Showing papers on "Dielectric loss published in 2013"
TL;DR: In this paper, the authors reported a facile solvothermal route to synthesize laminated magnetic graphene and showed that there have significant changes in the electromagnetic properties of magnetic graphene when compared with pure graphene.
Abstract: Graphene is highly desirable as an electromagnetic wave absorber because of its high dielectric loss and low density. Nevertheless, pure graphene is found to be non-magnetic and contributes to microwave energy absorption mostly because of its dielectric loss, and the electromagnetic parameters of pure graphene, which are out of balance, result in a bad impedance matching characteristic. In this paper, we report a facile solvothermal route to synthesize laminated magnetic graphene. The results show that there have been significant changes in the electromagnetic properties of magnetic graphene when compared with pure graphene. Especially the dielectric Cole–Cole semicircle suggests that there are Debye relaxation processes in the laminated magnetic graphene, which prove beneficial to enhance the dielectric loss. We also proposed an electromagnetic complementary theory to explain how laminated magnetic graphene, with the combined advantages of graphene and magnetic particles, helps to improve the standard of impedance matching for electromagnetic wave absorbing materials. Besides, microwave absorption properties indicate that the reflection loss of the as-prepared composite is below −10 dB (90% absorption) at 10.4–13.2 GHz with a coating layer thickness of 2.0 mm. This further confirms that the nanoscale surface modification of magnetic particles on graphene makes graphene-based composites have a certain research value in electromagnetic wave absorption.
663 citations
TL;DR: In this article, an ideal dielectric thermally conductive epoxy nanocomposite is successfully fabricated using polyhedral oligosilsesquioxane (POSS) functionalized boron nitride nanotubes (BNNTs) as fillers.
Abstract: Dielectric polymer composites with high thermal conductivity are very promising for microelectronic packaging and thermal management application in new energy systems such as solar cells and light emitting diodes (LEDs). However, a well-known paradox is that conventional composites with high thermal conductivity usually suffer from the high dielectric constant and high dielectric loss, while on the other hand, composite materials with excellent dielectric properties usually possess low thermal conductivity. In this work, an ideal dielectric thermally conductive epoxy nanocomposite is successfully fabricated using polyhedral oligosilsesquioxane (POSS) functionalized boron nitride nanotubes (BNNTs) as fillers. The nanocomposites with 30 wt% fraction of POSS modified BNNTs exhibit much lower dielectric constant, dielectric loss tangent, and coefficient of thermal expansion in comparison with the pure epoxy resin. As an example, below 100 Hz, the dielectric loss of the nanocomposites with 20 and 30 wt% BNNTs is reduced by one order of magnitude in comparison with the pure epoxy resin. Moreover, the nanocomposites show a dramatic thermal conductivity enhancement of 1360% in comparison with the pristine epoxy resin at a BNNT loading fraction of 30 wt%. The merits of the designed composites are suggested to originate from the excellent intrinsic properties of embedded BNNTs, effective surface modification by POSS molecules, and carefully developed composite preparation methods.
519 citations
TL;DR: Spectroscopic analysis demonstrates that the presence of GF hybrid structures facilitates strong polarization due to the formation of a solid-state charge-transfer complex between graphene and polyaniline, which leads to the high microwave absorption properties.
Abstract: The development of high-performance shielding materials against electromagnetic pollution requires mobile charge carriers and magnetic dipoles. Herein, we meet the challenge by building a three-dimensional (3D) nanostructure consisting of chemically modified graphene/Fe3O4(GF) incorporated polyaniline. Intercalated GF was synthesized by the in situ generation of Fe3O4 nanoparticles in a graphene oxide suspension followed by hydrazine reduction, and further in situ polymerization with aniline to form a polyaniline composite. Spectroscopic analysis demonstrates that the presence of GF hybrid structures facilitates strong polarization due to the formation of a solid-state charge-transfer complex between graphene and polyaniline. This provides proper impedance matching and higher dipole interaction, which leads to the high microwave absorption properties. The higher dielectric loss (e′′ = 30) and magnetic loss (μ′′ = 0.2) contribute to the microwave absorption value of 26 dB (>99.7% attenuation), which was found to depend on the concentration of GF in the polyaniline matrix. Moreover, the interactions between Fe3O4, graphene and polyaniline are responsible for superior material characteristics, such as excellent environmental (chemical and thermal) degradation stability and good electric conductivity (as high as 260 S m−1).
478 citations
TL;DR: This work reports the ferroelectric polymer networks exhibiting significantly reduced dielectric loss, superior polarization and greatly improved breakdown strength and reliability, while maintaining their fast discharge capability at a rate of microseconds, leading to unprecedented charge-discharge efficiencies and large values of the discharged energy density.
Abstract: Ferroelectric polymers are being actively explored as dielectric materials for electrical energy storage applications. However, their high dielectric constants and outstanding energy densities are accompanied by large dielectric loss due to ferroelectric hysteresis and electrical conduction, resulting in poor charge-discharge efficiencies under high electric fields. To address this long-standing problem, here we report the ferroelectric polymer networks exhibiting significantly reduced dielectric loss, superior polarization and greatly improved breakdown strength and reliability, while maintaining their fast discharge capability at a rate of microseconds. These concurrent improvements lead to unprecedented charge-discharge efficiencies and large values of the discharged energy density and also enable the operation of the ferroelectric polymers at elevated temperatures, which clearly outperforms the melt-extruded ferroelectric polymer films that represents the state of the art in dielectric polymers. The simplicity and scalability of the described method further suggest their potential for high energy density capacitors.
356 citations
TL;DR: In this paper, the authors report a novel strategy to improve the interface between the high dielectric constant nanoparticles (i.e., BaTiO3) and ferroelectric polymer.
Abstract: Polymer nanocomposites with high energy density and low dielectric loss are highly desirable in electronic and electric industry. Achieving the ability to tailor the interface between polymer and nanoparticle is the key issue to realize desirable dielectric properties and high energy density in the nanocomposites. However, the understanding of the role of interface on the dielectric properties and energy density of polymer nanocomposites is still very poor. In this work, we report a novel strategy to improve the interface between the high dielectric constant nanoparticles (i.e., BaTiO3) and ferroelectric polymer [i.e., poly(vinylidene fluoride-co-hexafluoro propylene)]. Core–shell structured BaTiO3 nanoparticles either with different shell thickness or with different molecular structure of the shell were prepared by grafting two types of fluoroalkyl acrylate monomers via surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. The dielectric properties and energy storage c...
318 citations
TL;DR: In this paper, a facile solvothermal route to synthesize reduced graphene oxide (RGO) nanosheets combined with surface modified γ-Fe2O3 colloidal nanoparticle clusters was reported.
Abstract: Graphene is highly desirable as an electromagnetic wave (EM) absorber because of its large interface, high dielectric loss, and low density. Nevertheless, the conductive and electromagnetic parameters of pure graphene are too high to meet the requirement of impedance match, which results in strong reflection and weak absorption. In this paper, we report a facile solvothermal route to synthesize reduced graphene oxide (RGO) nanosheets combined with surface-modified γ-Fe2O3 colloidal nanoparticle clusters. The obtained two-dimensional hybrids exhibit a relatively low EM reflection coefficient (RC) and wide effective absorption bandwidth, which are mainly attributed to the unique microstructure of colloidal nanoparticle clusters assembled on RGO. The nanoparticle clusters have more interfaces. The interfacial polarization within nanoparticle clusters and conductivity loss of RGO plays an important role in absorbing EM power. The minimum RC reaches −59.65 dB at 10.09 GHz with a matching thickness of 2.5 mm. T...
314 citations
TL;DR: The promise of aromatic, amorphous, polar polymers containing high dipolar moments with very low defect levels is demonstrated for future dielectric materials with ultrahigh electric-energy density, low loss at high applied fields, and ultrahigh breakdown strengths.
Abstract: The promise of aromatic, amorphous, polar polymers containing high dipolar moments with very low defect levels is demonstrated for future dielectric materials with ultrahigh electric-energy density, low loss at high applied fields, and ultrahigh breakdown strengths Specifically, aromatic polythiourea films exhibit an ultrahigh breakdown field (>1 GV m(-1)), which results in an energy density of ≈22 J cm(-3), as well as a low loss
267 citations
TL;DR: In this paper, a core@double-shell strategy was developed to prepare barium titanate (BT)-based high performance polymer nanocomposites, in which the first shell is hyperbranched aromatic polyamide (HBP) and the second shell is poly(methyl methacrylate) (PMMA).
Abstract: Polymer nanocomposites with high dielectric constant have extensive applications in the electronic and electrical industry because of ease of processing and low cost. Blending and in situ polymerization are two conventional methods for the preparation of polymer nanocomposites. However, the resulting nanocomposites, particularly highly filled nanocomposites, generally have some disadvantages such as high dielectric loss and low dielectric constant and thus show low energy density and low energy efficiency. Here we developed a core@double-shell strategy to prepare barium titanate (BT)-based high performance polymer nanocomposites, in which the first shell is hyperbranched aromatic polyamide (HBP) and the second shell is poly(methyl methacrylate) (PMMA). This method utilized the advantages of both polymer shells, resulting in superior dielectric property which cannot be achieved in nanocomposites prepared by the conventional blending methods. It is found that, compared with the conventional solution blended...
219 citations
TL;DR: In this article, homogeneous ceramics-polymer nanocomposites consisting of surface treated BaTiO3 (BT) particles as fillers and poly(vinylidene fluoride) polymer as matrix have been prepared using a solution casting process.
Abstract: In this work, homogeneous ceramics-polymer nanocomposites consisting of surface treated BaTiO3 (BT) particles as fillers and poly(vinylidene fluoride) polymer as matrix have been prepared using a solution casting process. The nanocomposites exhibit enhanced dielectric permittivity and reduced loss tangent. The frequency and temperature dependencies of the dielectric permittivity and loss tangent of the nanocomposites suggest that the introduced BT phase and interface areas contribute to the improvement of the dielectric responses. Meanwhile, the X-ray diffraction patterns and Differential Scanning Calorimetry (DSC) curves indicate that the incorporation of ceramic particles contributes to the decrease of the crystallite size, the increase of the crystallinity, and the shift of the crystallization temperature of the polymer matrix. Furthermore, the dielectric displacement and energy density of the nanocomposites are significantly enhanced and an energy density of 3.54 J/cm3 was obtained under an electric field of 200 MV/m with the BT concentration of 20 vol. %. The results indicate that the introduced ceramic fillers and interface areas have positive influences on the structure of the polymer matrix and contribute to the enhancement of the dielectric responses and energy storage properties of the nanocomposites.
210 citations
TL;DR: This strategy provides a new pathway to achieve CNT-based polymer composites with high dielectric performances for energy storage applications by designing and fabricated a new class of candidates composed of graphene oxide-encapsulated carbon nanotube (GO-e-CNT) hybrids.
Abstract: Polymer-based materials with a high dielectric constant show great potential for energy storage applications. Since the intrinsic dielectric constant of most polymers is very low, the integration of carbon nanotubes (CNTs) into the polymers provides an attractive and promising way to reach a high dielectric constant owing to their outstanding intrinsic physical performances. However, these CNT-based composites usually suffer from high dielectric loss, low breakdown strength and the difficulty to tailor the dielectric constant. Herein, we have designed and fabricated a new class of candidates composed of graphene oxide-encapsulated carbon nanotube (GO-e-CNT) hybrids. The obtained GO-e-CNT–polymer composites not only exhibit a high dielectric constant and low dielectric loss, but also have a highly enhanced breakdown strength and maximum energy storage density. Moreover, the dielectric constant of the composites can be tuned easily by tailoring the loading of GO-e-CNTs. It is believed that the GO shells around CNTs play an important role in realizing the high dielectric performances of the composites. GO shells can not only effectively improve the dispersion of CNTs, but also act as insulation barriers for suppressing leakage current and increasing breakdown strength. Our strategy provides a new pathway to achieve CNT-based polymer composites with high dielectric performances for energy storage applications.
178 citations
TL;DR: The fabrication and dielectric properties of a novel multi-component high-k composite system consisting of poly(vinylidene fluoride), surface-functionalized graphene nanosheets and BT nanoparticles (fRGO-BT/PVDF) were investigated in this article.
Abstract: The fabrication and dielectric properties of a novel multi-component high-k composite system consisting of poly(vinylidene fluoride), surface-functionalized graphene nanosheets and BT nanoparticles (fRGO–BT/PVDF) were investigated. The fRGO nanosheets were prepared through the π–π stacking of polyaniline and GO following in situ hydrazine reduction. The fRGO–BT/PVDF nanocomposites were fabricated by a solution casting and hot-pressing approach. SEM results confirm that fRGO and BT are well dispersed within the PVDF matrix. The dielectric properties of the binary fRGO/PVDF nanocomposites exhibit a typical percolation transition with the percolation threshold of 1.49 vol%. This type of nanocomposite, co-filled with conductive graphene nanosheets and high-k ceramics, shows a high kr (65) and a relatively low dielectric loss (tan δ = 0.35) at a high frequency of 1 MHz. Meanwhile, the dielectric properties of the fRGO–BT/PVDF nanocomposites show temperature independent behavior over a wide temperature range. These flexible, high-k fRGO–BT/PVDF nanocomposites are potential flexible dielectric materials for use in high-frequency capacitors and electronic devices.
TL;DR: This study is a new example of a fully dense material showing a low k value and having good thermo/mechanical properties and high thermostability.
Abstract: A non-porous and amorphous fluoropolymer PFN with low dielectric constant of 2.33 and dielectric loss less than 1.2 × 10(-3) is reported here. PFN also exhibits good mechanical properties and high thermostability. This study is a new example of a fully dense material showing a low k value and having good thermo/mechanical properties.
TL;DR: It is found that, by using the core-satellite structured Ag@BT nanoassemblies as fillers, the polymer nanocomposites can not only have higher discharged energy density but also have high energy efficiency.
Abstract: Dielectric polymer nanocomposites with high dielectric constant have wide applications in high energy density electronic devices. The introduction of high dielectric constant ceramic nanoparticles into a polymer represents an important route to fabricate nanocomposites with high dielectric constant. However, the nanocomposites prepared by this method generally suffer from relatively low breakdown strength and high dielectric loss, which limit the further increase of energy density and energy efficiency of the nanocomposites. In this contribution, by using core–satellite structured ultra-small silver (Ag) decorated barium titanate (BT) nanoassemblies, we successfully fabricated high dielectric constant polymer nanocomposites with enhanced breakdown strength and lower dielectric loss in comparison with conventional polymer–ceramic particulate nanocomposites. The discharged energy density and energy efficiency are derived from the dielectric displacement–electric field loops of the polymer nanocomposites. It is found that, by using the core–satellite structured Ag@BT nanoassemblies as fillers, the polymer nanocomposites can not only have higher discharged energy density but also have high energy efficiency. The mechanism behind the improved electrical properties was attributed to the Coulomb blockade effect and the quantum confinement effect of the introduced ultra-small Ag nanoparticles. This study could serve as an inspiration to enhance the energy storage densities of dielectric polymer nanocomposites.
TL;DR: Data indicate that significant reduction in leakage currents and dielectric losses and improvement in dielectrics breakdown strengths resulted when electropositive phenyl, electron-withdrawing functional groups were located at the polymer-particle interface.
Abstract: The interface between the polymer and the particle has a critical role in altering the properties of a composite dielectric Polymer-ceramic nanocomposites are promising dielectric materials for many electronic and power devices, combining the high dielectric constant of ceramic particles with the high dielectric breakdown strength of a polymer Self-assembled monolayers of electron rich or electron poor organophosphate coupling groups were applied to affect the filler–polymer interface and investigate the role of this interface on composite behavior The interface has potential to influence dielectric properties, in particular the leakage and breakdown resistance The composite films synthesized from the modified filler particles dispersed into an epoxy polymer matrix were analyzed by dielectric spectroscopy, breakdown strength, and leakage current measurements The data indicate that significant reduction in leakage currents and dielectric losses and improvement in dielectric breakdown strengths resulte
TL;DR: In this article, the effect of nano-Al 2 O 3 ceramic filler concentration on the composite structure and its electrical properties at a frequency and temperature ranges of 0-10 5 ǫ and 293-323 K, respectively, was studied.
TL;DR: In this article, solid polymer electrolytes based on poly(−)-caprolactone (PCL) with lithium bis(oxalato)borate as a doping salt were prepared by solution cast technique using DMF as a solvent.
Abstract: In this work, solid polymer electrolytes based on poly(ɛ-caprolactone) (PCL) with lithium bis(oxalato)borate as a doping salt were prepared by solution cast technique using DMF as a solvent. The electrical DC conductivity and dielectric constant of the solid polymer electrolyte samples were investigated by electrochemical impedance spectroscopy over a frequency range from 50 Hz to 1 MHz. It was found that the DC conductivity increased with increase in the salt concentration to up to 4 wt% and thereafter decreased. Dielectric constant versus salt concentration was used to interpret the decrease in DC conductivity with increase in salt concentration. The DC conductivity as a function of temperature follows Arrhenius behavior in low temperature region, which reveals that ion conduction occurs through successful hopping. The curvature of DC conductivity at high temperatures indicates the contribution of segmental motion to ion conduction. High values for dielectric constant and dielectric loss were observed at low frequencies. The plateau of dielectric constant and dielectric loss at high frequencies can be observed as a result of rapid oscillation of the AC electric field. The HN dielectric function was utilized to study the dielectric relaxation. The experimental and theoretical data of dielectric constant are very close to each other at low temperatures. At high temperatures, the simulated data are more deviated from the experimental curve of dielectric constant due to the dominance of electrode polarization. The non-unity of relaxation parameters (α and β) reveals that the relaxation processes in PCL-based solid electrolyte is a non-Debye type of relaxation.
TL;DR: In this paper, the transverse piezoelectric coefficient e31,f of Al1-xScxN thin films was investigated as a function of composition, and the thickness strain response (d33,f) was found to increase proportionally to the ionic part of the dielectric constant.
Abstract: The transverse piezoelectric coefficient e31,f of Al1-xScxN thin films was investigated as a function of composition. It increased nearly 50% from x = 0 to x = 0.17. As the increase of the dielectric constant was only moderate, these films are very suitable for energy harvesting, giving a 60% higher transformation yield (x = 0.17) as compared to pure AlN. A higher doping might even lead to a 100% augmentation. The thickness strain response (d33,f) was found to increase proportionally to the ionic part of the dielectric constant. The e-type coefficients (stress response), however, did not augment so much as the structure becomes softer. As a result, the transverse voltage/strain response (h31,f-coefficient) was raised only slightly with Sc doping. The low dielectric loss obtained at all compositions suggests also the use of Al1−xScxN thin films in sensors.
TL;DR: In this article, the structural features of the aluminum substituted barium hexagonal ferrite particles BaAlxFe12−xO19 with 0≤x≤3.5 which were prepared by the solid state reaction method have been studied.
Abstract: Various parameters in the structural features of the aluminum substituted barium hexagonal ferrite particles BaAlxFe12−xO19 with 0≤x≤3.5 which were prepared by the solid state reaction method have been studied. The infrared transmission spectrum was measured in the wave number region 5000–200 cm−1 at room temperature. The results were interpreted in terms of the vibrations of the isolated molecular units in such a way to preserve the tetrahedral and octahedral clusters of metal oxides in the barium aluminum hexagonal ferrites. The infrared features are assigned to Fe–O and Ba–O bonds in M-type hexagonal ferrite (BaFe12O19) molecules. Also, the results explain the structural model, based on the effect of aluminum substitution “Al–O bond”. On the other hand, the magnetic behavior of the samples was studied using the vibrating sample magnetometer technique. The saturation magnetization (Ms) and magneton number (nB) decrease with increasing Al3+ substitution from 61.2 to 28.9 emu/g and from 12.2 to 5.3 µB respectively. Also, all samples were characterized using X-ray diffraction and the values of grain size, microstrain and dislocation density of all samples were calculated. The dielectric parameters and ac conductivity measurements were performed within a temperature range 293–493 K. The ac conductivity showed a linear relation with the frequency power law with an exponent s≈0.69–0.14 for BaFe12O19. It decreases with increasing temperature, indicating that the heterogeneous structures increase. While the dielectric constant (e′) and the dielectric loss (e″) decrease with increasing Al substitution.
TL;DR: In this article, X-ray diffraction and Raman spectroscopy reveals that all the ferrite samples are in single-phase with tetragonal structure for CFO and cubic spinel structure for CMFO samples.
TL;DR: In this article, the effects of substituting different cations (Mn, Zn, Mg and Co) at the A-site of AZrNb2O8 compounds on structural parameters such as packing fraction and B-site octahedral distortion were studied using X-ray powder diffraction in conjunction with Rietveld refinement.
TL;DR: Barium hexaferrites with general chemical formula BaFe 12−2 x Mg x Ti x O 19 ( x = 0, 1, 1.5, 2) were synthesized by the solid state diffusion method as discussed by the authors.
TL;DR: In this article, the effect of annealing temperature on the microstructure, phase composition, dielectric and wave-absorbing properties of ceramics was investigated, and it was shown that nano-sized SiC grains were formed in amorphous SiBCN, and the content and crystallization degree of SiC gradually intensified with annaling temperature increasing.
Abstract: Polymer derived SiBCN ceramics (PDCs-SiBCN) were prepared from polyborosilazane and then annealed at 1200–1800 °C in N 2 . Effects of annealing temperature on the microstructure, phase composition, dielectric and wave-absorbing properties of ceramics were investigated. Results showed that nano-sized SiC grains were formed in amorphous SiBCN after annealing and the content and crystallization degree of SiC gradually intensified with annealing temperature increasing. The permittivity, dielectric loss and electrical conductivity of PDCs-SiBCN gradually increased as the temperature rose due to the formation of conductivity network of SiC grains and the increase of nano-grain boundary. The increased content of SiC (as the dipole) and interface between SiC nano-grains and amorphous SiBCN phase led to a higher polarization ability and higher dielectric loss. The RC gradually decreased with the annealing temperature increasing, demonstrating the annealed ceramics had the superior wave-absorbing ability and high annealing temperature was conducive to the improvement of wave-absorbing property.
TL;DR: In this article, a polyvinylidene fluoride-carbonyl iron powder (PVDF-CIP) composites with different carbonyl-iron powder loading were developed for electromagnetic interference shielding applications in the X band.
TL;DR: In this article, double-layer materials with one layer being a polyethylene (PE) film and the other layer a multi-wall carbon nanotube (MWCNT)/cyanate ester (CE) resin composite, PE-MWCnt/CE, were prepared.
TL;DR: In this paper, the dielectric permittivity increased 10-fold at 10−2 Hz for RGO compared to EG filled composites at 5 wt% loading while preserving low deformation due to reducing polarization process to screen charge movement.
TL;DR: The realism of single phase cubic spinel creation of the synthesized ferrite samples was studied by the DTA-TGA, XRD, SEM, EDX, FT-IR, VSM and dielectric measurements.
TL;DR: In this paper, the effects of La3+ doping on the density, phase structure, morphology, dielectric and ferroelectric properties of multiferroic Bi1−xLaxFeO3 ceramics were investigated.
TL;DR: In this paper, a functional structure of Mn0.5Zn0.4 on polyaniline nanocomposites with high dielectric absorbing properties and electromagnetic shielding effectiveness at low frequencies was successfully fabricated through a facile in situ emulsion polymerization.
Abstract: A functional structure of Mn0.5Zn0.5Fe2O4-on-polyaniline nanocomposites with high dielectric absorbing properties and electromagnetic shielding effectiveness at low frequencies was successfully fabricated through a facile in situ emulsion polymerization. Polyaniline (PANI) was doped with hydrochloric acid to improve its electrical properties and interactions with ferrite nanoparticles. The electrostatic force, paramagnetic force and hydrogen bonding strongly bonded or assembled ferrite nanoparticles on the polyaniline surface and improved the thermal stability of the polyaniline nanostructure. Polyaniline nanofibers were found to have an average diameter of 100 nm and length of 500 nm, consisting of a bundle of smaller individual units, whereas ferrite nanoparticles were of spherical shape with an average diameter 30 nm. The research findings show that ferrite particles overcome the common problem of aggregation and evenly dispersed on the surface of polyaniline. The ferrite-grafted polyaniline nanostructures were demonstrated as a promising functional material for the absorbing of electromagnetic microwaves because of a large amount of dipole polarizations in the polymer backbone and at the interfaces of the ferrite nanoparticles and polyaniline nanofibers. Both the complex permittivity and shielding effectiveness of the ferrite-grafted polyaniline nanocomposites increased with the increasing weight percentage of PANI. There is also a good match of real and imaginary parts of the complex permittivity, giving rise to almost an equal dielectric loss angle tangent in the measured frequency (30 MHz to 1 GHz). This superior property allows the nanocomposites to function within an extended absorbing band.
TL;DR: A monofrequent dielectric model for moist soils taking into account dependences on the temperature and texture is proposed, in the case of an electromagnetic frequency equal to 1.4 GHz.
Abstract: In this letter, a monofrequent dielectric model for moist soils taking into account dependences on the temperature and texture is proposed, in the case of an electromagnetic frequency equal to 1.4 GHz. The proposed model is deduced from a more general model proposed by Mironov and Fomin (2009) that provides estimations of the complex relative permittivity (CRP) of moist soils as a function of frequency, temperature, moisture, and texture of soils. The latter employs the physical laws of Debye and Clausius-Mossotti and the law of ion conductance to calculate the CRP of water solutions in the soil. The parameters of the respective physical laws were determined by using the CRPs of moist soils measured by Curtis (1995) for a wide ensemble of soil textures (clay content from 0% to 76%), moistures (from drying at 105 °C to nearly saturation), temperatures (10 °C -40 °C), and frequencies (0.3-26.5 GHz). This model has standard deviations of calculated CRPs from the measured values equal to 1.9 and 1.3 for the real and imaginary parts of CRP, respectively. In the model proposed in this letter, the respective standard deviations were decreased to the values of 0.87 and 0.26. In addition, the equations to calculate the complex dielectric permittivity as a function of moisture, temperature, and texture were represented in a simple form of the refractive mixing dielectric model, which is commonly used in the algorithms of radiometric and radar remote sensing to retrieve moisture in the soil.
TL;DR: In this article, the dielectric parameters of Ni-doped nanocrystalline cobalt ferrite samples have been studied at room temperature in the frequency range 42 Hz−5MHz and is explained in the light of interfacial polarization arising from the heterogeneous nature of ferrite structure.