Dielectric loss

About: Dielectric loss is a research topic. Over the lifetime, 20296 publications have been published within this topic receiving 349254 citations.

Numerical Analysis of the Rectangular Dielectric Waveguide and its Modifications

Abstract: Dielectric waveguides suitable for millimeter and submillimeter wave integrated circuits are analyzed by applying the generalized telegraphist's equations. The dielectric waveguides treated in this paper are the rectangular dielectric image line, the cladded rectangular dielectric image line, the insulated image guide, and the strip dielectric guide. Numerical results of the propagation constant, the power distribution, and the field configuration in these dielectric waveguides are presented. Values for the propagation constants obtained by our method are compared with other theoretical results. Although this work is based on a closed waveguide model, it may be applicable to wide classes of dielectric waveguides with arbitrary dielectric profiles and cross sections.

Temperature and frequency dependencies of the complex dielectric constant of poly(ethylene oxide) under hydrostatic pressure

Abstract: Electrical impedance measurements have been made in the frequency range 5 Hz to 10 MHz in pure poly(ethylene oxide) having a molecular weight of 600,000 from 12 K nearly up to the melting point of the crystalline phase (about 330 K). A pronounced relaxation peak in the dielectric loss and a corresponding step in the dielectric constant have been observed at about 240 K, which can be readily related to the glass-rubber transition in the amorphous region of the polymer. As the temperature approaches the melting point there are large increases in the real e' and imaginary e parts of the dielectric constant. The frequency dependence of e' is characterized by a primary relaxation process, whose frequency increases with increasing temperature as a consequence of decrease of the average structural relaxation time. There is strong evidence that this low-frequency dispersion arises mainly from the diffusive transport of ionic charge carriers rather than a purely orientation relaxation process. In addition, the effects of hydrostatic pressures (0-0.25 GPa) on the frequency dependencies of the real e' and imaginary e parts of the dielectric constant have been measured in the temperature range from 254 to 329 K. An advantage of applying pressure is that it shifts the α a relaxation peak into an experimentally accessible frequency window of the equipment ; the lowering of frequency results from a decrease in the relaxation volume and a consequent reduction in the mobility of the molecular units. Results are discussed in terms of theoretical models of the effect of pressure on the glass transition, providing information on the cooperative dynamics.

Dielectric Properties of Ceramics in Ba (Co1/3 Nb2/3)O3–Ba(Zn1/3Nb2/3)O3 Solid Solution

Abstract: The dielectric properties of the Ba (Co1/3 Nb2/3)O3–Ba(Zn1/3Nb2/3)O3 system were determined. Ba (Co1/3 Nb2/3)O3–Ba(Zn1/3Nb2/3)O3 has a complex perovskite structure, a high dielectric constant, a low dielectric loss, and a low temperature coefficient of the resonant frequency. A solid-solution ceramic with 0.7Ba (Co1/3 Nb2/3)O3·0.3 Ba(Zn1/3Nb2/3)O3 has a dielectric constant of K=33.5, Q=11000 at 6.5 GHz, and a temperature coefficient of the resonant frequency of τf=0 ppm/°C. The temperature coefficient of resonant frequency can be varied by changing the composition. The Q values of the ceramics can be increased by annealing in a nitrogen atmosphere. These ceramics can be used for resonant elements and stabilized oscillators.