Showing papers on "Dielectric loss published in 1992"
TL;DR: The role of zinc oxide as a sintering aid and lanthanum and niobium as dopants, their effect upon microstructural development and their correlation with dielectric loss at microwave frequencies were investigated in this article.
Abstract: Ceramics with compositions in the solid solution region of the ZrO2-TiO2-SnO2 equilibrium diagram are finding wide application as dielectrics in filters for communications and radar systems operating at microwave frequencies. Commercially available compositions often incorporate sintering aids and dopants to reduce processing temperatures and modify the dielectric properties. However, the mechanism through which these additives influence dielectric loss is not obvious. The role of zinc oxide as a sintering aid and lanthanum and niobium as dopants, their effect upon microstructural development and their correlation with dielectric loss at microwave frequencies were investigated. For specimens of density greater than 90% theoretical, the influences of defect chemistry upon dielectric loss appear to dominate those of the microstructure. Properties close to those which might be considered intrinsic were attained through sintering for periods of up to 128h. Doping with lanthanum is detrimental to the dielectric loss, particularly after long sintering times.
252 citations
TL;DR: In this article, the dielectric loss tangent at microwave frequencies for the complex perovskite Ba(Zn1/3Ta2/3)O3 was calculated with respect to the degree of structural disorder on B sites.
Abstract: The dielectric loss tangent at microwave frequencies for the complex perovskite Ba(Zn1/3Ta2/3)O3 was calculated with respect to the degree of structural disorder on B sites. Starting out from the equations of ion motion, dielectric loss was expressed in terms of the pair-correlation functions corresponding to the ordering of Zn and Ta ions on B sites. The characteristic length included in the pair-correlation functions corresponds to the average size of the region containing disorder in ion arrangements on B sites; thus the relation between the structural disorder on the B site and the dielectric loss tangent at microwave frequencies was clarified theoretically. The numerical results show that the microwave loss tangent values change their power from – 3 to – 6 with increasing degree of order on the B site, which agrees well with the experimental observations. Results obtained here confirm the physical origin of the microwave loss of complex perovskite Ba(Zn1/3Ta2/3)O3.
152 citations
TL;DR: In this article, thin films of SrTiO3 were deposited on platinum coated silicon and bare silicon by excimer laser (248 nm) ablation at 400 and 500°C or ex situ crystallized.
Abstract: Thin films of SrTiO3 were deposited on platinum coated silicon and bare silicon by excimer laser (248 nm) ablation at 400 and 500 °C or ex situ crystallized. Films deposited at 500 °C showed good crystallinity and were characterized for dielectric constant, dielectric loss, leakage current and C‐V characteristics. The films showed a dielectric constant of 240, a dissipation factor of 0.02, a leakage current of 2×10−9 A/cm2, and a charge storage density of 42 fC/μm2 at a bias of 5 V. The C‐V behavior of both metal‐insulator‐metal (MIM) and metal‐insulator‐ semiconductor (MIS) structures indicated bulk dielectric permittivity in the accumulation region and also good Si/SrTiO3 interfaces.
146 citations
TL;DR: In this paper, an analysis of the imaginary part of the dielectric susceptibility has revealed the existence of a broad spectrum of relaxation times in the above temperature range, and the temperature dependence of the most probable frequency of the spectrum was obtained.
Abstract: An investigation was carried out on both the linear and nonlinear parts of the complex dielectric susceptibility in the frequency and temperature ranges 10-3-103 Hz and 100-450 K, respectively. The analysis of the imaginary part of the dielectric susceptibility has revealed the existence of a broad spectrum of relaxation times in the above temperature range. The temperature dependence of the most probable frequency of the spectrum was obtained. For temperatures T
106 citations
TL;DR: The high dielectric loss tangents of metal powders at 2450 MHz have been used to accelerate the synthesis of a wide range of metal chalcogenides in the solid state as mentioned in this paper.
Abstract: The high dielectric loss tangents of metal powders at 2450 MHz have been utilised to accelerate the syntheses of a wide range of metal chalcogenides in the solid state.
95 citations
TL;DR: The internal friction in potassium dihydrogen phosphate crystal and the dielectric loss in KDP and triglycine sulfate crystals are measured near T c in the kHz frequency range and are found to be associated with the viscous movement of domain walls.
Abstract: The internal friction in potassium dihydrogen phosphate (KDP) crystal and the dielectric loss in KDP and triglycine sulfate (TGS) crystals are measured near T c in the kHz frequency range. An internal-friction peak (P M2 ) and a dielectric loss peak (P D2 ) appear at about several degrees below T c , which are found to be associated with the viscous movement of domain walls
89 citations
TL;DR: In this article, the dielectric properties of a series of single-crystal and sintered polycrystalline zirconias have been measured at room temperature over the frequency range 1 − 12.5 kHz.
Abstract: The dielectric properties of a series of single-crystal and sintered polycrystalline zirconias have been measured at room temperature over the frequency range 1–12.5 kHz. The additive cations investigated were yttrium, magnesium, calcium and cerium. For monoclinic zirconia, it was found that the permittivity, ɛ′, was 23 at 10 kHz, in agreement with previous work. The addition of stabilizing cations causes a substantial increase in ɛ′ which then lies in the range 32–42 depending on the nature and amount of the stabilizing cation. Analysis of the separate contributions to the overall permittivity arising from the monoclinic, tetragonal or cubic phases has been made for some mixed-phase systems. The results suggest that the permittivity is principally determined by the crystallographic form rather than by the nature or amount of the added cation.
87 citations
TL;DR: In this paper, BaTiO3 was used for ablation at 600°C or ex situ crystallization at about the same annealing temperature, and the films showed a dielectric constant of 220, a dissipation factor of 0.02, a leakage current of 1.8×10−6 A/cm2 at a bias of 5 V, and a charge storage density of about 40 fC/μm2.
Abstract: Thin films of BaTiO3 were deposited on platinum coated silicon substrates by excimer laser (248 nm) ablation at 600 °C or ex situ crystallized at about the same annealing temperature. Films deposited at 600 °C showed good crystallinity and were characterized for ferroelectricity, dielectric constant, dielectric loss, leakage current, and C‐V characteristics. The films showed a dielectric constant of 220, a dissipation factor of 0.02, a leakage current of 1.8×10−6 A/cm2 at a bias of 5 V, and a charge storage density of about 40 fC/μm2 at a field of 0.15 MV/cm.
78 citations
TL;DR: The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone, and the loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.
Abstract: The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.
74 citations
TL;DR: In this paper, a very thin well-defined SiO2 layer was also formed at the HfO2/SiO2 interface as a result of annealing.
71 citations
TL;DR: In this article, BaTiO3-Ni mixed powders were sintered at 1300°C in Ar or air, and the sintering behavior and dielectric properties were investigated.
Abstract: BaTiO3-Ni mixed powders were sintered at 1300°C in Ar or air, and the sintering behavior and dielectric properties were investigated. The bulk density of sintered bodies was 95-99% of theoretical. BaTiO3-Ni composites were produced in Ar. When coarse Ni powder (4-7μm) and ultrafine BaTiO3 powder (0.02μm) were used, a large number of Ni particles were isolatedly dispersed in the BaTiO3 matrix. The dielectric constant increased remarkably with an increase in Ni content up to er′=11000 at 40vol% Ni according to the modified Maxwell formula. Although monolithic BaTiO3 sintered in Ar had a high dielectric loss owing to the formation of oxygen vacancies working as electron donor, BaTiO3-Ni composite had a low dielectric loss. This is because of the fact that a small amount of NiO dissolved into BaTiO3 and Ni ions worked as electron acceptor to compensate the charge of oxygen vacancies. Firing in air resulted in the oxidation of Ni to form BaTiO3-NiO composites with low dielectric constants and high dielectric losses.
TL;DR: In this paper, a method for determining the dielectric properties of general lossy dielectrics was proposed, which utilizes the measurement of the admittance of a rectangular waveguide radiating into such dielectors.
Abstract: A method for determining the dielectric properties of infinite half-space of generally lossy dielectric materials is described. This method utilizes the measurement of the admittance of a rectangular waveguide radiating into such dielectrics. It is shown that the real part of the admittance is relatively insensitive to the variations of the imaginary part of the dielectric constant. A numerical procedure is initiated which provides a simple and fast-converging approach for calculating the dielectric properties. This numerical procedure lends itself to implementation by personal computers. The theoretical formulation for the expression of the admittance of an open-ended waveguide and the numerical procedure are discussed in detail. Results of several measurements of freespace and lossy dielectric samples (rubber with carbon black) to verify the theory and the numerical scheme are given. The results give good agreement with other measurement schemes. Comments on the accuracy of the results are also provided. >
TL;DR: In this paper, the best deposition conditions for HfO2 films are RF power 200 W, substrate temperature 100°C and sputtering gas pure Ar. They are higher than any ever reported.
Abstract: Hafnium dioxide (HfO2) thin films are deposited on indium-tin-oxide (ITO)-coated glass substrates by the radio-frequency (RF) sputtering method using a HfO2 sintered target. The deposition conditions, dielectric loss and dielectric constant of HfO2 films before and after heat treatment are studied. The best deposition conditions for HfO2 films are RF power 200 W, substrate temperature 100°C and sputtering gas pure Ar. The maximum dielectric constants are about 150 and 45 with 1 kHz signal excitation before and after annealing, respectively. They are higher than any ever reported.
TL;DR: In this paper, the authors compared the dielectric properties of a blend of cottonseed and sunflower oils with conventional methods of analysis (viscosity, refractive index, iodine value, peroxide value and free fatty acids).
Abstract: Dielectric properties (dielectric constant e′ and dielectric loss e″) were compared to conventional methods of analysis (viscosity, refractive index, iodine value, peroxide value and free fatty acids) for evaluating the frying quality of a blend of cottonseed and sunflower oils. The apparent relaxation time, τ, the activation energy H and the entropy change S for dielectric relaxation of the heated oil samples were calculated. Results indicate that dielectric constant and dielectric loss are useful tools for predicting deterioration occurring during heating of the oil.
TL;DR: In this article, a cavity perturbation technique was used to measure the complex scalar permittivity of materials at frequencies between 50 MHz and 3 CHz, and up to a temperature of 1400°C.
Abstract: A system has been developed, based on the cavity perturbation technique, for measuring the complex scalar permittivity of materials at frequencies between 50 MHz and 3 CHz, and up to a temperature of 1400°C. Measurements have been made on several classes of materials, including metallic oxides, conventional and advanced ceramics, fabrics, earthenwares, geological and biological materials, foods, glasses, organics and ferrites. Some materials remain unchanged by thermal cycling, but many undergo irreversible changes; the latter are of interest in microwave processing. The system measures the complex dielectric constant of materials during conventional heating, curing or sintering. Correlating these microwave measurements with other diagnostic techniques will help in the understanding of these processes in several classes of materials.
TL;DR: In this article, a frequency dependent complex permittivity was used to describe the dielectric losses of a microstrip patch antenna, and the theoretical and experimental results for the usual parameters (input impedance, reflection coefficient and radiation pattern) of a rectangular micro strip patch were compared for a lossy and a non-lossy Dielectric.
Abstract: A frequency dependent complex permittivity is used to describe the dielectric losses of a microstrip patch antenna. The theoretical and experimental results for the usual parameters (input impedance, reflection coefficient and radiation pattern) of a rectangular microstrip patch are compared for a lossy and a nonlossy dielectric. Good agreement is obtained between the experimental measurements and theoretical results when the dielectric losses are considered.
TL;DR: SrTiO3 thin films having perovskite structure were fabricated by sol-gel technique with a postdeposition rapid thermal annealing treatment at 550 °C for 60 s.
Abstract: SrTiO3 thin films having perovskite structure were fabricated by sol‐gel technique with a post‐deposition rapid thermal annealing treatment at 550 °C for 60 s. The films exhibited good structural, dielectric, and insulating properties. The measured dielectric constant and loss factor at 100 kHz were 225 and 0.008, respectively. Unit area capacitance of 3.5 fF/μm2 and leakage current density of less than 10−8 A/cm2 were obtained for 500–800 nm thick films. A charge storage density of 18.3 fC/μm2 was obtained at an applied electric field of 100 kV/cm. The resistivity of these films was in the range of 1010–1013 Ω cm. The C‐V measurements on films in metal‐insulator‐semiconductor (MIS) configuration indicated good Si/SrTiO3 interface characteristics.
TL;DR: In this article, the aging of both the dielectric constant and the loss was examined with respect to grain size, temperature, and frequency in coarse-grained BaTiO 3 ceramics.
Abstract: BaTiO 3 ceramics with grain sizes of 0.6 to 6 mm and relative densities of 89% to 92% were prepared by hot forging and conventional sintering from high-purity oxalate-derived powder. The aging of both the dielectric constant and the dielectric loss was examined with respect to grain size, temperature, and frequency. It is suggested that the main aging mechanism in coarse-grained BaTiO 3 is the aging of hysteretic domain wall motion. The dielectric aging is a thermally activated process and shows two aging rates when observed at a temperature of 8°C for coarse-grained ceramics
TL;DR: In this paper, the spectral properties of multilayer, multiconductor MIS microstrip structures with the spectral-domain approach over a wide range of frequency and substrate loss were analyzed for both Si-SiO/sub 2/ and GaAs configurations.
Abstract: Lossy multilayer, multiconductor MIS microstrip structures are analyzed with the spectral-domain approach over a wide range of frequency and substrate loss. The modal attenuation and propagation constants are presented for two- and four-conductor structures as a function of the substrate loss tangent. Single-conductor structures are characterized with contour plots showing the complex effective dielectric constant as a function of both frequency and conductivity. MIS slow-wave structures are analyzed for both Si-SiO/sub 2/ and GaAs configurations. >
TL;DR: In this paper, the authors studied dielectric ceramic compositions for microwave applications belonging to the (BaO (Sm2O3) (TiO2) ternary phase diagram.
Abstract: Dielectric ceramic compositions for microwave applications belonging to the (BaO) (Sm2O3) (TiO2) ternary phase diagram were studied. Calcination, sintering, microwave properties and influence of secondary phases were investigated. By varying composition and/or sintering process, a high dielectric constant with low dielectric losses and modulable negative or positive temperature coefficient of the resonant frequency can be reach.
18 May 1992
TL;DR: In this article, an effort to determine the high-frequency electrical characteristics of the HDI (high-density interconnect) process and validate models and analytical tools was described, and seven different designs fabricated, five with only passive structures and two with both passive and active structures.
Abstract: An effort to determine the high-frequency electrical characteristics of the HDI (high-density interconnect) process and validate models and analytical tools is described. There were seven different designs fabricated, five with only passive structures and two with both passive and active structures. These coupons were designed with many different line structures in order to determine the electrical characteristics of HDI at high (>500-MHz) frequencies. A few of the structures used on the coupons and their respective electrical performances are discussed. The analytical tools derived from basic transmission line theory appear adequate to explain observed values of insertion loss, reflection loss, and crosstalk. In addition, the measurements confirmed the commonly accepted values for the electrical parameters of the GE HDI process (dielectric constant, loss tangent, and electrical resistivity). The crosstalk measurements demonstrate that sufficient isolation exists for practical system designs up to frequencies of 9 GHz in the stripline configuration, and even in the less-tolerant microstrip configuration good isolation is obtained without use of excessive spacing or guard conductors. The major limitation at the higher frequencies appears to be the insertion loss, which approaches 10 dB in some of the longer-length lines considered. >
TL;DR: In this paper, the electrical properties of EPR are compared with those of PE at liquid helium temperature, and an extruded EPR-insulated cable was fabricated and its 15m length was cooled down to liquid hydrogen temperature successfully.
Abstract: Mechanical and electrical properties of ethylene propylene rubber (EPR) pieces were studied in comparison with polyethylene (PE) in the cryogenic temperature region to examine the possibility of its use as solid electrical insulating material in superconducting cables. The mechanical properties of EPR are preferable to those of PE mainly because of its low shrinkage. The electric strength and dielectric loss tangent of EPR are comparable with those of PE at liquid helium temperature. Based on the encouraging results, an extruded EPR-insulated cable was fabricated and its 15-m length was cooled down to liquid helium temperature successfully. Partial discharge experiments at that temperature showed good electrical characteristics. This is a breakthrough in terms of the electrical insulation design of cryogenic cables. >
01 Jun 1992
TL;DR: In this article, the authors developed a new method for the detection of AC dissipation in dielectric materials under high AC field, and they used this technique to measure the high-field loss properties of low-density polyethylene (LDPE) films, and showed that the large increase of tan delta in the high field and high temperature region is related to the loss due to DC-like carrier motion.
Abstract: The authors have developed a new method for the detection of AC dissipation in dielectric materials under high AC field. Using this technique, high-field dielectric loss properties and their relation to AC dissipation current of low-density polyethylene (LDPE) films are measured. Near room temperature, tan delta of a LDPE film has small electric field dependence. In this temperature region, the dissipation current shows saturation around the voltage peaks in phase even with high-field application. At higher temperatures, however, the high-field tan delta tends to have a strong field dependence, and the AC dissipation current deforms and is nonlinear near the voltage peaks. The nonlinearity of the AC dissipation current decreases under the decrease of tan delta with the voltage application period. These results show that the large increase of tan delta in the high-field and high-temperature region is related to the loss due to DC-like carrier motion. >
DSM1
TL;DR: In this article, a theoretical interlayer model for the complex dielectric constant of a composite in which the filler particles are enveloped with a layer of interfacial material is presented.
Abstract: A theoretical interlayer model (IL) has been developed for the complex dielectric constant of a composite in which the filler particles are enveloped with a layer of interfacial material. The filler particles can be of any ellipsoidal shape. Special cases such as spherical particles, needles, and fabrics are shown to be covered by the model. The analytical formula as derived describes the composite properties as a function of the volume fractions of the filler, the layer and the matrix material, their dielectric properties and the filler particle shape factor. In the case of a two-phase composite the model reduces to the well-known Sillars relation for the complex dielectric constant of composite which contains filler particles of ellipsoidal shape. The effect of an interfacial layer on the static dielectric constant of the composite is discussed using the model. Next, the special case of a conductive interfacial layer in an otherwise non-conductive composite is discussed; it illustrates the effect of interfacially adsorbed water on the electrical properties of composites. Some practical examples are shown.
TL;DR: In this paper, the aging of both the dielectric constant and the Dielectric loss was examined at weak and strong fields with respect to grain size and frequency, and it was concluded that the main aging mechanism is the ageing of hysteretic domain wall motion for coarse-grained ceramics.
Abstract: BaTiO3 ceramics with grain sizes from 0.6 to 60 μm and relative densities of 89% to 92% were prepared by hot forging and conventional sintering from very pure-oxalate-derived powder. The aging of both the dielectric constant and the dielectric loss was examined at weak and strong fields with respect to grain size and frequency. It was concluded that the main aging mechanism is the aging of hysteretic domain wall motion for coarse-grained ceramics. At grain size of less than 1 μm, the lack of frequency and EAC dependence, along with a lower aging rate, suggests that domain motions or hysteretic domain wall motions are restricted in finegrained ceramic BaTiO3 and contribute little to the aging.
18 Oct 1992
TL;DR: Apical, Upilex, Kapton, Teflon AF, and PEEK polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 degrees C as mentioned in this paper.
Abstract: Apical, Upilex, Kapton, Teflon AF, and PEEK polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 degrees C The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present The effects of thermal aging on the properties of the films are determined after 15 h of exposure at 200 and 250 degrees C The preliminary data indicate that most of the tested films remain relatively stable when exposed to temperature as high as 250 degrees C The PEEK film however tends to display some wrinkling and exhibit discoloration when exposed to temperatures of about 200 degrees C and higher All other films displayed good dielectric and physical properties even up to 250 degrees C >
TL;DR: In this article, the permittivity, ϵ, and dielectric loss of Neoprene vulcanized with tetramethyl-thiourea (TMTU) and loaded with four different types of carbon black in increasing quantities were investigated in the frequency range from 1 kHz to 40 MHz at room temperature.
TL;DR: The dielectric permittivity and loss tangent of hyperquenched glassy water (HGW) have been measured for fixed frequencies of 1 and 10 kHz from 80 K to its crystallization temperature and corresponding measurements have been made of the crystallized forms as discussed by the authors.
Abstract: The dielectric permittivity and loss tangent of hyperquenched glassy water (HGW) have been measured for fixed frequencies of 1 and 10 kHz from 80 K to its crystallization temperature and corresponding measurements have been made of the crystallized forms. The effect of thermal cycling has been investigated. Except for a shoulder at T