Showing papers on "Dielectric loss published in 1983"

Ba(Zn1/3Ta2/3)O3 Ceramics with Low Dielectric Loss at Microwave Frequencies

Abstract: The dielectric properties at microwave frequencies of Ba(Zn1/3Ta2/3)O3 ceramics prepared by sintering were investigated. These ceramics had lower density but higher loss quality than ceramics hot-pressed at 1400°C. Loss quality was greatly improved by prolonged sintering. The Q of the ceramics measured by the dielectric resonator method was 14 000 at 12 GHz. The ceramics were investigated by X-ray diffraction analysis. It was found that Q improvement corresponds with increased Zn and Ta ordered structures in the ceramics.

Ceramics for microwave dielectric resonator

Abstract: The present investigation relates ceramics with a temperature-stable high dielectric constant and low dielectric loss, suitable for use in dielectric resonators in an SHF band. A small amount of Mn addition not only favorably affects sinterbility of ceramics but also advantageously heightens the unloaded Q. A value of Q higher than l04 is obtained in 10 GHz band.

Precise Millimeter-Wave Measurements of Complex Refractive Index, Complex Dielectric Permittivity and Loss Tangent of GaAs, Si, SiO/sub 2/, A1/sub 2/O/sub 3/, BeO, Macor, and Glass

Abstract: Highly accurate continuous spectra of the complex refractive index and complex dielectric permittivity are given in the millimeter range for a variety of potentially useful materials. The absorption coefficient is found to increase monotonically with increasing frequencies. Small amounts of glassy inclusions or water were found to increase losses at all frequencies, but impurities and radiation damage (except in semiconductors) have not yet proved to be detrimental to performance. Materials have been found for which the millimeter-wave losses can be tolerated when used as dielectric waveguide, high-power windows, and other applications. Nominal consideration must be given, however, to the conditions of preparation and the nature of contaminants, The measurements were made in a modular, polarizing, dispersive Fourier-transform spectrometer.

The ferroelectric phase in AgNbO3

Abstract: For ceramic AgNb03 the occurrence of a ferroelectric phase was ascertained at temperatures less than about 75°C. In the vicinity of this temperature, the functions of dielectric permittivity ∊, loss tangent tan δ, spontaneous polarisation Ps, total pyroelectric coefficient pt and the piezoelectric coefficient d33 versus temperature were investigated. At temperature 20°C, Ps = 0.04 μC/cm2, pt = -0.1 nC/cm2 K, d33 = 0.24 pC/N.

Dielectric properties of ocular tissues at 37 degrees C

Abstract: Values of the relative permittivity, dielectric loss and conductivity are given for various rabbit ocular tissues at frequencies in the range 10 MHz-10 GHz. The tissues measured were cornea, retina, choroid, iris, and the cortical and nuclear zones of the lens. The dielectric parameters were determined using the technique of multiple response time domain spectroscopy. For all tissues the water relaxation could be characterised by a Debye dispersion with a relaxation time longer than that of pure water, indicating that its dielectric behaviour was affected by the presence of the biological macromolecules.

Electrical properties of plasma-polymerized thin organic films

Abstract: The electrical properties of plasma-polymerized films are summarized and compared to those of conventional polymers. Particular attention is devoted to the dielectric relaxation, dielectric breakdown, electric conductivity and photoconductivity, and their control via control of the plasma parameters.

A dielectric study of the glass transition region in segmented polyether-urethane copolymers

Abstract: Ten polyether-urethane thermoplastic elastomers of varying chemical structure have been characterized by dielectric spectroscopy and scanning calorimetry. In the temperature range corresponding to the glass-rubber transition of the predominantly polyether phase, modification of the primary dielectric transition and the occurrence of a second transition at somewhat higher temperature have been observed. Through comparison with calorimetric data, these events have been related to supercooling of crystallizable polyether segments. Supercooling suppresses dielectric loss processes in some regimes and enhances losses in others. By systematic variation of chemical structure these phenomena have been classified.

On the Complex Resonant Frequency of Open Dielectric Resonators

Abstract: An analytical method is presented for calculating accurately the complex resonant frequency of dielectric pillbox resonators. In this method, an approximated field of the resonator is expanded into a truncated series of solutions of the Hehnholtz equation in the spherical coordinates, and the boundary condtion on the resonator surface is treated in the least-squares sense. The resonant frequency and the intrinsic Q value due to radiation loss are obtained in the form of approximation converging to the exact values. Numericaf results are compared with previously published calculations, which show that the present method is a relatively simple and effective one.

Substrates for superconductive analog signal processing devices

Abstract: Superconductive analog devices are being developed which utilize long electromagnetic delay lines, typically 2 to 50 m long on a single planar substrate Criteria for the choice of substrates for these devices are established. Desirable characteristics are low dielectric loss, low dispersion, high dielectric constant, dielectric isotropy and compatibility with fine-line lithography of robust superconductive films such as niobium. A number of different substrates have been examined including crystalline and vitreous quartz, sapphire of various orientations, alumina, calcium fluoride, and silicon. Silicon is shown to be an excellent substrate for most envisioned devices. Experimental results indicate that a 100-m long line with a total loss of 8 dB at 5 GHz is feasible. A technique to allow the use of a 25-μm-thick, 5-cm-diameter silicon substrate to realize an 18-m-long niobibm line is discussed.

An Accurate Determination of Dielectric Loss Effect in Monolithic Microwave Integrated Circuits Including Microstrip and Coupled Microstrip Lines

Abstract: For the first time, by a rigorous analysis, the performance of MIC planar transmission lines with Iossy substrates can be studied accurately. The generaf structural shape chosen for the analysis includes infinitely thin metallic strips embedded within the layers of homogeneous dielectric substrates. The rigor of the analysis was guaranteed by the assumption of the propagation of an electromagnetic hybrid wave (i.e., TE+TM) along tbe planar transmission lines. An efficient computation was, however, achieved by implementing the spectral domain approach as the basis for the analysis. To test the analysis, phase constants, characteristic impedances, and attenuations, due to dielectric losses, were computed for microstrip and coupled microstrip lines. The results obtained were compared with those given previously by the spectral domain analysis in which dielectric losses were not included directly [1]. The comparison showed an excellent agreement between the two theories for low-loss substrates. However, for Iossy substrates the present method is more accurate.

Phase transitions in PbNb0.5B0.5O3(B-Sc, In)

Abstract: When studying the compounds of the PbNb05B05O3 series it has been established that with a critical ionic radius RB = 085A there occurs a transition from ferroelectric (B-Cr, Fe, Mn, Sc, In) to antiferroelectric (B-Lu, Yb, Tm) The structure of crystals and polycrystalline specimens has been studied by X-ray diffraction techniques, and also the dielectric properties of PbNb05Sc05O3 and PbNb05In05O3 located near the transition boundary from ferroelectrics to antiferroelectrics are discussed It has been established that PbNb05In05O3 corresponds to a ferroelectric with a diffuse phase transition The phase transition in PbNb05Sc05O3 shows a small diffuse nature The temperature-dependences of the unit cell parameters, dielectric constants and loss tangents have been obtained It has been established for the first time that PbNb05In05O3 at room temperature is rhombohedral (R3m) with cell parameters a = 41132 ± 00004A, α = 8997 ± 002° A preliminary determination of the PbNb05Sc05O3

Dielectric normal mode process in dilute solutions of poly(2,6-dichloro-1,4-phenylene oxide)

Abstract: Relaxation dielectrique due a la fluctuation de la distance bout a bout des chaines du polymere dans le chlorobenzene. Influence de la masse moleculaire et de la ramification de chaine

Novel Techniques for Electronic Tuning of Dielectric Resonators

Abstract: Two techniques for electronically tuning the TE01 mode resonant frequency of a dielectric resonator are presented and compared. A compact tunable dielectric resonator assembly is described which offers greater than .75% tuning range and an unloaded Q maintained at above 1000, features which are most desirable where low noise frequency agile sources are required.

Low and high frequency dielectric properties of ferroelectric tungsten bronze Sr2KNb5O15 crystals

Abstract: Single crystals of Sr2KNb5O15 (SKN), approximately 5-8 mm in diameter and 10-20 mm long, have successfully been grown by the Czochralski technique. The crystal has a ferroelectric tetragonal tungsten bronze structure with a Curie temperature of about 150°C. The dielectric and electromechanical coupling constants for this crystal have been established: the polar axis dielectric constant, K33, exceeds 20,000 at the Curie temperature while the coupling constants are K33 = 0.52 and K31 = 0.19, respectively. High frequency dielectric properties of SKN samples were also determined between 90-100 GHz. These measurements indicate that the bulk of the polar axis permittivity has relaxed below 90 GHz, implying that the low frequency dielectric response is not soft-mode controlled.

Dielectric properties of SrTiO3 glass-ceramics

Abstract: Strontium titanate glass-ceramics, prepared by the crystallization of strontium titanate-aluminosilicate glasses have been investigated for possible application as low-loss dielectric materials at microwave and millimeter wave frequencies. Under suitable crystallization conditions, these glass-ceramics exhibit temperature compensated dielectric permittivity, a consequence of the balance between the negative temperature coefficient of the SrTiO3 crystalline phase and the positive temperature coefficient of the residual aluminosilicate glass phase. Temperature coefficients of less than 10 ppm/°C with dielectric constants in the range of 16–18 have been achieved over a temperature range of -55 to 125°C. Dielectric losses at frequencies up to 4MHz are extremely low (tan δ < 0·0005). However, dielectric measurements in the range of 100–1000MHz have shown that the losses increase as the frequency approaches the millimeter wave region, indicating that these glass-ceramics might not be acceptable as mill...

Dielectric properties of ion plated titanium oxide thin films

Abstract: Titanium oxide thin films have been deposited by an ion plating technique under rf glow. The structure of the deposited film has been found to be amorphous and the composition has been analysed by IR spectrum. Aging and annealing studies of the titanium oxide capacitors have been made. The dielectric constant of the film at 1 kHz has been estimated to be 12.4. The dependence of the capacitance and dielectric loss on frequency and temperature have been studied, and the results are discussed. The temperature coefficient of the capacitance has also been calculated.

Time domain spectroscopy of the membrane capacitance in frog skeletal muscle.

Abstract: Dielectric spectra representing the frequency dependence of the complex permitivity at a range of depolarizations were obtained from voltage-clamped frog skeletal muscle membranes. This employed an analysis that derived the Fourier coefficients defining the capacitative transients to 10 mV steps as continuous functions of frequency, and so could examine closely the relevant frequencies at which non-linear components occurred. Non-linear capacitative components were identified through their appearance at lower frequencies than those of the linear components as obtained at the -85 mV control voltage, from spectra representing a logarithmic scale of frequencies. Permitivities from small depolarizing steps between about -75 and -50 mV gave single q beta dielectric loss peaks; the real permitivities declined monotonically with increasing frequency. Simple arc loci were obtained in the complex plane. With further depolarization, an additional q gamma loss peak at low frequencies and a resonant frequency in the real spectra occurred over a narrow voltage range around -45 mV. The complex loci then showed features implying an increased movement of charge not explicable through the simple effect of an electric field on a dielectric species. Spectra from small hyperpolarizing steps possessed only single dielectric loss peaks and real permitivities that declined monotonically with increasing frequency. However, in the complex plane, the loss tangents at the higher frequencies implied a population of two or more dielectric relaxations. The potential dependence of the frequency at maximum dielectric loss obtained from depolarizing steps showed a discontinuity at the onset of q gamma. In contrast, in hyperpolarizing responses, this dependence was smooth. The q beta relaxations obtained after q gamma was abolished by 1 mM-tetracaine gave dielectric spectra that were similar whether to depolarizing or hyperpolarizing potential steps. They gave single dielectric loss peaks and semicircular complex plane loci. The singularities in the dielectric spectra thus result from the q gamma charge movement component. They may reflect co-operative mechanisms that might also produce its steep voltage dependence and kinetics, and consequently those of the physiological processes it may control. These are discussed in terms of the mechanisms expected in allosteric proteins.

Effect of a filler on the dielectric properties of an epoxy resin

Abstract: The effect of aluminum hydroxide upon the dielectric properties of an epoxy resin has been studied in a wide frequency and temperature range. An interfacial polarization effect, known as the Maxwell–Wagner–Sillars polarization is evidenced for the filled resin, which shows a higher permittivity, a higher dielectric loss, and a β transition with a larger relaxation time. The glass transition temperature is, on the contrary, mostly unaffected by the presence of the filler.

The Q-Factor of Coaxial Resonators Partially Loaded with High Dielectric Constant Microwave Ceramics

Abstract: The quality factor of partially loaded dielectric coaxial stepped impedance resonatop (PDSIR) has been analyzed, including analysis of the dielectric constant epsilon/sub r/ and the dielectric loss tan delta of the ceramics. The Q-factor of several resonators is also calculated and compared with the experimental results. This shows that the Q-factor degradation lessens even though the resonator length becomes small when the total length L/sub t/>1//spl radic/epsilon/sub r/ and becomes large when L/sub t/ < 1//spl radic/epsilon/sub r/.

Dielectric properties of ferroelectric tungsten bronze Ba2-xSrxK1-yNayNb5O15 crystals at RF and millimeter wave frequencies

Abstract: Permittivity and dielectric loss have been measured for a number of single crystal samples of barium strontium potassium sodium niobate (BSKNN) in three frequency ranges: 0–1 MHz, 30–40 GHz, and 90–100 GHz. This work is part of an ongoing study of millimeter wave properties of ferroelectrics with potential applications in active components such as phase shifters, modulators, and switches. BSKNN has been selected as typifying one extreme in the tungsten bronze family, where all 15- and 12-fold coordinated cation sites are occupied. Measurements on these crystals show significantly lower millimeter wave absorption than is found in strontium barium niobate (SBN) crystals grown by the same techniques. The permittivities along the principal crystal axes showed a substantial decrease with increasing frequencies over the range of observations, which may be indicative of a relaxation mechanism occurring in the GHz frequency region.

Design of Dielectric Ridge Waveguides for Millimeter-Wave Integrated Circuits

Abstract: All-dielectric ridge waveguides may be useful as elements of millimeter- and submillimeter-wave integrated circuits; A planar metallic V-coupler can be used to couple energy between the guide and small circuit elements such as diodes. Desirable characteristics in such a guide/coupler system are a) quasi-single mode propagation; b) low radiation loss in bendy c) low coupling loss between guide and devices and d) adequate physical strength. In this paper, we discuss the general problem of designing guides and couplers to obtain the desired characteristics. The principal method used is simulation in the range 2-7 GHz. We find that with good compromise designs, typical coupling loss between waveguide and a small device is about 1.4 dB, exclusive of dielectric loss and ohmic loss in the coupler.

Measurement of Small Dielectric Loss by Time-Domain Spectroscopy: Application to Water/Oil Emulsions

Abstract: Total reflection time-domain spectroscopic method as applied to moderate to strongly polar liquids is described. A difference method based on total reflection is applied to the study of dielectric properties of water/oil emulsions. Measurement of maximum dielectric loss as small as Emax = 0.005 is discussed.

Densification effect on physical properties of atactic polystyrene

Abstract: Atactic polystyrene has been densified under hydrostatic pressure, up to 2 kbar, at about 180°C. Dielectric measurements were made on densified and nondensified polystyrene samples by using the thermally stimulated depolarization current (TSDC) and the absorption and resorption current methods. The dielectric loss is modified by the densification. This effect can be explained in terms of the free-volume reduction and the internal stress induced in the material during densification.

Microwave and far-infra-red dielectric absorption inn-alkanes

Abstract: The power absorption coefficient (α) forn-hexane (C6),n-heptane (C7),n-dodecane (C12) andn-tetradecane (C14), benzene and cyclohexane has been studied at 20 °C, in the wave number range 20 to 300 cm−1 within an accuracy of 2%. The power absorption measurements onn-alkanes (C5−C14 except for C8, C11 and C13) are discussed in conjunction with the dielectric loss in the frequency range (9⋎140) GHz. The results indicate that, unlike other nonpolar liquids,n-alkanes show a broad dielectric dispersion in the microwave frequency range followed by a second dispersion in the far infra-red. The results are interpreted in terms of a dipole moment of 0.09 D in alkanes. A possible explanation for the origin of the dipole moment is discussed. A reference is also made to measurements of the dielectric loss and the Stark effect on the lower-series alkanes in the gas phase.

On the dielectric properties of semiconducting materials as obtained from impedance measurements on Schottky barriers

Abstract: Dielectric properties of several semiconducting materials were studied by impedance measurements of metal/semiconductor and electrolyte/semiconductor Schottky barriers. Power laws of the frequency were observed analogous to those reported for insulating materials. Also the relationship between the tangent of the loss angle and the bandgap of the semiconductor appeared to be similar to that observed on insulators. The results indicate that the residual frequency dispersion of the Schottky-barrier capacitance, persisting after careful pretreatment of the semiconductor surface, can be ascribed to the dielectric properties of the space-charge layer.