Showing papers on "Dielectric loss published in 2010"
TL;DR: In this article, the effects of geometric factors and intrinsic properties of the fillers and the matrix on electric and dielectric properties near percolation have been discussed, and an outlook on the future possibilities and scientific challenges in the field is given.
Abstract: Dramatic changes in the physical properties of composites occur when filler particles form a percolating network through the composite, particularly when the difference between the properties of the constitutive phases is large. By use of electric conductivity and dielectric properties as examples, recent studies on the physical properties of composites near percolation are reviewed. The effects of geometric factors and intrinsic properties of the fillers and the matrix, and especially of the interface between fillers and matrix, on electric and dielectric properties near percolation are discussed. Contact resistivity at the interface is less desirable for enhancing electrical conductivity. By contrast, an interface with high resistivity suppresses tunneling between adjacent fillers and leads to percolative composites with higher dielectric constant but lower dielectric loss. This review concludes with an outlook on the future possibilities and scientific challenges in the field.
811 citations
TL;DR: In this paper, the possibility of obtaining relatively high dielectric constant polymer-ceramic composite by incorporating the CaCu3Ti4O12 (CCTO) in a polyvinylidene fluoride (PVDF) polymer matrix by melt mixing and hot pressing process was demonstrated.
253 citations
TL;DR: In this article, the authors provide an overall summary on the recent progress in developing electrically tunable dielectric materials, based on ferroelectrics and non-ferroelectric, with a specific attention to the strategies employed to improve the performances of ferroelectric materials for microwave device applications.
233 citations
TL;DR: In this article, chemical co-precipitation was used to synthesize strontium hexaferrite nanoparticles by using Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy, Transmission Electron microscopy, DC electrical resistivity and dielectric measurements.
191 citations
TL;DR: In this paper, low-density ordered mesoporous carbon−silica nanocomposites with different Fe contents have been prepared by a facile solvent-evaporation-induced self-assembly approach.
Abstract: Low-density ordered mesoporous carbon−silica nanocomposites with different Fe contents have been prepared by a facile solvent-evaporation-induced self-assembly approach. Magnetic metal nanocrystallines are highly dispersed in the composites due to in situ carbothermal reduction. The optimal reflection loss calculated from the measured permittivity and permeability is −34.4 dB at 13.1 GHz. Moreover, the electromagnetic wave absorption less than −10 dB is found to exceed 5.0 GHz for an absorber thickness of 2 mm. The microwave enhancement absorption of the mesoporous C−SiO2−Fe nanocomposites is contributed to the better match between dielectric loss and magnetic loss, which originates from the high absorption by the incorporation of magnetic species as well as the multiple reflections by the ordered mesoporous structure. The mesoporous C−SiO2−Fe nanocomposites also exhibit a lower infrared emissivity in the wavelength from 8 to 14 μm than that of Fe-free powder.
190 citations
TL;DR: In this article, the different composition of PVA-LiCF 3 SO 3 polymer electrolyte has been prepared by solution cast technique using DMSO as solvent and the FTIR study confirms the polymer-salt complex formation.
Abstract: The development of polymeric systems with high ionic conductivity is one of the main objectives in Li rechargeable battery. In the present study, the different composition of PVA–LiCF 3 SO 3 polymer electrolyte has been prepared by solution cast technique using DMSO as solvent. The FTIR study confirms the polymer–salt complex formation. The amorphous nature of the polymer has been confirmed by XRD analysis. DSC measurements show decrease in T g with increasing salt concentration. The temperature dependent conductivity obeys Arrhenius relationship. The maximum conductivity has been observed in the order of 7 × 10 − 4 S cm − 1 for 25 mol% of LiCF 3 SO 3 . The activation energy has been found to be 0.16 eV. The two peaks have been observed in the dielectric loss spectrum which shows two types of relaxation α and β.
178 citations
TL;DR: In this paper, a hybrid core/shell Co/graphite nanoparticles synthesized by an arc-discharge method exhibit an enhanced dielectric loss property in the frequency range of 2-18 GHz.
Abstract: Hybrid core/shell Co/graphite nanoparticles synthesized by an arc-discharge method exhibit an enhanced dielectric loss property in the frequency range of 2–18 GHz. Complex permittivity expressed by Debye dipolar polarization approximate show that three kinds of dielectric polarizations coexist in this hybrid system. Combined with theoretical simulation, we further clarified that the dielectric polarizations are ascribed to the high defective graphite shells, and additional interfacial polarizations arising from the special core/shell architecture.
148 citations
TL;DR: In this article, the influence of Y3+ substitution on the structural, electrical and dielectric properties of Ni-Y ferrites was studied in the ferrite series NiY2xFe2−2xO4 where x=0.12 in steps of 0.06.
Abstract: The influence of Y3+ substitution on the structural, electrical and dielectric properties of Ni–Y ferrites was studied in the ferrite series NiY2xFe2−2xO4 where x=0–0.12 in steps of 0.02. This series was prepared by conventional double sintering ceramic method. XRD analysis reveals single phase samples up to x=0.06. At x≥0.08, a secondary phase of iron yttrium oxide (YFeO3) appears along with the spinel phase. The incorporation of Y3+ for Fe3+ ions results in a slight increase of lattice constant due to larger ionic radius of the substituted ions. It was inferred that the substitution of yttrium limits the grain growth. The physical densities are about 90% of their X-ray densities. FTIR spectra obtained at room temperature in the wave number range 370–1100 cm−1 show splitting of the two fundamental absorption bands, thereby confirming the completion of solid state reaction. The increase in dc resistivity has been found with the increase in Y3+ contents. Dielectric constant ( e ′ ) and loss tangent ( tan δ ) were measured at room temperature in the frequency range from 10 Hz to10 MHz. A significant reduction in the values of dielectric constant and dielectric loss tangent has been observed with the increase of Y3+ ions. The high dc resistivity and low dielectric losses are the desired characteristics of Ni–Y ferrites used to prepare microwave devices.
140 citations
TL;DR: In this article, the average size of the prepared ZnO nanoparticles is found to be 50nm and the frequency-dependent dielectric dispersion of the sample is investigated in the temperature range from 293 to 383 K and in a frequency range from 100 Hz to 1 MHz by impedance spectroscopy.
138 citations
TL;DR: In this paper, the structural properties of polyvinyl alcohol (PVA) doped with titanium chloride (TiCl 3 ) at different weight percent ratios were examined by XRD and FTIR studies.
Abstract: Polymeric films based on polyvinyl alcohol (PVA) doped with titanium chloride (TiCl 3 ) at different weight percent ratios were prepared using the solvent cast technique. The structural properties of these polymeric films are examined by XRD and FTIR studies. The complexation of the dopant with the polymer was confirmed by FTIR studies. The XRD pattern reveals that the amorphous domains of PVA polymer matrix increased with raising the TiCl 3 content. The optical properties of these polymeric films were examined by optical absorption and emission spectroscopy. Electrical conductivity was measured at room temperature of pure PVA and PVA doped with different concentrations of TiCl 3 from 20 Hz to 3 MHz. The conductivity was found to increase with the increase in dopant concentration. The dielectric constant ( e ′) indicates a strong dielectric dispersion in the studied frequency range and increases as dopant content increases. This increase in both σ and e ′ is attributed to the increase in the localized charges distribution. Moreover, a loss peak was identified in the dielectric loss spectra and it is attributed to the orientation of polar groups.
137 citations
TL;DR: In this article, the average crystallite size was calculated using the Scherrer formula and found within 17-27nm range, and the optical absorption spectra of all the samples showed two clear electronic transitions, first is around 0.75 eV while the second at about 0.84 eV.
TL;DR: In this article, Lanthanum doped cobalt ferrite ferrites with improved dielectric and magnetic properties have been synthesized by co-precipitation technique.
TL;DR: In this article, lead zirconate titanate (PbZr0.52Ti0.48O3−PZT) thin films with different thicknesses were deposited on Pt(111)/Ti/SiO2/Si substrates by a sol-gel method.
Abstract: Lead zirconate titanate (PbZr0.52Ti0.48O3−PZT) thin films with different thicknesses were deposited on Pt(111)/Ti/SiO2/Si substrates by a sol-gel method. Single perovskite phase with (111)-texture was obtained in the thinnest films, whereas with the increase in thickness the films changed to a highly (100)-oriented state. An increase in the mean grain size as the film thickness increased was also observed. Dielectric, ferroelectric, and piezoelectric properties were analyzed as a function of the film thickness and explained based on film orientation, grain size, domain structure, domain wall motion, and nonswitching interface layers. Both serial and parallel capacitor models were used to analyze the influence of the nonswitching interface layer in the dielectric properties and the effect of substrate clamping in the microscopic piezoelectric response as the film thickness decreased. The scanning force microscopy technique was used to study the effect of thickness on the microscopic piezoresponse. Signific...
TL;DR: Experimental results show that the values of e′, e″ and tan δ are a strong function of the temperature, and results indicate the interfacial polarization can be more easily occurred at high temperatures.
TL;DR: In this article, the authors reported quality factors of up to 500x10³ in superconducting resonators at the single photon levels needed for circuit quantum electrodynamics.
Abstract: We report quality factors of up to 500x10³ in superconducting resonators at the single photon levels needed for circuit quantum electrodynamics. This result is achieved by using NbTiN and removing the dielectric from regions with high electric fields. As demonstrated by a comparison with Ta, the crucial sources of intensity-dependent loss are dielectrics on the surface of the metal and substrate.
TL;DR: It was found that PPEK displayed excellent stability of the dielectric properties over a broad frequency and temperature range, and a linear correlation between the AC conductance and the angular frequency implied that the hopping as a dominant conduction process contributed to theDielectric loss.
Abstract: The synthesis and characterization of poly(phthalazinone ether ketone) (PPEK) for high-temperature electric energy storage applications is described. It was found that PPEK displayed excellent stability of the dielectric properties over a broad frequency and temperature range. Little change in the breakdown field and discharge time has been observed in PPEK with the increase of temperature up to 190 °C. A linear correlation between the AC conductance and the angular frequency implied that the hopping as a dominant conduction process contributed to the dielectric loss. Superior energy densities, remarkable breakdown strengths, and fast discharge speeds have been demonstrated in PPEK at various temperatures.
TL;DR: Through designing multi-layered structures with carbon nanofiber (CNF)/poly(vinylidene fluoride) (PVDF) composites intercalated by a pure PVDF layer, enhanced dielectric constant and low loss were achieved.
Abstract: The enhancement of dielectric constant in a polymer while maintaining low loss through composite methods has been challenging. In this paper, we report that through designing multi-layered structures with carbon nanofiber (CNF)/poly(vinylidene fluoride) (PVDF) composites intercalated by a pure PVDF layer, enhanced dielectric constant and low loss were achieved. The dielectric loss was similar to that of pure PVDF at high frequencies and even lower than pure PVDF at low frequencies. The results were achieved by designing special multi-layered structures including CNF/PVDF composite layers. The multi-layered sandwich-like or laminate structure composites with transversely heterogeneous CNF distributions were prepared using a simple two-step processing including solution casting and compression molding methods. The dielectric constant obtained from the sandwich structure containing 5, 7 and 15 wt% CNF/PVDF composite layers is even more independent of the frequency in a wide range from 10(2) to 10(6) Hz. Furthermore, the effects of the heterogeneous CNF distribution on the dielectric properties were studied by designing different multi-layered composite structures with varying architecture while maintaining the same CNF concentration level. It is shown that varying this stack-up architecture of different CNF distributions plays an important role in the enhancement level of the dielectric constant while having negligible effect on the dielectric loss of the nanocomposite, which is determined mainly by the CNF loading content.
TL;DR: In this paper, the loss of amorphous hydrogenated silicon nitride (a-SiNx:H) is measured at 30 mK and 5 GHz using a superconducting LC resonator down to energies where a single photon is stored, and analyzed with an independent two-level system defect model.
Abstract: The loss of amorphous hydrogenated silicon nitride (a-SiNx:H) is measured at 30 mK and 5 GHz using a superconducting LC resonator down to energies where a single-photon is stored, and analyzed with an independent two-level system defect model. Each a-SiNx:H film was deposited with different concentrations of hydrogen impurities. We find that quantum-regime dielectric loss tangent tan δ0 in a-SiNx:H is strongly correlated with N–H impurities, including NH2. By slightly reducing x we are able to reduce tan δ0 by approximately a factor of 50, where the best films show tan δ0≃3×10−5.
TL;DR: A model assuming a reduced mobility at the pore-matrix interface is shown to provide a quantitative explanation for the remarkable decrease of effective transport quantities of the ionic liquid in non-silanized membranes.
Abstract: Charge transport in 1-hexyl-3-methylimidazolium hexafluorophosphate ionic liquid in oxidized nanoporous silicon membranes is investigated in a wide frequency and temperature range by a combination of Broadband Dielectric Spectroscopy (BDS) and Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR). By applying the Einstein–Smoluchowski relations to the dielectric spectra, diffusion coefficient is obtained in quantitative agreement with independent PFG NMR measurements. More than 10-fold systematic decrease in the effective diffusion coefficient from the bulk value is observed in hydrophilic silica nanopores. A model assuming a reduced mobility at the pore–matrix interface is shown to provide a quantitative explanation for the remarkable decrease of effective transport quantities (such as diffusion coefficient, dc conductivity and consequently, the dielectric loss) of the ionic liquid in non-silanized membranes. This approach is supported by the observation that silanization of porous silica membranes results in a significant increase of the effective diffusion coefficient, which approaches the value for the bulk liquid.
TL;DR: The Drude oscillator model is applied to the molecular ionic liquid 1-ethyl-3-methyl-imidazolium triflate and the influence on the structure, single particle dynamics, and collective dielectric properties is investigated.
Abstract: The Drude oscillator model is applied to the molecular ionic liquid 1-ethyl-3-methyl-imidazolium triflate. The range of manageable Drude charges is tested. The strength of the polarizability is systematically varied from 0% to 100%. The influence on the structure, single particle dynamics, and collective dielectric properties is investigated. The generalized dielectric constant can be decomposed into a dielectric permittivity, a dielectric conductivity, and an optical dielectric constant ɛ(∞). The major part of the static generalized dielectric constant comes from the collective rotation of the ions, i.e., the dielectric permittivity. The translational contribution from the dielectric conductivity is about 58% of the dielectric permittivity. For the evaluation of the optical dielectric contribution, the computational dielectric theory was adapted to the case of heterogeneous polarizabilities. In case of 100% polarizability, it reaches a value of approximately 2.
TL;DR: In this paper, the complex permittivity and permeability of paraffin wax and Fe3O4-carbon sphere composite with different volume fraction of the composite were measured by vector network analysis.
TL;DR: In this article, morphotropic phase boundary (Bi,Na)TiO3-(Bi,K),(Bi and N) TiO3,(Bi K,N),BaTiOO3 epitaxial thin films of 350 nm thickness were reported.
Abstract: Dielectric and piezoelectric properties of morphotropic phase boundary (Bi,Na)TiO3–(Bi,K)TiO3–BaTiO3 epitaxial thin films deposited on SrRuO3 coated SrTiO3 substrates were reported. Thin films of 350 nm thickness exhibited small signal dielectric permittivity and loss tangent values of 750 and 0.15, respectively, at 1 kHz. Ferroelectric hysteresis measurements indicated a remanent polarization value of 30 μC/cm2 with a coercive field of 85–100 kV/cm. The thin film transverse piezoelectric coefficient (e31,f) of these films after poling at 600 kV/cm was found to be −2.2 C/m2. The results indicate that these BNT-based thin films are a potential candidate for lead-free piezoelectric devices.
TL;DR: A metamaterial consisting of cut-wire structures which shows near-perfect absorption at microwave frequencies is reported, and the analysis of the spectra and retrieved electromagnetic parameters demonstrate that the mismatch is attributed to the considerable influence of the dielectric loss on the strength of the electric and magnetic resonances.
Abstract: The authors report a metamaterial (MM) consisting of cut-wire structures which shows near-perfect absorption at microwave frequencies. Experimental results show slight lower performance than simulation. The analysis of the spectra and retrieved electromagnetic parameters demonstrate that the mismatch is attributed to the considerable influence of the dielectric loss on the strength of the electric and magnetic resonances, which largely determines the ability of the MM absorber. Such dependence on dielectric loss provides an important clue for the design of MM absorber aiming at specific applications where high efficiency energy collection in dielectric is needed.
TL;DR: In this paper, the potential of polypropylene (PP)-silica nanocomposite with a view to high voltage applications, especially power capacitors, has been discussed.
Abstract: This paper presents the results of the dielectric properties and partial discharge endurance measurements conducted on polypropylene (PP)-silica nanocomposite. The material compounds were analyzed with micro-Raman spectroscopy, X-ray tomography and transmission electron microscopy (TEM). ac and dc breakdown strength of the materials was measured. Dielectric response, capacitance and loss factor of the film samples were measured as a function of temperature and frequency. Partial discharge (PD) endurance of the reference PP and PP Silica nanocomposite was studied as a function of ac voltage. Material surfaces were analyzed after PD stress with optical microscopy. All dielectric measurements were done for oriented thin films with a thickness of 11-23 μm. The results were analyzed statistically to determine the effects of the additive on the properties of PP. The paper discusses the potential of PP Silica nanocomposite with a view to high voltage applications, especially power capacitors.
TL;DR: Three-phase-percolative composites with ZnO radial nanoclusters (R-ZnO) and BaTiO(3) (BT) nanoparticles embedded into polyvinylidene fluoride (PVDF) were prepared by using a simple blending and hot-molding technique, and the percolation theory was used to explain the experimental results.
Abstract: Three-phase-percolative composites with ZnO radial nanoclusters (R-ZnO) and BaTiO3 (BT) nanoparticles embedded into polyvinylidene fluoride (PVDF) were prepared by using a simple blending and hot-molding technique. The BT + PVDF composite with a volume fraction of 30 vol % BT particles were employed as a thermoplastic-ceramic matrix. Compared with the two-phase-percolative composites of R-ZnO/PVDF, the three-phase-percolative (R-ZnO/(BT + PVDF)) composites showed enhanced dielectric constant and decreased dielectric loss. The percolation theory was used to explain the experimental results. The increased percolation threshold was studied in detail, and the thermal stability was also investigated.
TL;DR: In this article, single photon level quality factors of 500x10^3 were shown in NbTiN superconducting resonators at millikelvin temperatures, which originates from the intrinsic low dielectric loss.
Abstract: Single photon level quality factors of 500x10^3 are shown in NbTiN superconducting resonators at millikelvin temperatures. This result originates from the intrinsic low dielectric loss of NbTiN, as demonstrated by comparison with Ta, and by removing unnecessary parts of the dielectric substrate.
TL;DR: In this paper, the dielectric properties of undoped, Nb-, and Fe-doped Pb(Zr,Ti)O3 ceramics with composition near morphotropic phase boundary were investigated in the frequency range from 1 MHz to 20.2 GHz at room temperature.
Abstract: The dielectric properties of undoped, Nb-, and Fe-doped Pb(Zr,Ti)O3 ceramics with composition near morphotropic phase boundary were investigated in the frequency range from 1 MHz to 20.2 GHz at room temperature. Temperature dependences of dielectric permittivity e′ and loss e″ are measured at 100 kHz from 50 to 300 K and around 13.4 GHz from 100 to 300 K. These measurements permit estimation of the upper limit of the intrinsic permittivity and lower limit of the extrinsic contributions to the permittivity as a function of temperature. The extrinsic contributions account for more than 50% of the quasistatic dielectric permittivity in studied samples.
TL;DR: In this article, a dielectric loss peak is observed at around 450 K and 100 Hz and it shifts to higher temperature with increasing frequency, and a Cole-Cole fitting to loss peaks reveals a weaker correlation among oxygen vacancies for such materials compared with that of ferroelectrics.
Abstract: Quantum paraelectric SrTiO3 has resulted in many investigations because of the anomalous properties. Here, using the conventional solid-state reaction method, we fabricated polycrystalline SrTiO3 ceramics with pure cubic perovskite structure. A dielectric loss peak is observed at around 450 K and 100 Hz and it shifts to higher temperature with increasing frequency. The typical high-temperature dielectric relaxation process is confirmed to be related to the oxygen vacancies (OVs) inside ceramics. More interestingly, a Cole–Cole fitting to loss peaks reveals a weaker correlation among OVs for such dielectric materials compared with that of ferroelectrics.
TL;DR: In this article, the X-ray powder diffraction study reveals that all the prepared samples have pure anatase phase tetragonal system and the average crystallite size of the prepared sample is 14nm, when found through transmission electron microscope.
TL;DR: In this article, the dielectric properties of pure yellow locust, jujube and rape flower honey and their water-adulterated products with water content from 18% to 42.6% were measured with open-ended coaxial-line probe technology and a network analyzer from 10 to 4500 MHz at 25 °C.