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Dielectric loss
About: Dielectric loss is a research topic. Over the lifetime, 20296 publications have been published within this topic receiving 349254 citations.
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TL;DR: In this paper, a broad phonon spectra and the frequency independent dielectric losses at low temperatures are compatible with the existence of nanoscopic polar regions and disorder to liquid He temperatures similar to relaxor ferroelectrics.
Abstract: Infrared reflectivity, time-domain terahertz transmission, high-frequency dielectric measurements and Raman spectroscopy of Na0.5Bi0.5TiO3 complex ferroelectric perovskite were performed in a broad temperature range. The results were analysed considering the macroscopic symmetry as well as symmetry resulting from local Na–Bi ordering in all three known phases. An overdamped infrared soft mode was revealed in the THz range which, together with central-mode type dispersion in the GHz range, contribute to the strong and broad dielectric permittivity maximum around 600 K. Anharmonic Bi and/or Na vibrations and local hopping, respectively, are suggested to be the main origins of these excitations. The broad phonon spectra and the frequency independent dielectric losses at low temperatures are compatible with the existence of nanoscopic polar regions and disorder to liquid He temperatures similar to relaxor ferroelectrics.
163 citations
TL;DR: In this article, the dielectric relaxation of several molecular organic supercooled liquids, αβ-tris-naphthylbenzene (C36H24 and C36H10D14), squalane, and decahydroisoquinoline, was studied in the frequency range 10−2-107'Hz, equivalent to temperatures between Tg and approximately 1.2Tg.
Abstract: We have measured the dielectric relaxation of several molecular organic supercooled liquids, ααβ-tris-naphthylbenzene (C36H24 and C36H10D14), squalane, and decahydroisoquinoline. The dynamics is studied in the frequency range 10−2–107 Hz, equivalent to temperatures between Tg and approximately 1.2×Tg. For the very low dielectric loss materials, a resolution of tan δ≈3×10−5 is required in order to observe the details of the relaxation behavior. Characteristic quantities like fragility, relaxation time dispersion, time–temperature superposition, and the slow Johari–Goldstein type β relaxation are among the properties discussed.
163 citations
TL;DR: In this paper, the compositional variation of DC resistivity and dielectric constant show the inverse trend with each other, while the dielectral constant increases slowly with temperature in the beginning and then abruptly at about 473 K and above.
162 citations
TL;DR: Transparent PZT thin films with perovskite structure were successfully obtained by thermal decomposition of organometallic compounds at the temperatures of 500 to 700° C as discussed by the authors.
Abstract: Transparent PZT thin films with perovskite structure were successfully obtained by thermal decomposition of organometallic compounds at the temperatures of 500 to 700° C. The films deposited on platinum substrates were smooth and uniform, but microcrackings were observed in the films deposited on fused silica substrates. The ratio of metal composition in the PZT film agreed with that in the mixture of starting materials. Films obtained at 700° C on platinum substrate showed a hysteresis loop. A spontaneous polarization was 35.65μC cm−2, a saturation remanent polarization was 30.56μC cm−2 and a coercive field was 45 kV cm−1. Dielectric constant and dielectric loss angle were about 300 and 0.05, respectively.
162 citations
TL;DR: In this article, a combined electromagnetic and thermal procedure is proposed to take into account the influence of the temperature on the electrical properties of materials, and a realistic model is proposed and validated.
Abstract: It Is well known that the temperature rise in a material modifies its physical properties and, particularly, its dielectric permittivity. The dissipated electromagnetic power involved in microwave heating processes depending on /spl epsi/(/spl omega/), the electrical characteristics of the heated media must vary with the temperature to achieve realistic simulations. In this paper, we present a fast and accurate algorithm allowing, through a combined electromagnetic and thermal procedure, to take into account the influence of the temperature on the electrical properties of materials. First, the temperature dependence of the complex permittivity ruled by a Debye relaxation equation is investigated, and a realistic model is proposed and validated. Then, a frequency-dependent finite-differences time-domain ((FD)/sup 2/TD) method is used to assess the instantaneous electromagnetic power lost by dielectric hysteresis. Within the same iteration, a time-scaled form of the heat transfer equation allows one to calculate the temperature distribution in the heated medium and then to correct the dielectric properties of the material using the proposed model. These new characteristics will be taken into account by the EM solver at the next iteration. This combined algorithm allows a significant reduction of computation time. An application to a microwave oven is proposed.
162 citations