Dielectric Loss Values Research Articles

Impact of Process Parameters and Dopant Concentration on Structural, Magnetic, and Dielectric Properties of Dysprosium-doped Nickel-Zinc Ferrites Synthesized by Microwave Hydrothermal Method

This study aims to investigate the impact of substituting Dy3+ ions on the structural, magnetic and dielectric properties of Nickel Zinc (Ni-Zn) ferrites, which have the chemical formula Ni0.5Zn0.5DyxFe2-xO4 (where x = 0, 0.01, 0.03, 0.05, 0.07, and 0.09). These ferrites were synthesized using a microwave hydrothermal technique with different process parameters. Structural characterization of the synthesized powders was carried out using X-ray diffraction (XRD) and Fourier transformation infrared spectroscopy (FTIR). The XRD analysis confirmed the presence of a pure spinel phase for Dy concentrations (x) up to 0.05. However, when x ≥ 0.07, an additional orthoferrite phase (DyFeO3) was observed along with the spinel phase. FTIR spectra revealed a shift in low-frequency wave numbers due to Dy3+ ion substitution. The size and morphology of the synthesized powder particles were examined using field emission scanning electron microscopy (FESEM). The powder compacts were sintered using microwave processing at 900 °C for 40 min. The increase in dc. resistivity is observed with an increase in Dy3+ concentration, mainly due to the change in the hopping mechanism with the substitution concentration. Dielectric properties such as dielectric constant and loss are measured in the frequency range of 100 Hz to 1.8 GHz. The high value of dielectric constant and loss observed in the low-frequency region compared to the high-frequency region. Maxwell’s Wagner model and ‘Koop’s theory explains the variation in dielectric properties with the frequency. The magnetic hysteresis loops were measured at different temperatures and observed to enhance the low-temperature magnetic properties compared to room temperature. The results suggest that the magnetic and dielectric properties of the investigated samples can be adjusted by varying the concentration of Dy3+ ions, providing the ability to tailor these properties according to specific application requirements.

Investigation of Structural and Dielectric Properties of Sr doped LaCrO3Synthesized by Auto-Combustion Method

We synthesized the undoped lanthanum chromium oxide, LaCrO3 (LCO), and Strontium (Sr) doped La1-xSrxCrO3 (x=0.1) perovskite compounds using auto-combution method. X-ray Diffraction technique reveals that both the samples possess Cubic crystal structure with Pm-3m space group. Furthermore, room temperature dielectrical properties of both the samples were emphasized. Dielectric constant and loss value of both the samples decreases as frequency increases attributed to Maxwell-Wagner type of relaxation.

Impact of Sm2O3 doping on PZT-PMI-PZS ternary ceramics: Phase structure, microstructure, and dielectric characteristics

This study aims to comprehensively evaluate the impact of Sm2O3 doping on PZT ceramics, specifically focusing on the phase structure, microstructure, and dielectric characteristics of Pb1-xSmx[(Zr0.52Ti0.48)0.9(Mo1/3In2/3)0.05(Zn1/3Sb2/3)0.05]O3 samples namely PSZT-PSMI-PSZS ceramics. Sm2O3 was doped at site A within the range of 0.00 ≤ x ≤ 0.08 using the solid-state reaction method and sintering at 1150 °C. The examination of the results revealed that the samples exhibited a perovskite structure, along with a secondary phase, with increasing intensity of the said phase as Sm content increased. XRD, Rietveld refinement, and Raman spectroscopy analysis indicate a decrease in the rhombohedral phase ratio (R) and an increase in the tetrahedral phase ratio (T) with higher Sm content. Microscopic examination using SEM demonstrates variations in microstructure, with the highest density and grain size observed at a small increment of Sm content (x ≤ 0.02). Optimal electrical properties were achieved at x = 0.00, including a high dielectric constant (εr = 8578), Curie temperature (Tc) of 303 °C, and dielectric loss (tanδ) value of 0.34. Conductivity studies indicate a negative temperature coefficient of resistance (NTCR) for all samples. Additionally, the relationship between electrical characteristics and Sm2O3 doping is discussed. This research provides valuable insights into the structural, microstructural, and electrical properties of PZT ceramics affected by Sm2O3 doping.

The effect of silica addition on dielectric properties of barium titanate nanoparticles

The effect of silicon dioxide (SiO2) nanoparticles on the dielectric constant was studied. Different weight percentages of silica (3, 5, and 7 %) were added to BaTiO3 nanoparticles. The structure, morphology, and dielectric properties were obtained using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and an LCR meter. The diffraction patterns were shown that the crystallite size of BaTiO3 increased with the addition of SiO2. The dielectric constant and the dielectric loss were measured with various temperatures ranging from 27 to 180 °C at a constant frequency of 10 kHz. It was found that the value of the dielectric constant for the pure BaTiO3 is the highest at the Curie temperature (128 °C). The Curie temperature shifted to a higher value and the dielectric constant was decreased when the silica was added to BaTiO3. Moreover, with increasing the silica percentage, the variation in the dielectric loss values with the temperature was observed.

Investigation and characterization of dielectric, thermal, and chemical properties of recycledhigh‐density polyethyleneblended with virginpolyethylene

AbstractDielectric performance of post‐consumer recycled HDPE blended with virgin HDPE was investigated to evaluate the possibility of using these materials for the insulation of electrical wires and cables. The presence of organic and inorganic impurities was investigated using thermal and chemical methods (TGA, DSC, and EDX). The characterization of impurities revealed different amount of inorganic impurities in recycled material that was depending on the execution of melt filtration by the recycler to prepare the recycled material. Higher values of both dielectric losses and dielectric constant were observed for post‐consumer recycled PE, with the dielectric loss of recycled material almost 17 times higher than the one of virgin PE at power frequency (60 Hz). The short‐term breakdown strength of post‐consumer recycled HDPE was observed to be slightly lower than that of virgin PE. The experimental result showed that blending the recycled stream with virgin materials was effective in order to enhance dielectric properties of recycled material. In this regards, dielectric losses decreased by almost 50% when 50% of virgin HDPE was added to the recycled material. In addition, breakdown strength was improved when virgin HDPE was added.

Improving the optical, photoluminescence, and electrical properties of PEO/NaAlg-WO3 nanocomposites for optoelectronic and nanodielectric applications

Nanocomposites based on polyethylene oxide (PEO)/Sodium Alginate (NaAlg) with varying content of tungsten trioxide nanoparticles (WO3 NPs) have been synthesized by using a green solvent casting method. Through the use of X-ray diffraction (XRD), Fourier transforms infrared (FTIR), and Ultraviolet–visible spectroscopy (UV–Vis.), the interaction of mixed components has been evaluated. Studies using spectroscopy have shown that WO3 nanoparticles and the blend's component parts interact strongly at their interfaces. XRD confirms the increasing amorphous propensity of the PEO/NaAlg film with increasing nanofiller loading. FTIR implies the development of molecular complex of the polymer with the nanofiller. From UV–Vis analysis, Tauc's relation was used to specify the direct and indirect bandgap energy. The Eg (direct) of pure PEO/NaAlg was considerably decreased from 4.23 to 3.04 eV by adding 2.0 wt% of WO3 NPs. The fluorescence for various WO3 NPs concentrations in PEO/NaAlg blend films was analyzed. The PEO/NaAlg blend's fluorescence intensity decreased with increased doped with WO3 NPs. The films made of nanocomposites also had their dielectric behavior and electrical conductivity examined. In contrast to the electrical conductivity (AC), the dielectric constant and dielectric loss of PEO/NaAlg-WO3 nanocomposites drop as the frequency of the electric field rises. The investigation revealed that an increase in WO3 concentration led to a corresponding rise in the nanocomposites' dielectric loss and dielectric constant values. The fabricated system of PEO/NaAlg-WO3 NPs nanocomposites films showing improved in AC conductivity and dielectric characteristics and could be suggested in optoelectronic and nanodielectric devices.

Valorization of agricultural waste to polybenzoxazine-carbon composites: Studies on microstructure, thermal and dielectric properties

Agricultural waste valorization has become a necessity to reduce global warming. In this context, absolute bio-waste derived cardanol, furfurylamine (ffa), and benzaldehyde were utilized for the synthesis of a novel card-bisphenol (BBC) and its benzoxazine (BBC-ffa) resin. Further, the reinforcement of carbon building blocks derived from three different sustainable resources, viz. Anacardium occidentale, Borassus flabellifer, and Tamarindus indica and named cashew apple carbon (CC), palmyra palm inflorescence (spadix) carbon (PC), and tamarind seed carbon (TC), respectively. The derived carbons were reinforced (1–20 wt%) separately with BBC-ffa polymer matrix [poly(BBC-ffa)] for the engineering of carbon integrated polybenzoxazine composites [poly(BBC-ffa)–CC/PC/TC] to achieve high-k dielectrics. Because the carbon with different functionalities intrinsically exhibit higher polarization and lower specific surface area. Dielectric constant (k) of the polybenzoxazine matrix (k = 4.62) has been increased to 8.58, 9.43, 10.60 for the reinforcement of 20 wt% of each CC, PC, and TC polybenzoxazine composites, respectively and the value of dielectric loss was also significantly decreased for the same. The dissemination of reinforced carbon particles in the polybenzoxazine matrix was ascertained through the surface analysis of the composites by FE-SEM. Based on the results of TGA, the carbon reinforced composites showed slightly lower thermal stability and about two-fold higher char yield than that of neat polybenzoxazine. Hydrophobicity of the composites enhanced with increasing the carbon content. The resulting sustainable polybenzoxazine-carbon composites could be effectively utilized as a gate dielectric in microelectronics.

Study of synthesis and characterization of triple ions modified bismuth ferrite for electronic devices: (Bi1/2Li1/2)(Fe1/3Mn1/3W1/3)O3

A high-temperature solid-state reaction technique was used to create a lead-free complex perovskite compound of a chemical composition (Bi1/2Li1/2)(Fe1/3Mn1/3W1/3)O3 (BLFMWO) The X-ray diffraction structural study reveals the monoclinic structure of the compound with cell parameters; a= 12.219Å, b= 6.119 Å, c= 9.513Å with β=109.37°. The detailed examination of the room-temperature scanning electron micrograph reveals a distinct microstructure with large and small grains. Extensive studies of the frequency and temperature dependence of capacitive (dielectric) and resistive (impedance and conductivity) behaviors over a wide temperature (25°-500°C) and frequency (1 kHz-1 MHz) range have revealed the dielectric dispersion, relaxation, and non-Debye type of conduction mechanism of the material. The ac conductivity study provides details regarding the conduction mechanism and semiconducting characteristics of the compound. The band gap energy of 3.62 eV emerges from the UV-visible spectrum, indicating that optoelectronic devices might utilize the material. FTIR spectra in the 500 cm-1- 4000 cm-1 range were used to investigate the bonding nature of the produced BLFMWO material. The specific capacitance of BLFMWO is 69.7524 F/g, having significant rate capabilities with pseudo-capacitive performance for super-capacitor applications. A low value of dielectric loss in high-frequency regions is applicable for application in microwave devices.

Structural, magnetic and ferroelectric properties of magnetoelectrically coupled xBa0.95Sr0.05TiO3-(1–x)BiFe0.90Sm0.10O3 ceramics

ABSTRACT The standard solid state reaction method was followed to synthesize the polycrystalline xBa0.95Sr0.05TiO3-(1–x)BiFe0.9Sm0.1O3 [xBST-(1–x)BFSmO, x = 0–0.35] ceramics. The XRD pattern revealed a structural transition of the prepared ceramics from rhombohedral to cubic symmetry. The mean grain size was estimated in the micrometer range, with values ranging from 0.40 to 1.95 μm. The maximum real part of the complex initial permeability of 28.26 was noticed for x = 0.30 multiferroic ceramics. The highest remanent magnetization determined for the x = 0.30 sample was 3.4 10−2 emu/g. For the sample with x = 0.35 the maximum recorded dielectric constant was found to be 677 at 103 Hz. A small value of dielectric loss (<5%) was observed. The compound exhibited significant remanent polarization and a reduction in the leakage current. In addition, the investigated materials comprise large magnetoelectric coefficients and the optimum magnetoelectric coefficient of 0.662 mV.cm−1.Oe−1was obtained for the x = 0.30 composition.

Fabrication and characterizations of nanocomposite flexible films of ZnO and polyvinyl chloride/poly(N-vinyl carbazole) polymers for dielectric capacitors

Polymer-based energy storage has recently attracted the attention of researchers. Herein, via the sol–gel method, we prepared zinc oxide nanoparticles (ZnO NPs), as nanofiller up to 5 wt% filling levels, and a host polymeric blend matrix of polyvinyl chloride (PVC) and poly (N-vinyl carbazole) (PVK) were taken to synthesize nanocomposite films via the solution casting. The ratio of PVC: PVK was 90:10 wt%. The X-ray diffraction (XRD) results indicated that the prepared nanocomposite films’ crystallinity decreased as ZnO NPs content increased; it decreased from 54.23 to 22.14 %. The scanning electron microscope (SEM) micrographs revealed good miscibility of the prepared PVC/PVK blend and the homogeneous distribution of ZnO NPs within the host blend matrix. The thermal stability of the prepared nanocomposites was studied through the TGA technique, and the thermal activation energy was calculated using the Coats-Redfern method. In the optical results, the optical absorption spectra revealed that the energy gap for the allowed direct transition reduced under adding ZnO NPs; it reduced from 3.61 eV for the pure PVC/PVK blend to 2.96 eV for the nanocomposite film with ZnO nanofiller content of 5 wt%. AC conductivity experiments revealed that the electrical/dielectric properties of the nanocomposite films get enhanced by increasing the ZnO NPs content. Following the incorporation of the ZnO NPs, the AC electrical conductivity (σac), dc electrical conductivity (σdc), dielectric constant (ε′), and dielectric loss (ε″) values of PVC/PVK/ZnO nanocomposite films get improved; the σdc values increased from 6.46 × 10−16 S/cm for the blend PVC/PVK matrix to 3.63 × 10−13 S/cm for nanocomposites with ZnO NPs content of 5 wt%. Additionally, both ε′ and ε″ values increased while increasing the ZnO NPs content. These findings could suggest that the prepared PVC/PVK/ZnO nanocomposite films could be a promise for the applications of dielectric energy storage polymer-based capacitors.

Raveling out the effect of Pr3+ ions substitution on different properties of nano-sized hexagonal ferrites

The development of a new stable phase/type, a rare earth element Pr3+ substitution in Ca2-xPrxFe8O14 (T-type) of hexagonal ferrites with composition (x = 0.0, 0.02, 0.06, 0.1), using the sol–gel auto-combustion method was endeavoured in the current study. The x-ray diffraction analysis proved that all samples possess single-phase structures. All computed structural characteristics varied with Pr3+ substitution. The particles with random shapes and sizes were examined from TEM analysis and particle sizes ranged from 14 to 44 nm. With Pr-contents, the saturation and remanent magnetization increased and the coercivity decreased. All samples have high values of dielectric loss, dielectric constant, and tangent loss at low-frequency values and these high values declined with rising frequency. The peaks in real part of the electric modulus migrated toward the low-frequency region; it was the confirmation that grain boundaries are incredibly active to participate in resistance. The uneven trend in the imaginary part of the electric modulus, which is demised with increasing frequency and peaks, was described by the Sillars model. The band gap (Eg) of the samples reduced linearly from 4.60 to 4.32 eV with the addition of Pr3+ ions, as observed from the UV–visible absorbance spectra. The polarization vs electric field (P-E) loops of synthesized samples displayed lossy behavior and this loosy behavior decreased with Pr-additives. On the basis of properties exhibited by the present synthesized T-type hexagonal ferrites, it can be hoped that these materials are applicable in high-frequency devices, antenna, radar applications, and opto-magneto applications.

Structural, optical, microstructure, and giant dielectric behavior of parent, Cu and Sr doped La0.55Li0.35TiO3‐δ

AbstractOptimization of energy storage performance in dielectric ceramics has been a focus in recent decades due to the benefits of high energy storage density, efficiency, and exceptional temperature stability. In this work, we report huge dielectric constant in La0.55Li0.35TiO3‐δand sharp decrease in its value with the substitution of Sr and Cu at Ti position. These samples La0.55Li0.35TiO3‐δ(LLTO), La0.55Li0.35Ti0.9Cu0.1O3‐δ(LLTCO) and La0.55Li0.35Sr0.1Ti0.9O3‐δ(LLSTO) were prepared by solid state reaction method. The interfacial polarization of lithium ion aggregation close to the grain boundaries and the dipoles of Li ions in the sample are suggested to be the source of the enormous dielectric values. Parent composition (LLTO) shows highest dielectric constant value (6.29 × 105at frequency 10 Hz, 7.30×104at 1 kHz) recorded at room temperature while the lowest dielectric loss value (0.124) was observed for LLSTO at frequency 1 kHz. Structural characterization has been done using X‐ray diffraction (XRD) technique to investigate the crystal structure of the prepared compositions. The XRD patterns show the similar crystal structure for all the compositions with the parent composition LLTO. The optical band gap is calculated by Kulbeka Munk function and Tauc plot using UV–visible diffuse reflectance spectroscopy technique. The maximum band gap value (3.32 eV) is obtained for parent composition while doping of Cu and Sr at Ti site in La0.55Li0.35TiO3‐δdecreases the band gap value. Optical microscopy shows the micron size grains in these samples. Doping of Sr and Cu in perovskite structure of LLTO brings tunability in dielectric and optical properties.

The Effect of Transition Metals Co-Doped ZnO Nanotubes Based-Diluted Magnetic Semiconductor for Spintronic Applications

The Impact of Co and Gd on the structural, magnetic and dielectric properties of ZnO nanotubes synthesized by co-precipitation is reported. The results demonstrate that incorporating Co and Gd into ZnO diminished crystallinity while retaining the optimum orientation. The outcomes of transmission electron microscopy and scanning electron microscopy examined that the Co and Gd dopants had no effect on the morphology of the produced nanotubes. It was also discovered that as the frequency and concentration of Gd co-dopant decreased, the dielectric constant and loss values increased. When doping was present, the dielectric constant and ac electrical conductivity response was found to be inversely related. Ultimately, at 300K, Co and Gd co-doped ZnO nanotubes exhibited ferromagnetic properties. When Gd doping was increased to 3%, the ferromagnetic response increased. Since then, increasing the Gd co-doping, the ferromagnetic response decreased. For the same sample (Zn0.96−xCo0.04Gd0.03O nanotubes), the electrical conductivity exhibited also superior to pure and low Gd doped ZnO. Its high ferromagnetism is usually caused by magnetic impurities replaced on the ZnO side. Therefore, considering the behaviour of these nanotubes, it can be sued spin-based electronics.

Effects of Gamma Radiation Doses on the AC Electrical Properties of Epoxy Reinforced with Nano-Silica Composites

This study reports the effects of gamma radiation on the AC electrical properties of epoxy nano-silica composite sheets with an average thickness of 3 mm. Epoxy reinforced with different nano-silica concentrations of 0, 5, 10, and 15 wt.%. The epoxy nano-silica composites were exposed to different gamma radiation dosages of 1, 3, and 5 kGy. The data were analyzed before and after gamma irradiation and the results showed that the AC electrical properties of the gamma-irradiated epoxy nano-silica composites varied from those of the non-irradiated samples. We found that there were significant changes in the impedance, dielectric constant, dielectric loss, and AC electrical conductivity values of the epoxy nano-silica composites after irradiation, and the AC electrical conductivity and dielectric constant values of the nano-silica composites were enhanced by exposing the samples to gamma radiation because more free electrons were released inside the epoxy nano-silica composites. The AC electrical properties, such as impedance, dielectric constant, dielectric loss, and electrical conductivity, of the epoxy nano-silica composites were studied and discussed before and after gamma radiation with different dosages. We found that these AC electrical properties marginally increased with increasing doses of gamma irradiation.

Study of the structural, electrical, dielectric properties and transport mechanisms of Cu0.5Fe2.5O4 ferrite nanoparticles for energy storage, photocatalytic and microelectronic applications

Cu0.5Fe2.5O4 nanoparticles were synthesized by the self-combustion method whose XRD and FTIR analyzes confirm the formation of the desired spinel phase. The thermal evolution of conduction shows a semiconductor behaviour explained by a polaronic transport mechanism governed by the Non-overlapping Small Polaron Tunnelling (NSPT) model. DC conductivity and hopping frequency are positively correlated. The scaling of the conductivity leads to a single universal curve where the scaling parameter α has positive values, which testifies to the presence of Coulomb interactions between the mobile particles. Conduction and relaxation processes are positively correlated by similar activation energies. Nyquist diagrams are characterized by semicircular arcs perfectly modeled by an equivalent electrical circuit (R//C//CPE) indicating the contribution of the grains. The dielectric behaviour shows a strong predominance of conduction by the phenomenological theory of Maxwell-Wagner. The low values of electrical conductivity and dielectric loss and the high value of permittivity, make our compound a promising candidate for energy storage, photocatalytic and microelectronic applications.

Tuning of structural, electrical and transport behaviour of cobalt nanoferrite by dysprosium ions substitution

Present study explores the structural, electrical and transport properties of dysprosium cation (Dy3+) substitution on (Fe+3) site in cobalt nonoferrites [CoFe2-xDyxO4 (Dy(x) = 0.00, 0.05, 0.10 & 0.15)] prepared by sol-gel chemical route. X-ray diffraction pattern confirms the pure cubic spinel structure for all samples. The average crystallite size was found in the range of 49 to 72 nm with no linear variation with incresing doping concentration of (Dy3+) ions. The values of lattice parametres is found to be changed from 8.34 to 8.39 Å for pristine cobalt nanoferrite (CoFe2O4) and sample having highest doping concentration i.e. Dy(x) = 0.15 respectively. The porosity observed to be decrease linearly with increasing (Dy3+) ion concentration. The electrical properties have been investigated by analyzing dielectric behaviour in the frequency range of 75 kHz- 5 MHz and temperature range of 100K– 400K. The frequency dependent dielectric behaviour at different temperatures is explained in terms of Maxwell–Wagner and Koop’s phenomenological models. Ferrite with Dy(x) = 0.15 have achieved highest dielectric constant in the range of 441 to 5234 which was measured at 100K (5 MHz) and 400K (75 kHz) respectively. The electrical resistivity of each of the ferrite sample reduces with rising temperature representing the semiconductor behaviour of all ferrites which is due to the thermally triggered charge carriers hopping between (Fe2+) and (Fe3+) ions and associated with higher drift mobility. The increase in drift mobility at room temperature with increasing (Dy3+) ion concentration is considered to be a sign of improved transport behaviour. The high value of dielectric constant and low dielectric loss of all these ferrites make them suitable for the memory storage devices.

Effect of Cr3+ substitution on the magnetic and dielectric properties of cobalt ferrites

Co(Fe1-xCrx)2O4 (x = 0.02, 0.10, 0.15, 0.30, 0.50) samples are synthesized by the sol-gel method. The XRD patterns and subsequent Rietveld refinement provided structural analysis and confirmation of the samples' single-phase formation. XPS measurement reveals the existence of the elements Co, Cr and Fe in 2+ and 3+ oxidation states. The saturation magnetization (Ms), coercivity (Hc) and magnetocrystalline anisotropy (K1) are observed to decline to as low as 10 emu/g, 35 Oe and 0.50 (106 erg/cm3) following Cr substitution, which indicated that the samples transform to a soft magnetic material. Cr substitution also lowers the ferrimagnetic (FiM) to paramagnetic (PM) transition temperature, Tc, from 752 K for x = 0.02 to 307 K for x = 0.50. With Cr replacement, the dielectric constant and dielectric loss values decrease, indicating it to be a potential contender for high frequency applications. The dielectric constant for x = 0.30 and x = 0.50 samples rises sharply around 1 MHz owing to the LC resonance effect between the samples and the measurement leads. The ac conductivity plots are found to be in conformity with Jonscher's single power law, and the conduction process is revealed to be attributable to the small polaron hopping mechanism.

Tuning the dielectric properties of CaCu3Ti4O12 ceramic by Cu2O addition and microstructural modifications

Cuprous (I) oxide (Cu2O) was used instead of Cupric (II) oxide (CuO) for the synthesis of CCTO ceramic by solid-state reaction. The impact of sintering time on the structure stability, grain size, and dielectric performance of Cu2O-based CCTO ceramics was discussed. XRD analysis indicates that the CaCu3Ti4O12 cubic phase was successfully synthetized. The studied samples manifested high permittivity and quite low dielectric loss values in the frequency range (20–106 Hz); with optimum values of 15,423 and 0.083 respectively achieved after sintering at 1050 °C for 14 h while for longer sintering times of 19 h and 24 h resulted in higher values of permittivity of 19,943 and 21,392 respectively were obtained and associated with an improved loss tangent of ∼0.114 and 0.127, respectively. It was found that a longer sintering time of Cu2O-based CCTO ceramics resulted in an important improvement of the dielectric properties.

Phase formation and electrical properties study of PVDF thick films synthesized by solution casting method

Abstract In this study, polyvinylidene fluoride (PVDF) thick films with thickness ∼180 µm were synthesized by solution casting. X-ray diffraction study established the co-existence of both α and β-phases. Raman spectroscopy of the synthesized PVDF thick films corroborated the existence of α and β-phases in 0.71:1 ratio. Surface micrographs of PVDF thick films showed dense microstructure with grain size ∼10 µm. Additionally, the room temperature values of dielectric constant and dielectric loss at 100 kHz were measured to be ∼20 and 0.33, respectively. Furthermore, ferroelectric behavior of PVDF thick films was confirmed by the polarization versus electric field (P–E) hysteresis loop study. A leakage current density of 1.55 × 10−5 A cm−2 at an applied electric field of 500 kV cm−1 was obtained in PVDF thick films.

Optical investigation of the effect of laser radiation on lignosulfonate–polyvinyl alcohol/nickel oxide nanocomposite membrane

In the present work, we used the solgel and ex situ casting techniques to synthesize a nanocomposite membrane (NCM) composed of lignosulfonate (LGS), polyvinyl alcohol (PVA), and nickel oxide (NiO) nanoparticles. Samples from the synthesized NCM were exposed to different laser fluences in the range 2–22 J/cm2. UV–vis spectroscopy and the CIE methodology were used to study the resultant effect of laser on the optical and color characteristics of the NCM. The increase of fluence up to 22 J/cm2 causes a drop in the optical bandgap (Eg) values from 5.88 to 5.56 eV when n = 1/2, associated with a rise in the refractive index. We attribute these changes to cross-linking that destroys the ordered regions and thus increases the amorphous phase. This cross-linking can lead to a more compacted structure of the LGS–PVA/NiO NCM. Additionally, the values of optical dielectric loss were calculated and plotted versus energy. The values of Eg attained from ɛ″ versus energy are nearby to those values attained by means of Tauc's relation when n = 1/2, indicating that the LGS–PVA/NiO NCM exhibited direct allowed transition. Furthermore, the CIE method was used to evaluate the color differences between the exposed NCMs and the pristine ones. We found that the value of color intensity is more than 5, suggesting permanent color changes.