Higher permittivity

C = Q/V. In a vacuum, the charge density on the surfaces of the conductors is affected by the permittivity of free space, q. When a dielectric material is placed between the conductors, the capacitance increases because of the higher permittivity, e, of the material. The ratio of e and q gives the dielectric constant, K, of the material, k = e/eg The dielectric constant of siHca glass is 3.8. 

As outlined in Section 1.3, the solvent acidity and basicity have a significant influence on the reactions and equilibria in solutions. In particular, differences in reactions or equilibria among the solvents of higher permittivities are often caused by differences in solvent acidity and/or basicity. Because of the importance of solvent acidity and basicity, various empirical parameters have been proposed in order to express them quantitatively [1, 2]. Examples of the solvent acidity scales are Kosower s Z-values [8], Dimroth and Reichard s Er scale [1, 9], Mayer, Gutmann and Gergefs acceptor number (AN) [10, 11], and Taft and Kalmefs a parameter [12]. On the other hand, examples of the solvent basicity scales are Gut-... 

A higher-permittivity dielectric based on CaTi03 is sometimes used. It has a relative permittivity of about 140 and a dissipation factor of 2 x 10 4. The TCC is about double that of rutile-based dielectrics. 

Donor-doped PZTs have higher permittivities and d coefficients than acceptor-doped materials and are therefore more suitable for converting mechanical into electrical vibrations. They have higher dissipation factors than acceptor-doped materials and are therefore not as suitable for wave filters. If this were not the case, their low ageing coefficients would be an advantage. 

Dynamic solvent effect — is a phenomenon typical for adiabatic -> electron transfer and -> proton transfer reactions. This effect is responsible for a dependence of the reaction rate on solvent relaxation parameters. The initial search for a dynamic solvent effect (conventionally assumed to be a feature of reaction adiabatic-ity) consisted in checking the viscosity effect. However, this approach can lead to controversial conclusions because the viscosity cannot be varied without changing the -> permittivity, i.e. a dynamic solvent effect cannot be unambiguously separated from a -> static solvent effect [i]. Typically a slower solvent relaxation goes along with a higher permittivity, and the interplay of the two solvents effects can easily look as if either of them is weaker. The problems of theoretical treatment of the dynamic solvent effect of solvents having several relaxation times are considered in refs, [ii-iii]. 

Obviously, the dieleetrie behavior of systems with ion pairing is much more complex than those without it. The presence of the ion pair gives the solution a higher permittivity at lower frequencies than it otherwise would have. This feature is important in understanding the equilibrium properties of these solutions. The permittivity data for the low-frequency process may be used to determine the ion pairing equilibrium constant and the rate constants for formation and breakup of this species. Thus, dielectric relaxation experiments in electrolytes provide valuable information about ion association equilibria. 

Fig. 4.10. Schematic side and top view of the electron cloud in a small molecule electron-rich organic semiconductor (e.g. an ohgothophene or an acene). Because hydrogen is more electronegative than carbon the peripheral hydrogens attract the pi electrons leading to a herringbone stacking. The higher permittivity of neighboring standing molecules leads to the nearly vertical orientation for the first few deposited layers.

The only exception is the case of the Hg-H20-Cl interface [267,271] in which the A value was close to 1. It allows one to conclude on the absence of a noticeable charge loss by this ion as well as on close values of the characteristic lengths, Lh and Lj in Eq. (88b), that is, of the corresponding capacitances. However, the latter does not mean that the physical location of the adsorbed ion is close to the outer Helmholtz plane. There are various indirect indications (in particular, presented in previous sections) that the effective dielectric permittivity, e(z), is quite nonuniform across the compact layer , its lower values being within the tail of the metal electrons while the external part of the compact layer possesses a much higher permittivity (but still much lower than the one in the bulk solvent). Then the adsorbed ion can be localized at the distance of 0.1 to 0.2 nm from the ion skeleton of the metal, that is, deeply inside the compact layer having a thickness of about 0.3 nm, Eq. (12), but A can be close to 1. 

The specific adsorption reduces the work of surface formation because of the difference in the energetic states of solvent molecules on the surface and in the bulk of the solution, and also because of the lateral interactions in the adsorbed layer. For neutral organic molecules, as a rule, the decrease in y is observed only in the vicinity of the pzc, because at high ctm I the organic molecules are squeezed out by the solvent of a higher permittivity. 

Eq. (3.4), resulting in a higher permittivity. A substance in the liquid state is therefore more strongly polarized than in the solid state ice has lower permittivity than water. 

Pyroelectric sensors utilize a wide range of material forms crystals, bulk ceramics, thick layers, and thin films. Noteworthy among new compositions with improved performance is the class of relaxor pyroelectrics. Many novel pyroelectric sensors utilize thin and thick films. Bulk pyroelectric ceramics for room temperature, and pyroelectric sensors, are widely available. New compositions with higher permittivity are available now. 

The preceding examples illustrate the variety of polymer networks which can be used to prepare dimensionally stable electrolytes with high ambient temperature conductivity. When the plasticizer is a low molecular weight polyether room temperature conductivities of about lO Sem" are obtained. On the other hand, conductivities >10" Scm at 25°C are obtained when a higher permittivity solvent such as PC, EC or EC/PC mixture is used as the plasticizer. The use of a mixture of EC and PC not only led to high room temperature conductivity but also yielded conductivities of 10 Scm" at temperatures as low as — 10°C [33]. 

As seen in Figure 15.12(a), the a transition (T ) in Nylon 6,6 is identified by the peak in the dielectric loss factor e") curve. The first temperature scan has a higher permittivity e ), a higher loss factor (e"), and a lower than those recorded during the second temperature scan. 

For a sufficient sensitivity possibly a high permittivity or capacitance of the sensor is required to compensate electrical losses via the cables. However, it is important to consider that a higher permittivity according to the relation above, implies a decrease of the voltage coefficient. 

As the water-ethanol mixture has lower permittivity ( = 50) than water (e 80), while the water-N-methylpropionamide mixture has higher permittivity (e 140), it is somewhat surprising that ESR spectra for FS counterions in an aqueous solution of PDADMAC are not consistent with the charged cylindrical cell model. The most likely cause for the failure of the model for pure water are differences in solvation of the polyelectrolyte chain compared to the mixed solvents. The organic components of both solvent mixtures feature ethyl groups that are better suited than water for solvating the hydrophobic parts of the PDADMAC chains. They may thus prevent a local hydrophobic collapse of the chain. 

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