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[IEEE 2018 18th International Symposium on Antenna Technology and Applied Electromagnetics (ANTEM) - Waterloo, ON (2018.8.19-2018.8.22)] 2018 18th International Symposium on Antenna Technology and Applied Electromagnetics (ANTEM) - Cavity Perturbation Technique to Characterize Dielectric Materials at Ka-band
摘要： The characterization of permittivity and dielectric loss of dielectric materials using a perturbation technique is conducted in simulation. The working frequency of this technique has been extended to the Ka-band. Simulation results demonstrate this perturbation technique is suitable for characterization of high permittivity dielectric materials for mm-wave and maintains good accuracy.
关键词： dielectric loss measurement,permittivity measurement,cavity perturbation technique,dielectric materials,Ka-band
更新于2025-09-23 15:23:52
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Crystal growth and characterization of γ-glycine grown from AgSO4 for nonlinear optical applications
摘要： In the present work 0.1 M to 0.5 M proportions of silver sulphate (AgSO4) added glycine single crystals were grown by slow solvent evaporation method. The Powder XRD study confirms that the grown crystals have γ-glycine crystal structure and it crystallizes into a hexagonal structure with a non-centrosymmetric space group of P31. The dielectric constant and dielectric loss of grown crystal was carried out as a function of frequency and the results were discussed. The positive photoconducting nature of the grown crystals was studied by the photoconductivity study. Second harmonic generation (SHG) efficiency of the grown γ-glycine crystal was assessed by using Nd: YAG laser. The results confirms that the grown crystals have higher efficiency compared to the reference (KDP) crystal.
关键词： B2. Dielectric Materials,A1. X-ray diffraction,A1. Crystal structure,B2. Nonlinear optic materials
更新于2025-09-23 15:23:52
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A CSRR-Based Sensor for Full Characterization of Magneto-Dielectric Materials
摘要： In this paper, a novel complementary split-ring resonator (CSRR)-based sensor for full characterization of magneto-dielectric materials is proposed. In general, the operation of microwave resonance-based sensor hinges on the shift in the resonance frequency and the change in the quality factor of the loaded structure. However, both the electric permittivity and the magnetic permeability of the material under test (MUT) have similar effect on the response of the sensor that makes the simultaneous determination of the permittivity and permeability challenging. To remove this difficulty, the main idea behind this paper is to localize the highest intensity of the electric and magnetic fields in two separate zones. By the analysis of the measured resonance frequency and quality factor, the real and imaginary parts of the electric permittivity and the magnetic permeability of the MUT can be determined. Although the characterization of the permittivity and permeability of materials using split-ring resonator and CSRR-based sensors has been widely used, to the best of our knowledge, the full characterization of magneto-dielectric materials using a single sensor has not yet been reported in this paper. As a proof of concept, the sensor was fabricated and used to measure the permittivity and permeability of several materials. Strong agreement between the extracted values and the reference data was achieved.
关键词： sensor,Complementary split ring resonator (CSRR),material characterization,split ring resonator (SRR),magneto-dielectric materials,permittivity and permeability
更新于2025-09-23 15:23:52
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Thermal analysis and crystal growth of doped Nb2O5
摘要： The systems Nb2O5–Ta2O5 and Nb2O5–V2O5 were investigated using thermal analysis, X-ray powder diffraction and thermodynamic simulations. Solid solution formation is possible for both systems; furthermore, both contain one intermediate compound, VNb9O25 or Ta2Nb4O15, respectively. Phase relationships for pure niobium(V)-oxide and tantalum(V)-oxide were studied under ambient pressure. It was found that both compounds can occur in two stable solid modifications. For niobium(V)-oxide this are the monoclinic high-temperature modification (H-Nb2O5) and an orthorhombic low-temperature modification (T-Nb2O5) and for tantalum(V)-oxide a tetragonal high-temperature form (α-Ta2O5) and an orthorhombic low-temperature form (β-Ta2O5). Based on these results, crystal growth experiments with various compositions from both systems were carried out using the optical floating zone (OZF) technique.
关键词： B2. dielectric materials,A2. growth from melt,A1. doping,A1. phase diagrams,B1. niobates
更新于2025-09-23 15:23:52
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Lead-free Ag <sub/> 1-3 <i>x</i> </sub> La <sub/><i>x</i> </sub> NbO <sub/>3</sub> Antiferroelectric Ceramics with High Energy Storage Density and Efficiency
摘要： Environmentally benign lead-free bulk ceramics with high recoverable energy density (Wrec) are very attractive in advanced pulsed power capacitors. In this work, composition engineering was adopted by La3+ modification to improve the energy storage performance of Ag1-3xLaxNbO3 ceramics. It was found the antiferroelectric (AFE) phase was stabilized after La3+ substitution, as a result of the reduced tolerance factor t. Significant improvement of Wrec and energy storage efficiency (η) were achieved with value of 3.12 J/cm3 and 0.63 for x=0.02 at an electric field of 230 kV/cm, more than 1.5 times the value of pure AgNbO3 (Wrec=1.9 J/cm3, η=0.40). The excellent energy storage properties are resulted from the increased antiferroelectric-ferroelectric phase transition electric field (EF), ferroelectric-antiferroelectric phase transition electric field (EA) and breakdown electric field (Eb). The enhanced Eb was ascribed to the decreased grain size and increased electrical resistivity upon La3+ modification. The feature makes Ag1-3xLaxNbO3 a potential candidate for energy storage applications.
关键词： energy storage,ferroelectricity/ferroelectric materials,lead-free ceramics,dielectric materials/properties
更新于2025-09-23 15:22:29
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Characterization of the lossy dielectric materials using contour mapping
摘要： The imaginary part of the complex permittivity of a lossy dielectric material is large and couples with its real part. The resonant frequency of a cavity with the sample depends not only on the real part of the complex permittivity of the sample but also the imaginary part, resulting in serious ambiguity in determining the sample’s complex permittivity. This work proposes a contour mapping method to determine the complex permittivity. The full-wave simulation gives us the contours of the resonant frequency and the quality factor, which are functions of the relative dielectric constant and the loss tangent. By mapping the measured resonant frequency and the measured quality factor, one can uniquely determine the complex permittivity of the sample. Five liquids were examined, including three low-loss materials for benchmarking and two lossy materials. The measured complex permittivities of the three low-loss materials agree very well with the other methods. As for the lossy materials, the measured relative dielectric constant and the loss tangent of alcohol are 6.786 and 0.895, respectively. Besides, the measured dielectric constant of glycerin is 6.811, and its loss tangent is 0.562. The proposed contour mapping technique can be employed to measure the complex permittivity of liquids and solids from lossless to lossy materials.
关键词： lossy dielectric materials,resonant frequency,contour mapping,complex permittivity,quality factor
更新于2025-09-23 15:21:21
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Spatial Retrieval of Broadband Dielectric Spectra
摘要： A broadband soil dielectric spectra retrieval approach (1 MHz–2 GHz) has been implemented for a layered half space. The inversion kernel consists of a two-port transmission line forward model in the frequency domain and a constitutive material equation based on a power law soil mixture rule (Complex Refractive Index Model—CRIM). The spatially-distributed retrieval of broadband dielectric spectra was achieved with a global optimization approach based on a Shuffled Complex Evolution (SCE) algorithm using the full set of the scattering parameters. For each layer, the broadband dielectric spectra were retrieved with the corresponding parameters thickness, porosity, water saturation and electrical conductivity of the aqueous pore solution. For the validation of the approach, a coaxial transmission line cell measured with a network analyzer was used. The possibilities and limitations of the inverse parameter estimation were numerically analyzed in four scenarios. Expected and retrieved layer thicknesses, soil properties and broadband dielectric spectra in each scenario were in reasonable agreement. Hence, the model is suitable for an estimation of in-homogeneous material parameter distributions. Moreover, the proposed frequency domain approach allows an automatic adaptation of layer number and thickness or regular grids in time and/or space.
关键词： soil measurements,electromagnetic scattering inverse problems,dielectric measurements,modeling,microwave propagation,dielectric materials
更新于2025-09-23 15:21:01
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Giant Dielectric Constant and Tunable Phase-Transition Characteristics of ZnF <sub/>2</sub> /BaF <sub/>2</sub> -Modified BaTiO <sub/>3</sub> Thick Films
摘要： High performance capacitors have been investigated to meet higher integration density with optimized charge-storing capability. Here we introduce nonconventional thick film dielectric compositions based on 95BaTiO3-xZnF2-(2-x)BaF2-3glass (x=0.5, 1.0 and 1.5) where the relative content of ZnF2/BaF2 is critical in controlling dielectric behavior. The thick films were prepared on Cu foils by regular screen-printing and then firing at 950oC in inert atmosphere. As an optimal example, thick film composition modified with 1.0ZnF2/1.0BaF2 exhibited a dielectric constant of ~1,903 and a dielectric loss of ~0.04 at 1 MHz with dispersive dielectric relaxation behavior, which are far better than any reported corresponding values so far. Particularly, it was very interesting to observe that Curie Temperature was tunable from -19 oC to +34 oC, depending on the relative content of fluoride additives only within the 2 mol% range. Dependency of the relative contents of the fluorides is primarily investigated in regard to microstructure and dielectric properties.
关键词： dielectric materials/properties,printing,titanates
更新于2025-09-23 15:21:01
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Core–shell structured poly(vinylidene fluoride)- <i>grafted</i> -BaTiO <sub/>3</sub> nanocomposites prepared <i>via</i> reversible addition–fragmentation chain transfer (RAFT) polymerization of VDF for high energy storage capacitors
摘要： Core–shell structured poly(vinylidene fluoride)-grafted-barium titanate (PVDF-g-BaTiO3) nanocomposites were prepared by surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization of VDF from the surface of functionalized BaTiO3 nanoparticles. The ceramic fillers were first surface-modified with xanthate functions to further allow the RAFT grafting of VDF. A series of structured core shells were synthesized by tuning the feed [initiator functionalized nanoparticles]0 : [monomer]0 ratio, varying from 3 to 5, 10 and 20 wt%. Fourier transform infrared spectroscopy (FTIR), high resolution magic angle spinning (HRMAS) NMR and thermogravimetric analysis (TGA) confirmed the successful surface functionalization of the ceramic filler and the grafting of the PVDF shell onto the surface of the BaTiO3 cores. Transmission electron microscopy results revealed that BaTiO3 nanoparticles are covered by thin shells of PVDF, with thickness varying from 2.2 to 5.1 nm, forming a core–shell structure. HRMAS 19F indicated a grafting of 39–50 units of VDF. X-ray diffraction measurements together with FTIR measurements revealed that PVDF was present in the α form. Thermal properties also indicated that the addition of a small amount of the BaTiO3 filler to the PVDF matrix increased the melting temperature from 168 °C for neat PVDF to 173 °C for PVDF-g-BaTiO3 (20 wt%) and decreased the crystallinity of PVDF from 47% to 21%.
关键词： Nanocomposites,Core-Shell Structure,BaTiO3,PVDF,RAFT Polymerization,Polymer Chemistry,Dielectric Materials
更新于2025-09-19 17:15:36
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Additively Manufactured Dielectric Waveguides for Advanced Concepts for Millimeter-Wave Interconnects
摘要： Technology mega trends, such as autonomous driving, multiple-input multiple-output (MIMO), or multi-gigabit communication, drastically increase the demand for ultra-broadband millimeter-wave (mmW) transmission line technologies. A broadband and robust signal and data transmission between components and modules at low cost is a mandatory requirement to ensure high-performance functionality of advanced communication and radar systems. Dielectric waveguides (DWGs) are a highly suitable technology to meet these requirements due to their outstanding transmission capabilities for mmW signals coupled with their high flexibility, low weight, and low cost. Additive manufacturing (AM) processes based on dielectric materials open up new perspectives for fully automated wiring of mmW modules and systems, and they enable cost-efficient application-specific solutions. In this article, we propose novel printed DWG designs with optimized transmission performance. Measurement results of different DWG designs demonstrate the excellent functionality of the proposed transmission line and interconnection concepts. These results and the shown resiliency and practicality of the presented approaches illustrate attractive opportunities for new interconnect technologies based on new manufacturing processes.
关键词： transmission line measurements,Dielectric materials,millimeter-wave (mmW) measurements,waveguides (WGs)
更新于2025-09-16 10:30:52