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Showing papers on "Dielectric loss published in 1995"


Journal ArticleDOI
TL;DR: In this article, the dynamics of α-relaxation in homogeneous mixtures of polystyrene (PS) and poly(cyclohexyl acrylate-stat-butyl methacrylate) (PCHA-stat BMA)) are analyzed within the framework of a concentration fluctuation model.
Abstract: The dynamics of the α-relaxation in homogeneous mixtures of polystyrene (PS) and poly(cyclohexyl acrylate-stat-butyl methacrylate) (P(CHA-stat-BMA)) is analyzed within the framework of a concentration fluctuation model. The shape and widths of the dielectric relaxation spectra as well as the range of calorimetric glass transition in the mixtures are respectively associated with distributions of relaxation time and T arising from the presence of concentration fluctuations. The magnitude of these fluctuations is obtained by fitting the dielectric loss curves to a model function obtained as a convolution of a relaxation time distribution for the mixture with a function describing the dielectric loss of the dielectrically active component. The relaxation time distribution is calculated from William-Landel-Ferry (WLF) or Vogel-Fulcher-Tammann (VFT) free volume scaling with the assumption of a Gaussian concentration distribution in the samples. Fits of the measured α-relaxation spectra which are dominated by P(CHA-stat-BMA) offer as a reset the mean square concentration fluctuations in the mixtures. The fluctuations are interpreted in terms of the random phase approximation, and it is shown that is correlated to the length scale of cooperativity governing the relaxation process near the glass transition. The temperature and composition dependence of both and the size of the domains of cooperativity in PS/P(CHA-stat-BMA) are determined

142 citations


Journal ArticleDOI
TL;DR: In this paper, the epitaxial nature of both Ba0.5Sr 0.5TiO3 (BST) thin films was determined by the measurement of inplane orientation with respect to the major axes of the substrate.
Abstract: Epitaxial Ba0.5Sr0.5TiO3 (BST) thin films were deposited on LaAlO3 substrates with the conductive metallic oxide SrRuO3 (SRO) as a bottom electrode by pulsed laser deposition. The BST and SRO films were (h00) and (00l) oriented normal to the substrate surface, respectively. The epitaxial nature of both BST and SRO layers was determined by the measurement of in‐plane orientation with respect to the major axes of the substrate. Ion beam channeling with a minimum yield of around 10% from Rutherford backscattering spectrometry demonstrated the films to be of high crystallinity. A dielectric constant around 500 and dielectric loss less than 0.01 at a frequency of 10 kHz were measured on the capacitors with a configuration of Ag/BST/SRO. Electrical measurements on such epitaxial BST films showed a breakdown voltage above 106 V/cm and a leakage current density of less than 5×10−8 A/cm at a field intensity of 2×105 V/cm. These results prove the BST/SRO heterostructure to be a good combination for microelectronic device applications.

133 citations


Journal ArticleDOI
TL;DR: In this article, the dielectric dispersion of (Ba 0.5Sr0.5)TiO3 thin films with high electric resistivity was measured in the frequency range of 10-2-106 Hz.
Abstract: The dielectric relaxation of (Ba0.5Sr0.5)TiO3 thin films with high electric resistivity is investigated. The films are deposited by an rf-magnetron sputtering method in an atmosphere of argon and oxygen. The dielectric dispersion of the films is measured in the frequency range of 10-2-106 Hz. It is found that the dielectric constant e slightly decreases with frequency, following the relationship of de/d(log 10 f)∼-0.01e, and the dielectric loss is almost constant at less than 1% in the measured frequency range. This type of dielectric relaxation causes absorption current which is inversely proportional to time, as the result of the dielectric aftereffect. In a dynamic random access memory (DRAM) operation, the dielectric relaxation would result in less than 10% loss of storage charge during the refresh cycle, and the film's DC leakage less affects the device operation.

91 citations


Journal ArticleDOI
01 Jan 1995
TL;DR: The structural phase transition in titanite near 500 K and a second anomaly around 900 K have been studied using infrared spectroscopy on single crystals aqnd powder samples, measurements of the dielectric properties and the specific heat as discussed by the authors.
Abstract: The structural phase transition in titanite near 500 K (averaged symmetries A2/a→P2 1/a) and a second anomaly around 900 K have been studied using infrared spectroscopy on single crystals aqnd powder samples, measurements of the dielectric properties and the specific heat. The same synthetic single crystal was used in all experiments. The phase transition near 500 K is associated with a break in the temperature evolution of phonon frequencies and absorption intensities. Some phonon signals decrease rapidly under further heating and their extrapolated intensities disappear at ca. 850 K. The most dominant temperature effect relates to Ti-O phonons with amplitudes along the crystallographic a axis. These phonons show large LO-To splitting and continue to soften under heating even at temperatures above the transitions point (ca. 500 K). The softening of these modes correlates directly with the increase of the real part of the dielectric constant with a well-pronounced anomaly at 500 K. The dielectric losses also increse with increasing temperature. Measurements under strong field do not show antiferroelectricity. The transition at 500 K generates a small but sharp λ-anomaly in the excess specific heat. A second, weaker anomaly was found near 850 K. The results are discussed in terms of thermodynamic models.

78 citations


Journal ArticleDOI
TL;DR: In this paper, the dielectric properties of iron and vanadium phosphate glasses containing different glass modifiers have been studied in a broad range of frequency and temperature by the absorption current and with an ac transformer bridge.
Abstract: Dielectric properties of iron and vanadium phosphate glasses containing different glass modifiers have been studied in a broad range of frequency and temperature by the absorption current and with an ac transformer bridge. The dielectric spectra exhibit a peak that can be related to the electron transfer between iron atoms in different valency states. This peak and the dc conductivity revealed a similar activation energy. The data obtained were interpreted in the framework of a new model of relaxation in glasses recently proposed by Hunt.

67 citations


Journal ArticleDOI
TL;DR: Inclusion of all types of foods (meats, fruits, and vegetables) inhibited any useful correlation with composition, and both dielectric constant and loss increased with water and salt content.
Abstract: Prediction of accurate dielectric property data from fundamental principles for systems as complex as foods has not been possible. Simple prediction models based on easily measurable composition data can serve many useful purposes. Literature dielectric data on foods and their composition were statistically correlated. Dielectric data on salt solutions were measured to explain some of the results. When composition data were not available, standard handbook compositions were used. Inclusion of all types of foods (meats, fruits, and vegetables) inhibited any useful correlation with composition. Based on a smaller data set of meats, both dielectric constant and loss increased with water and salt content. Dielectric constant generally decreased with temperature whereas dielectric loss decreased with temperature at lower salt concentrations and increased with temperature at higher salt concentrations.

67 citations


Journal ArticleDOI
TL;DR: The role of donor and acceptor ions in the dielectric loss tangent of (Zr,Sn)TiO 4 was investigated at frequencies from 0.1 kHz to 9 GHz as discussed by the authors.
Abstract: The role of donor and acceptor ions in the dielectric loss tangent of (Zr,Sn)TiO 4 was investigated at frequencies from 0.1 kHz to 9 GHz. When a specimen was doped with Fe 2 O 3 , the loss tangent increased drastically at microwave frequencies. This increase is explained by a large concentration of Fe- 3+ ions and oxygen vacancies in the grains. When the specimen was doped with Ta 2 O 5 and then annealed in a reducing atmosphere, electrical resistivity decreased and tan δ increased extremely at low frequencies but trivially at microwave frequencies. The high microwave δ value of Ta-doped specimens is explained by assuming the Ta ions in the crystal to be tetravalent. Dielectric loss is determined predominantly by space charge polarization at low frequencies and by the disordered charge distribution at microwave frequencies

61 citations


Journal ArticleDOI
TL;DR: In this article, the MSXX force field was used to calculate dielectric constants and losses for amorphous poly(vinylidene fluoride) and crystalline PVDF.
Abstract: Molecular dynamics (MD) simulations at 300 and 400 K were used to calculate dielectric constants and dielectric loss for crystalline and amorphous poly(vinylidene fluoride). These calculations used the MSXX force field derived from first principles and tested previously for crystalline PVDF. In agreement with experiment the calculations lead to a dielectric constant of e o = 8-13 for amorphous PVDF but e 0 = 2-3 for crystalline PVDF. We show that the high e 0 for amorphous PVDF arises from rapid changes in the torsion angles (and hence rapid modulation of the dipole moment perpendicular to the chain axis) during MD. These changes are enhanced by soliton-like defects in the chain that diffuse during the MD. The dielectric losses lead initially to a stretched exponential decay function, Φ(t) = exp-[-(t/τ) β ], with τ = 60 ps and β = 0.62 at 300 K.

60 citations


Journal ArticleDOI
TL;DR: In this article, it is shown that the final result of Trukhan is correct, in spite of some errors and odd procedures in the original derivation, and the theory is generalised to binary electrolytes of any charge type.
Abstract: The theory of Trukhan [Sov. Phys. Solid State (Engl. Transl.), 1963, 4, 2560] for the calculation of the complex permittivity of a conducting dielectric film containing a binary 1 : 1 electrolyte is critically reviewed. It is shown that the final result of Trukhan is correct, in spite of some errors and odd procedures in the original derivation. The method of Trukhan is changed to a more concise procedure which is better suited to generalisations, and the theory is generalised to binary electrolytes of any charge type. The dimensionless excess impedance (over and above the Maxwell–Wagner–Sillars impedance) and the complex relative permittivity are functions of the type of electrolyte, the dimensionless frequency, the ratio of the ionic diffusion coefficients and the film thickness scaled by the Debye length. The complex relative permittivity has a Debye-like relaxation, but for very different values of the two diffusion coefficients and for films which are thin compared with the Debye length, one can clearly distinguish two dielectric relaxations, one for each ion. The peak in the dielectric loss corresponding to the ion of higher valency, is dominating in thin films. When the film is thicker, (or when the electrolyte concentration is increased) the low-frequency peak diminishes relative to the high-frequency peak. The maximum in the loss tangent is positioned at higher frequencies than the maximum in the dielectric loss. Therefore it is often an advantage to fit the loss tangents to actual measurements, since measurements at low frequencies are generally more difficult. Two applications of the theory are treated: the low-frequency dielectric relaxation of a dry copolymer of vinylidene cyanide and vinyl acetate with conducting ions (T. Furukawa, M. Date, K. Nakajima, T. Kosaka and I. Seo, Jpn. J. Appl. Phys., 1986, 25, 1178) and a wet membrane of dense cellulose acetate (I. W. Plesner, B. Malmgren-Hansen and T. S. Sorensen, J. Chem. Soc., Faraday Trans., 1994, 90, 2381). The use of the so-called ‘constant-phase element’ is discussed and criticised. The constant-phase element leads to infinite dissipation at zero frequency in contrast with the generalised Trukhan theory (and common sense). The constant-phase element is just superficially fitting the data in a limited range of frequency and no physical information (e.g. diffusion coefficients) is obtained from the fitted parameters of such an element.

54 citations


Journal ArticleDOI
TL;DR: In this paper, a method of dielectric spectroscopy was used to determine the electric properties of chemically synthesized polyaniline (PANI) with special emphasis on the influence of acid and water doping levels on the polymer properties.
Abstract: A method of dielectric spectroscopy was used to determine the electric properties of chemically synthesized polyaniline (PANI) with special emphasis on the influence of acid and water doping levels on the polymer properties. The dependence of the dielectric loss factor (tan δ) on the temperature (in the range from − 100 to + 100°C) and the frequencies of the ac voltage (F = 0.1–30 000 Hz; amplitude of the voltage 1 V) were measured. They were subsequently transformed into the temperature and frequency dependences of a complex electric modulus, M∗ . Tan δ(F, T) and M(F, T)) presentations were both used in the analysis of the electric properties of PANI samples to compare their informative possibilities. At least two modes of the polymer response to varying temperature and frequency were resolved. Each mode corresponds to a certain area in an electric map of the system (log F versus 1/T plane) with their positions displaced towards higher frequencies and lower temperature with increases of both acid and water concentration in PANI. This effect is interpreted in terms of a unified mechanism of interaction of water and acid molecules with polymer backbone.

51 citations


Journal ArticleDOI
TL;DR: In this article, the authors developed quantitative models for dielectric loss in both SrTiO3 and BaxSr1−xTiOO3 (BST) that give dependences upon temperature, frequency, and especially voltage or field.
Abstract: The use of high-dielectric films for microwave devices, especially phased-array radar systems, in the tens of GHz regime requires very low-loss (0.01 to 0.1) films. Unfortunately most ferroelectrics have losses that diverge (greater than unity) in this frequency range. We develop in the present study quantitative models for dielectric loss in both SrTiO3 and BaxSr1−xTiO3 (BST) that give dependences upon temperature, frequency, and especially voltage or field. In pure strontium titanate we find that loss is intrinsic, with quality factor “Q” greater than 1000; and a dramatic voltage dependence of tan δ is observed to fit the C3/2(V) dependence upon capacitance predicted for three- and four-phonon anharmonicity for voltages up to 5V (E = 250 kV/cm). In most barium strontium titanate ceramic films the loss is extrinsic at 100 MHz, and the surface layer model of Neumann and Hofmann describes the dependence of tan δ upon thickness D rather well, with tan δ increasing from 0.001 at D = 5 microns to 0.1...

Journal ArticleDOI
TL;DR: In this article, single crystal fibers of A(B1/2 B2 1/2 )O 3 perovskites were grown successfully for the first time, using a laser-heated pedestal growth (LHPG) technique.
Abstract: Single crystal fibers of A(B1 1/2 B2 1/2 )O 3 perovskites type with compositions Sr(Al 1/2 Ta 1/2 )O 3 (SAT) and Sr(Al 1/2 Nb 1/2 )O 3 (SAN) were grown successfully for the first time, using a laser-heated pedestal growth (LHPG) technique. Their crystallographic structures were found to be simple cubic perovskite with lattice parameters a = 3.8952 A (SAT) and a = 3.8995 A (SAN) that are close lattice matches to the YBCO superconductors. No structural phase transitions or twins have been found, and the average coefficients of the thermal expansion match well with the YBCO superconductor materials. We report that SAT is one of the most promising substrates to date for the epitaxial growth of HTSC thin films suitable for microwave device applications as it has low dielectric constants ( K ∼ 11–12, at 100 Hz–10 GHz and 300 K) and low dielectric loss (∼4 × 10 −5 at 10 kHz and 80 K), together with lattice parameter matching, thermal expansion matching, and chemical compatibility with the high T c superconductors (YBCO).

Journal ArticleDOI
TL;DR: In this article, an automated measuring system is described which enables the complex microwave permittivity of liquids to be determined at particular frequencies and a special cell design offers the possibility of precisely measuring a range of liquids from low to high loss.
Abstract: An automated measuring system is described which enables the complex microwave permittivity of liquids to be determined at particular frequencies. A special cell design offers the possibility of precisely measuring a range of liquids from low to high loss. Constructional details of the sample cell are presented together with a system diagram of the microwave apparatus and a description of the analysis of primary data. Possible experimental errors are considered and results for measurements in the XN- and Ku-waveguide bands (5.3-8.4 and 12.5-18 GHz) are discussed.

Journal ArticleDOI
TL;DR: In this article, the reflection coefficient of dielectric thin film capacitors is measured with a network analyzer. And the relative error between the high-frequency and low-frequency is estimated to be within 10%.
Abstract: Using dielectric thin film capacitors and devices specially designed for correcting stray effect around the capacitors, the dielectric constant and dielectric loss up to 50 GHz can be successfully measured by the reflection coefficient measured with a network analyzer. The high-frequency characteristics are consistent with low-frequency characteristics measured with an LCR bridge. The relative error between the high-frequency and the low-frequency is estimated to be within 10%. The method is a practical way to obtain the characteristics of dielectric thin films accurately and quickly in final form.

Journal ArticleDOI
TL;DR: In this article, the authors studied the dielectric constant (e′) and the loss (tan δ) for hexaferrites BaCo2−xZnxFe16O27 as a function of frequency (f), temperature (T), and composition (x).

Journal ArticleDOI
TL;DR: In this article, the dielectric constant was measured at different frequencies and temperatures from room temperature to 600 K using the phase detector technique (lock-in amplifier) and the results showed that the loss decreases with increasing frequency and Cr substitution at room temperature.

Journal ArticleDOI
TL;DR: In this paper, the tensile strength and elongation of polyethylene-2,6-naphthalenedicarboxylate at 77 K were found to decrease with an increase in the degree of crystallinity, indicating that this peak is closely associated with motion in an amorphous region of the polymer.

Journal ArticleDOI
TL;DR: In this article, the dielectric behavior of polycrystalline (Ba, Sr) TiO3 thin films deposited by liquid-source metalorganic chemical vapor deposition was investigated.
Abstract: We have investigated the dielectric behavior of polycrystalline (Ba, Sr) TiO3 thin films deposited by liquid-source metalorganic chemical vapor deposition. The time-domain polarization current, the frequency dependence of the permittivity, and the dielectric loss for these CVD films are all described by a single set of parameters via the phenomenology of Curie - von Schweidler behavior. No change in the general form of the permittivity is found out to 1.5 GHz, suggesting that this description of the response is valid into the frequency range of interest for many applications. Low-frequency dispersion is found to be controllable, leading to films with very low dissipation factors and almost frequency-independent dielectric response. Finally, a non-zero intercept of the inverse of capacitance versus film thickness suggests the existence of a series interfacial capacitance, arising from either microstructural inhomogeneity or energy barriers to carrier transport at the film-electrode interfaces.

Journal ArticleDOI
01 Apr 1995
TL;DR: In this paper, the permittivity and dielectric loss tangent of cross-linked polystyrene (Rexolite), polytetrafluoroethylene (Teflon), and single-crystal quartz were measured at microwave frequencies and at temperatures of 77 K and 300 K.
Abstract: The permittivity and dielectric loss tangent of cross-linked polystyrene (Rexolite), polytetrafluoroethylene (Teflon), and single-crystal quartz were measured at microwave frequencies and at temperatures of 77 K and 300 K using a dielectric resonator technique. Dielectric loss tangents as low as 7/spl times/10/sup -6/ at 77 K were determined by applying high-temperature superconducting (HTS) films as the endplates of the dielectric resonator. Two permittivity tensor components for uniaxially anisotropic crystalline quartz were measured. Although the permittivities at 77 K changed very little from their room temperature values at 300 K, large changes in dielectric losses were observed. The decreased losses of these microelectronic substrates can markedly improve the performance of many microwave devices at cryogenic temperatures. >

Journal ArticleDOI
TL;DR: In this paper, the formation of the single phase and its basic crystal structure of polycrystalline samples of calcium-doped lead germanate Pb 4.8 Ca 0.2 Ge 3 O 11 were prepared by a solid-state reaction technique.

Journal ArticleDOI
TL;DR: In this paper, the sol-gel derived Pb[Mg 1 3 Nb 2 3 ) x Ti 1−x ]O 3 (PMNT) thin films of x = 0.5 − 1.0 were prepared on (111)-textured Pt and (100-textured LaNiO 3 electrodes.

Journal ArticleDOI
01 Jan 1995-EPL
TL;DR: In this article, an anomalies in both the linear and non-linear dielectric permittivity of weakly doped Sr1-xCaxTiO3 (x = 0.002) and strongly rising dielectoric loss in the low-frequency regime evidence coupling of Ca+ + centred polar nanoregions with the predicted coherent quantum state of the host lattice.
Abstract: Anomalies in both the linear and the non-linear dielectric permittivity of weakly doped Sr1-xCaxTiO3 (x = 0.002) and strongly rising dielectric loss in the low-frequency regime evidence coupling of Ca+ + centred polar nanoregions with the predicted coherent quantum state of the host lattice. Glassiness of the nanoregion system is modelled by Lacroix-Bene-type polydispersivity with an extrapolated freezing temperature Tg ≈ 4 K.

Journal ArticleDOI
TL;DR: In this article, the authors studied the temperature dependence of the loss factor of triglycine selenate crystals in the frequency range from 20 Hz to 1 MHz for several a.c. field amplitudes.

Journal ArticleDOI
TL;DR: In this article, a double anomaly of the dielectric permittivity was found as a function of temperature, and the origin of this phenomenon was assumed to be closely related to a sequence of phase transitions like those already observed in other mixed Aurivillius phases.
Abstract: Ceramic materials have been prepared by natural sintering and hot-forging MIIBi8Ti7O27(MII = Ca, Sr, Ba and Pb) powders synthesized using a molten salt technique. The materials are ferroelectric at room temperature and show strong dielectric anisotropy in connection with the crystal structure. In each case, a double anomaly of the dielectric permittivity was found as a function of temperature. The temperatures at which it occurs are dependent on MII. The origin of this phenomenon is assumed to be closely related to a sequence of phase transitions like those already observed in other mixed Aurivillius phases.

Journal ArticleDOI
TL;DR: The experimental results indicated that the DC and AC electrical resistivity, Curie temperature (Tc) and activation energies for electrical conduction (Ep and Ef) decrease as the sintering temperature increases.
Abstract: DC, AC electrical resistivity (ρdc and ρac (ω) and dielectric properties (e' and tan δ) were studied for Zn0.8Co0.2Fe2O4 ferrite samples prepared at sintering temperatures (Ts) in the range 1273 to 1473 K by the usual ceramic technique. The experimental results indicated that the DC and AC electrical resistivity, Curie temperature (Tc) and activation energies for electrical conduction (Ep and Ef) decrease as the sintering temperature increases. The DC electrical conductivity increases as the temperature increases. It was found that e', tan δ and ρ'ac (ω) decrease as frequency increases.

Journal ArticleDOI
TL;DR: In this article, the thermal conductivity, heat capacity and heat generation properties of two poled piezoceramic materials, a "soft" PZT-5H and a "hard" PU-4S, were measured over the temperature range from 20 K to above 150 K.
Abstract: The thermal conductivity, heat capacity and heat generation properties of two poled piezoceramic materials, a "soft" PZT-5H and a "hard" PZT-4S, were measured over the temperature range from 20 K to above 150 K. A single sample was used for each test type.The thermal conductivity (in the poling direction) of PZT-5H increased from 0.010 W/m-K at 15 K to 0.14 W/m-K at 300 K. The thermal conductivity of PZT-4S was generally higher, increasing from 0.018 to 0.34 W/m-K over the same temperature range.The heat capacity of PZT-5H increased from 23.3 J/kg-K at 23 K to 348 J/kg-K at 153 K, while the heat capacity of PZT-4S increased from 42.6 to 159 J/kg-K over the same range.Heat generation varied with drive amplitude and frequency as well as temperature, and is presented as an effective dielectric loss property. The dielectric loss for PZT-5H at 100 Hz varied from 4.15 (20 K) to 23.1 (150 K), and at 2000 Hz from 9.8 (20K) to 26.5 (150 K). As expected, the dielectric loss for the "hard" PZT-4S was lower, and vari...

Journal ArticleDOI
TL;DR: In this paper, it has been demonstrated that the dielectric loss due to the main relaxation in 1-propanol exhibits the Debye width up to timescales of 1000 s.
Abstract: By combining time- and frequency-domain techniques, the dielectric response of 1-propanol has been measured in a spectral range covering eleven decades. In particular it has been demonstrated that the dielectric loss due to the main relaxation in 1-propanol exhibits the Debye width up to timescales of 1000 s. In order to extend the range in which the dynamics of propanol can be exploited to high temperatures, conductivity relaxation due to ionic impurities has been used. The occurrence of high-frequency relaxation processes has been studied in both isomers of propanol. It is shown that the 1-propanol data yield a master curve in a previously suggested scaling representation. However, owing to the presence of the high-frequency excitations, no agreement with the universal scaling form is obtained.

Journal ArticleDOI
TL;DR: In this paper, the variations of the dielectric constant, the loss tan and the conductivity with the temperature and frequency are analyzed, and the functional relationship between the different values of these values is determined by fitting the observed data with the respective polymeric expressions of the type ϵ ′ = a 0 + a 1 T 2 - lnσ = a + b (T - T 0 ) 2.
Abstract: Results of dielectric measurements conducted on lanthanum heptamolybdate grown by a gel technique employing the system La(NO 3 ) 3 MoO 3 NH 4 OHHNO 3 Na 2 SiO 3 are presented. The variations of the dielectric constant e′, dielectric loss tan δ and conductivity σ with the temperature and frequency are critically analyzed. The dielectric constant increases with temperature at lower frequencies (10 3 Hz), reaching a maximum value of 320 at 125 °C, after which it abruptly decreases. The dielectric loss tan δ and conductivity σ show both a temperature as well as a frequency dependence. The sharp increase in e′ with temperature is attributed to total polarization resulting from a space charge effect. The functional relationship between the dielectric constant, conductivity and temperature is determined by fitting the observed data with the respective polymeric expressions of the type ϵ ′ = a 0 + a 1 T 2 - lnσ = a + b ( T - T 0 ) 2 The non-linearities and anomalous behaviour of the dielectric constant near the transition temperature, supported by hysteresis studies, indicate the possibility of these materials ferroelectric.

Journal ArticleDOI
TL;DR: In this paper, a variational formulation is derived from the vector wave equation without any assumption or simplifications, and therefore the formulation is the full-wave analysis, and propagation modes are obtained by solving the large scale generalized eigenvalue and eigenvector equations employing the subspace iteration method.
Abstract: A new functional is rigorously selected for the edge element method to solve the 2-D/sup 1///sub 2/ guided wave problems. The variational formulation is derived from the vector wave equation without any assumption or simplifications, and therefore the formulation is the full-wave analysis. Moderate to heavy ohmic loss and dielectric loss are taken into account in a natural and consistent manner. As a result, finite cross-section of arbitrary shape and finite conductivity can be handled without imposing the impedance boundary condition (IBC). The DEC may no longer be held for high-speed microelectronics applications, where the cross-section dimension may have been in the same order of the skin depths of some frequency components. The propagation modes are obtained by solving the large scale generalized eigenvalue and eigenvector equations employing the subspace iteration method. The spurious modes are totally suppressed in the whole frequency range of interest. Numerical examples of dielectric waveguides and microstrip transmission lines with finite conductivity are conducted. >

Journal Article
TL;DR: In this article, the dielectric properties of hydrated whey protein isolate (WPI), Ca-caseinate, and wheat starch, alone or in combination, were measured at ambient temperature and during heating to 90 o C.
Abstract: The dielectric properties of hydrated whey protein isolate (WPI), Ca-caseinate, and wheat starch, alone or in combination, were measured at ambient temperature and during heating to 90 o C. At lower moisture contents and ambient temperature, WPI exhibited higher dielectric properties than starch, whereas Ca-caseinate had a lower dielectric constant than either WPI or starch. At higher moisture contents, the dielectric properties were similar. At moisture contents of 30-80%, WPI showed increasing microwave absorption properties with increasing temperature; at higher moisture contents, microwave absorption by Ca-caseinate decreased with temperature. Adding WPI affected the dielectric loss and absorptivity of starch during heating but such an effect was not evident with Ca-caseinate. The dielectric properties of these systems were compared with their hydration properties by electron spin resonance using TEMPO, a water and oil-soluble noninteractive probe to correlate water mobility results to dielectric relaxation phenomena. All systems were equally effective in slowing the motion of TEMPO. However, their dielectric properties differed, indicating that the dielectric properties are not only influenced by the water but by the macromolecules present as well