loaded with nanosheets of reduced graphene oxide (RGO) have been prepared via solution casting method. The structure of RGO nanosheets have been examined through X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Raman spectroscopy technique. FTIR studies revealed that the enhancement of β-phase from 53 to 70% has been observed by adding RGO nanosheets in PVDF matrix. The frequency dependent dielectric constant and dielectric loss have been studied. Ultraviolet–visible spectra show a decrease in optical band gap with increases RGO concentration in nanocomposite films. The ferroelectric behavior of RGO loaded PVDF nanocomposite films showed remarkable improvement in remnant polarization values as compared to bare PVDF. The piezo-response of RGO loaded nanocomposite films showed significant enhancement in output voltage from 0.886 to 1.915 V. On exposure to ultraviolet–visible light, RGO loaded nanocomposite PVDF films showed about 13.8% enhancement in piezo- voltage with action of same pressure.

Proton dynamics in superprotonic Rb3H(SeO4)2 crystal by broadband dielectric spectroscopy

Broadband dielectric and AC conductivity spectra (1 Hz to 1 THz) of the superprotonic single crystal Rb3H(SeO4)2 (RHSe) along the c axis were studied in a wide temperature range 10 K < T < 475 K that covers the ferroelastic (T < 453 K) and superprotonic (T > 453 K) phases. A contribution of the interfacial electrode polarization layers was separated from the bulk electrical properties and the bulk DC conductivity was evaluated above room temperature. The phase transition to the superprotonic phase was shown to be connected with the steep but almost continuous increase in bulk DC conductivity, and with giant permittivity effects due to the enhanced bulk proton hopping and interfacial electrode polarization layers. The AC conductivity scaling analysis confirms validity of the first universality above room temperature. At low temperatures, although the conductivity was low, the frequency dependence of dielectric loss indicates no clear evidence of the nearly constant loss effect, so-called second universality. The bulk (intrinsic) dielectric properties, AC and DC conductivity of the RHSe crystal at frequencies up to 1 GHz are shown to be caused by the thermally activated proton hopping. The increase of the AC conductivity above 100 GHz could be assigned to the low-frequency wing of proton vibrational modes.

Evolution of dielectric relaxation under elevated electric field of polypropylene-based films

Extensive research has been performed on polypropylene (PP) based films focusing on the improvement of energy storage performance for power capacitor application. The increase of energy storage density was often accompanied with the rising of dielectric losses, especially under high electric field. The gap of electric field between the laboratorial level (0.006 ∼ 0.02 kV mm−1) and practical working condition of capacitor (more than 50 kV mm−1) could be thousands of times, which was often neglected in most research. In the present paper, the systematical study of the dielectric relaxation processes on elevated electric field was carried out on neat PP and three typical kinds of PP-based films, i.e. PP/ZrO2 nanocomposite, PP/maleic anhydride grafted polypropylene (PP-g-MAH) blends, and PP/PP-g-MAH/ZrO2 ternary nanocomposite with the energy storage density 17.3% higher than neat PP. The frequency dependence of dielectric losses under elevated field showed that even under 20 kV mm−1, the loss of ternary PP increased little, while the losses of the binary sample increased much more. The space charge test as well as the DC conductivity test revealed the origin of increased dielectric loss, which was the consequence of extrinsic ion hopping stimulated by the elevated field. Meanwhile, in the ternary PP/PP-g-MAH/ZrO2 nanocomposite, the activation energy of ion hopping was greatly improved due to the enhanced interaction between molecules, so the dielectric loss under high field, the space charge accumulation and the DC conductivity of the ternary sample all showed an extremely low level. This study has directive significance for the application of nanocompositse.

Yttrium-doped strontium hexaferrite particles for microwave absorption application in X-band

Yttrium-doped strontium hexaferrites particles, Sr1−xYxFe12O19 (x = 0.1, 0.2 and 0.3), are developed using auto combustion method. The doping resulted in partial replacement of Fe3+ ions with Fe2+ ions which is found to be an effective method to tune microwave absorption properties of strontium hexaferrite. The XRD spectrum confirmed the formation of ferrite with no secondary phase present. All the developed samples showed platelet-like morphology with an average particle size of 590 nm for the undoped sample. The average particle size decreased with the increase in the Y doping. The hysteresis loop revealed that the saturation magnetization increased with increase in doping concentration of yttrium in strontium hexaferrite. On the contrary, coercivity decreased from 296 to 209 G due to decrease in the magnetic anisotropy of the ferrite. The frequency-dependent dielectric and magnetic loss tangent are increased with the increase of Y doping. The sample with x = 0.3 showed the best impedance matching with the free space with an average normalized impedance of 1.28. The attenuation constant was also found to be maximum i.e., 85.6 for x = 0.3. The reflection loss is investigated for a frequency range from 8.2 GHz to 12.4 GHz (X-band) and indicated maximum reflection loss of -18.91 dB with -10 dB bandwidth of 2.18 GHz for x = 0.3 for coating thickness of 2.6 mm. The current study presents the Yttrium-doped strontium hexaferrites, Sr0.7Y0.3Fe12O19, as a strong candidate for the microwave absorption application.

Radiation response of zirconium silicate P-MOS capacitor

The chemical bonding of zirconium silicate films were examined by FTIR. The capacitance-voltage (C-V) measurements before and after irradiation were performed at high frequency. Furthermore, significant changes were observed depending on the radiation dose of the oxide traps and the intensity of the interface state. The sensitivity of this MOS capacitor is 4.3, 31.3 and 15.6 times less sensitive compared to the same thickness as Sm2O3, Al2O3 and Gd2O3. Therefore, it can be used as radiation-resistant material in nuclear reactors and space applications due to its stable electrical characteristics compared to other defined dielectrics. Interface states, (Nit) Barrier potential (Φb) and oxide traps (Not) have also been investigated depending on the radiation effects. Φb is one of these important electrical properties. Φb values decreased with increasing in radiation dose. Besides, radiation and frequency dependent dielectric constant (ε′), dielectric loss (ε″) and dielectric loss tangent (tanδ) and conductivity (σac) of zirconium silicate were investigated. It is concluded that high-k zirconium Silicate is suitable for electronics applications in radiation harsh environment.

Structural, electrical transport and magnetic properties of Nd3+ substituted Mn–Cu nanoferrites

Abstract In present study, a series of spinel ferrite nanoparticles (NPs) with general formula Mn1-xCuxNd0.15Fe1.85O4 (x = 0.0, 0.1, 0.3 and 0.5) have been prepared by sol-gel route. The powder X-ray diffraction (XRD) and Raman spectroscopy revealed the formation of single phase of cubic spinel structure in doped samples. However, a formation of NdFeO3 secondary ortho-ferrite phase has been observed for higher content of x = 0.5. The average crystallite size calculated from Scherrer’s formula has been found in the range 6.5–16.5 nm. The lattice constant (a) estimated using XRD data has been found to increase from 8.4265 A to 8.4501 A on incorporation of Cu2+ ions. FTIR spectra of prepared NPs exhibit two prominent absorption peaks near 600 cm−1 and 400 cm−1 associated to 596 cm−1 and 496 cm−1 band. The dc resistivity measurements with a rise in temperature divulge the typical semiconducting behavior of the as-synthesized samples. The activation energies of the samples have been calculated from Arrhenius plot and found to be in between 0.29 eV and 0.59 eV. Furthermore, the frequency dependent dielectric permittivity, loss tangent and ac conductivity revealed the usual dielectric dispersion. The behavior of dielectric properties highlighted the Debye relaxation peak which is interpreted in the view of Koop’s theory in the light of the Maxwell-Wagner model. Real ( Z ’ ) and imaginary ( Z ’ ’ ) part of impedance confirm the relaxation mechanism associated to the grains and grain boundaries effect. Electron paramagnetic resonance (EPR) pattern shows a broad sharp resonance signal with Lange g-factor varies from 2.04 to 2.18, which is due to dominant spin-exchange interaction between Fe3+, Mn2+, and Cu2+ ions. P-E hysteresis loops found the ferroelectric nature of the ferrite samples. Typical soft ferrimagnetic behavior of Nd3+ substituted Mn–Cu ferrites have been observed at room temperature. The low losses, giant dielectric constant and high resistivity of prepared ferrite NPs can offer several applications like power transformers and microwave devices.

Electrical, dielectric and photocatalytic applications of iron-based nanocomposites

A series of iron-based nanocomposites such as Cu–Fe (CFNCs), Ni–Fe (NFNCs), Ag–Fe (SFNCs) and Al–Fe (AFNCs) were fabricated via sol–gel route. An extensive investigation about crystallinity, microstructure, electrical and optical properties was carried out by utilizing X-ray diffractometer (XRD), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) and scanning electron microscopy (SEM). The frequency-dependent AC conductivity, dielectric constant and dielectric loss were measured in the frequency range of 25 kHz–2 MHz at room temperature via an LCR meter. The highest conductivity ~ 2.85 × 10−7S/m was revealed by AFNCs as compared to other nanocomposites. The Maxwell–Wagner model for induced polarization and Koop’s phenomenological theory of dielectrics were followed by all the fabricated nanocomposites in the temperature range of 30–600 °C. The maximum dielectric constant ~ 930 was measured for AFNCs at a temperature of 200 °C. Furthermore, the synthesized nanocomposites effectively degraded a toxic organic dye Rhodamine B (RhB) and the degradation (%) ~ 77, 85, 86, and 87 within the time of 50, 40, 50 and 70 min was recorded for CFNCs, NFNCs, SFNCs and AFNCs, respectively.

Impedance Characteristics and Chip-Parasitics Extraction of High-Performance VCSELs

In order to analyze the physical limitations and develop highly performing vertical-cavity surface-emitting lasers (VCSELs), it is essential to have an in-depth understanding of their intrinsic laser dynamics. However, the high-speed performance of such devices is impaired by its extrinsic dynamic response associated with the VCSEL chip parasitics. A first-order low-pass filter transfer function is traditionally used to de-embed this parasitic part from the total VCSEL modulation response. However, this oversimplification results in large discrepancies between the modeled and the measured parasitic-network response, leading to a high level of uncertainty in the extracted circuit component values. Further, intrinsic parameters can only be gained to a frequency range, where the parasitic response is flat and de-embedding not critical. In this work, a novel advanced parasitic-network model that well describes the extrinsic behavior of high-performance VCSELs is reported. In this model, besides the standard parasitic elements, the contact-pads with their capacitance with frequency-dependent dielectric losses and their inductance are considered. Moreover, for this advanced parasitic-network model to reveal its full potential, a rigorous fitting methodology is also described in this work. This proposed novel model, along with the strict fitting procedure, accurately replicate the delicate $S_{{11}}$ data even at high-frequencies and enable the extraction of highly reliable circuit component values. This model can not only describe and model the parastitic chip response accurately but can be implemented to optimize the chip design, hence improving the parasitic bandwidth limitations in high-speed VCSELs.

Dielectric and optical properties of Ni-doped LaFeO3 nanoparticles

Un-doped and Ni-doped lanthanum ferrite nanoparticles were synthesized by solid-state method. Ni concentration-dependent structural, dielectric and optical properties of synthesized nanoparticles were investigated. X-ray diffraction patterns confirmed predominant single-phase orthorhombic crystal structure with space group Pbnm in all samples. Average crystallite size was found to vary from 19 to 21 nm with Ni concentration. The field emission scanning electron microscopy revealed nanocrystalline structure with homogenous distribution of particles. UV–Vis–NIR diffuse spectra captured at room temperature indicate that La1−xNixFeO3 is an indirect band gap material. The band gap varies from 1.70 to 1.85 eV with changing Ni concentration. Frequency-dependent dielectric constant, dielectric loss and ac conductivity were studied at room temperature. The dielectric constant was found to increase with increasing Ni content at high frequency. The loss factor resulted from domain wall resonance exhibited an identical dispersion behavior of dielectric constant. At high frequencies, the dielectric losses of orthoferrites were found to be low. This is attributed to the restricted motion of domain wall pointing its plausible practical applications in magnetically tunable filters and oscillators.

Ion Transport Study in CS: POZ Based Polymer Membrane Electrolytes Using Trukhan Model.

In this work, analysis of ion transport parameters of polymer blend electrolytes incorporated with magnesium trifluoromethanesulfonate (Mg(CF3SO3)2) was carried out by employing the Trukhan model. A solution cast technique was used to obtain the polymer blend electrolytes composed of chitosan (CS) and poly (2-ethyl-2-oxazoline) (POZ). From X-ray diffraction (XRD) patterns, improvement in amorphous phase for the blend samples has been observed in comparison to the pure state of CS. From impedance plot, bulk resistance (Rb) was found to decrease with increasing temperature. Based on direct current (DC) conductivity (σdc) patterns, considerations on the ion transport models of Arrhenius and Vogel–Tammann–Fulcher (VTF) were given. Analysis of the dielectric properties was carried out at different temperatures and the obtained results were linked to the ion transport mechanism. It is demonstrated in the real part of electrical modulus that chitosan-salt systems are extremely capacitive. The asymmetric peak of the imaginary part (Mi) of electric modulus indicated that there is non-Debye type of relaxation for ions. From frequency dependence of dielectric loss (ε″) and the imaginary part (Mi) of electric modulus, suitable coupling among polymer segmental and ionic motions was identified. Two techniques were used to analyze the viscoelastic relaxation dynamic of ions. The Trukhan model was used to determine the diffusion coefficient (D) by using the frequency related to peak frequencies and loss tangent maximum heights (tanδmax). The Einstein–Nernst equation was applied to determine the carrier number density (n) and mobility. The ion transport parameters, such as D, n and mobility (μ), at room temperature, were found to be 4 × 10−5 cm2/s, 3.4 × 1015 cm−3, and 1.2 × 10−4 cm2/Vs, respectively. Finally, it was shown that an increase in temperature can also cause these parameters to increase.

Ba3Co2Fe24O41/polyimide composites with magnetic and dielectric properties

Ba3Co2Fe24O41(Co2Z)/polyimide(PI) composites were synthesized via in-situ polymerization process, using the micron-sized Co2Z particles prepared by the solid-state reaction. X-ray diffractometer (XRD) pattern shows the existence and purity of the aimed phase. Scanning electron microscope (SEM) images show that the Co2Z particles are uniformly dispersed in the composites. The testing results of dielectric properties of composites reveal that the dielectric constants of the composites increase with the Co2Z content increasing. The frequency-dependent dielectric loss shows that the dielectric loss of samples has the same trend, and that a peak can be observed at about 10 MHz. The saturation magnetization (Ms) of composites depends on the ferrite content, and the Ms. value can reach 8.9 emu/g when the ferrite content is 40 wt% in Co2Z/PI composites. Additionally, the coercivity (Hc) of composites show almost no change as the ferrite content increasing, about 100 Oe. The results indicate that the obtained magnetic dielectric composites are new candidates for antenna applications.

Investigation of Structural, Electrical and Thermal Characteristics of NdFeO3 Ceramic

The synthesis of single phase polycrystalline ceramic sample of NdFeO₃ by high temperature solid state reaction technique using high purity oxides has been reported. The structural parameters were investigated by Rietveld refinement program. The prepared ceramics show orthorhombic structure with space group Pnma. The frequency and temperature dependent dielectric constant, dielectric loss and ac conductivity of the compound have been studied. The dc conductivity has also been measured and its activation energies were calculated using Arrhenius relation. The calculated heat capacity (ΔCp) and enthalpy change (ΔH) of the compound are 0.068 J/gK and 2.3664 J/g respectively.<div><br></div>