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Dielectric constant low frequency

Here e , is the high frequ y limit of s, So is the static dielectric constant (low frequency limit of s ). So - Soo = A is the dielectric increment, fR is the relaxation frequency, a is the Cole-Cole distribution parameter, and P is the asymmetry parameter. The relaxation frequency is related to the relaxation time by fa = (27It) A simple exponential decay of P (oc,P = 0) is characterised by a single relaxation time (Debye-process [1]), P = 0 and 1 < a < 0 describe a Cole-Cole-relaxation [2] with a symmetrical distribution function of t whereas the Havriliak-Negami equation (EQN (4)) is used for an asymmetric distribution of x [3]. The symmetry can be readily seen by plotting s versus s" as the so-called Cole-Cole plot [4-6]. [Pg.203]

The terms polarizability constant and dielectric constant can be utilized interchangeably in the qualitative discussion of the magnitude of the dielectric constant. The k values obtained utilizing dc and low-frequency measurements are a summation of electronic E, atomic A, dipole P0, and interfacial /, polarizations. Only the contribution by electronic polarizations is evident at high frequencies. The variation of dielectric constant with frequency for a material having interfacial, dipole, atomic, and electronic polarization contributions is shown in Figure 6.1. [Pg.74]

This is true when the dielectric constant is measured at sufficiently low frequencies. Variation of dielectric constant with frequency is discussed below. [Pg.155]

In compound crystals, the ujn values considered are wlo, the frequency of the longitudinal optical phonons on the high-energy (h-e) side, and wto, the frequency of the transverse optical phonons, on the low-energy side. The dielectric constant at frequencies above c lo is denoted as while that below wto is denoted as s (the index s represents static, despite the fact that s shows a small dispersion between the value just below ujto and the one at radiofrequencies1). It can be seen from expressions (3.14) and (3.15) that above ujo, the ionic contribution decreases such that qo is smaller than s. Typical values are given in Table 3.1. [Pg.49]

Figure 4.157 Dielectric constant vs. frequency at 23°C for BASF Ultradur S4090 G4—low warpage PBT/ASA blend, 20% glass fiber polyester alloy/blend resin. Figure 4.157 Dielectric constant vs. frequency at 23°C for BASF Ultradur S4090 G4—low warpage PBT/ASA blend, 20% glass fiber polyester alloy/blend resin.
Typically, LCP s have a high mechanical strength at high temperature, extreme chemical resistance, inherent flame retardancy, and good weather ability features. They come in a variety of forms from sinterable high temperature compounds to injection moldable formulations. Due to their various properties, LCP s are useful for electrical and mechanical parts, food containers, and other applications that require chemical inertness and high strength. They are particularly attractive for microwave frequency electronic uses due to their low relative dielectric constants, low dissipation features, and commercial availability of laminates. [Pg.1462]

The important feature of LC polyesters is a low coeffident of thermal expansion a < 1 x 10 grad that is comparable with the value for inorganic glasses (5 x 10 grad ) and significantly less in comparison with ordinary polymers (1 x 10 grad" ). These properties have led to the use of Vectra LC polymers in many electronic applications such as sockets, switches, bobbins, connectors, chip carriers, and sensors. Vectra LC polymers have replaced stainless steel in medical applications. The LC polyesters are particularly attractive for miaowave frequency electronics due to low relative dielectric constants, low dissipation factors, and the commerdal availability of laminates. [Pg.271]

Figure 7 shows the variation of dielectric constant with frequency at room temperature for SPE and NCPE films. It is observed that dielectric constant decrease with increasing field frequency. High value of dielectric constant at low frequency can be explained by the presence of space charge effects due to acciunulation of enhanced charge carrier density near the electrode. As frequency increases, the periodic reversal of the electric field occurs so fast that there is restriction of excess ion diffusion in the direction of applied field and hence dielectric constant decreases. Thus conductivity... [Pg.79]

Higher operating frequencies can also impact each of the three main components of base materials. Circuits operating at high frequencies are driving the use of materials with low dielectric constants, low dissipation factors, and tighter thickness tolerances. These performance issues and the impact to the printed circuit manufacturing process are discussed in this chapter. [Pg.181]

The TSDC method is a dielectric method in the temperature domain, which allows for a fast characterization of the dielectric response of the material under investigation. The method consists of measuring the thermally activated release of stored dielectric polarization. It corresponds to measuring dielectric losses against temperature at constant low frequencies of Hz [25,26]. The... [Pg.386]

The dielectric constant (permittivity) tabulated is the relative dielectric constant, which is the ratio of the actual electric displacement to the electric field strength when an external field is applied to the substance, which is the ratio of the actual dielectric constant to the dielectric constant of a vacuum. The table gives the static dielectric constant e, measured in static fields or at relatively low frequencies where no relaxation effects occur. [Pg.464]

Tetralluoroethylene polymer has the lowest coefficient of friction of any solid. It has remarkable chemical resistance and a very low brittleness temperature ( — 100°C). Its dielectric constant and loss factor are low and stable across a broad temperature and frequency range. Its impact strength is high. [Pg.1016]

This copolymer has useful properties from cryogenic temperatures to 180°C. Its dielectric constant is low and stable over a broad temperature and frequency range. [Pg.1017]

In air, PTFE has a damage threshold of 200—700 Gy (2 x 10 — 7 x 10 rad) and retains 50% of initial tensile strength after a dose of 10" Gy (1 Mrad), 40% of initial tensile strength after a dose of 10 Gy (10 lad), and ultimate elongation of 100% or more for doses up to 2—5 kGy (2 X 10 — 5 X 10 rad). During irradiation, resistivity decreases, whereas the dielectric constant and the dissipation factor increase. After irradiation, these properties tend to return to their preexposure values. Dielectric properties at high frequency are less sensitive to radiation than are properties at low frequency. Radiation has veryHtde effect on dielectric strength (86). [Pg.352]

For low frequency electrical insulation appHcations, the dielectric constant of the insulation is ideaUy as low as possible (see Insulation, electrical). The lower the density of the ceUular polymer, the lower the dielectric constant and the better the electrical insulation. Dielectric strength is also reduced at... [Pg.416]

For most commercial voltages and frequencies used in power distribution, the capacitance effects are negligible. At relatively high voltages the current due to capacitance may reach sufficient value to affect the circuit, and insulation for such an appHcation is designed for a moderately low dielectric constant. [Pg.326]

Electrical Properties. AH polyolefins have low dielectric constants and can be used as insulators in particular, PMP has the lowest dielectric constant among all synthetic resins. As a result, PMP has excellent dielectric properties and alow dielectric loss factor, surpassing those of other polyolefin resins and polytetrafluoroethylene (Teflon). These properties remain nearly constant over a wide temperature range. The dielectric characteristics of poly(vinylcyclohexane) are especially attractive its dielectric loss remains constant between —180 and 160°C, which makes it a prospective high frequency dielectric material of high thermal stabiUty. [Pg.429]

Electrical Properties. Polysulfones offer excellent electrical insulative capabiUties and other electrical properties as can be seen from the data in Table 7. The resins exhibit low dielectric constants and dissipation factors even in the GH2 (microwave) frequency range. This performance is retained over a wide temperature range and has permitted appHcations such as printed wiring board substrates, electronic connectors, lighting sockets, business machine components, and automotive fuse housings, to name a few. The desirable electrical properties along with the inherent flame retardancy of polysulfones make these polymers prime candidates in many high temperature electrical and electronic appHcations. [Pg.467]

Because of very high dielectric constants k > 20, 000), lead-based relaxor ferroelectrics, Pb(B, B2)02, where B is typically a low valence cation and B2 is a high valence cation, have been iavestigated for multilayer capacitor appHcations. Relaxor ferroelectrics are dielectric materials that display frequency dependent dielectric constant versus temperature behavior near the Curie transition. Dielectric properties result from the compositional disorder ia the B and B2 cation distribution and the associated dipolar and ferroelectric polarization mechanisms. Close control of the processiag conditions is requited for property optimization. Capacitor compositions are often based on lead magnesium niobate (PMN), Pb(Mg2 3Nb2 3)02, and lead ziac niobate (PZN), Pb(Zn 3Nb2 3)03. [Pg.343]

Polymers with outstandingly high resistivity, low dielectric constant and negligible power factor, all substantially unaffected by temperature, frequency and humidity over the usual range of service conditions. [Pg.110]

In the case of symmetrical molecules such as carbon tetrachloride, benzene, polyethylene and polyisobutylene the only polarisation effect is electronic and such materials have low dielectric constants. Since electronic polarisation may be assumed to be instantaneous, the influence of frequency and temperature will be very small. Furthermore, since the charge displacement is able to remain in phase with the alternating field there are negligible power losses. [Pg.112]


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See also in sourсe #XX -- [ Pg.16 , Pg.455 ]




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