Topic
Permittivity
About: Permittivity is a research topic. Over the lifetime, 35736 publications have been published within this topic receiving 687533 citations. The topic is also known as: electric permittivity & absolute permittivity.
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TL;DR: In this article, the authors studied the dielectric properties, lattice and microstructure of ceramic BaTiO3 showing grain sizes of 0.3-100 μm and showed that at grain sizes <10 μm the width of ferroelectric 90° domains decreases proportionally to the square root of the grain diameter.
Abstract: Dielectric properties, lattice‐ and microstructure of ceramic BaTiO3 showing grain sizes of 0.3–100 μm were studied. At grain sizes <10 μm the width of ferroelectric 90° domains decreases proportionally to the square root of the grain diameter. The decreasing width of the domains can be theoretically explained by the equilibrium of elastic field energy and domain wall energy. The smaller the grains, the more the dielectric and the elastic constants are determined by the contribution of 90° domain walls. The permittivity below the Curie point shows a pronounced maximum er ≊5000 at grain sizes 0.8–1 μm. At grain sizes <0.7 μm the permittivity strongly decreases and the lattice gradually changes from tetragonal to pseudocubic.
1,742 citations
TL;DR: Optical conductivity measurements on the perovskite-related oxide CaCu3Ti4O12 provide a hint of the physics underlying the observed giant dielectric effect in this material, suggesting the presence of a strong absorption at very low frequencies due to dipole relaxation.
Abstract: Optical conductivity measurements on the perovskite-related oxide CaCu3Ti4O12 provide a hint of the physics underlying the observed giant dielectric effect in this material. A low-frequency vibration displays anomalous behavior, implying that there is a redistribution of charge within the unit cell at low temperature. At infrared frequencies (terahertz), the value for the dielectric constant is approximately 80 at room temperature, which is far smaller than the value of approximately 10(5) obtained at lower radio frequencies (kilohertz). This discrepancy implies the presence of a strong absorption at very low frequencies due to dipole relaxation. At room temperature, the characteristic relaxation times are fast (less than or approximately 500 nanoseconds) but increase dramatically at low temperature, suggesting that the large change in dielectric constant may be due to a relaxor-like dynamical slowing down of dipolar fluctuations in nanosize domains.
1,540 citations
TL;DR: In this paper, a dielectric spectroscopy of short carbon fiber/silica composite in the frequency range from 8.2 to 12.4 GHz at temperatures between 30 and 600°C has been performed.
1,540 citations
TL;DR: The measured optical spectra of the nanofabricated gold structures come very close to the theoretical expectations and additional numerical simulations show that the structures exhibit a frequency range with negative permeability for a beam configuration in which the magnetic field couples to the LC resonance.
Abstract: An array of single nonmagnetic metallic split rings can be used to implement a magnetic resonance, which arises from an inductor-capacitor circuit (LC) resonance, at 100-terahertz frequency. The excitation of the LC resonance in the normal-incidence geometry used in our experiments occurs through the coupling of the electric field of the incident light to the capacitance. The measured optical spectra of the nanofabricated gold structures come very close to the theoretical expectations. Additional numerical simulations show that our structures exhibit a frequency range with negative permeability for a beam configuration in which the magnetic field couples to the LC resonance. Together with an electric response that has negative permittivity, this can lead to materials with a negative index of refraction.
1,448 citations
TL;DR: Subramanian et al. as discussed by the authors attributed the giant-dielectric phenomenon to a grain boundary (internal) barrier layer capacitance (IBLC) instead of an intrinsic property associated with the crystal structure.
Abstract: There has been much recent interest in a so-called “giant-dielectric phenomenon” displayed by an unusual cubic perovskite-type material, CaCu3Ti4O12; however, the origin of the high permittivity has been unclear [M. A. Subramanian, L. Dong, N. Duan, B. A. Reisner, and A. W. Sleight, J. Solid State Chem. 151, 323 (2000); C. C. Homes, T. Vogt, S. M. Shapiro, S. Wakimoto, and A. P. Ramirez, Science 293, 673 (2001); A. P. Ramirez, M. A. Subramanian, M. Gardel, G. Blumberg, D. Li, T. Vogt, and S. M. Shapiro, Solid State Commun. 115, 217 (2000)]. Impedance spectroscopy on CaCu3Ti4O12 ceramics demonstrates that they are electrically heterogeneous and consist of semiconducting grains with insulating grain boundaries. The giant-dielectric phenomenon is therefore attributed to a grain boundary (internal) barrier layer capacitance (IBLC) instead of an intrinsic property associated with the crystal structure. This barrier layer electrical microstructure with effective permittivity values in excess of 10 000 can be fa...
1,438 citations