Showing papers on "Dielectric published in 1979"
Book•
01 Jan 1979
TL;DR: In this paper, the authors present applications of electro-active and conductive polymers in static fields and static charges, including Ionic conduction, particulate and molecular composites.
Abstract: 1. Introduction 2. Dielectrics in static fields 3. Dielectric relaxation 4. Electronic conduction in polymers 5. Measurement of electrical properties 6. Dielectric breakdown 7. Static charges 8. Ionic conduction, particulate and molecular composites 9. Intrinsically conductive polymers 10. Applications of electro-active and conductive polymers 11. References 12. Index.
833 citations
TL;DR: The observed dielectric response of most materials is seldom in accord with Debye behaviour, but has been found experimentally to exhibit a remarkable "universality".
Abstract: The observed dielectric response of most materials is seldom in accord with Debye behaviour, but has been found experimentally to exhibit a remarkable ‘universality.’ It is proposed that this universality is a consequence of some ubiquitous correlated states which exhibit an infrared (IR) divergent-like response to induced transitions of the polarising species.
292 citations
TL;DR: A scheme of procedure is proposed that applies to the determination of electrical parameters associated with the specific “double-shell” model consisting of a spherical core and three layers of concentric phases by using a set of parameter values pertinent to a lymphoma cell.
255 citations
TL;DR: In this article, a focused ion-beam sputtering technique was used to sample lead zirconate titanate (ZrxTi1−x)O3 in an O2 atmosphere.
Abstract: Lead zirconate titanate is a solid solution with nominal composition Pb(ZrxTi1−x)O3. Ferroelectric thin films of this material have been successfully deposited by a focused ion‐beam sputtering technique in an O2 atmosphere. These films were characterized according to composition, crystal structure, and dielectric and ferroelectric properties. The effects of deposition temperature, heat treatment after deposition, and substrate and target material were investigated. The composition of the films was within 1 at.% of the composition of the multicomponent PZT target for substrate temperatures up to 200 °C. The Pb concentration decreased for substrate temperatures above 200 °C. Films deposited at substrate temperatures below 250 °C were microcrystalline. At 300 °C, the pyrochlore phase was obtained. Films with the ferroelectric perovskite structure were deposited above 400 °C, which is the lowest deposition temperature ever reported for this phase. O2 losses during postdeposition annealing resulted in a collap...
182 citations
TL;DR: In this paper, a universal dielectric response was proposed for very low energy excitations in condensed matter, which exhibit an infrared-divergent-like response to transitions of the polarizing species induced by a time-varying electric field in the dielectrics.
Abstract: The dielectric response of condensed matter below microwave frequencies has been known to depart from the Debye behavior, sometimes to the point of being unrecognizable and yet the generally accepted interpretations of the departures have seldom deviated from the Debye philosophy of simple relaxation phenomena in noninteracting systems. It was recently recognized, from a synoptic view of the experimental data involving a wide range of materials, that there exists a remarkable universality of dielectric response behavior regardless of physical structure, types of bonding, chemical type, polarizing species, and geometrical configurations. This strongly suggests that there should exist a correspondingly universal mechanism of dielectric polarization in condensed matter. The present work proposes such a universal mechanism associated with the existence of some ubiquitous very-low-energy excitations in the system. These excitations exhibit an infrared-divergent-like response to transitions of the polarizing species induced by a time-varying electric field in the dielectric and give rise to the universal dielectric response.
176 citations
29 Jun 1979
TL;DR: In this paper, a universal dielectric response mechanism was proposed, associated with the existence of very low energy excitations in the system, which exhibit an infrared divergent-like response to transitions of the polarizing species induced by a time-varying electric field in the dielectrics.
Abstract: : The dielectric response of condensed matter below microwave frequencies has been known to depart from the Debye behavior, sometimes to the point of being unrecognizable and yet the generally accepted interpretations of the departures have seldom deviated from the Debye philosophy of simple relaxation phenomena in non-interacting systems. It was recently recognized, from a synoptic view of the experimental data involving a wide range of materials, that there exists a remarkable universality of dielectric response behavior regardless of physical structure types of bonding, chemical type, polarizing species and geometrical configurations. This strongly suggests that there should exist a correspondingly universal mechanism of dielectric polarization in condensed matter. The present work proposes such a universal mechanism associated with the existence of some ubiquitous very low energy excitations in the system. These excitations exhibit an infrared divergent-like response to transitions of the polarizing species induced by a time-varying electric field in the dielectric and give rise to the universal dielectric response. (Author)
173 citations
TL;DR: Empirical equations are given to summarise the dielectric properties of 'average' brain tissue at 37 degrees C for future theoretical studies of microwave absorption in the head.
Abstract: Dielectric permittivity and conductivity are reported for grey and white matter from dog brain tissue between 0.01 and 10 GHz. Between 0.01 and approximately 1 GHz, the permittivity decreases and conductivity increases as a power law of frequency. Above 1 GHz, the conductivity increases quadratically with frequency due to dipolar reorientation of free water molecules in tissue; the apparent rotational relaxation frequency at 37 degrees C is 21--25 GHz, slightly below the 25 GHz characteristic frequency of pure water at that temperature. The microwave data are analysed using the Maxwell mixture theory applicable for a suspension of nonconducting, low permittivity spheres in bulk water. From the increase in conductivity above 1 GHz, and the tissue permittivity at 2--4 GHz, the apparent volume fraction of water is approximately 0.70 and 0.55 for grey and white matter, respectively, about 10--15% lower than respective values from the literature. This discrepancy is apparently due to a small fraction of water which does not contribute to the tissue permittivity above 1 GHz. Empirical equations are given to summarise the dielectric properties of 'average' brain tissue at 37 degrees C for future theoretical studies of microwave absorption in the head.
155 citations
TL;DR: In this paper, the relationship for evaluating dielectric parameters from changes in resonance frequency and Q of a cylindrical TM/sub 010/-mode cavity has been derived for thin samples of length less than the height of the cavity.
Abstract: Relations for evaluating dielectric parameters from changes in resonance frequency and Q of a cylindrical TM/sub 010/-mode cavity have been derived for thin samples of length less than the height of the cavity. Although derived under some simplifying assumptions, they reduce to the standard form when the length of the specimen equals the height of the cavity, and yield consistent results when applied to different lengths of the same material.
149 citations
TL;DR: Increasing the dielectric constant of an artificial bilayer increases its permeability to perchlorate or thiocyanate by a factor of 1000, to a value comparable to that of mitochondrial membranes.
Abstract: The Born charging equation predicts that the permeability of a phospholipid bilayer membrane to ions should depend markedly on the dielectric constant of the membrane. Increasing the dielectric constant of an artificial bilayer increases its permeability to perchlorate or thiocyanate by a factor of 1000, to a value comparable to that of mitochondrial membranes.
148 citations
TL;DR: In this article, the dielectric constant epsilon e or the conductivity sigma e of a two-phase composite is calculated for a simple cubic array of identical spherical inclusions embedded in a homogeneous host.
Abstract: New methods are described for calculating the dielectric constant epsilon e or the conductivity sigma e of a two-phase composite and these are applied to a simple cubic array of identical spherical inclusions embedded in a homogeneous host. A spectral representation is derived for epsilon e, and numerical results are presented for the poles and the residues. Analytical and numerical methods are used to discuss the conductivity threshold of the cubic array, which occurs when the host is an insulator and the conducting spheres begin to touch each other. It is argued that sigma e as a function of sigma 1/ sigma 2 has an essential singularity at the conductivity threshold.
TL;DR: BaMnF4 as mentioned in this paper is a pyroelectric ferromagnet which displays a number of unusual physical characteristics, some of which are unique, such as its dielectric anomalies at its Neel temperature.
Abstract: BaMnF4 is a pyroelectric ferromagnet which displays a number of unusual physical characteristics, some of which are unique. It has the only known continuous antiferroelectric phase transition. It has two- and three-dimensional antiferromagnetic ordering temperatures. It is a weak ferromagnet with ferromagnetism caused by the linear magnetoelectric effect-the only case yet known. It exhibits dielectric anomalies at its Neel temperature. At high temperatures its dielectric constant diverges with increasing temperature; a ferroelectric phase transition would occur if the crystals did not melt first. At high temperatures BaMnF4 is also an anisotropic ionic conductor. The antiferroelectric phase is incommensurate. The incommensurate phase appears unusual in that its translation vector is temperature-independent. Sound velocity measurements made near the antiferroelectric phase transition temperature demonstrate the presence of and characteristics for a relaxational mode; this mode couples strongly to transverse acoustic phonons and is probably the 'phason' predicted theoretically for incommensurate lattices. This article reviews theory and experiment for this unusual material, including neutron, Raman and Brillouin scattering; X-ray, dielectric and conductivity measurements; magnetic resonance and susceptibility studies.
TL;DR: In this paper, the anomalous rise in birefringence with temperature is interpreted in terms of lattice strain and dielectric polarization, and the lattice parameters of PbTiO3 single crystals are described as a function of temperature.
Abstract: Measurements of lattice parameters and birefringence of PbTiO3 single crystals are described as a function of temperature. The anomalous rise in birefringence with temperature is interpreted in terms of lattice strain and dielectric polarization.
TL;DR: In this article, a microscopic theory of the kinetic dielectric decrement in ionic solutions is developed, which clarifies the physical origin of the effect, showing that it is analogous to the electrophoretic effect, and corrects a violation of the reciprocity relations in the original continuum treatment of Hubbard and Onsager.
Abstract: A microscopic theory of the kinetic dielectric decrement in ionic solutions is developed. The theory clarifies the physical origin of the effect, showing that it is analogous to the electrophoretic effect, and corrects a violation of the reciprocity relations in the original continuum treatment of Hubbard and Onsager. We discuss the concept of the dielectric constant of an electrolyte solution. Calculations indicate that there are specific ion effects, in contrast with the universal behavior predicted by the continuum theory. A critical comparison with present experimental measurements is made.
TL;DR: In this paper, the authors developed a theory for the intensity and the depolarization ratio of the light scattered by an absorbed molecule, where the optical properties of the system can be described by the polarizability of the molecule and the dielectric constant of two media.
Abstract: We develop a classical theory for the intensity and the depolarization ratio of the light scattered (Raman or Rayleigh) by an absorbed molecule. It is assumed that the optical properties of the system can be described by the polarizability of the molecule and the dielectric constant of the two media. The presence of the surface modifies the field incident upon the molecule as well as the field emitted by the induced dipole. We compute these effects, exactly, by using a dyadic Green’s function method, and approximately, by using a perfect mirror model. The theory provides the angular distribution of the scattered radiation, and its polarization as a function of the polarization, the frequency and the direction of incidence of the incoming radiation, as well as of the dielectric properties of the metal and the position of the molecule with respect to the surface. We use these equations to analyze the possible sources for the experimentally observed enhancement of the scattering caused by the presence of the metallic surface.
TL;DR: In this article, the authors derived the dielectrophoretic force on insulating and finite conducting dielectric spheres immersed in a non-uniform electric field using various methods.
TL;DR: In this paper, the dielectric function of Si−SiO2 and Si•Si3N4 composites is obtained by combining the Si−centered tetrahedral model of Philipp with composite media theory.
Abstract: Expressions for the dielectric function of Si‐SiO2 and Si‐Si3N4 composites are obtained by combining the Si‐centered tetrahedral model of Philipp with composite‐media theory. The similarity between dielectric‐function spectra of a‐Si and Si3N4, with scaling parameters related by the plasma sum rule and the dielectric theory of Phillips and Van Vechten is used to obtain the polarization response function for the bond part of a given tetrahedron. By treating the N and O contributions on an equal basis with Si, reasonable agreement to existing spectra is obtained for these materials over an energy range of 0–8 eV.
TL;DR: In this paper, the authors generalized the theory of average dielectric constant developed by Genzel and Martin to the case of randomly oriented ellipsoidal particles having anisotropic Dielectric constants and incorporated effects which result from the mixture of different types of particles.
Abstract: Theory of average dielectric constant developed by Genzel and Martin is generalized to the case of randomly oriented ellipsoidal particles having anisotropic dielectric constants Effects which result from the mixture of different types of particles are also incorporated in the theory The generalized theory is applied to the calculation of infrared absorption spectra of ZnO small particles The present calculation can reproduce fairly well the experimental spectra of ZnO smoke reported by Yamamoto et al
TL;DR: In this paper, the dielectric measurements carried out for a variety of threshold and memory alloys of glassy As-GeTe and Se-Ge-Te at different temperatures (83 to 373 K) and various frequencies (0.2, 0.5, 1.0, 2.6 and 5.0 MHz).
Abstract: The paper reports dielectric measurements carried out for a variety of threshold and memory alloys of glassy AsGeTe and SeGeTe at different temperatures (83 to 373 K) and various frequencies (0.2, 0.5, 1.0, 2.6 and 5.0 MHz). It is found that the glassy system of chalcogenides exists in the form of molecular dipoles which remain frozen at low temperatures and, as the temperature is increased, the molecules attain freedom of rotation at temperatures which are sometimes as low as 253 K. All the materials displayed dielectric dispersion in the radio frequency range. Gevers' formula has been used to calculate the dielectric loss (ϵ′') and loss-angle (tan δ) from the measured values of the real part of dielectric constant (ϵ′). The curves: log ϵ′ versus temperature, ϵ′ versus log ω, ϵ″ versus log ω, tan δ versus log ω and tan δ versus temperature, gave a direct evidence of the existence of a Debye-type relaxation having a wide distribution of relaxation times. Cole-Cole diagrams have been used to determine the distribution parameter (α) and the molecular relaxation time (τ). The temperature dependence of α and τ for all the alloys is consistent with the “molecular relaxation mechanism”. The paper also reports accurate values of the static and optical dielectric constants for all the alloys. Eyring's relaxation rate equations have been used to determine the free energy of activation (ΔF), and enthalpy of activation (ΔH) for all the alloys. These results indicate the existence of a stronger intermolecular interaction for SeGeTe alloys. mott's concept of “dangling bonds” has also been used to explain the existence of a stronger intermolecular interaction, and hence a greater density of defect states in case of SeGeTe as compared with AsGeTe alloys. It has been finally concluded that the dielectric behaviour of chalcogenide glasses, in general, can be successfully explained by using the theory of molecular relaxation.
TL;DR: The optical transmittance of thin PdO films has been measured in the range 0.5-5.4 eV by Kramers-Kronig analysis as mentioned in this paper.
Abstract: The optical transmittance of thin PdO films has been measured in the range 0.5-5.4 eV. From these data the optical constants have been determined by Kramers-Kronig analysis. A small band gap (0.8 eV) and a high dielectric constant (8.0) have been found.
TL;DR: In this article, the separation between the isotropic and anisotropic component of some Raman bands of polar molecules is studied as a function of concentration in different solvents.
Abstract: The separation between the isotropic and the anisotropic component of some Raman bands of polar molecules is studied as a function of concentration in different solvents. It is found that it depends linearly on the ratio between the volume fraction and the static dielectric constant of the solution, and becomes zero at a finite concentration. It is suggested that this concentration threshold is related to the relaxation time of the vibrational energy. An explanation is proposed for the observed dependence on the dielectric constant.
TL;DR: In this paper, the authors considered the situation of a small dielectric sphere or shell with finite conductivity submerged in a liquid of finite conductivities and found that the strength of the dielectrophoretic force depends on the effective dipole moment which is directly related to the induced dipole field.
TL;DR: In this paper, the dielectric behavior of binary mixtures in the vicinity of a consolute critical point was investigated. And the results showed that along the critical isochore, one may expect the static permittivity eE(T) to remain finite but to exhibit a cusp, whereas the nonlinear dielectrics effect, the Kerr effect, and the Cotton-Mouton effect all diverged strongly with the universal exponent Ψ=2γ−dν.
Abstract: We present here some further developments of the droplet model recently proposed by Oxtoby, which appears quite suitable for an extensive phenomenological analysis of the dielectric behavior of binary mixtures in the vicinity of a consolute critical point. Along the critical isochore, one may expect the static permittivity eE(T) to remain finite but to exhibit a cusp, whereas the nonlinear dielectric effect, the Kerr effect, and the Cotton–Mouton effect all are predicted to diverge strongly with the universal exponent Ψ=2γ−dν. These predictions are supported by recent experimental evidence.
TL;DR: In this article, pressure dependences of the dielectric properties and phase transitions of squaric acid, H2C4O4 and its deuterated analog, D2C 4O4, were investigated.
Abstract: The pressure dependences of the dielectric properties and phase transitions of squaric acid, H2C4O4, and its deuterated analog, D2C4O4, were investigated. The transition temperatures at 1 bar are 375.5±1.0 K and 527.5±2.0 K, respectively, and decrease with pressure at initial rates of 105.6±2.0 K/GPa and 102.5±2.0K/GPa. It is argued that the large hydrogen isotope effect on Tc can be accounted for on the basis of the elongation of the O–H⋅⋅⋅O bond resulting from deuteration. This elongation causes a modification of the double‐well potential along this bond. It is not necessary to invoke proton tunneling. The lack of an appreciable isotope effect on dTc/dP supports the absence of tunneling. An interesting aspect of the results is the appearance of a dome‐shaped feature in the real part of the dielectric constant just above Tc in both crystals. This feature, which is reminiscent of the behavior of the magnetic susceptibility of antiferromagnets above the Neel temperature, is discussed. The results on D2C4O4...
TL;DR: In this paper, a simple approximate method for predicting the resonant frequencies of the TE modes of a cylindrical dielectric post resonator was developed, and the accuracy of the method was shown to be better than 3.5 percent.
Abstract: A cylindrical sample of low-loss high epsilon/sub r/ placed between two parallel conducting plates perpendicular to the sample axis forms a microwave resonator. A simple approximate method for predicting the resonant frequencies of the TE modes of this structure is developed. The method becomes exact for the fitting case of this structure which is known as a dielectric post resonator. In all cases, the accuracy of the method is shown to be better than 3.5 percent. The TE/sub 01delta/ mode chart presented allows the determination of the resonant frequency and the tuning range of any cylindrical dielectric resonator for which epsilon/sub r/ >or= 10. The properties of the dielectric resonator as a TEM line element are demonstrated experimentally.
Patent•
04 Sep 1979TL;DR: A method for manufacturing variable capacitance pressure transducers and an intermediate article of manufacture produced in the practice of this method is described in this article, where a wafer or doped silicon or other semiconductor material is removed from spaced areas to form a plurality of recesses in the surface of the material.
Abstract: A method for manufacturing variable capacitance pressure transducers and an intermediate article of manufacture produced in the practice of this method. In the method, a wafer or doped silicon or other semiconductor material has portions of the semiconductor material removed from spaced areas to form a plurality of recesses in the surface of the semiconductor material. The material is doped to enhance its electrical conductivity. A dielectric material has one of its surfaces coated with spaces areas of electrically conductive material. The semiconductor material is attached to the coated surface of the dielectric material such that the surface recesses in the semiconductor material are in alignment with the conductive areas on the dielectric material. This produces a plurality of electrical capacitors suitable for use as pressure transducers. The capacitance of these transducers is varied as a function of changes in one or more fluid pressures acting on the plates of each of the capacitors, one of these plates being the doped semiconductor material and the other being a conductive area on the dielectric material. Fluid pressure between the plates may be established during manufacture. The intermediate article of manufacture produced by this process may then be cut into a plurality of separate pressure transducers.
TL;DR: In this paper, the scattering from eccentrically stratified spheres is considered and the method of separation of variables is used in conjunction with translational addition theorems for spherical vector waves.
Abstract: In this paper the scattering from eccentrically stratified spheres is considered. For the case of a spherical inhomogeneity embedded inside a dielectric sphere, the method of separation of variables is used in conjunction with translational addition theorems for spherical vector waves. Analytical results are obtained when the difference in the dielectric constants of the two spheres is small by employing a special perturbation technique. Scattering properties such as distortion of the scattering patterns, variation of total and backscattering cross sections, and depolarization for randomly oriented scatterers are investigated. Methods of detection and identification of inhomogeneities are discussed.
TL;DR: In this paper, a smectic C liquid crystal exhibiting positive dielectric anisotropy was oriented with the director parallel to the glass substrates, and when an electric field was applied normal to the director direction, a Dielectric reorientation (Freedericksz transition) occurred.
Abstract: A smectic C liquid crystal exhibiting positive dielectric anisotropy was oriented with the director parallel to the glass substrates. When an electric field was applied normal to the director direction a dielectric reorientation (Freedericksz transition) occurred. Dissolving a dichroic dye in the smectic C phase and applying an electric field, a guest host effect similar to nematic phases was observed. From the dielectric reorientation the tilt angle of the smectic C phase was determined at different temperatures. The tilt angles obtained by the electrooptical measurements agree sufficiently with the values measured by x ray investigations.