Tanδ Values Research Articles

Effect of Mn2+ substitution on the dielectric properties of NaMg(PO3)3 ceramics at microwave and terahertz frequencies

In this study, NaMg1-xMnx(PO3)3 (0.00 ≤ x ≤ 0.0625) ceramics with low dielectric constant were prepared via the solid-state reaction method. The effects of Mn2+ substitution on the microstructure and dielectric properties (at microwave and terahertz frequencies) of the NaMg(PO3)3 ceramics were studied by means of the Rietveld refinement, morphology, and ionic polarizability analysis. It is obtained that the NaMg0.0975Mn0.025(PO3)3 ceramic sintered at 880 °C for 4 h exhibited optimal dielectric properties at microwave frequencies, where εr = 4.585, Q × f = 48,313 GHz (@17.228 GHz), and τf = −40.83 ppm/°C. The Q × f and τf values were changed by 74.2 % and 27.8 %, as compared to the values of 27,728 GHz and −56.52 ppm/°C for the pure NaMg(PO3)3 ceramic, respectively. For terahertz frequencies (0.2–1.0 THz), the εr values were decreased to 3.79–3.98, and the tanδ values were between 0.0203 and 0.1152. All the experimental results indicate that this system exhibits great potentials both at microwave and terahertz frequencies.

The Effect of Solvent on the Structural, Morphological, Optical and Dielectric Properties of SnO2 Nanostructures

We investigate the effect of solvent, i.e., ethanol and deionized (DI) water, on the structural, optical, and dielectric characteristics of SnO2 nanostructures, synthesized via the hydrothermal method. Utilizing X-ray diffraction (XRD), we find the rutile phase for both nanostructures with average crystallite sizes of 12.53 nm and 6.62 nm for the samples synthesized using ethanol and DI water as solvents, respectively. The energy-dispersive X-ray spectroscopy (EDX) confirms the presence of Sn and O elements in both samples. Scanning electron microscopy (SEM) reveals that the samples prepared using ethanol and DI water exhibit nanorods and nanoflowers structures, respectively. The calculated band gap for SnO2 based on ethanol and DI water solvents is found to be 3.54 eV and 3.45 eV, respectively. The SnO2 nanostructure prepared by ethanol solvent demonstrates a higher dielectric constant which is attributed to higher defect density and more grain boundaries in it than in the sample synthesized using DI water. At low frequencies, the high tanδ values in the case of both nanostructures are explained based on space-charge polarization (SPC). The SnO2 prepared by DI water exhibits higher tangent loss than the one synthesized using ethanol because of its significant surface area. The significant amount of conducting grains in the SnO2 nanostructure while using ethanol solvent makes it a better conductive. Furthermore, the dielectric constant increases with increasing temperature which suggests considerable changes in the polarization behavior, while the tangent loss and conductivity demonstrate dependency on the temperature, indicating the promise of the nanostructures for electrical applications.

Investigation of the effects of psyllium powder addition on the quality of fresh and frozen gluten-free bread

The interest in gluten-free (GF) products has been growing since both the increase in prevalence of celiac disease and the preferences of GF diet. In this study, the contribution of psyllium powder (PP) to gluten-free (GF) bread quality, dough rheology and volatile compounds (VCs) profile was investigated throughout the frozen storage period of GF dough (-30 °C for 0, 7, 15, and 30 days). GF doughs containing 7.5% PP (PSY1) and 15% PP (PSY2) had lower tanδ value than GF control dough (p<0.05) according to the results obtained from fundamental rheological analysis. Frozen storage caused no effect on the tanδ value of PSY1 and PSY2 (p ≥ 0.05). PP addition increased the specific volume (SV) of GF breads (p<0.05). No significant effect of frozen storage on SV was shown for PSY2 while SV values of GF control bread (GFB) and PSY1 decreased (p<0.05). Lower crumb hardness was shown for PSY1 and PSY2 on day 0. Significant effect of frozen storage on crumb hardness was observed for PSY1 on day 30 while harder crumb structure was shown for GFB throughout the frozen storage (p<0.05). Psyllium addition led to a significant reduction in both L* value of crust and crumb color (p<0.05). In the VCs analysis performed by HS/GC-MS, ethanol and 1-butanol, 3-methyl from alcohol group, butanal, 3-methyl- and hexanal from aldehydes were common for GFB and GF breads containing psyllium. 1-butanol, 3-methyl-, butanal, 3-methyl- and hexanal were the VCs of PSY1 and they were also shown after frozen storage. This study suggested that quality deterioration due to frozen storage was less in gluten-free breads containing psyllium.

Voltage-frequency dependence of the complex dielectric and electric modulus and the determination of the interface-state density distribution from the capacitance-frequency measurements of Al/p-Si/Al and Al/V2O5/p-Si/Al structures

The energy distribution of the interface states (Nss) and relaxation time (τ) are calculated from the capacitance-frequency (C-f) characteristics for Al/p-type Si/Al metal-semiconductor and Al/V2O5/p-type Si/Al metal–interfacial layer–semiconductor diodes with and without anodic surface passivation. The experimental results show that the density of the interface states and the relaxation times increase almost exponentially with the bias from the top of the valence band to the center of the gap for each diode produced. At the same time, using the C-f characteristics, the dielectric properties such as the dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ), real and imaginary portions of the electric modulus (M’ and M″) and ac electrical conductivity (σac) are investigated in this study. The analysis was performed at room temperature, in the frequency range from 1 kHz to 10 MHz, and the voltage range from 0 to 0.24 V. The experimental results show that the ε′, ε″ and tanδ values decrease with increasing frequency while σac, M′ and M″ values increase. This results will show that dielectric parameters are strongly frequency dependent.

Synthesis, dielectric and ferroelectric properties in BSCT ceramics

The present work is on the investigation of dielectric and ferroelectric properties of Ba(0.70-x) SmxCa0.30TiO3; BSCT (x = 0.000, 0.005, 0.010, 0.015, 0.020 and 0.030) ceramics. The samples were prepared by the conventional solid-state reaction route method. The perovskite tetragonal structure was confirmed by X-ray diffraction analysis. The dielectric constant ‘ε’ and tangent loss ‘tanδ’ was measured over a temperature range (30 °C–150 °C) and frequency (100 Hz–100 kHz). All the samples show very small value of tanδ (<3 %) at 30 °C. The Curie temperature ‘Tc’ was found to decreases with increase the Sm-content. PE hysteresis loops were recorded at the different electric fields at 30 °C. The maximum value of electric field induced strain was observed for the sample with x = 0.015. The results show that the prepared samples are suitable for potential actuator and capacitor applications.

Improved Temperature Sensitivity of the Microwave and Radiofrequency Properties of the Ceramic Matrix Li2LaNbTiO7

This study presents experimental investigations and numerical simulations of the microwave (MW) dielectric and evaluation of the electrical properties in the radiofrequency region (RF). The ceramic matrix Li2LaNbTiO7 (LLNT) is obtained through the solid‐state reaction method. The synthesis of LLNT is confirmed using the X‐ray diffraction technique. In the complex impedance spectroscopy study, permittivity (ε′r) and loss tangent (tanδ) values are analyzed at room temperature. The study of the conductivity spectrum at different temperatures demonstrates that the conduction process is thermally activated, presenting a value of 0.65 eV for the activation energy. Numerical simulations are employed to evaluate the behavior of the LLNT matrix as dielectric resonator antennas (DRA), whereas this ceramics demonstrated a reflection coefficient of less than −10 dB at the resonant frequency, achieving a gain of 3.71 dBi, a bandwidth of 144 MHz and a radiation efficiency greater than 97%. The results indicate that the LLNT matrix would be a promising candidate for RF and MW operating devices.

Magnetic and dielectric properties of the new YFeO3/BiFeO3 nanocomposite ceramics prepared via reverse chemical co-precipitation followed by spark plasma sintering

New xYFeO3 – (1-x) BiFeO3 (0.0 ≤ x ≤ 1.0) multiferroic composites were prepared successfully via the chemical co-precipitation followed by high energy mechanical blending. For the structural analysis, assessment of phase purity, and characterization of oxidation states, XRD, FTIR and XPS methods were utilized, respectively. Furthermore, morphological investigations and elemental distribution within the composite samples were elucidated through FESEM and TEM imaging techniques. The VSM results indicated that the values of Ms and Mr increase alternately from 0.553emu/g and 0.049emu/g to 1.210emu/g and 0.166emu/g, respectively, with an increase in the YFO content from 20 % to 80 %. These values of Ms do not follow a linear combination of the base phases, and the magnetization of each composite sample is accompanied by an additional value. This additional value may arise from the residual strain and interfacial magnetic and electrical interactions between the parent phases. The measurements of dielectric properties disclosed that the behavior of the samples follows the Maxwell-Wagner polarization. Moreover, the values of ε′ at the frequency of 200 Hz increased from 149 to 303 as the BFO content rose from 20 % to 80 %. In addition, the lowest recorded tanδ value was 0.56 for the 6Y4B sample at 200 Hz. Furthermore, the conductivity measurements showed that the behavior of all samples follows Johnscher's power law.

Improved wet skid resistance of NR/SBR composites induced by irradiation vulcanised styrene-butadiene rubber particles

Improving the wet skid resistance of tire tread is very important for the safety of vehicle driving. Using a novel ultrafine full-vulcanised powdered styrene-butadiene rubber (UFPSBR), this work prepared an advanced UFPSBR/nature rubber (NR)/styrene-butadiene rubber (SBR) composites used for the tire tread. On one hand, the UFPSBR improves the loss factor (tanδ) values of the UFPSBR/NR/SBR composites in temperature range from 0 °C to 10 °C, indicating that the UFPSBR modified tire tread has better wet skid resistance. On the other hand, the UFPSBR increases the surface roughness and complex modulus of the UFPSBR/NR/SBR composites while decreasing the water contact angle of the UFPSBR/NR/SBR composites, which is conducive to increasing the wet skid resistance of tire tread by puncturing the water film or leading a thinner water film between tire tread surface and road surface. Above researches are more comprehensive and benefit for studying the advanced green tire with high wet skid resistance.

Naphthalimide-linked carbazole derivative: Synthesis, gelation and naked eye detection of Cu2+ and Fe3+-ions under different conditions

Naphthalimide-labeled carbazole derivative NC has been synthesized, characterized, and tested for sensing of metal ions in different conditions. Compound NC acts as Low Molecular Weight Gelator (LMWG) and exhibits gelation from aqueous DMF, DMSO, and 1,4-dioxane. Morphologies of the gels are fibrous and their packing varies with the nature of the gelling solvent. All the gels reveal good viscoelastic response. Based on the different morphologies, the rheological behavior of gels differs. DMSO/H2O and DMF/H2O gels with lower tanδ values intimate considerable mechanical strength. As an application, the brown gel derived from DMF: H2O (1:1, v/v) is Cu2+ and Fe3+ responsive involving a gel-to-sol conversion, and validates the naked eye detection. The Fe3+-broken gel is is sharply distinguished from the Cu2+-broken gel by adding F− ions. In CH3CN, compound NC also shows interaction with Cu2+ and Fe3+ ions through a color change (yellow to colorless) and fluorescence quenching. The metal ions are fluorimetrically differentiated in aqueous CH3CN using F− ions although compound NC was incapable of showing selectivity in aqueous CH3CN. The detection limits for Cu2+ and Fe3+ ions are calculated using emission data as 2.02 x 10−7 M and 2.09 x 10−7 M, respectively. Compound NC also recognizes Cu2+ and Fe3+ ions through paper strips under UV light and the ions are distinguished by F− solution. The binding and spectroscopic observations are explained by theoretical calculations. The structure of the copper complex as obtained from single crystal x-ray analysis gives additional support to the observation.

Characterization of the Gluten Aggregation, Dough Rheological, and Physicochemical Properties of Flours Used in the Production of Flat Breads in Eskişehir

In this study, the physical, chemical, technological, gluten aggregation, and dough rheological properties of flat bread flours (“Bazlama", "Pide", "Gözleme", "Lavash") produced in Eskişehir were evaluated in detail by comparing them with “Bread” flour. The highest SRC lactic acid and GPI (gluten performance indeks) values (118.1% and 0.648, respectively) were found in "Gözleme" flour; however, "Lavash" and "Pide" flours had values close to “Bread” flour. The lowest SRC lactic acid and GPI values were obtained in "Bazlama" flour (84.13% and 0.531, respectively). The protein content of “Lavash” flour was close to bread flour (10.60%), while the protein content of "Pide" and "Gözleme" flours was higher (11.07% and 10.94%, respectively). The protein content of “Bazlama” flour was significantly lower than that of other flours (9.84%). Again, the sedimentation value of “Gözleme” flour was above that of other flours (65.0 ml). Lavash flour also had a high sedimentation value (60.0 ml). The sedimentation values of “Pide” and “Bread” flour were similar (approximately 53.0 ml) and lower. “Bazlama” flour gave a low sedimentation value (43.0 ml). Unlike bread flour, flat bread flours had a gluten indeks (GI) value higher than 90.0%. The ash content of flat bread flours varied between approximately 0.550 and 0.650%. “Bread” flour had the longest GlutoPeak peak maximum time (PMT) (102.0 s). “Bazlama” flour had the lowest torque 15 s before the maximum torque (BM), maximum torque (BEM), torque 15 s after the maximum torque (PM), energy, and water absorption (19,3 BU; 36,3 BU; 22,0 BU; %9,07; %18,57, 26,0 J ve %53,5, respectively). The BEM value of “Lavash”, “Gözleme” and “Pide” flours was higher than bread flour (around 45 BU). Of these three flours, “Pide” and “Lavash” flours maintained their high BEM after 15 s and gave a high PM (37.7 BU and 31.7 BU, respectively). “Bazlama” flour had the lowest PM value (22.0 BU). Particularly, “Gözleme” and “Pide” flours had high gluten-aggregation properties. Although the gluten and protein content values of “Lavash” flour were similar to those of “Bread” flour, its energy and water absorption values were higher (127.3 J and 58.0%). The difference between “Lavash” and “Pide” flours was a short PMT value (around 50 s). “Gözleme” flour had the highest stability (4.15 min.) and the lowest softening degree (49.5 FU) in the farinograph. Farinograph stability, development time, and softening degree values were also better in “Pide” flour (3.05 min., 2.85 min., and 85.0 BU, respectively). The farinograph qulaity number (FQN) values of these two flours were also high (65.5 and 50.0). “Bazlama” flour had low stability, FQN, and high softening degree. The “Bazlama” flour had the highest softening value (243.5 FU). Farinograph rheological properties of “Lavash” and control “Bread” flour were similar to each other. While the G' value of “Gözleme” and “Pide” flours, which were more stable in the farinograph, was found to be higher (27200 Pa and 24525 Pa), the G' value of “Lavash” flour was the lowest (around 12215 Pa). The G' values of “Bazlama” and “Bread” flour were similar (18050 Pa and 16590 Pa). The “Gözleme” and “Pide” flours with higher storage resistance (G') had higher G'' values (around 12000 Pa). “Lavash” flour had the lowest G'' value (6433.5 Pa). The lowest G'' values of “Bazlama” and “Bread” flour were found to be similar. “Gözleme” flour had the lowest Tanδ value (0.464). It is also low in “Pide” flour (0.491). The dough from these flours had an elastic structure. The “Lavash” and “Bazlama” flours had the highest Tanδ value (0.531 and 0.537). As a result, “Lavash” and “Bazlama” flours were found to have weaker and more extensible viscoelastic properties.

Excellent piezoelectric response and low dielectric loss of PIN-PHT ceramics obtained through synergy of defect engineering and localized heterostructure

Pb-based piezoelectric ceramics with excellent piezoelectric response and low dielectric loss are crucial for advanced applications but still challenging to achieve. Herein, an approach based on synergistic effect of defect engineering and localized heterogeneous structures was developed to prepare 0.11 Pb(In0.5Nb0.5)O3-0.89 Pb(Hf0.47Ti0.53)O3+xmol%(Sb5++Nd3+) advanced piezoelectric ceramics by solid phase reaction method. Effects of ion co-doping on physical phase structures, defect concentrations, and electric domain morphologies of ceramics were all investigated. A mapping relationship between defect concentration, formation of localized heterogeneous structure, and modulation of piezoelectric and dielectric properties of ceramics was extracted. Values of d33, TC, εr, tanδ (%), and kp of ceramics obtained at x = 0.4 mol% were determined as respectively 607 pC/N, 313.1°C, 3407.81, 1.42, and 0.66, showing excellent overall performances. The doping of (Sb5++Nd3+) skillfully modulated the concentration of defects inside ceramics, resulting in excellent piezoelectric response and reduced dielectric loss. On the other hand, lattice distortion induced by doping generated nanodomains formed localized heterostructures and significantly reduced the Gibbs free-energy barrier, resulting in excellent piezoelectric response and dielectric properties. These effects can mainly be attributed to synergistic action of defect engineering and localized heterostructures. Overall, proposed ceramics and strategy look promising for preparing Pb-based piezoelectric ceramics with excellent comprehensive performance.

Partial Replacement of Carbon Black with Graphene in Tire Compounds: Transport Properties, Thermal Stability and Dynamic Mechanical Analysis

In this study, natural rubber (NR)/polybutadiene rubber (PB) blend-based composites were prepared using graphene as a partial replacement for carbon black (CB) in different parts per hundred rubber (phr) percentages. In a previous study, the vulcanization characteristics, viscoelastic behavior, and static mechanical properties were reported, and the compound labeled as compound 2 (with 2.5 phr of graphene and 52.5 phr of carbon black) showed optimum properties. Herein, we report the dynamic mechanical properties and the transport properties of the formulations to establish further characterization of the compounds. Three different organic solvents comprising benzene, toluene, and xylene were employed to analyze the sorption characteristics. The obtained data were also modeled with different theoretical predictions. The dynamic mechanical properties showed that certain compounds can be considered to be green tire formulations, as there were appreciable changes in the tanδ values at different temperatures (−25 °C to 60 °C). The thermogravimetric analysis showed that compound 2, with 2.5 phr of graphene, has a higher t50 value among the studied formulations, which indicates higher thermal stability than the base compound. The partial replacement of 2.5 phr of graphene in place of carbon black (total 55 phr) led to appreciable improvements in terms of thermal stability, transport properties, and dynamic mechanical properties.

Characteristics of a CaO–B2O3–SiO2–Al2O3–ZnO-based sandwich substrate and its dielectric properties in the 5G millimeter-wave band

In this study, a 34.5CaO–23B2O3–33.5SiO2–6Al2O3–3ZnO (CBSAZ) glass-ceramic substrate was prepared using a sol–gel method. A porous CaO–B2O3–SiO2–Al2O3–ZnO layer (CBSAZ0.5C) with a porosity of 72.6 % and thickness of 365 μm was inserted between two ∼120 μm thick dense CBSAZ layers to form a tri-layer substrate (CBSAZ/CBSAZ0.5C/CBSAZ). The dielectric constants (εr) and dielectric losses (tanδ) of the dense CBSAZ substrate at 20 and 60 GHz were 6.90 and 0.029, respectively, and 6.96 and 0.017, respectively. These values were almost independent of frequency. In contrast, the εr and tanδ values of the CBSAZ/CBSAZ0.5C/CBSAZ sandwich substrate at 20 and 60 GHz were 3.59 and 0.022, respectively, and 3.11 and 0.020, respectively. Thus, the εr value of the CBSAZ/CBSAZ0.5C/CBSAZ sandwich substrate was significantly lower than that of the CBSAZ substrate, whereas the tanδ and κ values of the CBSAZ/CBSAZ0.5C/CBSAZ and CBSAZ substrates were similar.

Investigation of Dielectric Properties and Structural Changes in XLPE Composite Insulation of Covered Conductor due to Thermal Aging

Investigating the dielectric characteristics and structural alterations in XLPE composites, commonly employed in the insulation of covered conductors, stands as a pivotal research focus. In this study, we examined the variation in dielectric loss (tanδ) concerning frequency and voltage, influenced by thermal aging in XLPE insulation. To achieve this, the samples underwent aging at 120°C for six periods, a total of 450 hours. Furthermore, we conducted PD tests, FTIR, and SEM assessments on the insulation both before and after the aging process. A comprehensive analysis of the material's property changes during thermal aging was performed by comparing the PD test results with the tanδ measurements. In order to delve deeper into the interpretation of these findings because of thermal aging, we explored both internal and surface structural modifications, which directly impact tanδ and PD values, utilizing FTIR and SEM techniques.

Bond theory, vibrational spectroscopy, and dielectric responses of trirutile ATa2O6 (A = Mg, Ni) microwave ceramics

This study established the connection between structure and dielectric responses by synergistically evaluating the chemical bond characteristics and lattice vibrational spectroscopies of trirutile ATa2O6 (A = Mg, Ni) microwave ceramics. The MgTa2O6 ceramic exhibits a uniform grain size distribution and a dense microstructure, with dielectric characteristics at microwave range of a εr value of 27.27, a high Q×f value of 109,203 GHz (8.73 GHz), and a τf of approximately 53.38 ppm/°C when sintered at 1300 °C, while the NiTa2O6 ceramic presents a smaller average grain size and minor micropores, with dielectric characteristics at microwave range of εr = 24.58, Q×f = 27,610 GHz (9.25 GHz), and τf = 33.94 ppm/°C, sintered at 1250 °C. The structural refinement and atomic arrangements confirm a trirutile structure along the [001], [100], and [3 3‾1‾] zone axes. Ta–O bonds are found to contribute the most to the ionic character of a bond, bond susceptibility, lattice stability, thermal expansion behaviors, and strength of bonding ability, indicating their significant influence on dielectric polarization, lattice stability, and temperature coefficient of resonant frequency. Raman scattering spectra analysis reveals that the A1g mode near 700 cm−1 mainly controls the Raman vibrational behaviors. The theoretical dielectric properties calculated from the infrared spectrum and dielectric properties analysis consistent with the measured dielectric performances, suggesting that the dielectric characteristics at the microwave range are mainly determined by the oscillatory absorption of structural phonons, with the first two modes at 210.48 cm−1 and 232.87 cm−1 contributing 72.02% to the εr value and 90.45% to the tanδ value, respectively.

Microstructures and Dielectric Permittivity Properties of Fe3O4/Cdots Nanocomposites Synthesized by Green Route Utilizing Moringa Oleifera Extract and Watermelon Peel

Dielectric materials are beneficial for storing electrical energy due to their insulating and polarization properties in response to external electric fields. Magnetite has shown promise as a dielectric material among other materials due to its good magnetic properties, low toxicity, and biocompatibility. However, the weakness of Fe3O4, which has low stability and easy agglomeration, requires a modification on its surface by using Carbon dots (Cdots). This research investigates the dielectric properties of Fe3O4/Cdots obtained through the green synthesis method. Fe3O4 nanoparticles were synthesized using the co-precipitation method with Moringa oleifera leaf extract as a reducing and stabilizing agent. In contrast, Cdots were synthesized using the hydrothermal method with watermelon peel waste as a carbon source. The Fe3O4 composite nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), ultraviolet-visible spectroscopy (UV-Vis), and impedance spectroscopy. The XRD spectra revealed the existence of cubic inverse spinel and a reduction in crystal size as the concentration of Cdots increased, measuring 7.8 and 7.1 nm, respectively. SEM-EDX revealed that the sample is composed of Fe, O, and C elements and has a spherical shape with Cdots distributed on the surface of Fe3O4. The UV-Vis spectrum showed the absorption peak of Cdots at 282 nm. The Fe3O4 absorption peak is identical to the Fe3O4/Cdots absorption peak at 193 nm. The increase in band gap energy from 2.96 to 3.33 eV is related to the increase in Cdots concentration. In the 10-900 kHz frequency range, dielectric property tests demonstrated peak dielectric permittivity values (real and imaginary). A substantial decrease was observed between 10 kHz and 200 kHz, followed by a relatively stable pattern up to 900 kHz. The loss tangent value obtained has a tanδ value <0.5, which means that the addition of Cdots affects reducing the energy loss stored in Fe3O4.

The dielectric properties of silicone-multiwall carbon nanotubes nanocomposite in the frequency range from 0.5 to 20 GHz

Integrating carbon nanotubes (CNTs) into a polymer matrix can significantly modify its physical properties, providing that the challenges associated with CNT dispersion are successfully resolved. In this work, we investigate the enhancement of the dielectric properties of silicone when multiwall carbon nanotubes (MWCNTs) are introduced to its polymer matrix as a filler in the frequency range from 0.5 to 20 GHz. An optimized procedure is used to prepare nanocomposites with MWCNTs concentrations by weight of 0%, 0.5%, 1.0%, 1.5%, and 2.0%. The investigated dielectric properties for the prepared nanocomposites are the real dielectric constant ɛ′, the imaginary dielectric constant ɛ″, the loss tangent tan δ, and the AC conductivity σAC. The dispersion of the MWCNTs in the silicone matrix is confirmed using the Fourier-transform infrared (FTIR) spectroscopy and the scanning electron microscope. This study shows that the dielectric properties of the nanocomposite are enhanced as the MWCNT’s concentration is increased over the entire frequency range. For example, the enhancement in ɛ′ value was from 3.2 up to 21.6 at 0.5 GHz and from 2.5 to 10.6 at 20 GHz as the concentration increased from 0% to 2.0%. For the ɛ″ value, the enhancement was from less than 0.1 to 8.6 at 0.5 GHz and to 2.0 at 20 GHz, respectively. Based on the obtained tanδ values, the nanocomposites with MWCNTs of 0.5% and 1.0% can be classified as low-loss dielectrics, while the other nanocomposites with MWCNTs of 1.5% and 2.0% are classified as lossy dielectrics.

Notably enhanced dielectric response with low loss in PVDF composites filled with RuO2–BaTiO3 hybrid particles

This study delineates the process of fabricating and the results of investigating the dielectric properties of hybrid particles created through the integration of Poly(vinylidene fluoride) (PVDF) filled with RuO2 coated on BaTiO3 nanoparticles (nBT), designated as RuO2–nBT. These hybrid particles were successfully synthesized employing a simple and cost–effective solid–state reaction method. The inclusion of RuO2–nBT in the PVDF matrix engendered a notable enhancement in its dielectric properties. Notably, a RuO2–nBT fraction of 0.5 manifested a dielectric constant (ε′) of 107.4 and a dielectric loss tangent (tanδ) value of 0.062 at 30 °C and 1 kHz. These findings signify the effective role of interfacial polarization occurring between the PVDF matrix and the RuO2–nBT hybrid particles, leading to a marked improvement in dielectric attributes. Moreover, the observed low tanδ value indicates the elimination of conductive pathways, an inhibitory effect attributed to the incorporation of RuO2–nBT hybrid particles. This study underscores the promising potential of RuO2–nBT hybrid particles in fine–tuning and augmenting the dielectric properties of polymer composites, particularly in scenarios necessitating low tanδ and high ε′ values.

Enhanced dielectric properties of PVDF polymer nanocomposites: A study on gold−decorated, surface−modified multiwalled carbon nanotubes

The integration of surface-modified multiwalled carbon nanotubes (fMWCNTs) into polymer nanocomposites has been extensively studied for their potential to enhance dielectric properties. This study, however, pioneers the use of a novel hybrid filler comprising fMWCNTs coated with metal nanoparticles, specifically aimed at augmenting the dielectric performance of polymers. In our research, poly(vinylidene fluoride) (PVDF) nanocomposite films were synthesized using fMWCNTs with a diameter of ∼6–9 nm and a length of 5 μm, adorned with gold nanoparticles (nAu) of ∼5.4 ± 0.9 nm via an adapted Turkevich method. Comprehensive analyses were conducted on nAu−fMWCNTs hybrid powder and their nanocomposites in PVDF with varying filler concentrations, confirming the formation of nAu−fMWCNTs with a weight ratio of 1.1 : 98.9. Three−phase percolative nanocomposites were produced by dispersing the hybrid filler in N,N−dimethylformamide, facilitated by interactions between the negative charge of nAu−fMWCNTs (zeta potential of ∼ −40.43 ± 0.46 mV) and polar phases of PVDF. This was verified through zeta potential and Fourier−transform infrared spectroscopy analyses. The dielectric permittivity (ε′) of the nanocomposites significantly increased from 17.8 to 524.8 (at 1 kHz) with filler loadings from 0.005 to 0.01 vol%, while the dielectric loss tangent (tanδ) showed a minor increase from 0.05 to 1.18. These enhancements are attributed to the elevated permittivity of nAu−fMWCNTs hybrid powder, PVDF's transition to the β−phase, and interfacial polarization effects. The restrained growth of nAu on fMWCNTs and the inhibition of conductive pathways in the polymer matrix contributed to the low tanδ values.

Tuning enhanced dielectric properties of (Sc3+–Ta5+) substituted TiO2 via insulating surface layers

In this study, we achieved significantly enhanced giant dielectric properties (EG-DPs) in Sc3+–Ta5+ co-doped rutile-TiO2 (STTO) ceramics with a low loss tangent (tanδ ≈ 0.05) and high dielectric permittivity (ε′ ≈ 2.4 × 104 at 1 kHz). We focused on investigating the influence of insulating surface layers on the nonlinear electrical properties and the giant dielectric response. Our experimental observations revealed that these properties are not directly correlated with the grain size of the ceramics. Furthermore, first-principles calculations indicated the preferred formation of complex defects, specifically 2Ta diamond and 2ScVo triangular-shaped complexes, within the rutile structure of STTO; however, these too showed no correlation. Consequently, the non-Ohmic properties and EG-DPs of STTO ceramics cannot be predominantly attributed to the grain boundary barrier layer capacitor model or to electron-pinned defect-dipole effects. We also found that the semiconducting grains in STTO ceramics primarily arise from Ta5+, while Sc3+ plays a crucial role in forming a highly resistive outer surface layer. Notably, a significant impact of grain boundary resistance on the nonlinear electrical properties was observed only at lower co-dopant concentrations in STTO ceramics (1 at%). The combination of low tanδ values and high ε′ in these ceramics is primarily associated with a highly resistive, thin outer-surface layer, which substantially influences their non-Ohmic characteristics.