Dielectric loss coefficient

Dielectric constant, e33/e9 frequency - 103 Hz frequency -106 Hz Dielectric losses, tan S (along OZ) frequency -103 Hz frequency -106 Hz Pyroelectric coefficient p l(f9 C cni2 -K1... 

Typically, large-scale gas filling makes the main characteristics of foam plastics — coefficients of heat and temperature conductivity, dielectric permeability, and the tangent of the dielectric loss angle — totally independent of the chemical structure of the original polymer [1],... 

Thin-film dielectrics (Ba0 92Ca108)(Ti0 92Zr0 08)O3 for the thin-film capacitors were prepared using Ba, Ca, and Zr ethoxides and Ti isopropoxide in refluxed methoxyethanol solutions as precursors. Films were deposited on a usual platinized Si substrate. Crystalline thin films after heat treatment at 800°C demonstrated dielectric permittivity of 1200, dielectric loss of0.5%, nonlinear coefficient a = 0.92, and break-down voltage of980 V [1595],... 

Figure 25. Frequency dependence of the absorption coefficient (a) and dielectric loss (b). Liquid fluoromethane CH F at 133 K calculated for that hat-curved model (solid lines). Dashed curve in Fig. (a) refers to the experimental [43] data, vertical line in Fig. (b) marks the experimental position of the maximum dielectric loss. The parameters of the hat-curved model are presented in Table VIII.

Figure 32. Absorption coefficient (a, b, c) and dielectric loss (d, e, f). Water H20 at 27°C (a, d), water H20 at 22.2°C (b, e), and water D20 at 22.2°C (c, f) Solid lines Calculation for the hat-curved model experimental [42, 51] values of absorption (squares) and loss (dashed lines), calculation from empirical formula [17] (dashed-and-dotted lines). Contribution to absorption due to nonrigidity of dipoles is shown by dots.

Figure 43. Wideband FIR spectra calculated for the composite hat-curved-cosine-squared potential model (solid lines) dashed-and-dotted lines mark the contribution due to dipoles vibrating in the shallow CS well. Water H20 (a, c, e) and water D20 (b, d, f) at 22.2°C. Absorption coefficient (a-d) and dielectric loss (e, f) in Figs, a, b, e, f, dashed lines refer to the experiment [17, 51, 54]. In Figs, c, d dahsed lines mark the contribution to absorption due to dipoles reorienting in a deep hat-curved well.

Figure 52. Frequency dependencies of dielectric loss (a, c) and of absorption coefficient (b, d) calculated for NaCl-water solution at concentration 0.5 mol/liter, temperature 20° C. Other explanations are given in the text.

In expression (5), sm is the high-frequency dielectric constant of metal caused by interband transitions. The value sm in the first approximation can be taken to be equal to 1 [16]. The imaginary part of coefficient at E in the formula (4) represents dielectric losses s" from conductivity electrons... 

In forsterite ceramics the mineral forsterite (Mg2Si04) crystallizes. They have excellent low-dielectric-loss characteristics but a high thermal expansion coefficient which imparts poor thermal shock resistance. During the 1960s they were manufactured for parts of rather specialized high-power devices constructed from titanium and forsterite and for which the operating temperature precluded the use of a glass-metal construction. The close match between the thermal expansion coefficients of titanium and forsterite made this possible. Today alumina-metal constructions have completely replaced those based on titanium-forsterite and the ceramic is now manufactured only to meet the occasional special request. 

Donor doping in PZT would be expected to reduce the concentration of oxygen vacancies, leading to a reduction in the concentration of domain-stabilizing defect pairs and so to lower ageing rates. The resulting increase in wall mobility causes the observed increases in permittivity, dielectric losses, elastic compliance and coupling coefficients, and reductions in mechanical Q and coercivity. 

The contribution E(ds/dT) (Eq. (7.3)) can be made by all dielectrics, whether polar or not, but since the temperature coefficients of permittivity of ferroelectric materials are high, in their case the effect can be comparable in magnitude with the true pyroelectric effect. This is also the case above the Curie point and where, because of the absence of domains, the dielectric losses of ferroelectrics are reduced, which is important in some applications. However, the provision of a very stable biasing field is not always convenient. 

For convenience (and to avoid confusion) we write n as . k is known as the extinction coefficient and is responsible for attenuation of light in the same manner as is responsible for attenuation of electrical field causing dielectric loss. 

For the frequency range 10-1000 cm-1 we present in Fig. 20a, b by solid lines the far-IR ice spectra of the absorption coefficient a(v) and of dielectric loss e"(v) calculated for the temperature — 7°C. The symbols V, T, L refer, respectively, to the V-, translational, and librational bands. The open circles mark the experimental data by Warren [49] these data are reproduced in Table IX. The fitted model and molecular parameters, used in this calculation, are given in Table X. 

Figure 20 Frequency dependences of absorption coefficient (a, c) and of dielectric loss (c, d) and Cole-Cole plot for water (e). Solid lines represent calculation for ice at —7°C (a, b) and for liquid water at 27°C (c, d). Open circles refer to the experimental data obtained for ice by Warren [49] and for water by Downing and Williams [22] and Liebe et al. [19].

Dielectric Relaxations Analysis Figure 2.11 shows the permittivity loss coefficient (e") data for dry annealed chitin before (80 °C, solid triangles) and after dc conductivity correction (open triangles). From dielectric measurements the frequencies at which contact/polarization effects become relevant (about 2 Hz for the contact effects... 

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