Showing papers on "Dielectric loss published in 1985"
TL;DR: In this paper, a technique for measuring the effective surface resistance R/sub s/ of the conducting plates is proposed to allow the accurate measurement of the loss tangent tan delta.
Abstract: Improvements both in accuracy and speed are described for the technique of measuring the microwave dielectric properties of low-loss materials by using a dielectric rod resonator short-circuited at both ends by two parallel conducting plates. A technique for measuring the effective surface resistance R/sub s/ of the conducting plates is proposed to allow the accurate measurement of the loss tangent tan delta. By means of the first-order approximation, the expressions are analytically derived for estimating the errors of the measured values of relative permittivity epsilon/sub r/, tan delta, and R/sub r/, for measuring the temperature coefficient of epsilon/sub r/, and for determining the required size of the conducting plates. Computer-aided measurements are realized by using these expressions. It is shown that the temperature dependence of R/sub s/, should be considered in the tan delta measurement. The copper plates used in this experiment have the relative conductivity of 91.0+-2.7 percent at 20°C, estimated from the measured R/sub s/ value. For a 99.9-percent alumina ceramic rod sample, the results measured at 7.69 GHz and 25°C show that epsilon/sub r/,= 9.687+-0.003 and tan delta = (1.6+-0.2)x 10/sup -5/. The temperature coefficients measured between 25 and 100°C are 112x10/sup -6//°C for epsilon/sub r/, and 23x10/sup -4//°C for tan delta.
605 citations
TL;DR: A review of the dielectric loss spectra of polymers at microwave frequencies has been carried out in this paper, where a large volume of data for low loss polymers (polyethylene, polypropylene and poly(tetrafluoroethylene)), which are used in the communications industry, was available for review.
159 citations
153 citations
01 Jan 1985
TL;DR: In this paper, the authors compared the Mach-Zehnder-IMPATT spectrometer with the openresonator and compared the open-resonators with a polarizing interferometer, showing that the dielectric loss increases with frequency in the millimeter.
Abstract: It is no longer necessary to use extrapolated microwave dielectric values when designing millimeter-wave components and systems. Very recently, highly accurate millimeter-wave (5- to 1/2-mm) data on complex dielectric permittivity and loss tangent have become available to engineers for a variety of materials such as common ceramics, semiconductors, crystalline, and glass materials. One quasi-optical measurement method has proved to be most accurate and reproducible, namely, dispersive Fourier transform spectroscopy (DFTS) applied to a polarizing interferometer. The openresonator method and the Mach-Zehnder-IMPATT spectrometer will also be described and compared. The fact that the dielectric loss increases with frequency in the millimeter, unlike the microwave, is an important feature of these data. Reliable measurements also reveal that the methods of preparation of nominally identical specimens can change the dielectric losses by a factor of three.
128 citations
TL;DR: In this paper, the authors compare des temps de relaxation for les deux processus, i.e., mode normal, mode segmental, and mode normal (mode segmental).
Abstract: Relaxation dielectrique due a la fluctuation de la distance bout a bout appelee «mode normal» et une autre due au mode segmental. Comparaison des temps de relaxation pour les deux processus
119 citations
TL;DR: Si3N4 is a suitable material for high temperature radome applications because of its good thermomechanical and dielectric properties The process parameters employed in pressureless sintering to obtain high density material were investigated as discussed by the authors.
117 citations
TL;DR: In this paper, the dielectric constants and loss tangents of tetravalent titanium-substituted Ni-Zn ferrites were measured at room temperature in the frequency range 100 Hz -500 kHz.
Abstract: The dielectric constants and dielectric loss tangents of tetravalent titanium-substituted Ni-Zn ferrites Zn 0.25 Ni 0.75 + t Ti t Fe 2−2 t O 4 with various titanium concentrations were measured at room temperature in the frequency range 100 Hz – 500 kHz. The variation of these parameters with composition and frequency is explained qualitatively. Peaks in the dielectric loss tangent versus frequency curves are observed in two of the ferrites. The possible mechanisms are discussed.
99 citations
TL;DR: In this paper, two approaches due to the complex frequency and to the perturbation theory are described to compute accurately the Q-factors of the circularly-symmetric TEO modes for dielectric rod resonators placed between two parallel conductor plates and in a conductor cavity.
Abstract: Two approaches due to the complex frequency and to the perturbation theory are described to compute accurately the Q-factors of the circularly-symmetric TEO modes for dielectric rod resonators placed between two parallel conductor plates and in a conductor cavity. These techniques allow us to estimate separately the Q-factors due to radiation, conductor, and dielectric losses from only the computation of resonant frequencies by means of the mode-matching method. Validity of the theories is verified by experiments. The influence of the conductor shields on the Q-factors is discussed from the computed results. A possibility of realizing high-Q dielectric resonators is suggested.
83 citations
TL;DR: In this article, the dielectric properties of a sheet-like polymer of copper-phthalocyanine have been studied at 1, 5 and 10 kHz in the temperature range 30-240°.
68 citations
TL;DR: In this paper, complex refractive index and complex dielectric permittivity and loss tangent data for polyethylene, polypropylene, poly-4 methyl-perrtene1 (TPX), and polytetrafluorethylene (Teflon) are presented over the frequency range 60-300 GHz.
Abstract: Complex refractive index and complex dielectric permittivity and loss tangent data for polyethylene, polypropylene, poly-4 methyl-perrtene1 (TPX), and polytetrafluorethylene (Teflon) are presented over the frequency range 60-300 GHz. All of these nonpolar polymers are extremely low-loss materials. As in the microwave region, polyethylene demonstrates exceptionally low-loss characteristics in the entire millimeter-wave region. Polar polymers such as nylon and plexiglass exhibit much higher absorption (nearly an order of magnitude higher) loss compared to nonpolar polymers.
41 citations
TL;DR: In this paper, the volume current method was used to calculate the radiation loss of dielectric waveguide Y-branch structures in the power-dividing mode, obtaining proper zero loss in the limit of the zero branching angle.
Abstract: Volume current method is used to calculate the radiation loss of dielectric waveguide Y-branch structures. Radiation loss of a Y-branch in the power-dividing mode of operation is calculated accurately for the first time, obtaining proper zero loss in the limit of the zero branching angle. Radiation loss of a Y-branch with parallel output guides is calculated and compared to the loss of a three guide coupler-divider; the Y-branch has smaller loss. Simple analytical formulas are given for approximate loss calculation in these structures.
TL;DR: In this paper, a two-layer model was used to explain the properties of the materials in terms of a two layer model and the observed behaviour was attributed to cluster formation at the grain boundaries.
Abstract: Zinc-substituted lithium ferrites Li 0.5− z 2 Zn z Fe 2.5− z 2 O 4 with z varying from 0 to 0.7 were prepared. Small amounts of bismuth oxide were used to reduce the sintering temperature. In dense materials prepared in this way Bi 2 O 3 segregates at grain boundaries and the grains consist of only the basic ferrite. Electrical properties such as the resistivity, the dielectric constant and the loss factor were measured over a wide frequency range. The parameters obtained at direct current and high frequencies were used to explain the properties of the materials in terms of a two-layer model. In samples with z > 0.4 the observed behaviour was attributed to cluster formation at the grain boundaries.
TL;DR: In this article, the dielectric constant of mixed Mn-Mg ferrites of various compositions was measured at room temperature in the frequency range 10 3 -10 5 Hz using a capacitance bridge.
Abstract: The dielectric constant and dielectric loss tangent of mixed Mn-Mg ferrites of various compositions were measured at room temperature in the frequency range 10 3 –10 5 Hz using a capacitance bridge. A qualitative explanation is given for the composition and frequency dependence of the dielectric constant. The dielectric constant for these mixed ferrites is approximately inversely proportional to the square root of the resistivity.
TL;DR: In this paper, a charge transfer theory for fully oxidized polypyrrole is described, which gives an excellent account of the temperature dependence, carrier density dependence, and magnitude of electrical conductivity.
Abstract: Experimental electrical conductivity and optical absorption data are presented for fully oxidized polypyrrole. A charge transfer theory is described which gives an excellent account of the temperature dependence, carrier density dependence, and magnitude of electrical conductivity. The reorganization energy calculated from the temperature dependence of conductivity, 0.23 eV, is in good agreement with the value obtained from the near IR dielectric loss spectrum, ∼0.25 eV. Self‐consistent hopping distances of about 5–10 A are obtained from the reorganization energy, conductivity preexponential factor, and carrier density. Hopping between localized sites associated with the counteranion is indicated.
TL;DR: In this paper, the dielectric loss tangent is nearly constant at 0.5 to 1.0 percent over the frequency range from 1 to 100 kHz, and the dc resistivity is above 10 to the 13th ohm cm.
Abstract: Metal-carbon-metal structures were fabricated using either gold or aluminum evaporated electrodes and RF plasma (methane) deposited 'diamondlike' carbon films. Alternating-current conductance and capacitance versus voltage and frequency (10 Hz to 13 MHz) data were taken to determine the dielectric properties of these films. Conductance versus frequency data fit a generalized power law, consistent with both dc and hopping conduction components. The capacitance versus frequency data are well matched to the conductance versus frequency data, as predicted by a Kramers-Kronig analysis. The dielectric loss tangent is nearly constant at 0.5 to 1.0 percent over the frequency range from 1 to 100 kHz. The dc resistivity is above 10 to the 13th ohm cm, and the dc breakdown strength is above 8 x 10 to the 6th V/cm is properly prepared samples.
TL;DR: In this paper, temperature characteristics for multilayer piezoelectric ceramic actuator have been investigated and the authors suggest that a main origin for a temperature rise is dielectric loss.
Abstract: Temperature characteristics for multilayer piezoelectric ceramic actuator have been investigated. Thermal expansion coefficient with DC 150 V application is negative, -6×10-6/°C, at 20°C. Between 0°C and 100°C, an available net displacement under DC 150 V is less changed, within 5%. Temperature rise and dissipation power due to dielectric loss were observed while driving at 0.3~1.5 kHz. They are about 70°C and 0.7 J/sec at 1.5 kHz, with 150V peak voltage, respectively. The results suggest that a main origin for a temperature rise is dielectric loss.
TL;DR: In this article, the Rayleigh-Ritz method is used to calculate the resonant frequencies and intrinsic Q factors due to dielectric losses of quasi TE/sub onm/ modes of dielectrics.
Abstract: The Rayleigh-Ritz method is described, which is used to calculate the resonant frequencies and intrinsic Q factors due to dielectric losses of quasi TE/sub onm/ modes of dielectric resonators. Electromagnetic fields of an auxiliary post dielectric resonator are taken as an electrodynamics basis for approximate solutions of this problem. The method provides upper bounds for true resonant frequencies. Numerical results are compared with previously published complementary calculations. The influence of a dielectic substrate on resonant frequencies and intrinsic Q values is demonstrated.
TL;DR: In this paper, the complex permittivity of aqueous solution of dipolar solutes has been measured as a function of frequency between 1 MHz and 40 GHz, and a relaxation spectral function based on a model of the solutions has been fitted to the measured frequency dependence.
TL;DR: In this article, deux polyarylates nitrile ayant des groupes d'espace differents (CH 2 ) 2 ou ( CH 2 ) 6 ] were compared.
Abstract: Comparaison de deux polyarylates nitrile ayant des groupes d'espace differents [(CH 2 ) 2 ou (CH 2 ) 6 ]
TL;DR: In this article, the authors used dielectric relaxation techniques to better understand the behavior of defects that affect the frequency stability of α-quartz crystals and found that α:β equilibrium is frozen-in below 300 K and can be varied, by heat treatment.
TL;DR: The dipole moments of the oxides from benzophenone and dibenzosurberone are 4.0 and 3.8 D, respectively as discussed by the authors, which is the best known dipole moment for carbenes.
TL;DR: In this paper, temperature variation of the dielectric permittivity, refractive indices, birefringence, density and order parameter of nematic liquid crystalline mixtures 1333, RO-TN 605, 2855, E-43 and ZLI-1565 are reported.
Abstract: Temperature variation of the dielectric permittivity, refractive indices, birefringence, density and order parameter of nematic liquid crystalline mixtures 1333, RO-TN 605, 2855, E-43 and ZLI-1565 are reported. The dielectric studies are in the frequency range 1 KHz to 3.5 MHz. The dielectric permittivity component parallel to the director (e′‖) exhibits relaxation in the radio frequency region. Two dielectric loss peaks are observed in these mixtures except ZLI-1565, which has only one peak. The two peaks are due to the presence of widely different size molecules in these mixtures while in case of ZLI-1565, one peak may be due to molecules having nearly same size.The birefringence of ZLI-1565 is found to be low as compared with other mixtures. The values of order parameter evaluated by using Vuk's and Neugeabauer's approach are found to be nearly the same for these mixtures.
TL;DR: In this paper, the Williams-Watts relaxation function φα(t)=exp(exp(t/τ)α] [−(0)−e(∞) ) is estimated from dielectric loss data.
Abstract: There are many polymeric materials whose dielectric properties can be derived from the Williams–Watts relaxation function φα(t)=exp [−(t/τ)α] . In this paper we propose a method for estimating the parameters α, τ, and e(0)−e(∞), from dielectric loss data. In contrast to earlier techniques the parameters can be estimated one at a time. Simple approximations to the required functions are given accurate to better than 1%.
01 Aug 1985-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, an internal heating effect was discovered during the electrochemical etching of some polymeric dosimeters such as polycarbonate (PC) and allyl diglycol carbonate (CR-39) employing a new multi-chamber ECE system capable of etching a large number of foils separately using small-volume chambers in parallel.
Abstract: An “internal heating effect” was discovered during the electrochemical etching (ECE) of some polymeric dosimeters such as polycarbonate (PC) and allyl diglycol carbonate (CR-39) employing a new multi-chamber ECE system capable of etching a large number of foils separately using small-volume chambers in parallel. The rate of heating is high enough to raise the etchant temperature significantly in a short period of time, e.g. from 25°C to 47°C in 20 min in CR-39. The rate of heating was smaller in polycarbonate. This heating effect was experimentally and theoretically investigated and discussed to be due to the “dielectric loss” in the polymer. The rate of heating is proportional to the polymer loss index (ϵ′ tan δ), square of field strength, and frequency. Significant dimensional changes found in the foils, especially at high field strengths, were discussed to be due to the “electrostriction” phenomenon. In this paper, the results on the above findings and the effects of parameters are reported and discussed with a hope to partially understand some unknowns and to stimulate further research on the ECE mechanisms.
TL;DR: In this paper, a computer program was developed to analyse TSDC relaxation peaks, taking dipole-dipole interactions into account Relaxation parameters and dipole concentrations are presented, and extrapolates to the high-temperature conductivity determined previously with impedance spectroscopy.
TL;DR: In this article, the excitation and scattering of guided modes on a cylindrical dielectric waveguide with a corrugated surface is investigated with the consequence that both the amplitude and phase of the interacting modes are evaluated.
Abstract: The excitation and scattering of guided modes on a cylindrical dielectric waveguide with a corrugated surface is investigated. The interactions between the finite number of radiation modes and an infinite number of surface modes are considered with the consequence that both the amplitude and phase of the interacting modes are evaluated. The excitation by a two‐dimensional beam is analyzed and the transverse electric and transverse magnetic modes are investigated. The power conservation relation of a corrugated cylinder is established and the reciprocity relations are investigated in general terms starting from the principle of time reversal. The fields of a finite length corrugated cylinder are used to obtain the far‐field radiation pattern and treat its frequency characteristics. The effects of dielectric permittivity, dielectric losses, dephasing measure, and the grating profile are investigated.
TL;DR: In this article, the dielectric characteristics at microwave frequency calculated from the dispersion parameters are in preferable agreement with the measured values, and the damping constant of these materials are discussed.
Abstract: Ba(Zn1/3Ta2/3)O3–BaZrO3 dielectric ceramic material has a extremely low dielectric loss at microwave frequencies. In order to investigate the lattice vibrations of the system Ba(Zn, Ta)O3–BaZrO3, far infrared reflection spectra were measured from 50 to 4000 cm-1 at room and low temperature using a Fourier transform infrared spectrometer. These data have been analyzed by the classical dispersion theory. The damping constant of these materials are discussed. The dielectric characteristics at microwave frequency calculated from the dispersion parameters are in preferable agreement with the measured values.
Patent•
26 Nov 1985TL;DR: In this article, a perovskite dielectric material has been used for microwave-dielectric ceramics, where the temperature coefficient of the resonance frequency can be controlled to a small value within a certain range.
Abstract: Disclosed is a dielectric ceramic material having a chemical composition represented by the formula Sr(Ni 1/3 Nb 2/3 )O 3 or (1-x)Sr(Ni 1/3 Nb 2/3 )O 3 .xBaTiO 3 in which x is a positive number of up to 0.3 and also having a perovskite structure. This dielectric material has a small dielectric loss and a large dielectric constant, and the temperature coefficient of the resonance frequency can be controlled to a small value within a certain range. The dielectric ceramic material is valuably used for microwave dielectric ceramics.
TL;DR: In this paper, the dielectric parameters of dilute solutions of N,N-dimethylformamide (DMF), acetronitrile (AN) and four binary mixtures of DMF and AN have been measured using a standing wave X-band microwave technique.
Abstract: Using a standing wave X-band microwave technique, the dielectric constant ( epsilon ") and dielectric loss ( epsilon ') of dilute solutions of N,N-dimethylformamide (DMF), acetronitrile (AN) and four binary mixtures of DMF and AN have been measured. Measurements were carried out in benzene solution at 9.885 GHz and 15 degrees C. Similar measurements have also been made on a (DMF+AN) mixture containing 50 mol.% AN at 15, 20, 25 and 30 degrees C. Following the single-frequency concentration variational method, the dielectric relaxation times ( tau ) for all these systems have been evaluated. The variation of relaxation time as a function of AN molar fraction in (DMF+AN) mixtures shows a solute-solute type of molecular association between DMF and AN at all compositions. The energy parameters ( Delta Fepsilon , Delta Hepsilon , Delta Sepsilon ) for the dielectric relaxation of the 50:50 mol.% mixture at various temperatures have been found to be in fairly good agreement with the corresponding energy parameters for the viscous flow. The entropy of activation for the relaxation process and for the viscous flow has been found to be negative.