Dielectric Loss Values Research Articles

Effect of AgI doping on electrical conductivity and dielectric relaxation in silver phosphate glass nanocomposite systems

A series of ternary silver iodide (AgI)-doped glassy samples of xAgI–(1-x)(0.35P2O5–0.65Ag2O) composition with x = 0.1, 0.2, 0.3 and 0.4 have been processed by well-accepted melt quench technique. The composition-dependent thermal properties of the glassy systems have been analyzed by differential scanning calorimetric (DSC) results. Both density and thermal stability of the nanocomposites increases with the inclusion of AgI content (x). The diminishing nature of ac and dc activation energy enhances ac and dc conductivity with rising AgI content (x). The falling response of the inter-nuclear spacing of Ag+ ion (RAg) is responsible for the enhancement of ionic conductivity. The dielectric constant (ε/) and dielectric loss (ε//) values expand with increasing temperature and reduce with rising frequency. The scaled spectra of complex electric modulus (M/ and M//) indicate that conductivity or dielectric relaxation mechanism is not Debye type, as β < 1 and temperature independent, whereas composition dependent.

Structural, dielectric and EMI shielding properties of polyvinyl alcohol/chitosan blend nanocomposites integrated with graphite oxide and nickel oxide nanofillers

Polyvinyl alcohol (PVA) and Chitosan (CS)-based novel composites were prepared using solution casting technique by introducing graphite oxide (GO) and nickel oxide (NiO) as nanofillers. The structural, thermal and mechanical properties of PVA/CS/GO/NiO nanocomposites were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The dielectric and electromagnetic interference (EMI) shielding properties of synthesized nanocomposites were also investigated. The addition of dual nanofillers in the PVA/CS blend resulted in improved thermal stability of nanocomposites through the interaction of nanofillers with OH groups of polymer matrices. The DMA results displayed higher storage and loss modulus at low temperature for nanocomposite with 1.5/15 wt% of GO/NiO loading. The maximum values of dielectric constant and dielectric loss obtained are 1315.5 and 11.1 at the low-frequency region, respectively. The absorption dominated EMI shielding effectiveness (SE) was observed with a maximum EMI SE value of 12 dB for nanocomposite film containing 3.0/30 wt% of GO/NiO as compared to EMI SE value of 0.3 dB for PVA/CS blend in Ku-band (12–18 GHz) region. The electrical network formation by GO and NiO in the polymer matrix resulted in an improved EMI SE which further emphasizes the potential use of these nanocomposite films as an effective EMI shielding material.

Dielectric studies of polycrystalline bismuth titanate Bi12TiO20 ceramic synthesized via economical chemical route

Bismuth titanate nanostructure, Bi12TiO20, (BTO) belonging to sillenite family was synthesized by chemical route at the sintering temperature 800 °C for a period of 6 h. The crystalline phase of the materials was investigated by the X-ray diffraction method. The morphology and particle size of the BTO sample were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis, respectively. The SEM images displayed the bimodal structure, and average grain size was found to be in the range of 0.6–3.7 µm. TEM observation confirmed the nanocrystalline nature of the particle having size of 50 ± 20 nm. The value of dielectric constant and dielectric loss for Bi12TiO20 ceramic was found to be 8.29 × 103 and 3.27, respectively, at the temperature 468 K and frequency 100 Hz.

Fabrication of highly resistive La–Zn co-substituted spinel strontium nanoferrites for high frequency devices applications

The spinel La–Zn co-doped strontium nanoferrites having general formula of Sr1-xLaxFe2-yZnyO4 (0.0≤x ≤ 0.1, 0.0≤y ≤ 1.0) have been synthesized. X-ray diffraction studies have been revealed successful fabrication of ferrites. Scanning electron microscopy results have shown that size of the particle of the ferrite samples lie in nano-range. DC electrical resistivity at room temperature increases with La3+ and Zn2+ ions concentration while dielectric parameters and AC conductivity decreases with concentration of these ions. Frequency dependent behavior of dielectric parameters has shown that values of these dielectric parameters decrease with frequency initially at lower values of frequency and then become almost constant at higher values of frequency. Electrochemical impedance spectroscopy data shows that the charge transfer phenomenon is mainly controlled by grain boundaries. Further, enhanced DC resistivity ranging from 1.08 × 109 to 1.67 × 109 Ω cm and low dielectric loss values of the La–Zn co-doped strontium nanoferrites suggest their applications in high frequency devices.

Highly Transparent and Colorless Polyimide Film with Low Dielectric Constant by Introducing Meta-substituted Structure and Trifluoromethyl Groups

An effective design strategy for preparing highly transparent polyimide film with low dielectric constant is presented. The key to the strategy is to simultaneously introduce meta-substituted structure and trifluoromethyl in polymer chains. By using this design strategy, a highly transparent polyimide film with low-k was synthesized from 3,5-diaminobenzotrifluoride (m-TFPDA) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) through a two-step method. The obtained m-TFPDA/6FDA (CPI) film (∼30 µm) possesses high optical transparency (λcutoff=334 nm, T450nm=85.26%, Haze=0.31) and is close to colorless (L*=96.03, a*=−0.34, b*=2.12, yellow index=3.96). The intrinsic k and dielectric loss value of the film are 2.27 and 0.0013 at 10 kHz, respectively. More importantly, such low dielectric performance could remain stable up to 280 °C, and the film shows a low moisture rate (∼0.51%), which helps to maintain the low-k property stability in different humid environments. Meanwhile, the film also shows good thermal stability and mechanical properties, with a glass transition temperature (Tg) of 296 °C and the 5 wt% decomposition temperature (Td,5%) of 522 °C under N2. The tensile strength and tensile modulus of the film are 85.1 MPa and 1.96 GPa, respectively. In addition, the film is soluble in common solvents, which allows simple solution processing and low-cost, continuous roll-to-roll processes. This design strategy is beneficial to improving the transparency, lightening yellow color, lowering the dielectric constant and meanwhile maintaining the comprehensive properties of polyimide films, which is mainly due to the introduced meta-substituted and trifluoromethyl structures effectively inhibiting the transfer of charge transfer complex (CTC) effects and increasing the free volume of film. This design strategy could also be extended to other high-performance polymer systems.

Electro-mechanical characterization of alumina-based porcelain insulator doped with BaTiO3 at high temperature with frequency variation

In this article, the doping effect of BaTiO3 (0–2 wt%) on the physical, electro-mechanical and dielectric strength of prepared porcelain insulator were investigated. Green powder samples were sintered at 1350 °C with 2 h soaking time, applying uniaxial pressure techniques with a constant load of 160 MPa. The surface, morphological, elemental and phase analysis characterization was done by using scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD) to recognize the microstructure-surface property relationship of the insulator. Various characterization like physical, electro-mechanical and alternating current (AC) dielectric strength of prepared sintered porcelain composition at 1350 °C were investigated. AC dielectric behavior, conductivity, and resistivity were measured at frequencies ranging from 20 Hz to 1 MHz. AC Dielectric constant and loss value from 2 GHz to 20 GHz with frequency and temperature variation were measured. The highest recorded value of AC dielectric strength for a sample having BT (2 wt%) is 25.75 ± 0.5 kV/mm. The investigated composition having 0.5 wt% showed excellent electro-mechanical and high voltage dielectric strength as compared to the conventional porcelain insulators.

Tertiary Ni0.7-xZn0.3MxFe2O4 (M=Mn, Co, and Cu) spinel ferrites: Electrical and dielectric properties

Three systems of polycrystalline Ni0.7-xZn0.3MxFe2O4 ferrite (M = Mn2+, Co2+, and Cu2+; x = 0.0, 0.1, 0.3, 0.5, and 0.7) have been prepared using the citrate method. The dc conductivity (σdc), ac conductivity (σac), dielectric constant (ε’), and dielectric loss (ε”) of Ni–Zn ferrite doped with Mn/Co/Cu ions have been thoroughly inspected. Variations in dc and ac conductivity for each ferrite series have been evaluated with temperature elevation from 293 up to 848 K and altered frequencies from 102 to 106 Hz. The conductivity for dc and ac displayed both metallic and semiconductor-like behavior with temperature. The magnitudes of activation energies (Eσ) are estimated and discussed for the three investigated systems from Arrhenius plots. Small polaron hopping between Fe3+ and Fe2+ ions is accountable for the conduction mechanism in existing systems. Moreover, the behavior of dielectric parameters with increasing Mn/Co/Cu concentrations has been evolved independently. The enhanced values of conductivity, dielectric constant, and small dielectric loss are attained in copper doped Ni–Zn ferrite compositions particularly at high concentrations. This is a very promising feature for high-frequency and power applications of ferrites.

Dielectric and magnetic response of iron oxide nanoparticles embedded in unsaturated polyester resin

A series of nanocomposites are synthesized by dispersion method with different weight percentages (0–1.5%) of iron oxide nanoparticles in unsaturated polyester resins. X-ray diffraction (XRD) patterns confirmed the amorphous nature of all the samples. A random dispersion of nanofillers in the polymer matrix is revealed by scanning electron microscope (SEM) images. Higher value of dielectric constant (78) and tangent loss (0.45) is observed at 100 Hz for 1.5% nanoparticles. The relationship between conduction mechanism and contents of nanoparticles reveals that conductivity of nanocomposites enhanced by increasing the nanoparticles’ percentage showing values between 1 × 10−4 to 2.5 × 10−3 S/cm. Vibrating sample magnetometer (VSM) results showed that synthesized nanocomposites exhibit a ferromagnetic behavior. Moreover, VSM analysis displays that magnetic parameters such as saturation magnetization, coercivity and retentivity of the nanocomposites increase by increasing the nanoparticles concentration.

The Effect of MWCNTs Filler on the Absorbing Properties of OPEFB/PLA Composites Using Microstrip Line at Microwave Frequency.

Oil palm empty fruit bunch (OPEFB) fiber/polylactic acid (PLA)-based composites filled with 6–22 wt.% multi-walled carbon nanotubes (MWCNTs) were prepared using a melt blend method. The composites were analyzed using X-ray diffraction (XRD), Fourier transforms infrared (FTIR), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) of the MWCNTs. The composites were characterized for complex permittivity using the coaxial probe at 8–12 GHz range and the transmission/reflection coefficients were measured through micro strip line. The dielectric permittivity measurements carried out at X-band frequency revealed that 22 wt.% MWCNTs nanocomposite display higher dielectric constant () and dielectric loss () values of 4.23 and 0.65, respectively. A maximum absorption loss of 15.2 dB was obtained for the 22 wt.% nanocomposites at 11.75 GHz. This result suggests that PLA/OPEFB/MWCNTs composites are a promising cheap and lightweight material for the effective microwave absorption in the X-band frequency range.

Micro-emulsion synthesis of La1 − xCrxFeO3 nanoparticles: effect of Cr doping on ferroelectric, dielectric and photocatalytic properties

AbstractIn the present study, La1 − xCrxFeO3(x = 0.0, 0.3, 0.6, 0.9, 1.0) was synthesized by micro-emulsion route and characterized by X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning electron microscope (SEM), Energy-dispersive X-ray (EDX) techniques. The dielectric, ferroelectric and photocatalytic properties were investigated and compared with un-doped material. The XRD analysis revealed orthorhombic geometry of La1 − xCrxFeO3(x = 0.0, 0.3, 0.6, 0.9, 1.0), Cr was doped successfully into the lattice structure of LaFeO3and particles were spherical and in agglomerated form. The grain sizes were recorded to be 15, 16.9, 17.1, 17.65 and 18.3 (nm) for La1 − xCrxFeO3(x = 0.0, 0.3, 0.6, 0.9, 1.0), respectively. EDX analysis confirmed the purity of LaCrFeO3samples. The lattice parameters, bulk density, X-ray density, crystalline size and porosity were determined were also determined of all the La1 − xCrxFeO3samples. The dielectric constant and dielectric loss values decreased at higher frequency and Cr concentration affected the dielectric properties. The photocatalytic activity (PCA) was evaluated by degrading Congo Red (CR) dye under solar light irradiation and up to 85.43% dye degradation was achieved within 45 min of irradiation. Phyto-toxicity analysis before and after dye degradation was performed, which revealed the toxicity reduction in response of dye degradation. Results revealed that lanthanum ferrite (perovskite) doping with Cr could possibly be employed to enhance the ferroelectric, dielectric and photocatalytic properties.

Thermal and dielectric properties of epoxy-based composites filled with flake and whisker type hexagonal boron nitride materials

In this work, the epoxy-based composites filled with 3-Aminopropyltriethoxysilane (KH-550) modified binary filler of hexagonal boron nitride (h-BN) flakes and h-BN whiskers were fabricated, and the thermal and dielectric properties of composites were systematically investigated. Adding h-BN whiskers to the filler could effectively form heat conduction paths and improve the phonon transmission efficiency, thereby improving the thermal conductivity of the composites. According to our results, the thermal conductivity of composite with 27 wt% h-BN flakes and 3 wt% h-BN whiskers reached up to 0.819 W·m−1·K−1, which was 3.9 times that of pure epoxy resin. At the same time, the dielectric loss value and dielectric constant of this composite at 1 MHz were 0.02678 and 4.55, respectively, while pure epoxy resin were 0.03602 and 4.33. In addition, introducing h-BN whiskers into the matrix could effectively improve the thermal stability and heat dissipation performance of composites.

Structural and electrical properties of Ba-substituted spinel ferrites

Spinel ferrites with configuration Co1-xBaxFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were created by sol-gel technique. X-ray diffraction pattern showed that the entire specimen possessed singular phase. The standards of lattice constant increased, while densities as well as porosity decreased with the increment of barium ions. The room temperature resistivity and activation energy increased with the addition of barium ions. The temperature dependent resistivity presented the decreasing trend with the increase of barium ions which proves its semiconducting nature. The magnetization decreased while coerecivity was increased with the substitution of barium ions, as applied field changed from −2 KOe to +2 KOe. Dielectric properties were also measured from 3 MHz to 1 G Hz. Due to high value of dc resistivity and low dielectric loss, these samples might be suitable for high-frequency devices.

Lattice vibrational characteristics and structures-properties relationships of non-stoichiometric Nd[Mg0.5Sn0.5(1+x)]O3 ceramics

Non-stoichiometric Nd[Mg0.5Sn0.5(1+x)]O3 (− 0.04 ≤ x ≤ + 0.04)—type samples were prepared using a traditional two-step solid-state sintering process. Their crystal structures, phase compositions, dielectric properties and lattice vibrational characteristics were identified in detail. The double perovskite Nd(Mg0.5Sn0.5)O3 with a monoclinic structure was distinguished as the main crystalline phase, and pure phase was obtained when x < 0. The sample [Nd(Mg0.5Sn0.49)O3] at x = − 0.02 shows the excellent dielectric properties: er = 18.74, Q × f = 47,979 GHz. The lattice vibrational characteristics were clarified with Raman and infrared active mode spectroscopy. The intrinsic properties were fitted by four-parameter semi-quantum model, which show that the low-frequency infrared modes yield a more significant contribution to permittivity and dielectric loss. Raman shifts of modes F2g(A) and F2g(B) correlate with dielectric constants negatively, which implies that the bond length has a positive correlation with permittivity. Full widths at half maximum of vibrational modes A1g(O) correlate with dielectric loss values positively and correlate with the degree of order (S) negatively.

An impact of La doping content on key physical properties of PbS spherical nanoparticles facilely synthesized via low temperature chemical route

Herein, we are reporting a facile chemical process to attain high-grade PbS spherical nanoparticles with diverse La doping contents at low temperature and named it as La@PbS SNPs. All the prepared La@PbS SNPs samples are of single-cubic phase with good crystalline nature confirmed from XRD and Rietveld refinement. Along with lattice constants several other structure-related parameters like size, dislocations, strain, stacking fault, density and specific surface area were calculated. EDX and SEM-e-mapping analyses confirm the presence of La in PbS with homogeneous distribution throughout the samples. For morphological investigation FESEM was employed, which approved the synthesis of SNPs of low dimensions at all La contents. FT-Raman analysis shows characteristics vibrational modes related to cubic-PbS and that is in good accordance with XRD outcomes. Energy gap values were determined through Kubelka–Munk procedure and noticed to lie between 1.01 to 1.103 eV ( $$ \Delta E = 0.093 \;{\text{eV}}) $$ , this shows a very minute shift in energy gap with La doping in PbS. Dielectric constant ( $$ \varepsilon ' $$ ), loss tangent, dielectric loss and impedance values were assessed and stable values of $$ \varepsilon ' $$ were noticed in 20–50 range and 5.0 wt % La@PbS SNPs possesses highest value. The ac electrical conductivity analysis revealed enhancement with La content in PbS. The correlated barrier hoping mechanism was involved in the prepared La@PbS SNPs. Furthermore, the DC electrical properties were studied and discussed the impact of La content.

Effect of Gd3+ Doping on Linear and Nonlinear Optical Properties of PbI2/FTO Thin Films for Optoelectronic and Nonlinear Applications

Herein, we have developed the thin Gd@PbI2 films on FTO via a facile spin coating route and subjected to various studies. The formation of (001) oriented hexagonal phase Gd:PbI2/FTO films was confirmed by X-ray diffraction & FT-Raman spectroscopy analyses. The size was determined through Scherrer formula in 11–16 nm range. The doping of Gd and its homogeneity was tested and approved by EDX and SEM e-mapping studies. The Gd doping impact on surface morphology was inspected via SEM images and found very low dimension grains formation throughout the films area. Tauc’s formula was employed to obtain energy gap and found in 2.46–2.74 eV for all Gd@PbI2 films. Absorption and refractive indices were estimated in 0.034–1.2 and 1.4–11 between 395 and 2400 nm wavelength regions. Respective dielectric constant and loss values were noted between 3.5 and 112, and 0.13 and 1.4, signify high dielectric constant and low loss values. The optical conductivity was calculated of 1016 order for all Gd@PbI2 films. SELF and VELF related values were also determined. The values of nonlinear optics related parameters were also calculated and revealed that the grown films are potential candidates for opto-nonlinear devices.

Investigations into the microwave shielding behavior of oriented Polycaprolactone/Carbonyl iron particles composites fabricated using magnetic field assisted extrusion 3D printing

In the present study, development of a novel oriented polymeric composite comprising of Polycaprolactone (PCL) polymer and carbonyl iron filler particles (CIP) is presented. Incorporation of permanent magnets into solvent based extrusion 3 D printing set up produced the oriented polymeric composites. The microwave absorption properties of the oriented composite were investigated and compared with non-oriented composite and pristine PCL by utilizing vector network analyzer (VNA) and Nicolson-Ross-Weir (NRW) methodology. Higher values of permeability, permittivity, dielectric loss and magnetic loss of the oriented composite indicated the micro capacitor behaviour and domain wall motion of the parallel aligned CIP chains in the PCL matrix. The reflection and transmission loss values for the oriented composite were found to be -34 dB and -26 dB respectively. The microwave absorption of the oriented PCL/CIP composite was found to be approximately 93% suggesting the efficacy of the 3 D printed oriented composite as an excellent microwave absorber.

Synthesis of La1-xCox Fe1-yCryO3 nano crystallites for enhanced ferroelectric, magnetic and photocatalytic properties

Cobalt (Co) and chromium (Cr) doped lanthanum ortho-ferrite with a composition of La1-xCox Fe1-yCryO3 (x, y = 0.0, 0.15, 0.30, 0.45, 0.60, 0.75) were fabricated by micro-emulsion route. The effect of Co2+ and Cr3+ cation substitution on the structural and dielectric properties was explored by XRD, FTIR, AFM, magnetic analysis, dielectric and ferroelectric measurements, which showed orthorhombic geometry. Various parameters like lattice constant (a, b, c), bulk density (ρm), X-ray density (ρx), porosity (P) and crystalline size were determined. By increasing dopant contents, the saturation magnetization was also increased and exhibited ferromagnetic property and LaFeO3 exhibits anti-ferromagnetism. The maximum value of magnetic saturation (0.841 emu) and Mr (0.420 emu) was found for highly substituted La0.40Co0.60Fe0.40Cr0.60O3 form. Through polarization electric (P-E) loops, the ferroelectric nature of fabricated nanoparticles was confirmed. It was observed that the values of dielectric constant (ɛ́ ), dielectric loss (ɛ ̋ ) and loss tangent (tanᵟ) were decreased with increasing the frequency. In addition, the conductivity is continuously increased with increasing frequency as well as dopant concentration. Furthermore, photocatalytic efficiency was evaluated by degrading methyl orange (MO) dye under UV irradiation and it was found that most substituted nanomaterial La0.40 Co0.60Fe0.40Cr0.60O3 exhibited maximum degradation of 91.01% of MO dye. Results revealed that the lanthanum ortho-ferrite properties can be tuned by doping with Cr and Co for practical applications in different filed since the ferroelectric, magnetic and photocatalytic properties were changed as a function of dopant concentration.

Exploration of structural, optical, dielectric properties and curve fittings of Yb3+-substituted β-type hexagonal ferrites

The rare-earth element Yb3+-substituted β-ferrites KFe11−xYbxO17 with composition (x = 0, 0.02, 0.06 and 0.1) have been synthesized by sol–gel auto combustion method and sintered at 950 °C. X-ray diffraction (XRD) analysis divulged the formation of single phase β-hexagonal ferrites structure for the whole series. The crystallite size varied in the range of 26–43 nm for all samples. FTIR spectra showed absorption bands at different wave numbers which also confirmed the single phase of the samples. The samples had high dielectric constant, dielectric loss, and tangent loss values at lower frequencies while these values declined with increase in frequency. This dielectric behavior of the samples had been explained on the basis of Maxwell–Wagner and Koop’s model. The dielectric constant results were fitted theoretically by using Debye function which indicated the involvement of more than one ion in dielectric relaxation process. The AC conductivity increased with the increase of frequency and the nonlinear fitting of AC conductivity was obtained through Jonscher’s power law that followed conduction model exactly. The semicircle of cole–cole plots adumbrated the contribution of both grains and grain boundaries to the resistive and capacitive behavior of the material.

Estimation of sea water salinity from dielectric measurements: Effect of temperature

Dielectric measurements have been carried out for distilled water and saline water solutions of salinities 10000, 20000, 30000, 40000 ppm, as well as sea water of Diu beach area, using Anritsu Shockline Vector Network Analyzer (VNA, model no: MS46322A) in the frequency range from 1 GHz to 20 GHz, over the temperatures of 20°, 30° and 40 °C. From the measured values of dielectric constant and dielectric loss, the values of tanδ, conductivity and emissivity of water solutions have been calculated. The variation in dielectric properties of water with salinity and temperature of measurement is compared with values calculated using Stogryn equations as well as Klein and Swift model and results are found to be in good agreement with corresponding values. From the dielectric loss values and the emissivity values of distilled water and saline water solutions at certain fixed frequencies, the salinity of sea water collected from Diu beach has been estimated to be 36,327 ppm which agrees very well with the physicochemical analysis report of laboratory.

Enhanced dielectric and thermal performance by fabricating coalesced network of alumina trihydrate/boron nitride in silicone rubber for electrical insulation

Silicone rubber filled with micron-alumina trihydrate (ATH) is a substantially used composite material for high voltage outdoor insulators. This article investigates the effect of nano-boron nitride (BN) addition on the dielectric, thermal stability and thermal conductivity of solely micron-ATH-filled silicone rubber by fabricating coalesced network of particles. Micron-ATH/nano-BN-filled hybrid silicone rubber composites are fabricated with a ratio of 30/0 wt% (ATH30), 29/1 wt% (ATBN1), 27/3 wt% (ATBN3), 25/5 wt% (ATBN5) and 23/7 wt% (ATBN7) using mechanical mixing and water bath sonication techniques. Results suggest that the hybrid batch of silicone rubber composites (ATBN) possess lower permittivity, dielectric loss, enhanced thermal stability and thermal conductivity relative to ATH30. ATBN1 offers low permittivity and dielectric loss values of 3.64 and 0.0086 at 1000 Hz relative to 3.87 and 0.0224 of ATH30, respectively. As far as thermal properties are concerned, ATBN5 emerges as the most promising candidate for electrical insulation with 31 and 200°C higher temperatures for 10 and 15% mass loss, whilst it has shown 20% higher thermal conductivity than ATH30.