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Showing papers on "Dielectric published in 1974"



Journal ArticleDOI
W.B. Weir1
01 Jan 1974
TL;DR: In this article, a system is employed that automatically measures the complex reflection and transmission coefficients that result when a sample of material is inserted in waveguide or a TEM transmission line.
Abstract: With the advent of the computer and automatic test equipment, new techniques for measuring complex dielectric constant (e) and permeability (µ) can be considered. Such a technique is described where a system is employed that automatically measures the complex reflection and transmission coefficients that result when a sample of material is inserted in waveguide or a TEM transmission line. Measurement results of e and µ for two common materials are presented.

2,002 citations


Journal ArticleDOI
01 Jan 1974
TL;DR: In this paper, the response of a low-loss dielectric slab waveguide sensor has been calculated in terms of the effective Dielectric constant of the soil-water mixture, in reasonable agreement with experiment when effects of ionic conduction are accounted for.
Abstract: Implantable soil moisture sensors suitable for long-term monitoring of moisture in highway subgrades and for similar applications are needed. Two candidate designs of microwave sensors (operating range 4 to 6 GHz) have been investigated for such applications. One design uses the fringing field of a low-loss dielectric slab waveguide (relative dielectric constant of 25) to obtain good resolution for finely divided soil such as bentonite clay with moisture ranging from 10 to 50 percent by dry weight for effective sample volumes of 20 to 40 cm2. The response of the dielectric waveguide sensor has been calculated in terms of the effective dielectric constant of the soil-water mixture. A model based on index of refraction yields an effective dielectric constant in reasonable agreement with experiment when effects of ionic conduction are accounted for. Another sensor design, better adapted for coarse materials, such as crushed limestone aggregate, uses waves launched from a tapered dielectric slab. By using either frequency or spatial averaging methods, the launched wave sensor accommodated aggregate particles passed by a 0.63-cm mesh sieve, and was found to have satisfactory resolution for the range of 0- to 10-percent moisture by dry weight.

699 citations



Journal ArticleDOI
TL;DR: In this article, the complex dielectric constant of four soils, including a sand, a silt, and two clays, was measured over the frequency range from 0.1 × 109 Hz to 26 ×109 Hz.
Abstract: The complex dielectric constant of four soils, including a sand, a silt, and two clays, was measured over the frequency range from 0.1 × 109 Hz to 26 × 109 Hz. The water content of the soils was varied from 0.0 g H2O/g soil to 0.15 g H2O/g soil, and the temperature from 24°C to 20°C. The dielectric relaxation spectrum of water in soils was found to be displaced to lower frequencies than the dielectric relaxation spectrum of water in bulk. The results showed that the relation between volumetric water content and the complex dielectric constant is relatively independent of soil type. At temperatures above freezing the complex dielectric constant of water in soils, at the water contents investigated, decreases with temperature, a type of behavior normally found only in solids. Below the freezing point the phase composition of water in soils determines the temperature dependence of the complex dielectric constant.

417 citations


Journal ArticleDOI
TL;DR: In this article, the dielectric properties of single-phase ceramics in the TiO2-rich region of the BaO-TiO2 system were investigated.
Abstract: The dielectric properties of ceramics in the TiO2-rich region of the BaO-TiO2 system were investigated. In the composition range between BaTi4O9 and TiO2, another compound, Ba2Ti9O20, can be obtained when calcining and sintering conditions are controlled carefully. When dense and single-phase, this ceramic has excellent dielectric and physical properties. At 4 GHz, the dielectric K= 39.8, Q= 8000, and τK (temperature coefficient of dielectric constant) =−24 ± 2 ppm/°C.

363 citations


Journal ArticleDOI
TL;DR: In this paper, a model is developed which proposes that each grain has a different transition temperature Tc. The Tc values are taken as following a Gaussian distribution and the behaviour of the dielectric constant against temperature is computed and checked with experimental results.
Abstract: Hot-pressed ceramics of the lead titanate zirconate system with different grain sizes were prepared and some of their electrical properties measured. The values of the dielectric and piezoelectric properties were analysed together with information on barium titanate ceramics already published in the literature. Many similarities were found between both systems. There are two main contributions to the properties; the single-crystal single-domain intrinsic effect and the contribution of the wall motion. The intrinsic effect is analysed considering the grains as monodomains. A model is developed which proposes that each grain has a different transition temperature Tc. The Tc values are taken as following a Gaussian distribution and the behaviour of the dielectric constant against temperature is computed and checked with experimental results. All the results can be explained qualitatively with the model; a connection between findings and the idea of diffuse phase transitions is outlined.

312 citations


Journal ArticleDOI
TL;DR: In this article, the complex dielectric constant of four soils, including a sand, a silt, and two clays, was measured over the frequency range from 0.1 × 109 Hz to 26 ×109 Hz.

208 citations


Journal ArticleDOI
TL;DR: In this article, a theory for surface polaritons associated with the planar surface of a semi-infinite anisotropic dielectric medium is presented for magnetic fields either perpendicular or parallel to the surface.
Abstract: A theory is presented for surface polaritons associated with the planar surface of a semi-infinite anisotropic dielectric medium. Retardation is included. In general, two attenuating components with different attenuation constants must be superposed within the medium in order to satisfy the boundary conditions, and the macroscopic electric field vector does not lie in the sagittal plane. For special cases, however, only one attenuating component is required, and the electric vector does lie in the sagittal plane. The theory is applied to the specific case of surface magnetoplasmons in a semiconductor for magnetic fields either perpendicular or parallel to the surface. In the latter case, propagation directions parallel and perpendicular to the magnetic field are considered. Possibilities for the experimental observation of the effects predicted are discussed.

169 citations


Journal ArticleDOI
TL;DR: In this paper, experimental measurements and model interpretations are given for properties of hot-pressed PZT-5 specimens with grain sizes from ∼2 to 5 μm, and the dielectric and piezoelectric parameters are studied as functions of temperature, of hydrostatic pressure up to 2800 kg cm−2, of grain size and of the poling history.
Abstract: Experimental measurements and model interpretations are given for properties of hot-pressed PZT-5 specimens with grain sizes from ∼2 to 5 μm. The dielectric and piezoelectric parameters are studied as functions of temperature, of hydrostatic pressure up to 2800 kg cm−2, of grain size and of the poling history, using a number of methods in order to disentangle domain wall effects from others. The models presented are a multi-grain model to describe the diffuse transition, and a model of moving 90° domain walls for the piezoelectric variations with grain size and with poling and with pressure. We suggest that some differences from the behaviour of barium titanate ceramics result from thinner domain walls.

146 citations


Journal ArticleDOI
TL;DR: A novel dielectric optical waveguide was made consisting of a guide pattern on a thin dielectrics film where almost all the power propagates in the thin film along the guide pattern.
Abstract: A novel dielectric optical waveguide was made consisting of a guide pattern on a thin dielectric film. Almost all the power propagates in the thin film along the guide pattern. The existence of propagation modes of this waveguide was verified both theoretically and experimentally.

Journal ArticleDOI
TL;DR: In this article, the diffuse, paraelectric/ferroelectric, phase transition of Potassium Strontium Niobate is discussed and several possible causes of the diffuse phase transition (DPT) are discussed.
Abstract: The diffuse, paraelectric/ferroelectric, phase transition of Potassium Strontium Niobate is discussed. It is found that the Curie point is strongly dependent on the K and Sr content. Several possible causes of the diffuse phase transition (DPT) are discussed. An empirical relationship describing the behaviour of the inverse dielectric constant in the transition region, is presented. A statistical analysis of the DPT is described in terms of microscopic composition variations within the crystal arising from non-stoichiometry. Plots of the polar dielectric constant and spontaneous polarization against temperature, derived from this model, compare well with the experimentally measured quantities.

Journal ArticleDOI
TL;DR: In this paper, a model for the incipient stages of intrinsic dielectric breakdown was proposed for a wideband gap insulator with a low hole mobility, and the model predicted an intrinsic breakdown voltage which approached a lower limit of V = 9+φ for very thin films, where φ is the cathode contact barrier in volts.
Abstract: A mechanism describing the incipient stages of intrinsic dielectric breakdown is formulated for the case of a wide‐band‐gap insulator with a low hole mobility. Dielectric instability results from the tunnel injection of electrons from the cathode contact and the subsequent impact ionization and field distortion which lead to dielectric breakdown. The model, evaluated for the parameters of SiO2, predicts an intrinsic breakdown voltage which approaches a lower limit of V=9+φ for very thin films, where φ is the cathode contact barrier in volts. As a result, both the electric field at breakdown and the critical current density increase rapidly as the film thickness is reduced below 200 A.

Journal ArticleDOI
TL;DR: In this paper, the total polarization due to molecular dipoles in a glassy electret is computed using an Onsager cavity approach, and all possible contributions to the piezoelectric and pyroelectric coefficients are considered.
Abstract: The total polarization due to molecular dipoles in a glassy electret is computed using an Onsager cavity approach. From this result, all the possible contributions to the piezoelectric and pyroelectric coefficients are considered. It is shown that there are major contributions from the variation in dielectric constant and, for pyroelectricity, from thermal motion. These results account well for experimental data for polyvinyl chloride.

Journal ArticleDOI
TL;DR: In this paper, the absorptivity or reflectivity of crystals of V, Ta, and Mo was measured from 0.1 to 35 eV. The data were Kramers-Kronig analyzed to determine the dielectric functions.
Abstract: The absorptivity or reflectivity of crystals of V, Ta, and Mo was measured from 0.1 to 35 eV. The data were Kramers-Kronig analyzed to determine the dielectric functions. The inadequacy of a simple Drude model to describe absorption at low energy is discussed. Structure in the dielectric functions is discussed in terms of direct interband transitions which extend to about 18 eV. Features below 6 eV are attributed to transitions near $\ensuremath{\Sigma}$, $G$, and perhaps along $P(D)N$ for V, Ta, and Mo, with additional transitions in Mo from the $\ensuremath{\Delta}$ portion of the Brillouin zone. High-lying energy bands are identified as giving rise to high-energy structure in the dielectric functions. Results obtained previously for Nb are reviewed and compared. The electron-energy-loss functions were calculated and are discussed in terms of volume and surface plasmons. These metals all exhibit two volume and two surface plasmons.

Journal ArticleDOI
TL;DR: In this article, the 1000-Hz 300°K dielectric constants were measured for crystalline α-quartz, sapphire, MgF2, and MgO.
Abstract: The 1000‐Hz 300°K dielectric constants were measured for crystalline α‐quartz, sapphire, MgF2, and MgO, and polycrystalline sapphire (Lucalox), magnesium fluoride (IRTRAN 1), and magnesium oxide (IRTRAN 5). The measurements were performed using the method of substitution (two‐fluid method). The results are as follows: single‐crystal α‐quartz, es∥=4.6368±0.001 and es⊥=4.5208±0.001; single‐crystal sapphire, es∥ = 11.589±0.005 and es⊥=9.395±0.005; polycrystalline sapphire (Lucalox), es=10.154±0.007; single‐crystal MgF2, es∥ =4.826±0.01 and es⊥=5.501±0.01; polycrystalline MgF2 (IRTRAN 1), es=5.289±0.001; single‐crystal MgO, es=9.830 ±0.001; and polycrystalline MgO (IRTRAN 5), es=9.833±0.001, where es∥ and es⊥ are the dielectric constants parallel and perpendicular, respectively, to the c axis.

Journal ArticleDOI
TL;DR: A theory is derived for the static and frequency dependent value of the electric permittivity for model systems representing a solution of a macromolecule bearing a large number of identical charges.

Journal ArticleDOI
TL;DR: In this paper, the bias characteristics of the dielectric constant of ferroelectric ceramics of the Pb(Zr,Ti)O3 type have been investigated.
Abstract: Bias (dc electric field) dependence of the dielectric constant of ferroelectric ceramics of the Pb(Zr,Ti)O3 type has been investigated. Measurements were carried out at various temperatures in the ferroelectric phase and at several frequencies between 1 kHz and 1 MHz. The bias characteristics of the dielectric constant show a temperature‐dependent asymmetry in the electric field direction. A model in which the coercive fields of the 180° and 90° domains are distributed around some average value is considered. The total dielectric constant of the material is calculated by considering the contributions of each type of domain, taking into account the difference between the differential and incremental dielectric constants. This model explains the dependence of dielectric constant on electric field. A comparison of the calculated and experimental results is presented.

Journal ArticleDOI
TL;DR: In this paper, a simple frequency-domain method for measurement of the dielectric properties of materials is described, and theoretical analysis of the frequency dependence of the reflection coefficient of a shunt lumped capacitor located at the end of a transmission line and filled with a very small amount of the Dielectric (typically a few microliters) is given.
Abstract: A simple frequency-domain method for measurement of the dielectric properties of materials is described. Theoretical analysis of the frequency dependence of the reflection coefficient of a shunt lumped capacitor located at the end of a transmission line and filled with a very small amount of the dielectric (typically a few microliters) is given. Analysis and calculations of the overall uncertainty in permittivity measurements, as well as experimental results for some normal alcohols, are presented and limitation of the method discussed.

Journal ArticleDOI
TL;DR: In this paper, the dispersion relation for the frequency of the surface plasmon polariton as a function of the wave vector parallel to the surface for each of the three cases is presented.
Abstract: We have solved Maxwell's equations for the fields localized near the surface of a doped semiconductor possessing either a depletion layer, an accumulation layer, or an inversion layer. We present the dispersion relation for the frequency of the surface plasmon polariton as a function of the wave vector parallel to the surface for each of the three cases. The effect of the space charge at the surface is taken into account by dividing the surface region into layers and assuming a linear position dependence for the free-carrier concentration and the local dielectric constant within each layer. We have found the solution for the fields within each layer and have satisfied the boundary conditions for the normal and tangential components of the fields at each interface between layers. We show that the features of the dispersion curve can be used to obtain information about the space-charge region. For illustration, we compare our calculations with measured dispersion curves of $n$-type InSb.

Journal ArticleDOI
TL;DR: In this paper, a free space and in-waveguide dielectric constant measurement facility at 10 and 35 GHz is described, and the results are interpreted in terms of a model of sea ice.
Abstract: A free‐space and in‐waveguide dielectric constant measurement facility at 10 and 35 GHz is described. Results are presented for the dielectric constant and loss of both fresh and sea ice at these frequencies, and are interpreted in terms of a dielectric model of sea ice. Suggestions are made for possible improvements in the model and the measurement technique.

Journal ArticleDOI
01 Jul 1974-Nature
TL;DR: In this paper, the usual interpretation as the sum of many Debye-like loss peaks is criticised and a new model is proposed in which charge carriers hop between localised sites in a polarisable medium.
Abstract: The loss in most dielectric materials shows a component that is ‘flat’ in frequency over several decades and does not depend strongly on temperature. The usual interpretation as the sum of many Debye-like loss peaks is criticised and a new model is proposed in which charge carriers hop between localised sites in a polarisable medium.

Journal ArticleDOI
TL;DR: In this paper, a detailed analysis is made of the appropriate form of the radiation condition in cylindrical and toroidal systems, and is applied to the calculation of radiation from curyed dielectric slabs and fibers.
Abstract: The form taken by the radiation condition in the local coordinate system, pertinent to the determination by perturbation methods of the radiation from curved radiating structures, is not the same as it is at very great distances. Specifically, it may contain a term that appears as if it were an incoming or growing wave. A detailed analysis is made of the appropriate form of the condition in cylindrical and toroidal systems, and is applied to the calculation of radiation from curyed dielectric slabs and fibers.

Journal ArticleDOI
TL;DR: In this paper, the dielectric response of a small metal particle to a perturbing potential is considered within the random phase approximation (RPA) and the static and dynamic electric polarizability, the position and the width of the surface plasma resonance are found in the limita/r 0≫ 1.
Abstract: The dielectric response of a small metal particle to a perturbing potentialv L =r L Y LM e iωt is considered within the random phase approximation (RPA). The static dielectric polarizability is found and the size dependence of the surface plasmon frequencies are then determined from sum rule calculations. When the particle radiusa is large compared to the Thomas-Fermi screening lengthr 0 the RPA equation is transformed into a form appropriate for an analytical solution. The dynamic electric polarizability, the position and the width of the surface plasma resonance are found in the limita/r 0≫1.

Journal ArticleDOI
TL;DR: In this paper, two different forms have been proposed for the relation between the frequency-dependent dielectric constant of a polar substance and the autocorrelation function for the net dipole moment of a small spherical region inside the dielectrics.
Abstract: Two different forms have been proposed for the relation between the frequency‐dependent dielectric constant of a polar substance and the autocorrelation function for the net dipole moment of a small spherical region inside the dielectric. We find that one of them is correct, while the other one describes a spherical sample embedded in a medium with a frequency‐independent dielectric constant equal to the static dielectric constant of the sample. A number of recent papers dealing with this question are analyzed. We discuss in particular the role played by fluctuations in the polarization of the surrounding medium near the surface of the embedded sphere.

Patent
13 Dec 1974
TL;DR: In this article, a semiconductor capacitance is proposed to increase the surface area by forming selectively spaced grooves in the surface of the semiconductor substrate by orientation dependent etches and utilizing the sidewalls of the grooves as surface.
Abstract: Disclosed is a semiconductor capacitor which utilizes the volume of the semiconductor substrate in which it is formed to create increased surface area and thereby to provide increased capacitance. The surface area is increased by forming selectively spaced grooves in the surface of the semiconductor substrate by orientation dependent etches and utilizing the sidewalls of the grooves as surface. Groove depth is limited to a predetermined value by etching time, geometrical constraints, or by etch stops. This provides for precise control of capacitance values on a batch or commercial basis. Increases up to at least 100-fold in capacitance as compared to a flat capacitor structure as possible. A thin layer of dielectric is formed over the increased surface area, and thereafter a conducting layer is formed over the dielectric layer to provide a dielectric capacitor. An active junction P-N capacitor may also be formed.

Journal ArticleDOI
TL;DR: The conclusion is reached that the high frequency dispersion and relaxation can be attributed to fluctuations in the distribution of bound counterions along limited parts of the macromolecule.

Journal ArticleDOI
TL;DR: In this article, it was shown that the average reflected power in the specular direction is a function of depth even in the case where the nonrandom part of the dielectric constant is independent of depth.
Abstract: The electromagnetic scattering properties of a medium bounded by a plane surface and whose (scalar) dielectric constant is the sum of a nonrandom part assumed to vary only with depth and a small random part are investigated by means of an approximate, first-order perturbation method. It is shown that the equivalent dielectric constant to be used in calculating the average reflected power in the specular direction is a function of depth even in the case where the nonrandom part of the dielectric constant is independent of depth. Further, the equivalent dielectric constant is shown to be a tensor. Nonspecular scattering is also considered.

Book ChapterDOI
TL;DR: In this article, a two-valence band model was proposed for lead-salt ionic semiconductors, based on the properties of PbS, PbSe, and PbTe.
Abstract: Publisher Summary Lead salts are ionic semiconductors with many properties in common. Their IV-VI electron configuration is relatively unusual, and appears to be reflected in the interesting phonon and dielectric properties they share. Among these are low values of the TO phonon frequency at Γ and high static dielectric constants. It is clear that the electronic structures of PbS, PbSe, and PbTe are much the same, with all three lead salts exhibiting a direct minimum energy gap E 0 at the L point. The surfaces of constant energy for both electrons and holes are ellipsoidal near the band edges, but approach a cylinder-like shape farther from the L point. The conduction and valence bands in all the lead salts are definitely nonparabolic, displaying a concomitant dependence of the effective mass on carrier concentration. Based primarily on studies of PbTe, a two-valence band model is well supported by experiment. The order of higher energy bands appears quite well established, and reliable values of the energies of several interband transitions have been obtained.

Journal ArticleDOI
TL;DR: In this article, the reflection coefficient of a flanged open-ended rectangular waveguide placed, next to a flat large sample is computed by a variational method as a function of the dielectric constant.
Abstract: A simple nondestructive method is presented for the measurement of the complex permittivity ?r of materials. The reflection coefficient ? of a flanged open-ended rectangular waveguide placed, next to a flat large sample is computed by a variational method as a function of the dielectric constant. Computer-generated charts and an optimization computer program are elaborated. ?r can then be easily determined from the measured amplitude and phase angle of the reflected wave in the waveguide. The method is best suited for materials having high dielectric constants and large losses.