Permittivity measurements

An alternative electrical method that has been used in the study of glass-ionomer cements has been the measurement of dielectric properties. Tay Braden (1981, 1984) measured the resistance and capacitance of setting cements at various times from mixing. From the results obtained, relative permittivity and resistivity were calculated. In general, as these cements set, their resistivity was found to fall rapidly, then to rise again. Both these results and the results of relative permittivity measurements were consistent with the cements comprising highly ionic and polar structures. 

Permittivity measurements have been used to study hydrogen bonding of phenol or carboxylic acids with trialkylphosphine oxides (154). The results can be explained in terms of a simple electrostatic model. The properties of trimethylphosphine oxide were different from the general properties of the series.189... 

When applying an alternating electric field to a polymer placed between two electrodes, the response is generally attenuated and the output current is out of phase compared with the input voltage. This response stems from the polymer s capacitive component and its conductive or loss component, as represented by a complex dielectric permittivity measured frequencies f, and temperatures T ... 

Klein, K. (2004) Permittivity measurements of high conductivity specimens using an open-ended coaxial probe-measurement limitations, Journal of Environmental Engineering Geophysics 9, 191-200... 

Klein, K. and Santamarina, J.C. (1997) Methods for broad-band dielectric permittivity measurements (soil-water mixtures, 5 Hz to 1.3 GHz), ASTM Geotechnical Testing Journal 20, 168-178... 

Or, D. and Wraith, J.M. (1999) Temperature effects on soil bulk dielectric permittivity measured by time domain reflectometry A physical model, Water Resources Research 35 Suppl. 2, 371-383... 

Much of the research on solvation dynamics has been devoted to polar solute-solvent systems. In these media, it has been found that the response to a change in solute dipole is due primarily to collective solvent reorientation and that it can be predicted reasonably well using information on pure solvent dipolar reorientation, for example, from dielectric permittivity measurements, as input [1,6,7,9],... 

Full details of the solution preparation procedure have appeared previously (jl). The permittivity measurements were obtained at 20 C using sample cells thermostatically controlled to - 0.1 Q The determinations were made at 45 frequencies and the mean value of at each frequency is shown in Figure 1. 

Fig. 2.40 Properties of single-crystal BaTi03 (a) unit-cell distortions of the polymorphs (b) lattice dimensions versus temperature (after R. Clarke J. Appl. Cryst. 9, 335, 1976) (c) spontaneous polarization versus temperature (d) relative permittivities measured in the a and c directions versus temperature (after W.J. Merz Phys. Rev. 76, 1221, 1949).

Where sE, sD are the elastic compliances and the superscripts denote the parameters held constant similarly sx denotes the permittivity measured at constant stress (the usual condition) to measure the permittivity at constant strain ex is more difficult to accomplish. 

However, the linear response of a dielectric to an applied field is an approximation the actual response is non-linear and is of the form indicated in Fig. 8.6. The electro-optic effect has its origins in this non-linearity, and the very large electric fields associated with high-intensity laser light lead to the non-linear optics technology discussed briefly in Section 8.1.4. Clearly the permittivity measured for small increments in field depends on the biasing field E0, from which it follows that the refractive index also depends on E0. The dependence can be expressed by the following polynomial ... 

Figure 1. RTV silicone cure study (A) Permittivity measurement, (B) Loss factor measurement with time at ambient temperature.

In this equation is the dielectric permittivity measured at infrared or micro-wave frequencies, which is up to five times higher than op. This dielectric permittivity has a very significant influence on the final values of Tl (see Eq. (37)). 

IIL High frequency permittivity measurements on electrolyte solutions and their solvents... 

This review article is concerned with the structure, bonding, and dynamic processes of water molecules in crystalline solid hydrates. The most important experimental techniques in this field are structural analyses by both X-ray and neutron diffraction as well as infrared and Raman spectroscopic measurements. However, nuclear magnetic resonance, inelastic and quasi elastic neutron scattering, and certain less frequently used techniques, such as nuclear quadrupole resonance, electron paramagnetic resonance, and conductivity and permittivity measurements, are also relevant to solid hydrate research. 

R. J. Sheppard, B. R Jordan, and E. H. Grant, "Least Squares Analysis of Complex Data with Applications to Permittivity Measurements," Journal of Physics D—Applied Physics, 3 (1970) 1759-1764. 

Some Remarks on the Microwave Permittivity Measurements of Organic Semiconductors 409... 

SOME REMARKS ON THE MICROWAVE PERMITTIVITY MEASUREMENTS OF ORGANIC SEMICONDUCTORS... 

The application of microwave contactless techniques to the complex permittivity measurements of organic semiconductors is briefly discussed. Special attention is paid to the cavity perturbation technique of Buravov and Shchegolev and the dielectric resonance technique of Jaklevic and Saillant. 

The relative permittivity measures the alignment of the solvent dipoles and production of induced dipoles by an electric field. An ion produces an intense field on bound solvent molecules, and will cause partial, if not complete, alignment of the dipoles of the solvent molecules affected by the ion. This results in a drop in the observed relative permittivity of the solution relative to the pure solvent. This drop is related to the number of bound solvent molecules. Controversy exists as to whether the effect is restricted to bound molecules only, or whether other solvent molecules are involved. Both theoretical and experimental studies have been carried out. The dependence of the relative permittivity on the distance from a given ion is of fundamental importance in theories of electrolyte solutions where generally the bulk relative permittivity is used in the theoretical expressions. But it is more likely that a varying relative permittivity should be used. 

Power Factor and Permittivity Measurements of dielectric constant and loss in polymeric solids and melts over a wide frequency range was described in detail elsewhere [Porter and Boyd, 1972]. 

The table gives the static relative permittivity i.e., the relative permittivity measured in static fields or at low frequencies where no relaxation effects occur. The fourth column of the table lists the value of at the temperature specified in the third column, usually 293.15 or 298.15 K. Otherwise, the temperature closest to 293.15 K was chosen, or (as it is the case for many of the substances included here) is given at the only temperature for which data are available. 

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