Showing papers on "Dielectric loss published in 2001"
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TL;DR: In this article, the present state of knowledge of the chemistry, structure, and dielectric properties of these materials, as well as examples of our own work, are described and compared.
Abstract: Dielectric ceramic materials have been studied for decades due
to both their application in important technologies and the fundamentally
interesting relationships among their crystal chemistry, crystal structures,
and physical properties. Recent dramatic changes in microelectronics and in
particular wireless communications technologies have made the importance of
materials with the unusual combination of high dielectric constant, low dielectric
loss and low temperature dependence of dielectric constant of great interest.
In this review, the present state of knowledge of the chemistry, structure,
and dielectric properties of these materials, as well as examples of our own
work, are described.
528 citations
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TL;DR: Measurements for the complex permittivity of FR-4 from power frequencies up to the microwave region are presented and simple closed-form expressions are given that approximate the measured data and provide a causal response in the time domain.
Abstract: FR-4 is one of the most widely used dielectric substrates in the fabrication of printed circuits for fast digital devices. This material exhibits substantial losses and the loss tangent is practically constant over a wide band of frequencies. This paper presents measured data for the complex permittivity of this material from power frequencies up to the microwave region. In addition it gives simple closed-form expressions that approximate the measured data and provide a causal response in the time domain.
321 citations
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TL;DR: It is found that heat generation at off-resonance is caused mainly by dielectric loss tan /spl delta/' (i.e., P-E hysteresis loss), not by mechanical loss, and that a significant decrease in mechanical Q/sub m/ with an increase of vibration level was observed in resonant piezoelectric ceramic devices.
Abstract: Losses in piezoelectrics are considered in general to have three different mechanisms: dielectric, mechanical, and piezoelectric losses. This paper deals with the phenomenology of losses first, then how to measure these losses separately in experiments. We found that heat generation at off-resonance is caused mainly by dielectric loss tan /spl delta/' (i.e., P-E hysteresis loss), not by mechanical loss, and that a significant decrease in mechanical Q/sub m/ with an increase of vibration level was observed in resonant piezoelectric ceramic devices, which is due to an increase in the extensive dielectric loss, not in the extensive mechanical loss. We propose the usage of the antiresonance mode rather than the conventional resonance mode, particularly for high power applications because the mechanical quality factor Q/sub B/ at an antiresonance frequency is larger than Q/sub A/ at a resonance frequency.
287 citations
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TL;DR: In this article, a series of BaTiO3/monomer suspensions were photocured into thin wafers, and the dielectric permittivity of the composites was investigated at frequencies from 100 Hz to 10 GHz and at temperatures from −140 to +150 °C.
Abstract: Dielectric properties of model BaTiO3/polymer composites were measured over a broad frequency and temperature range. A series of BaTiO3/monomer suspensions were photocured into thin wafers. The wafers were equipped with aluminum electrodes, and the dielectric permittivity of the composites was investigated at frequencies from 100 Hz to 10 GHz and at temperatures from −140 to +150 °C. It has been found that for the same BaTiO3 loading dielectric characteristics of the composites strongly depend of the type of polymer. Polar polymers increase dielectric constant of the composites at low frequencies but have little effect at gigahertz frequencies. Dielectric losses of the composites show a maximum at some intermediate frequency within megahertz to gigahertz range that reflects the relaxation behavior of the polymer matrix. The magnitude of the losses increases with increasing polarity of the polymer component. At constant frequency and temperature, the composites follow a linear relationship between logarith...
260 citations
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TL;DR: In this paper, the structures, morphologies, and dielectric properties of thin films with two compositions, Bi1.5Zn0.5 and Bi2(Zn1/3Nb2/3)2O7, were investigated.
Abstract: Bi2O3–ZnO–Nb2O5 pyrochlore thin films were prepared on platinum coated Si wafers using a metalorganic deposition process. The structures, morphologies, and dielectric properties of films with two compositions: (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 and Bi2(Zn1/3Nb2/3)2O7, were investigated. Thin films of (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 have a cubic pyrochlore phase when crystallized at 550 °C or higher. The crystal structure of Bi2(Zn1/3Nb2/3)2O7 thin films was dependent on the firing temperature; the films showed the cubic pyrochlore phase at temperatures below 650 °C, and a pseudo-orthorhombic pyrochlore structure at 750 °C. A mixture of cubic and pseudo-orthorhombic structures was found in thin films crystallized at 700 °C. (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 films fired at 750 °C had a dielectric constant of ∼150 and a negative temperature coefficient of capacitance of −400 ppm/°C. Bi2(Zn1/3Nb2/3)2O7 thin films fired at 750 °C had a smaller dielectric constant of ∼80 and a positive temperature coefficient of capacitance of 150...
238 citations
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TL;DR: In this article, the dielectric spectra of all three glass-formers measured at temperatures above T_(g) were analyzed as a sum of a α-relaxation modeled by the Fourier transform of a Kohlrausch-Williams-Watts function and a β-rewarding model modeled by a Cole-Cole function.
Abstract: Previous dielectric relaxation measurements of glycerol and propylene carbonate and new results on propylene glycol performed below the conventional glass transition temperatures T_(g) after long periods of aging all show that the excess wing (a second power law at higher frequencies) in the isothermal dielectric loss spectrum, develops into a shoulder. These results suggest that the excess wing, a characteristic feature of a variety of glass-formers, is the high frequency flank of a Johari–Goldstein β-relaxation loss peak submerged under the α-relaxation loss peak. With this interpretation of the excess wing assured, the dielectric spectra of all three glass-formers measured at temperatures above T_(g) are analyzed as a sum of a α-relaxation modeled by the Fourier transform of a Kohlrausch–Williams–Watts function and a β-relaxation modeled by a Cole–Cole function. Good fits to the experimental data have been achieved. In addition to the newly resolved β-relaxation on propylene glycol, the important results of this work are the properties of the β-relaxation in this class of glass-formers in the equilibrium liquid state obtained over broad frequency and temperature ranges.
225 citations
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TL;DR: In this paper, the thermal noise from the internal friction of dielectric coatings made from alternating layers of Ta2O5 and SiO2 deposited on fused silica substrates was investigated.
Abstract: We report on thermal noise from the internal friction of dielectric coatings made from alternating layers of Ta2O5 and SiO2 deposited on fused silica substrates. We present calculations of the thermal noise in gravitational wave interferometers due to optical coatings, when the material properties of the coating are different from those of the substrate and the mechanical loss angle in the coating is anisotropic. The loss angle in the coatings for strains parallel to the substrate surface was determined from ringdown experiments. We measured the mechanical quality factor of three fused silica samples with coatings deposited on them. The loss angle of the coating material for strains parallel to the coated surface was found to be (4.2 +- 0.3)*10^(-4) for coatings deposited on commercially polished slides and (1.0 +- 0.3)*10^{-4} for a coating deposited on a superpolished disk. Using these numbers, we estimate the effect of coatings on thermal noise in the initial LIGO and advanced LIGO interferometers. We also find that the corresponding prediction for thermal noise in the 40 m LIGO prototype at Caltech is consistent with the noise data. These results are complemented by results for a different type of coating, presented in a companion paper.
216 citations
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TL;DR: In this article, split-post dielectric resonators operating at frequencies 1.4-5 GHz were used to measure complex permittivity of single-crystal reference materials with well known dielectrics properties previously measured by other techniques.
Abstract: Split-post dielectric resonators operating at frequencies 1.4–5.5 GHz were used to measure complex permittivity of single crystal standard reference dielectric materials with well known dielectric properties previously measured by other techniques. Detailed error analysis of permittivity and dielectric loss tangent measurements has been performed. It was proved both theoretically and experimentally that using split post resonators it is possible to measure permittivity with uncertainty about 0.3% and dielectric loss tangent with resolution 2×10 −5 for well-machined laminar specimens.
188 citations
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TL;DR: In this article, the authors investigated the dielectric properties of BaTiO 3 /epoxy composites with different types of treated ceramic powders and measured the properties of these composites as functions of temperature and frequency.
Abstract: Multi-doped BaTiO 3 /epoxy composites with the different types of treated ceramic powders are under investigation. The ceramic/epoxy composite with the 900°C treated ceramic powder has the highest dielectric constant, while lower values for those with powders treated at higher temperatures. Longer grinding of 20 h can have different heat-treated composites with similar dielectric constants. Dielectric properties of these composites were measured as functions of temperature and frequency. The increase of dielectric loss at frequencies above 1 MHz is due to the mechanism of domain-wall motion. The composite with semi-conducting fillers can have a limited increase in dielectric constant, but a large increase in dielectric loss. To have the best dielectric properties of the multi-doped BaTiO 3 /epoxy composite thick films for the printed wiring boards, the ceramic ratio need to be maximized without losing the board flexibility. A proper powder treatment is required to maximize the powder loading and performance.
166 citations
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TL;DR: In this article, the frequency dispersion associated with dielectric relaxation phenomena in polycrystalline cubic pyrochlore with normal composition (Bi1.5Zn0.5)O7 is analyzed.
Abstract: Frequency dispersion associated with dielectric relaxation phenomena in polycrystalline cubic pyrochlore with normal composition (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 is analyzed. Measurements at cryogenic temperatures and high frequencies reveal a broad distribution of relaxation times. The associated dielectric loss data can be modeled with a function convoluting the Vogel–Fulcher law and a Gaussian distribution. This function, dependent only on measuring frequency and temperature, describes exceptionally well the phenomena observed over a frequency range covering seven decades and over 300 K.
158 citations
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TL;DR: In this article, the dielectric constant as a function of thickness was fitted, using the series capacitor model, for BST thicknesses greater than 70 nm, implying a highly visible parasitic dead layer within the capacitor structure.
Abstract: Thin-film capacitors, with barium strontium titanate (BST) dielectric layers between 7.5 and 950 nm in thickness, were fabricated by pulsed-laser deposition. Both crystallography and cation chemistry were consistent with successful growth of the BST perovskite. At room temperature, all capacitors displayed frequency dispersion such that e100 kHz/e100 Hz was greater than 0.75. The dielectric constant as a function of thickness was fitted, using the series capacitor model, for BST thicknesses greater than 70 nm. This yielded a large interfacial di/ei ratio of 0.40±0.05 nm, implying a highly visible parasitic dead layer within the capacitor structure. Modeled consideration of the dielectric behavior for BST films, whose total thickness was below that of the dead layer, predicted anomalies in the plots of d/e against d at the dead-layer thickness. In the capacitors studied here, no anomaly was observed. Hence, either (i) 7.5 nm is an upper limit for the total dead-layer thickness in the SRO/BST/Au system, or (ii) dielectric collapse is not associated with a distinct interfacial dead layer, and is instead due to a through-film effect.
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TL;DR: In this paper, a relaxor-like behavior is interpreted in terms of cation disorder due to the statistical repartition of (Na,Bi) and Pb (or Na and K).
Abstract: Ceramics with compositions belonging to the Na0.5Bi0.5TiO3–PbTiO3 and Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 systems were fabricated by natural sintering of powders prepared by thermal decomposition of adequate precursor solutions. The ferroelectric to paraelectric phase transitions were studied by variable temperature X-ray diffractometry, differential scanning calorimetry and impedance measurement in a wide range of temperature and frequency. In contrast with pure NBT, both the permittivity and dielectric loss of the NBT-rich solid solutions show a strongly temperature and frequency dependent behaviour. The permittivity decreases and its maximum is shifted towards high temperatures as the frequency increases. In the high temperature range, the thermal variation of the permittivity is well described by a law 1 e − 1 e m =C T−T m γ with γ close to 1.5. Such a relaxor-like behaviour is interpreted in terms of cation disorder due to the statistical repartition of (Na,Bi) and Pb (or Na and K). This would be one very rare case of relaxor phenomena correlated with the A-site occupancy in perovskite-like materials.
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TL;DR: In this paper, the frequency dependent dielectric properties of an ideal binary composite structure were investigated by using the finite element method in the frequency domain, where the material properties of the phases were assumed to be frequency independent and the inclusion phase was more conductive than the matrix phase.
Abstract: In this article, the frequency dependent dielectric properties, e(ω), of an “ideal” binary composite structure were investigated by using the finite element method in the frequency domain. The material properties of the phases, i.e., dielectric permittivity, e, and direct-current conductivity, σ, were assumed to be frequency independent. Moreover, the inclusion phase was more conductive than the matrix phase. The inclusions were infinitely long unidirectional cylinders which could be assumed to be hard disks in two dimensions in the direction perpendicular to the cylinder direction. Three different inclusion concentration levels were considered, e.g., low, intermediate, and high. The calculated dielectric relaxations were compared with those of the dielectric mixture formulas in the literature and it was found that there were no significant differences between the formulas and the numerical solutions at low inclusion concentration. Furthermore, the obtained responses were curve fitted by the addition of t...
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TL;DR: In this article, six sillenite compounds were synthesized to obtain ∼97% dense ceramics, and an analysis of their microwave dielectric properties, performed at ∼5.5 GHz, revealed a permittivity of ∼40 for all six compounds.
Abstract: Six sillenite compounds Bi12MO20-δ (M = Si, Ge, Ti, Pb, Mn, B1/2P1/2) were synthesized, and the resulting single-phase powders were then sintered to obtain ∼97% dense ceramics. An analysis of their microwave dielectric properties, performed at ∼5.5 GHz, revealed a permittivity of ∼40 for all six compounds. The temperature coefficient of resonant frequency was the lowest for the Pb analogue (−84 ppm/K) and was found to increase with increasing ionic radius of the B-site ion to a value of −20 ppm/K for the Bi12SiO20 and Bi12(B1/2P1/2)O20 compounds. The Q×f value is a maximum for Bi12SiO20 and Bi12GeO20 with 8100 and 7800 GHz, respectively. The dielectric properties of the sillenites have been correlated with the structure of the oxygen network of the sillenite crystal lattice. As a result of its low sintering temperature (850°C), chemical compatibility with silver, low dielectric losses, and temperature-stable permittivity, the Bi12SiO20 compound is a suitable material for applications in low-temperature cofiring ceramic (LTCC) technology.
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TL;DR: The giant relative dielectric permittivity of the La-modified PbTiO (3) (PLT) with A-site vacancy potentially makes it one of the most promising materials for numerous modern technological applications.
Abstract: Giant dielectric permittivity was observed in La-modified PbTiO (3) (PLT) with A-site vacancy. The observed values of PLT with A-site vacancy are 1 order of magnitude larger than those of relaxor ferroelectrics. The giant relative dielectric permittivity, coupled with a low dielectric loss (tandelta approximately 0.03) of the PLT, potentially makes it one of the most promising materials for numerous modern technological applications.
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TL;DR: In this article, the complex (electric) permittivity of aqueous solutions of d-glucose and d-fructose has been determined as a function of frequency υ between 300 kHz and 40 GHz.
Abstract: At some solute concentrations c between 1 and 5.4 mol/L, the complex (electric) permittivity of aqueous solutions of d-glucose and d-fructose has been determined as a function of frequency υ between 300 kHz and 40 GHz. The permittivity spectrum of the 5.4 mol/L d-fructose solution has been measured at six temperatures between 10 and 35 °C, and the other spectra have been taken at 25 °C. All dielectric spectra revealed one dispersion/dielectric loss region, which indicated a rather homogeneous relaxation of the solute and solvent dipole moments. Analytically, the measured spectra were represented by the Cole−Cole relaxation spectral function, which corresponds with a continuous, symmetrically bell shaped relaxation time distribution. The parameters of the spectral function are discussed to show that the monosaccharides exhibit unusual hydration properties. Particularly, when treated in terms of a wait-and-switch model of dipole reorientation, the principal dielectric relaxation time is indicative of the ex...
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TL;DR: In this article, the authors measured the dielectric properties of mixed Mn-Zn-Er ferrites having the compositional formula Mn0.58Zn0.37Er1.05−xErx04 (where itx = 0.2, 0.4, 0.,6, 0,8 and 1.0) at room temperature in the frequency range 1−13 MHz using a HP 4192A impedance analyser.
Abstract: Dielectric properties such as dielectric constant (e′) and dielectric loss tangent (tan□δ) of mixed Mn-Zn-Er ferrites having the compositional formula Mn0.58Zn0.37Fe2.05−xErx04 (where itx = 0.2, 0.4, 0.6, 0.8 and 1.0) were measured at room temperature in the frequency range 1–13 MHz using a HP 4192A impedance analyser. Plots of dielectric constant (e′) vs frequency show a normal dielectric behaviour of spinel ferrites. The frequency dependence of dielectric loss tangent (tan δ) was found to be abnormal, giving a peak at certain frequency for all mixed Mn-Zn-Er ferrites. A qualitative explanation is given for the composition and frequency dependence of the dielectric constant and dielectric loss tangent. Plots of dielectric constant vs temperature have shown a transition near the Curie temperature for all the samples of Mn-Zn-Er ferrites. However, Mn0.58Zn0.37Er1.0Fe1.05O4 does not show a transition. On the basis of these results an explanation for the dielectric mechanism in Mn-Zn-Er ferrites is suggested.
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TL;DR: In this paper, the key factors influencing microwave dielectric loss are examined and a comparison is made between single crystals and polycrystalline analogues, for temperatures between 20 and 300 K.
Abstract: The key factors influencing microwave dielectric loss are examined. A comparison is made between single crystals and polycrystalline analogues. Measurements of the temperature dependence of microwave dielectric losses in various materials are reported, for temperatures between 20 and 300 K. Single crystal and polycrystalline TiO2, LaAlO3, MgO and Al2O3 are considered. The temperature dependence of dielectric losses of certain single crystals (MgO and Al2O3) are found to be in good agreement with the theory of intrinsic losses for temperatures above 100 K. At lower temperatures losses due to defects and grain boundaries dominate. The absolute value of the loss predicted by theory is considerably lower than measured values.
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TL;DR: In this paper, the dielectric and ferroelectric properties were investigated along the a(b) axis and c axis, separately, at the Curie temperature of 520 °C.
Abstract: SrBi4Ti4O15 single crystals were grown, and their dielectric and ferroelectric properties were investigated along the a(b) axis and c axis, separately. The dielectric permittivity at 1 MHz was 1900 along the a(b) axis at the Curie temperature of 520 °C. This value was ten times higher than that along the c axis. With respect to the ferroelectricity, the saturated remanent polarization was 29 μC/cm2 and the saturated coercive field was 26 kV/cm along the a(b) axis under an electric field of 59 kV/cm, and ferroelectricity was not observed along the c axis.
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TL;DR: Ferroelectric thin films of barium titanate were fabricated by sol-gel technique on platinum substrates as discussed by the authors, and the films obtained with a thickness of 1.5 μm were dense, transparent, and showed ferroelectricity.
Abstract: Ferroelectric thin films of barium titanate were fabricated by sol–gel technique on platinum substrates. The processing temperature was 700 °C. The films obtained with a thickness of 1.5 μm were dense, transparent, and showed ferroelectricity. Scanning electron microscopy and x-ray diffraction were used for studying the surface morphology and crystallographic structure of the film. Films in the metal–ferroelectric–metal configuration (MFM) were used for the electrical measurements. Dielectric constant and loss tangent were found to be 430 and 0.015, respectively, at 10 kHz under ambient conditions. The e′(T) curve shows broad peak centered around 120 °C as in the case of diffuse phase transition. The ac conductivity is proportional to ω0.9 in the low frequency region and ω1.8 in the high frequency region. The dc conductivity versus temperature curve showed a change in the slope around 125 °C, corresponding to the phase transition. To study the low temperature phase transitions, dielectric parameters on th...
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TL;DR: In this paper, the microwave cavity technique was used to study high-frequency dielectric properties of A5B4O15 (A=Ba, Sr, Mg, Zn, Ca, B=Nb, Ta) ceramics.
Abstract: High-frequency dielectric properties of A5B4O15 (A=Ba, Sr, Mg, Zn, Ca; B=Nb, Ta) dielectric ceramics are studied by means of the microwave cavity technique, a combination of far-infrared reflection and transmission spectroscopy and time-resolved terahertz transmission spectroscopy Microwave permittivity e′ and Q×f factor vary, depending on the chemical composition, between 11 and 51, and 24 and 88 THz, respectively The temperature coefficient τf varies between −73 and 232 ppm/°C, and in two samples |τf| is less than 15 ppm/°C It is shown that the microwave permittivity e′ of the ceramics studied is determined by the polar phonon contributions and that linear extrapolation of the submillimeter dielectric loss e″ down to the microwave region is in agreement with the microwave data of single phase samples The relationship among phonon spectra, the crystal structure, and the unit cell volume is discussed
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TL;DR: In this article, the phase formation behavior and structural growth characteristics using x-ray diffraction and atomic force microscopy were characterized in terms of their dielectric properties, and a tentative mechanism of the epitaxial growth has been proposed.
Abstract: In the present work process methodology was optimized to synthesize oriented barium strontium titanate (BST) (50/50) and (60/40) thin films on strontium titanate (100) and lanthanum aluminate (LAO) (100) substrates by using the chemical solution deposition technique. These films were characterized in terms of their phase formation behavior and structural growth characteristics using x-ray diffraction and atomic force microscopy. A tentative mechanism of the epitaxial growth has been proposed. Films were also characterized in terms of their dielectric properties. The high tunability and low dielectric loss of these films make them attractive for fabricating tunable dielectric devices. Accordingly, we have fabricated eight element coupled microstrip phase shifters and tested them in terms of their degree of phase shift and insertion loss characteristics. An insertion loss of 8.435 dB, phase shift in the order of 320° (2.6–14.5 V/μm) and κ factor (phase shift/dB of loss) of about 38.0°/dB was achieved in BST (60/40) films deposited on LAO (100) substrate which is comparable to the films grown by other film deposition techniques reported in the literature. The microstructure of the sol–gel derived films show surface porosity which may be responsible for the low dielectric strength of these films. Presently, we are studying the sintering mechanism and kinetics of these films in order to improve the density which is believed to further improve the phase shift and lower insertion loss to result in an improved tunability.
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TL;DR: In this article, a dielectric composite consisting of a polymer coated onto a high-density metallized Kraft has been developed for application in pulse power capacitors, which can achieve 2 to 3 J/cm/sup 3/ whole capacitor energy density at voltage levels above 3.0 kV, and can maintain its physical properties to temperatures above 175/spl deg/C.
Abstract: A new dielectric composite consisting of a polymer coated onto a high-density metallized Kraft has been developed for application in pulse power capacitors. The polymer coating is custom formulated for high dielectric constant and strength with minimum dielectric losses. The composite can be wound and processed using conventional wound film capacitor manufacturing equipment. This new system has the potential to achieve 2 to 3 J/cm/sup 3/ whole capacitor energy density at voltage levels above 3.0 kV, and can maintain its physical properties to temperatures above 175/spl deg/C. The technical and manufacturing development of the composite material and fabrication into capacitors are summarized in this paper. Energy discharge testing, including capacitance and charge-discharge efficiency at normal and elevated temperatures, as well as DC life testing were performed on capacitors manufactured using this material. TPL (Albuquerque, NM) has developed the material and Aerovox (New Bedford, MA) has used the material to build and test model capacitors. The results of the testing will focus on pulse power applications specifically those found in electromagnetic armor and guns, high power microwave sources and defibrillators.
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TL;DR: The flash-photolysis time-resolved microwave conductivity technique (FP-TRMC) has been used to investigate the nature of the relaxed S(1) state of 9,9'-bianthryl, CAA, and 10,10'-dicyano-9, 9'-bianstryl (CAAC) and conclusively demonstrate the dipolar nature of S( 1) for all three compounds in the pseudopolar solvents benzene and 1
Abstract: The flash-photolysis time-resolved microwave conductivity technique (FP-TRMC) has been used to investigate the nature of the relaxed S1 state of 9,9‘-bianthryl (AA), 10-cyano-9,9‘-bianthryl (CAA), and 10,10‘-dicyano-9,9‘-bianthryl (CAAC). Changes in both the real, Δe‘ (dielectric constant), and imaginary, Δe‘ ‘ (dielectric loss), components of the complex permittivity have been measured. The dielectric loss transients conclusively demonstrate the dipolar nature of S1 for all three compounds in the pseudopolar solvents benzene and 1,4-dioxane, and even in the nonpolar solvents n-hexane and cyclohexane. The required symmetry breaking is considered to result from density and structural fluctuations in the solvent environment. The dipole relaxation times for AA (CAAC) are ca. 2 ps for the alkanes and 7.9 (5.3) and 14 (14) ps for benzene and dioxane, respectively. The time scale of dipole relaxation for the symmetrical compounds is much shorter than that for rotational diffusion and is attributed to intramolec...
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TL;DR: In this paper, improved dielectric properties of lead zirconate titanate (PZT) films deposited on a variety of foils using buffer layers are reported.
Abstract: Improved dielectric properties of lead zirconate titanate (PZT) films deposited on a variety of foils using buffer layers are reported. Foils include titanium, stainless steel, and nickel with LaNiO3(LNO) buffer layers which were prepared by sol–gel processing. High dielectric constant (330 for stainless steel, 420 for titanium, and 450 for nickel foils), low dielectric loss (<2.2% for titanium and 8% for stainless steel), symmetric ferroelectric C–V characteristics and P–E curves were obtained. The LNO layers are shown to provide an effective diffusion barrier for Ni and Cr and to restrict oxide layer formation (i.e., TiOx or NiOx) between the PZT film and the metallic foils during annealing in air.
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TL;DR: In this paper, the same crystal structure as that of strontium bismuth tantalate, SrBi2Ta2O9 (SBT), but an increased paraferroelectric transition temperature at ∼360°C as compared to 305°C for SBT.
Abstract: The strontium bismuth tantalate vanadate, SrBi2Ta1.8V0.2O9, (SBTV) layered perovskite ferroelectrics were made by solid state powder sintering. It was found that the SBTV ferroelectrics had the same crystal structure as that of strontium bismuth tantalate, SrBi2Ta2O9 (SBT), but an increased paraferroelectric transition temperature at ∼360 °C as compared to 305 °C for SBT. In addition, SBTV ferroelectrics showed a frequency dispersion at low frequencies and broadened dielectric peaks at the paraferroelectric transition temperature that shifted to a higher temperature with a reduced frequency. However, after a postsintering annealing at 850 °C in air for 60 h, SBTV ferroelectrics showed reduced dielectric constants and tangent loss, particularly at high temperatures. In addition, no frequency dependence of paraferroelectric transition was found in the annealed SBTV ferroelectrics. Furthermore, there was a significant reduction in dc conductivity with annealing. The prior results implied that the dielectric ...
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TL;DR: In this article, the dielectric permittivity of the phase Bi3Zn2Sb3O14 was studied by means of impedance spectroscopy, and the measurements were performed in the frequency range of 5 Hz-13 MHz and at temperatures ranging from 100°C to 500°C.
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TL;DR: In this article, the Maxwell-Wagner model was proposed to predict both the dielectric enhancement and frequency dependence when the individual layer thickness is more than 40 nm, which can predict the increase in dielectrics of polycrystalline BaTiO3/Ba0.6Sr0.8Sr 0.2TiO 3 thin films.
Abstract: Dielectric enhancement was observed in polycrystalline BaTiO3/Ba0.6Sr0.4TiO3 multilayered thin films deposited layer-by-layer on Pt/Ti/SiO2/Si substrates via pulsed laser deposition. The dielectric constant of the films was enhanced more than four times with the decrease of the individual layer thickness down to 30 nm, while the dielectric loss was kept at a low level comparable to that of the solid solution Ba0.8Sr0.2TiO3 thin films. The Maxwell-Wagner model is proposed to explain the experimental data, which can predict both the dielectric enhancement and frequency dependence when the individual layer thickness is more than 40 nm.
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TL;DR: In this article, a novel gel auto-combustion method was used to synthesize Mg-Zn-Cu ferrite powders with compositions of (Mg 0.5− x Cu x Zn 0.98)O(Fe 2 O 3 ) 0.20, 0.25,0.35, 040).
Abstract: A novel gel auto-combustion method was used to synthesize Mg–Zn–Cu ferrite powders with compositions of (Mg 0.5− x Cu x Zn 0.5 )O(Fe 2 O 3 ) 0.98 (where x =0.20, 0.25, 0.30, 0.35, 0.40). X-ray diffraction results showed that the dried gels, synthesized from metal nitrites and citric acid, transformed directly into nano-sized ferrite particles after an auto-combustion process in air. The synthesized powders exhibited high-sintering activity, and can be sintered at temperature less than 950 °C. The low-temperature sintered Mg–Zn–Cu ferrites prepared possess good electromagnetic properties, as well as fine-grained microstructures, making them become good materials for multilayer chip inductors with high-performance and low-cost. Copper content has significant influence on the electromagnetic properties, such as initial permeability, quality factor, DC resistivity, dielectric constant and dielectric loss tangent as well as their frequency dispersion for Mg–Zn–Cu ferrites. The possible reasons that are responsible for the composition dependence of main electromagnetic properties were discussed.
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TL;DR: In this paper, a polaron hopping mechanism was used to obtain the dielectric constant (e′), loss tangent (tan δ), and AC conductivity ( σ AC ) of magnetoelectric composites in the frequency range 100 Hz-1 MHz and also in the temperature range 30-400°C.
Abstract: Magnetoelectric composites with composition x BaTiO 3 +(1− x )MnFe 1.8 Cr 0.2 O 4 in which x varies as 1, 0.85, 0.7, 0.55 and 0 were prepared by a standard ceramic technique. X-Ray analysis confirms single-phase formation in x =1 and x =0 compositions whereas the presence of both phases in x =0.85, 0.7 and 0.55 compositions. The dielectric constant (e′), loss tangent (tan δ) and AC conductivity ( σ AC ) of the composites have been investigated in the frequency range 100 Hz–1 MHz and also in the temperature range 30–400 °C. The results obtained are interpreted in terms of a polaron hopping mechanism. Static magnetoelectric conversion factor (d E /d H ) as a function of magnetic field was measured in x =0.85, 0.70 and 0.55 compositions. The maximum value of d E /d H obtained was 150 μV/(cm −1 ×Oe) for x =0.85 composition.