Dielectric properties of solids

Microwave energy has been widely used to process and sinter ceramics and the following advantages compared to conventional heating have been quoted4  

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S. Zaromb and R. Brill. J. Chem. Phys. 24, 895-902 (1956). Dielectric properties of solid solutions of ice and NHar. 

There are many techniques used to measure the dielectric properties of solids. One of the more popular ones is known as ac impedance spectroscopy. described below. Another technique compares the response of the dielectric to that of a calibrated variable capacitor. In this method, the capacitance of a... 

CONCEPTS More about relaxation process within solids Typical loss peaks are broader and asymmetric in solids, and frequency is often too low compared with Debye peaks. A model using hypotheses based on nearest-neighbor interactions predicts a loss peak with broader width, asymmetric shape, and lower frequency [27]. This behavior is well suited to polymeric, glassy materials and ferroelectrics. Low temperature loss peaks typically observed for polymers need many-body interactions to be obtained. Although current understanding of these processes is not yet sufficient to enable quantitative forecasting the dielectric properties of solids may offer insight into the mechanisms of many-body interactions. 

The morphology of a polymer plays an important role in determining its properties, but the molecular motions that take place within the polymer play an equally important role. The later part of this chapter deals with the types of motion that can take place in solid polymers and the evidence for these motions. This topic of motion is taken up again in subsequent chapters, particularly in chapters 7 and 9, where the effects of motion on the mechanical and dielectric properties of solid polymers are discussed. 

J. Volger [1960] Dielectric Properties of Solids in Relation to Imperfections, in Progress in Semiconductors, Vol. 4, ed. 

As the theory of LPS provides a fairly general and physically sound basis to develop models for the dielectric behavior of sorbent-sorbate systems, we here will present some of its main results. These then are used to develop an electric network model which includes the well-known Debye model of dielectric materials as a special case [6.24]. Another approach to model dielectric properties of solid sorption systems has been discussed by Coelho in [6.29], which however will not be considered here. 

In this review the material has been selected to illustrate the main features of the dielectric properties of solid polymers in their amorphous, partially crystalline and liquid crystalline states and of polymers in solution. It should be apparent that the dielectric method provides a powerful and... 

Fig. 1. Effect of compositional variations on the dielectric properties of strontium titanate-barium titanate solid solutions. A, BaQ SrQ QTiO B,...

As shown in Fig. 7, a large increase in optical absorption occurs at higher photon energies above the HOMO-LUMO gap where electric dipole transitions become allowed. Transmission spectra taken in this range (see Fig. 7) confirm the similarity of the optical spectra for solid Ceo and Ceo in solution (decalin) [78], as well as a similarity to electron energy loss spectra shown as the inset to this figure. The optical properties of solid Ceo and C70 have been studied over a wide frequency range [78, 79, 80] and yield the complex refractive index n(cj) = n(cj) + and the optical dielectric function... 

The study of the effect of electric fields on the properties of solids dates back to Zener s (1934) investigation of electrical breakdown in solid dielectrics. Further pioneering work was carried out by Houston (1940) and Slater... 

R. Bartnikas, "Engineering Dielectrics Vol. IIA—Electrical Properties of Solid Insulating Materials Molecular Structure and Electrical Behavior," ASTM... 

Mudgett, R., Goldblith, S., Wang, D., and Westphal, W. 1977. Prediction of dielectric properties in solid food of high moisture content at ultrahigh and microwave frequencies. Journal of Food Processing and Preservation 1 119-151. 

Fuoss, R. M. Electrical properties of solids. VI. Dipole rotation in high polymers. J. Am. Chem. Soc. 63, 369—378 (1941). Note The dielectric data of Fig. 15 were taken from Document No. 1460, Amer. Documentation Inst. Library of Congress, Washington, D. C. 

Dielectric measurements have been established for nearly three decades as a technique for monitoring the cure of polymeric resins. Dramatic changes in the dielectric properties of the material accompany the transformation of the resin from a viscous liquid to a solid. 

Constant-phase elements were first used to explain dielectrical properties of polar liquids and solids, and were attributed to the presence of the investigated material properties as a partitioning between extreme conditions, rather than as constant or uniform parameters40. Furthermore in the... 

Theoretical considerations by Clarke and co-workers (Clarke, 1987 Clarke etal., 1993) show that an equilibrium film thickness arises from the competition between attractive dispersion forces determined by the dielectric properties of the grains and repulsive disjoining forces which can be steric forces and/ or double-layer forces. Wetting will occur when the solid-solid boundary energy, yb, is less than that of the wetted boundary, 2y, where y is the liquid-solid interfacial energy (Clarke, 1985), provided that there is a suitable source of liquid, for example as a consequence of liquid-phase sintering at high temperatures. 

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